The Gale Encyclopedia of Nursing and Allied Health

The GALE ENCYCLOPEDIA of

Nursing & Allied Health

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The GALE ENCYCLOPEDIA of

Nursing & Allied Health VOLUME 1 A-C

Kristine Krapp, Editor

The GALE ENCYCLOPEDIA of

Nursing & Allied Health VOLUME 2 D-H

Kristine Krapp, Editor

The GALE ENCYCLOPEDIA of

Nursing & Allied Health VOLUME 3 I-O

Kristine Krapp, Editor

The GALE ENCYCLOPEDIA of

Nursing & Allied Health VOLUME 4 P-S

Kristine Krapp, Editor

The GALE ENCYCLOPEDIA of

Nursing & Allied Health VOLUME 5 T- Z Appendix General Index

Kristine Krapp, Editor

The GALE ENCYCLOPEDIA of NURSING AND ALLIED HEALTH STAFF

Kristine Krapp, Coordinating Senior Editor Christine B. Jeryan, Managing Editor Deirdre S. Blanchfield, Associate Editor (Manuscript Coordination) Melissa C. McDade, Associate Editor (Photos and Illustrations) Stacey L. Blachford, Associate Editor Kate Kretschmann, Assistant Editor Donna Olendorf, Senior Editor Ryan Thomason, Assistant Editor Mark Springer, Technical Specialist Andrea Lopeman, Programmer/Analyst Barbara Yarrow, Manager, Imaging and Multimedia Content Robyn V. Young, Project Manager, Imaging and Multimedia Content Randy Bassett, Imaging Supervisor Dan Newell, Imaging Specialist Pamela A. Reed, Coordinator, Imaging and Multimedia Content Maria Franklin, Permissions Manager Margaret A. Chamberlain, Permissions Specialist Kenn Zorn, Product Manager Michelle DiMercurio, Senior Art Director Cynthia Baldwin, Senior Art Director Mary Beth Trimper, Manager, Composition, and Electronic Prepress Evi Seoud, Assistant Manager, Composition Purchasing, and Electronic Prepress Dorothy Maki, Manufacturing Manager Indexing provided by Synapse, the Knowledge Link Corporation.

Since this page cannot legibly accommodate all copyright notices, the acknowledgments constitute an extension of the copyright notice. While every effort has been made to ensure the reliability of the information presented in this publication, the Gale Group neither guarantees the accuracy of the data contained herein nor assumes any responsibility for errors, omissions or discrepancies. The Gale Group accepts no payment for listing, and inclusion in the publication of any organization, agency, institution, publication, service, or individual does not imply endorsement of the editor or publisher. Errors brought to the attention of the publisher and verified to the satisfaction of the publisher will be corrected in future editions. This book is printed on recycled paper that meets Environmental Protection Agency standards. The paper used in this publication meets the minimum requirements of American National Standard for Information Sciences-Permanence Paper for Printed Library Materials, ANSI Z39.48-1984. This publication is a creative work fully protected by all applicable copyright laws, as well as by misappropriation, trade secret, unfair competition, and other applicable laws. The authors and editor of this work have added value to the underlying factual material herein through one or more of the following: unique and original selection, coordination, expression, arrangement, and classification of the information. Gale Group and design is a trademark used herein under license. All rights to this publication will be vigorously defended. Copyright © 2002 Gale Group 27500 Drake Road Farmington Hills, MI 48331-3535 All rights reserved including the right of reproduction in whole or in part in any form. ISBN 0-7876-4934-1 (set) 0-7876-4935-X (Vol. 1) 0-7876-4936-8 (Vol. 2)

0-7876-4937-6 (Vol. 3) 0-7876-4938-4 (Vol. 4) 0-7876-4939-2 (Vol. 5)

Printed in Canada 10 9 8 7 6 5 4 3 2 1 Library of Congress Cataloging-in-Publication Data The Gale encyclopedia of nursing and allied health / Kristine Krapp, editor. p. cm. Includes bibliographical references and index. ISBN 0-7876-4934-1 (set : hardcover : alk. paper) ISBN 0-7876-4935-X (v. 1 : alk. paper) — ISBN 0-7876-4936-8 (v.2 : alk. paper) — ISBN 0-7876-4937-6 (v. 3 : alk. paper) — ISBN0-7876-4938-4 (v. 4 : alk. paper) — ISBN 0-7876-4939-2 (v. 5 : alk. paper) 1. Nursing Care—Encyclopedias—English. 2. Allied Health Personnel—Encyclopedias—English. 3. Nursing—Encyclopedias—English. WY 13 G151 2002] RT21 .G353 2002 610.73'03—dc21 2001040910

CONTENTS

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii Advisory Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Entries Volume 1: A-C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Volume 2: D-H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 641 Volume 3: I-O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1237 Volume 4: P-S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1797 Volume 5: T-Z . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2383 Appendix of Nursing and Allied Health Organizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2663 General Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2669

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PLEASE READ—IMPORTANT INFORMATION

The Gale Encyclopedia of Nursing and Allied Health is a medical reference product designed to inform and educate readers about a wide variety of diseases, treatments, tests and procedures, health issues, human biology, and nursing and allied health professions. The Gale Group believes the product to be comprehensive, but not necessarily definitive. While the Gale Group has made substantial efforts to provide information that is accurate, comprehensive, and up-to-date, the Gale Group makes no

representations or warranties of any kind, including without limitation, warranties of merchantability or fitness for a particular purpose, nor does it guarantee the accuracy, comprehensiveness, or timeliness of the information contained in this product. Readers should be aware that the universe of medical knowledge is constantly growing and changing, and that differences of medical opinion exist among authorities.

INTRODUCTION

The Gale Encyclopedia of Nursing and Allied Health is a unique and invaluable source of information for the nursing or allied health student. This collection of over 850 entries provides in-depth coverage of specific diseases and disorders, tests and procedures, equipment and tools, body systems, nursing and allied health professions, and current health issues. This book is designed to fill a gap between health information designed for laypeople and that provided for medical professionals, which may be too complicated for the beginning student to understand. The encyclopedia does use medical terminology, but explains it in a way that students can understand. SCOPE

The Gale Encyclopedia of Nursing and Allied Health covers a wide variety of topics relevant to the nursing or allied health student. Subjects covered include those important to students intending to become biomedical equipment technologists, dental hygienists, dieteticians, health care administrators, medical technologists/clinical laboratory sciencists, registered and licensed practical nurses, nurse anesthetists, nurse practitioners, nurse midwives, occupational therapists, optometrists, pharmacy technicians, physical therapists, radiologic technologists, and speech-language therapists. The encyclopedia also covers information on related general medical topics, classes of medication, mental health, public health, and human biology. Entries follow a standardized format that provides information at a glance. Rubrics include: Diseases/Disorders Definition Description Causes and symptoms Diagnosis Treatment Prognosis

Health care team roles Prevention Resources Key terms Tests/Procedures Definition Purpose Precautions Description Preparation Aftercare Complications Results Health care team roles Resources Key terms Equipment/Tools Definition Purpose Description Operation Maintenance Health care team roles Training Resources Key terms Human biology/Body systems Definition Description Function Role in human health Common diseases and disorders Resources Key terms

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Introduction

Nursing and allied health professions

HOW TO USE THIS BOOK

The Gale Encyclopedia of Nursing and Allied Health has been designed with ready reference in mind.

Definition Description Work settings Education and training Advanced education and training Future outlook Resources Key terms

• Straight alphabetical arrangement of topics allows users to locate information quickly. • Bold-faced terms within entries direct the reader to related articles. • Cross-references placed throughout the encyclopedia direct readers from alternate names and related topics to entries.

Current health issues

• A list of Key terms is provided where appropriate to define terms or concepts that may be unfamiliar to the student.

Definition Description Viewpoints Professional implications Resources Key terms

• The Resources section directs readers to additional sources of medical information on a topic. • Valuable contact information for medical, nursing, and allied health organizations is included with each entry. An Appendix of Nursing and Allied Health organizations in the back matter contains an extensive list of organizations arranged by subject.

INCLUSION CRITERIA

A preliminary list of topics was compiled from a wide variety of sources, including nursing and allied health textbooks, general medical encyclopedias, and consumer health guides. The advisory board, composed of advanced practice nurses, allied health professionals, health educators, and medical doctors, evaluated the topics and made suggestions for inclusion. Final selection of topics to include was made by the advisory board in conjunction with the Gale editor. ABOUT THE CONTRIBUTORS

The essays were compiled by experienced medical writers, including physicians, pharmacists, nurses, and allied health care professionals. The advisers reviewed the completed essays to ensure that they are appropriate, up-to-date, and medically accurate.

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• A comprehensive general index guides readers to significant topics mentioned in the text. GRAPHICS

The Gale Encyclopedia of Nursing and Allied Health is enhanced by over 400 black and white photos and illustrations, as well as over 50 tables. ACKNOWLEDGMENTS

The editor would like to express appreciation to all of the nursing and allied health professionals who wrote, reviewed, and copyedited entries for the Gale Encyclopedia of Nursing and Allied Health. Cover photos were reproduced by the permission of Delmar Publishers, Inc., Custom Medical Photos, and the Gale Group.

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ADVISORY BOARD A number of experts in the nursing and allied health communities provided invaluable assistance in the formulation of this encyclopedia. The advisory board performed a myriad of duties, from defining the scope of coverage to reviewing individual entries for accuracy and accessibility. The editor would like to express appreciation to them for their time and their expert contributions.

Dr. Isaac Bankman Principal Scientist Imaging and Laser Systems Section Johns Hopkins Applied Physics Laboratory Laurel, Maryland

Dr. Gregory M. Karst Associate Professor Division of Physical Therapy Education University of Nebraska Medical Center Omaha, Nebraska

Martha G. Bountress, M.S., CCC-SLP/A Clinical Instructor Speech-Language Pathology and Audiology Old Dominion University Norfolk, Virginia

Debra A. Kosko, R.N., M.N., FNP-C Instructor, Faculty Practice School of Nursing, Department of Medicine Johns Hopkins University Baltimore, Maryland

Michele Leonardi Darby Eminent Scholar, University Professor Graduate Program Director School of Dental Hygiene Old Dominion University Norfolk, Virginia

Timothy E. Moore, Ph.D., C Psych Professor of Psychology Glendon College York University Toronto, Ontario, Canada

Dr. Susan J. Gromacki Lecturer in Ophthalmology and Visual Sciences University of Michigan Medical School Ann Arbor, Michigan

Anne Nichols, C.R.N.P. Coordinator, Family Nurse Practitioner Program School of Nursing Widener University Chester, Pennsylvania

Dr. John E. Hall Guyton Professor and Chair Department of Physiology and Biophysics University of Mississippi Medical Center Jackson, Mississippi

Judith B. Paquet, R.N. Medical Communications Specialist Paquet Associates Clementon, New Jersey

Lisa F. Harper, B.S.D.H., M.P.H., R.D., L.D. Assistant Professor Baylor College of Dentistry Dallas, Texas

Lee A. Shratter, M.D. Radiologist Healthcare Safety and Medical Consultant Kentfield, California

Robert Harr, M.S. MT (ASCP) Associate Professor and Chair Department of Public and Allied Health Bowling Green State University Bowling Green, Ohio

Linda Wheeler, C.N.M., Ed.D. Associate Professor School of Nursing Oregon Health and Science University Portland, Oregon

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CONTRIBUTORS

Lisa Maria Andres, M.S., C.G.C San Jose, California

Rachael Tripi Brandt, M.S. Gettysburg, Pennsylvania

Greg Annussek New York, New York

Peggy Elaine Browning Olney, Texas

Maia Appleby Boynton Beach, Florida

Susan Joanne Cadwallader Cedarburg, Wisconsin

Bill Asenjo, M.S., C.R.C. Iowa City, Iowa

Barbara M. Chandler Sacramento, California

Lori Ann Beck, R.N., M.S.N., F.N.P.-C. Berkley, Michigan

Linda Chrisman Oakland, California

Mary Bekker Willow Grove, Pennsylvania

Rhonda Cloos, R.N. Austin, Texas

Linda K. Bennington, R.N.C., M.S.N., C.N.S. Virginia Beach, Virginia

L. Lee Culvert Alna, Massachusetts

Kenneth J. Berniker, M.D. El Cerrio, California

Tish Davidson Fremont, California

Mark A. Best Cleveland Heights, Ohio

Lori De Milto Sicklerville, New Jersey

Dean Andrew Bielanowski, R.N., B.Nurs.(QUT) Rochedale S., Brisbane, Australia

Victoria E. DeMoranville Lakeville, Massachusetts

Carole Birdsall, R.N. A.N.P. Ed.D. New York, New York

Janine Diebel, R.N. Gaylord, Michigan

Bethanne Black Buford, Georgia

Stéphanie Islane Dionne Ann Arbor, Michigan

Maggie Boleyn, R.N., B.S.N. Oak Park, Michigan

J. Paul Dow, Jr. Kansas City, Missouri

Barbara Boughton El Cerrito, California

Douglas Dupler Boulder, Colorado

Patricia L. Bounds, Ph.D. Zurich, Switzerland

Lorraine K. Ehresman Northfield, Quebec, Canada

Mary Boyle, Ph.D., C.C.C.-S.L.P., B.C.-N.C.D. Lincoln Park, New Jersey

L. Fleming Fallon, Jr., M.D., Dr.P.H. Bowling Green, Ohio

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Contributors

Diane Fanucchi-Faulkner, C.M.T., C.C.R.A. Oceano, California

Paul A. Johnson San Marcos, California

Janis O. Flores Sebastopol, Florida

Linda D. Jones, B.A., P.B.T.(A.S.C.P.) Asheboro, New York

Paula Ford-Martin Chaplin, Minnesota

Crystal Heather Kaczkowski, M.Sc. Dorval, Quebec, Canada

Janie F. Franz Grand Forks, North Dakota

Beth Kapes Bay Village, Ohio

Sallie Boineau Freeman, Ph.D. Atlanta, Georgia

Monique Laberge, Ph.D. Philadelphia, Pennsylvania

Rebecca Frey, Ph.D. New Haven, Connecticut

Aliene S. Linwood, B.S.N., R.N., D.P.A., F.A.C.H.E. Athens, Ohio

Lisa M. Gourley Bowling Green, Ohio

Jennifer Lee Losey, R.N. Madison Heights, Michigan

Meghan M. Gourley Germantown, Maryland

Liz Marshall Columbus, Ohio

Jill Ilene Granger, M.S. Ann Arbor, Michigan

Mary Elizabeth Martelli, R.N., B.S. Sebastian, Florida

Elliot Greene, M.A. Silver Spring, Maryland

Jacqueline N. Martin, M.S. Albrightsville, Pennsylvania

Stephen John Hage, A.A.A.S., R.T.(R), F.A.H.R.A. Chatsworth, California

Sally C. McFarlane-Parrott Mason, Michigan

Clare Hanrahan Asheville, North Carolina

Beverly G. Miller, M.T.(A.S.C.P.) Charlotte, North Carolina

Robert Harr Bowling Green, Ohio

Christine Miner Minderovic, B.S., R.T., R.D.M.S. Ann Arbor, Michigan

Daniel J. Harvey Wilmington, Delaware

Mark A. Mitchell, M.D. Bothell, Washington

Katherine Hauswirth, A.P.R.N. Deep River, Connecticut

Susan M. Mockus, Ph.D. Seattle, Washington

David L. Helwig London, Ontario, Canada

Timothy E. Moore, Ph.D. Toronto, Ontario, Canada

Lisette Hilton Boca Raton, Florida

Nancy J. Nordenson Minneapolis, Minnesota

René A. Jackson, R.N. Port Charlotte, Florida

Erika J. Norris Oak Harbor, Washington

Nadine M. Jacobson, R.N. Takoma Park, Maryland

Debra Novograd, B.S., R.T.(R)(M) Royal Oak, Michigan

Randi B. Jenkins New York, New York

Marianne F. O’Connor, M.T., M.P.H. Farmington Hills, Michigan

Michelle L. Johnson, M.S., J.D. Portland, Oregon

Carole Osborne-Sheets Poway, California

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Patricia Skinner Amman, Jordan

Patience Paradox Bainbridge Island, Washington

Genevieve Slomski New Britain, Connecticut

Deborah Eileen Parker, R.N. Lakewood, Washington

Bryan Ronain Smith Cincinnati, Ohio

Genevieve Pham-Kanter Chicago, Illinois

Allison Joan Spiwak, B.S., C.C.P. Gahanna, Ohio

Jane E. Phillips, Ph.D. Chapel Hill, North Carolina

Lorraine T. Steefel Morganville, New Jersey

Pamella A. Phillips Bowling Green, Ohio

Margaret A. Stockley, R.G.N. Boxborough, Massachusetts

Elaine R. Proseus, M.B.A./T.M., B.S.R.T., R.T.(R) Farmington Hills, Michigan

Amy Loerch Strumolo Bloomfield Hills, Michigan

Ann Quigley New York, New York

Liz Swain San Diego, California

Esther Csapo Rastegari, R.N., B.S.N., Ed.M. Holbrook, Massachusetts

Deanna M. Swartout-Corbeil, R.N. Thompsons Station, Tennessee

Anastasia Marie Raymer, Ph.D. Norfolk, Virginia

Peggy Campbell Torpey, M.P.T. Royal Oak, Michigan

Martha S. Reilly, O.D. Madison, Wisconsin

Mai Tran, Pharm.D. Troy, Michigan

Linda Richards, R.D., C.H.E.S. Flagstaff, Arizona

Carol A. Turkington Lancaster, Pennsylvania

Toni Rizzo Salt Lake City, Utah

Judith Turner, D.V.M. Sandy, Utah

Nancy Ross-Flanigan Belleville, Michigan

Samuel D. Uretsky, Pharm.D. Wantagh, New York

Mark Damian Rossi, Ph.D, P.T., C.S.C.S. Pembroke Pines, Florida

Michele R. Webb Overland Park, Kansas

Kausalya Santhanam Branford, Connecticut

Ken R. Wells Laguna Hills, California

Denise L. Schmutte, Ph.D. Shoreline, Washington

Barbara Wexler, M.P.H. Chatsworth, California

Joan M. Schonbeck Marlborough, Massachusetts

Gayle G. Wilkins, R.N., B.S.N., O.C.N. Willow Park, Texas

Kathleen Scogna Baltimore, Maryland

Jennifer F. Wilson Haddonfield, New Jersey

Cathy Hester Seckman, R.D.H. Calcutta, Ohio

Angela Woodward Madison, Wisconsin

Jennifer E. Sisk, M.A. Havertown, Pennsylvania

Jennifer Wurges Rochester Hills, Michigan

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Contributors

Cindy F. Ovard, R.D.A Spring Valley, California

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A Abdominal thrust see Heimlich maneuver

Abdominal ultrasound Definition Abdominal ultrasound uses high frequency sound waves to produce two-dimensional images of the body’s soft tissues, which are used for a variety of clinical applications, including diagnosis and guidance of treatment procedures. Ultrasound does not use ionizing radiation to produce images, and in comparison to other diagnostic imaging modalities, it is low cost, safe, fast, and versatile.

Purpose Abdominal ultrasound is used in the hospital radiology department and emergency department, as well as in physician offices for a number of clinical applications. Ultrasound has a great advantage over x-ray imaging technologies in that it does not damage tissues with ionizing radiation. Ultrasound is also generally far better than plain x-rays at distinguishing the subtle variations of soft tissue structures, and can be used in any of several modes, depending on the area of interest. As an imaging tool, abdominal ultrasound generally is indicated for patients afflicted with chronic or acute abdominal pain; abdominal trauma; an obvious or suspected abdominal mass; symptoms of liver disease, pancreatic disease, gallstones, spleen disease, kidney disease and urinary blockage; or symptoms of an abdominal aortic aneurysm. Specifically: • Abdominal pain. Whether acute or chronic, pain can signal a serious problem—from organ malfunction or injury to the presence of malignant growths.

Ultrasound scanning can help doctors quickly sort through potential causes when presented with general or ambiguous symptoms. All of the major abdominal organs can be studied for signs of disease that appear as changes in size, shape, and internal structure. • Abdominal trauma. After a serious accident, such as a car crash or a fall, internal bleeding from injured abdominal organs is often the most serious threat to survival. Neither the injuries nor the bleeding may be immediately apparent. Ultrasound is very useful as an initial scan when abdominal trauma is suspected, and it can be used to pinpoint the location, cause, and severity of hemorrhaging. In the case of puncture wounds, from a bullet for example, ultrasound can locate the foreign object and provide a preliminary survey of the damage. (CT scans are sometimes used in trauma settings.) • Abdominal mass. Abnormal growths—tumors, cysts, abscesses, scar tissue, and accessory organs—can be located and tentatively identified with ultrasound. In particular, potentially malignant solid tumors can be distinguished from benign fluid-filled cysts. Masses and malformations in any organ or part of the abdomen can be found. • Liver disease. The types and underlying causes of liver disease are numerous, though jaundice tends to be a general symptom. Ultrasound can differentiate between many of the types and causes of liver malfunction, and is particularly good at identifying obstruction of the bile ducts and cirrhosis, which is characterized by abnormal fibrous growths and reduced blood flow. • Pancreatic disease. Inflammation and malformation of the pancreas are readily identified by ultrasound, as are pancreatic stones (calculi), which can disrupt proper functioning. • Gallstones. Gallstones are an extremely common cause of hospital admissions. These calculi can cause painful inflammation of the gallbladder and also obstruct the bile ducts that carry digestive enzymes from the gall-

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bladder and liver to the intestines. Gallstones are readily identifiable with ultrasound. • Spleen disease. The spleen is particularly prone to injury during abdominal trauma. It may also become painfully inflamed when infected or cancerous. • Kidney disease. The kidneys are also prone to traumatic injury and are the organs most likely to form calculi, which can block the flow of urine and cause further systemic problems. A variety of diseases causing distinct changes in kidney morphology can also lead to complete kidney failure. Ultrasound imaging has proven extremely useful in diagnosing kidney disorders, including blockage or obstruction. • Abdominal aortic aneurysm. This is a bulging weak spot in the abdominal aorta, which supplies blood directly from the heart to the entire lower body. A ruptured aortic aneurysm is imminently life-threatening. However, it can be readily identified and monitored with ultrasound before acute complications result. • Appendicitis. Ultrasound is useful in diagnosing appendicitis, which causes abdominal pain. Ultrasound technology can also be used for treatment purposes, most frequently as a visual aid during surgical procedures—such as guiding needle placement to drain fluid from a cyst, or to guide biopsies.

Precautions Ultrasound waves of appropriate frequency and intensity are not known to cause or aggravate any medical condition. The value of ultrasound imaging as a medical tool, however, depends greatly on the quality of the equipment used and the skill of the medical personnel operating it. More accurate results are obtained when ultrasound is performed by a clinician skilled in sonography. Basic ultrasound equipment is relatively inexpensive to obtain, and any physician with the equipment can perform the procedure whether specifically trained in ultrasound scanning and interpretation or not. Patients should not hesitate to verify the credentials of technologists and physicians performing ultrasound scanning, as well as the quality of the equipment used and the benefits of the proposed procedure. In cases where ultrasound is used as a treatment tool, patients should educate themselves about the proposed procedure with the help of their doctors—as is appropriate before any surgical procedure. Also, any abdominal ultrasound procedure, diagnostic or therapeutic, may be hampered by a patient’s body type or other factors, such as the presence of excessive bowel gas (which is opaque 2

to ultrasound). In particular, very obese people are often not good candidates for abdominal ultrasound.

Description Ultrasound includes all sound waves above the frequency of human hearing—about 20 thousand hertz, or cycles per second. Medical ultrasound generally uses frequencies between one and 10 megahertz (1-10 MHz). Higher frequency ultrasound waves produce more detailed images, but are also more readily absorbed and so cannot penetrate as deeply into the body. Abdominal ultrasound imaging is generally performed at frequencies between 2-5 MHz. An ultrasound scanner consists of two parts: the transducer and the data processing unit. The transducer both produces the sound waves that penetrate the body and receives the reflected echoes. Transducers are built around piezoelectric ceramic chips. (Piezoelectric refers to electricity that is produced when you put pressure on certain crystals such as quartz.) These ceramic chips react to electric pulses by producing sound waves (they are transmitting waves) and react to sound waves by producing electric pulses (receiving). Bursts of high-frequency electric pulses supplied to the transducer cause it to produce the scanning sound waves. The transducer then receives the returning echoes, translates them back into electric pulses, and sends them to the data processing unit—a computer that organizes the data into an image on a television screen. Because sound waves travel through all the body’s tissues at nearly the same speed—about 3,400 miles per hour—the microseconds it takes for each echo to be received can be plotted on the screen as a distance into the body. The relative strength of each echo, a function of the specific tissue or organ boundary that produced it, can be plotted as a point of varying brightness. In this way, the echoes are translated into an image. Four different modes of ultrasound are used in medical imaging: • A-mode. This is the simplest type of ultrasound in which a single transducer scans a line through the body with the echoes plotted on screen as a function of depth. This method is used to measure distances within the body and the size of internal organs. • B-mode. In B-mode ultrasound, a linear array of transducers simultaneously scans a plane through the body that can be viewed as a two-dimensional image on screen. • M-Mode. The M stands for motion. A rapid sequence of B-mode scans whose images follow each other in sequence on screen enables doctors to see and measure range of motion, as the organ boundaries that produce reflections move relative to the probe. M-mode ultra-

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KEY TERMS Accessory organ—A lump of tissue adjacent to an organ that is similar to it, but which serves no important purpose, if functional at all. While not necessarily harmful, such organs can cause problems if they grow too large or become cancerous. Benign—In medical usage, benign is the opposite of malignant. It describes an abnormal growth that is stable, treatable, and generally not lifethreatening. Biopsy—The surgical removal and analysis of a tissue sample for diagnostic purposes. Usually, the term refers to the collection and analysis of tissue from a suspected tumor to establish malignancy. Calculus—Any type of hard concretion (stone) in the body, but usually found in the gallbladder, pancreas, and kidneys. Calculi (pl.) are formed by the accumulation of excess mineral salts and other organic material such as blood or mucous. They can cause problems by lodging in and obstructing the proper flow of fluids, such as bile to the intestines or urine to the bladder. Cirrhosis—A chronic liver disease characterized by the degeneration of proper functioning—jaundice is often an accompanying symptom. Causes of cirrhosis include alcoholism, metabolic diseases, syphilis, and congestive heart disease. Common bile duct—The branching passage through which bile—a necessary digestive enzyme—travels from the liver and gallbladder into the small intestine. Digestive enzymes from the pancreas also enter the intestines through the common bile duct. Computed tomography scan (CT scan)—A specialized type of x-ray imaging that uses highly focused and relatively low energy radiation to produce detailed two-dimensional images of soft tissue structures, particularly the brain. CT scans are the chief competitor to ultrasound and can yield higher quality images not disrupted by bone or gas. They are, however, more cumbersome, time consuming and expensive to perform, and they use ionizing radiation.

sound has been put to particular use in studying heart motion. • Doppler mode. Doppler ultrasonography includes the capability of accurately measuring velocities of moving

Doppler—The Doppler effect refers to the apparent change in frequency of sound wave echoes returning to a stationary source from a moving target. If the object is moving toward the source, the frequency increases; if the object is moving away, the frequency decreases. The size of this frequency shift can be used to compute the object’s speed— be it a car on the road or blood in an artery. The Doppler effect holds true for all types of radiation, not just sound. Frequency—Sound, whether traveling through air or the human body, produces vibrations—molecules bouncing into each other—as the shock wave travels along. The frequency of a sound is the number of vibrations per second. Within the audible range, frequency means pitch—the higher the frequency, the higher a sound’s pitch. Ionizing radiation—Radiation that can damage living tissue by disrupting and destroying individual cells at the molecular level. All types of nuclear radiation—x rays, gamma rays and beta rays—are potentially ionizing. Sound waves physically vibrate the material through which they pass, but do not ionize it. Jaundice—A condition that results in a yellow tint to the skin, eyes and body fluids. Bile retention in the liver, gallbladder and pancreas is the immediate cause, but the underlying cause could be as simple as obstruction of the common bile duct by a gallstone or as serious as pancreatic cancer. Ultrasound can distinguish between these conditions. Malignant—The term literally means growing worse and resisting treatment. It is used as a synonym for cancerous and connotes a harmful condition that generally is life-threatening. Morphology—Literally, the study of form. In medicine, morphology refers to the size, shape, and structure rather than the function of a given organ. As a diagnostic imaging technique, ultrasound facilitates the recognition of abnormal morphologies as symptoms of underlying conditions.

material, such as blood in arteries and veins. The principle is the same as that used in radar guns that measure the speed of a car on the highway. Doppler capability is most often combined with B-mode scanning to produce

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Preparation A patient undergoing abdominal ultrasound will be advised by the physician about what to expect and how to prepare. As mentioned above, preparations generally include fasting.

Aftercare In general, no aftercare related to the abdominal ultrasound procedure itself is required. Discomfort during the procedure is minimal.

Complications Properly performed, ultrasound imaging is virtually without risk or side effects. Some patients report feeling a slight tingling and/or warmth while being scanned, but most feel nothing at all.

An ultrasound screen shows a patient’s kidney. (Photograph by Brownie Harris. The Stock Market. Reproduced by permission.)

images of blood vessels from which blood flow can be directly measured. This technique is used extensively to investigate valve defects, arteriosclerosis, and hypertension, particularly in the heart, but also in the abdominal aorta and the portal vein of the liver. The actual procedure for a patient undergoing an abdominal ultrasound is relatively simple, regardless of the type of scan or its purpose. Fasting for at least eight hours prior to the procedure ensures that the stomach is empty and as small as possible, and that the intestines and bowels are relatively inactive. This also helps the gallbladder become more visible. Prior to scanning, an acoustic gel is applied to the skin of the patient’s abdomen to allow the ultrasound probe to glide easily across the skin and also to better transmit and receive ultrasonic pulses. The probe is moved around the abdomen’s surface to obtain different views of the target areas. The patient will likely be asked to change positions from side to side and to hold the breath as necessary to obtain the desired views. Usually, a scan will take from 20 to 45 minutes, depending on the patient’s condition and anatomical area being scanned. Ultrasound scanners are available in different configurations, with different scanning features. Portable units, which weigh only a few pounds and can be carried by hand, are available for bedside use, office use, or use outside the hospital, such as at sporting events and in ambulances. Portable scanners range in cost from $10,000 to $50,000. Mobile ultrasound scanners, which can be pushed to the patient bedside and between hospital departments, are the most common comfiguration and range in cost from $100,000 to over $250,000, depending on the scanning features purchased. 4

Results As a diagnostic imaging technique, a normal abdominal ultrasound is one that indicates the absence of the suspected condition that prompted the scan. For example, symptoms such as abdominal pain radiating to the back suggest the possibility of, among other things, an abdominal aortic aneurysm. An ultrasound scan that indicates the absence of an aneurysm would rule out this life-threatening condition and point to other, less serious causes. Because abdominal ultrasound imaging is generally undertaken to confirm a suspected condition, the results of a scan often will confirm the diagnosis, be it kidney stones, cirrhosis of the liver, or an aortic aneurysm. At that point, appropriate medical treatment as prescribed by a patient’s physician is in order.

Health care team roles Ultrasound scanning should be performed by a registered and trained ultrasonographer, either a technologist and/or a physician (radiologist, obstetrician/gynecologist). Ultrasound scanning in the emergency department may be performed by an emergency medicine physician, who should have appropriate training and experience in ultrasonography. Resources BOOKS

Dendy, P.P., Heaton, B. Physics for Diagnostic Radiology. 2nd ed. Philadelphia: Institute of Physics Publishing, 1999. Hall, Rebecca. The Ultrasonic Handbook: Clinical, etiologic and pathologic implications of sonographic findings. Philadelphia: Lippincott, 1993.

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PERIODICALS

Freundlich, Naomi. “Ultrasound: What’s Wrong with this Picture?” Business Week (15 September 1997): 84-85. Kuhn, M., Bonnin, R.L.L., Davey, M.J., Rowland, J.L., Langlois, S. “Emergency Department Ultrasound Scanning for Abdodminal Aortic Aneurysm: Accessible, Accurate, Advantageous. Annals of Emergency Medicine. (September 2000) 36(3):219-223. Sisk, Jennifer. “Ultrasound in the Emergency Department: Toward a Standard of Care.” Radiology Today (June 4, 2001) 2(1):8-10. ORGANIZATIONS

American College of Radiology. 1891 Preston White Drive, Reston, VA 20191-4397. (800)227-5463. . American Institute of Ultrasound in Medicine. 14750 Sweitzer Lane, Suite 100, Laurel, MD 20707-5906. (301) 4984100. . American Registry of Diagnostic Medical Sonographers. 600 Jefferson Plaza, Suite 360, Rockville, MD 20852-1150. (800) 541-9754. . American Society of Radiologic Technologists (ASRT). 15000 Central Avenue SE, Albuquerque, NM 87123-2778. (800) 444-2778. . Radiological Society of North America. 820 Jorie Boulevard, Oak Brook, IL 60523-2251. (630) 571-2670. . Society of Diagnostic Medical Sonography. 12770 Coit Road, Suite 708, Dallas, TX 75251-1319. (972) 239-7367. .

Jennifer E. Sisk, M.A.

ABO blood typing see Type and screen Abrasions see Wounds Abruptio placentae see Placental abruption

Abscess Definition An abscess is an enclosed collection of liquefied tissue, known as pus, somewhere in the body. It is the result of the body’s defensive reaction to foreign material.

Description There are two types of abscesses, septic and sterile. Most abscesses are septic, which means that they are the result of an infection. Septic abscesses can occur anywhere in the body. Only bacteria and the body’s immune response are required. In response to the invading bacteria, white blood cells gather at the infected site and begin producing chemicals called enzymes that attack the bacteria by first marking and then digesting it. These enzymes kill the bacteria and break them down into small pieces that can travel in the circulatory system prior to being eliminated from the body. Unfortunately, these chemicals also digest body tissues. In most cases, bacteria produce similar chemicals. The result is a thick, yellow liquid—pus—containing dead bacteria, digested tissue, white blood cells, and enzymes. An abscess is the last stage of a tissue infection that begins with a process called inflammation. Initially, as invading bacteria activate the body’s immune system, several events occur: • Blood flow to the area increases. • The temperature of the area increases due to the increased blood supply. • The area swells due to the accumulation of water, blood, and other liquids. • It turns red. • It hurts, due to irritation from the swelling and the chemical activity. These four signs—heat, swelling, redness, and pain—characterize inflammation. As the process progresses, the tissue begins to turn to liquid, and an abscess forms. It is the nature of an abscess to spread as the chemical digestion liquefies more and more tissue. Furthermore, the spreading follows the path of least resistance, commonly, the tissue that is most easily digested. A good example is an abscess just beneath the skin. It most easily continues along immediately beneath the surface rather than traveling up through the outermost layer or down through deeper structures where it could drain its toxic contents. The contents of an abscess can also leak into the general circulation and produce symptoms just like any other infection. These include chills, fever, aching, and general discomfort. Sterile abscesses are sometimes a milder form of the same process caused not by bacteria but by non-living irritants such as drugs. If an injected drug such as penicillin is not absorbed, it stays where it is injected and may cause enough irritation to generate a sterile abscess. Such an abscess is sterile because there is no infection involved. Sterile abscesses are quite likely to turn into

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Kevles, Bettyann Holtzmann. Naked to the Bone: Medical imaging in the twentieth century. New Brunswick, New Jersey: Rutgers University Press, 1997. Zaret, Barry L., ed. The Patient’s Guide to Medical Tests. Boston: Houghton Mifflin Company, 1997.

Abscess

Specific types of abscesses

KEY TERMS Cellulitis—Inflammation infection.

of

tissue

due

to

Enzyme—Any of a number of protein chemicals that can initiate chemical reactions at body temperature. Fallopian tubes—Part of the internal female anatomy that carries eggs from the ovaries to the uterus. Flora—Living inhabitants of a region or area. Pyogenic—Capable of generating pus. Streptococcus, Staphocococcus, and bowel bacteria are the primary pyogenic organisms. Sebaceous glands—Tiny structures in the skin that produce oil (sebum). If they become plugged, sebum collects inside and forms a nurturing place for germs to grow. Septicemia—The spread of an infectious agent throughout the body by means of the blood stream. Sinus—A tubular channel connecting one body part with another or with the outside.

hard, solid lumps as they scar, rather than remaining pockets of pus.

Causes and symptoms Many different agents cause abscesses. The most common are the pus-forming (pyogenic) bacteria such as Staphylococcus aureus, which is a very common cause of abscesses under the skin. Abscesses near the large bowel, particularly around the anus, may be caused by any of the numerous bacteria found within the large bowel. Brain abscesses and liver abscesses can be caused by any organism that can travel there through the blood stream. Bacteria, amoebae, and certain fungi can travel in this fashion. Abscesses in other parts of the body are caused by organisms that normally inhabit nearby structures or that infect them. Some common causes of specific abscesses are: • skin abscesses by normal skin flora • dental and throat abscesses by mouth flora • lung abscesses by normal airway flora, bacteria that cause pneumonia or tuberculosis • abdominal and anal abscesses by normal bowel flora 6

Listed below are some of the more common and important abscesses. • Carbuncles and other boils. Skin oil glands (sebaceous glands) on the back or the back of the neck are the ones usually infected. The most commonly involved bacteria is Staphylococcus aureus. Acne is a similar condition involving sebaceous glands on the face and back. • Pilonidal cyst. Many people have as a birth defect a tiny opening in the skin just above the anus. Fecal bacteria can enter this opening, causing an infection and subsequent abscess. • Retropharyngeal, parapharyngeal, peritonsillar abscess. As a result of throat infections such as strep throat and tonsillitis, bacteria can invade the deeper tissues of the throat and cause an abscess. These abscesses can compromise swallowing and even breathing. • Lung abscess. During or after pneumonia, whether it’s due to bacteria [common pneumonia], tuberculosis, fungi, parasites, or other bacteria, abscesses can develop as a complication. • Liver abscess. Bacteria or amoeba from the intestines can spread through the blood to the liver and cause abscesses. • Psoas abscess. Deep in the back of the abdomen, on either side of the lumbar spine, lie the psoas muscles. They flex the hips. An abscess can develop in one of these muscles, usually when it spreads from the appendix, the large bowel, or the fallopian tubes.

Diagnosis The common findings of inflammation—heat, redness, swelling, and pain—easily identify superficial abscesses. Abscesses in other places may produce only generalized symptoms such as fever and discomfort. If an individual’s symptoms and the results of a physical examination do not help, a physician may have to resort to a battery of tests to locate the site of an abscess. Usually something in the initial evaluation directs the search. Recent or chronic disease in an organ suggests it may be the site of an abscess. Dysfunction of an organ or system, for instance seizures or altered bowel function, may provide the clue. Pain and tenderness on physical examination are common findings. Sometimes a deep abscess will eat a small channel (sinus) to the surface and begin leaking pus. A sterile abscess may cause only a painful lump deep in the buttock where a shot was given.

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Abscess

Treatment Since skin is very resistant to the spread of infection, it acts as a barrier, often keeping the toxic chemicals of an abscess from escaping the body on their own. Thus, the pus must be drained from the abscess by a physician. The surgeon determines when the abscess is ready for drainage and opens a path to the outside, allowing the pus to escape. Ordinarily, the body handles the remaining infection, sometimes with the help of antibiotics or other drugs. The surgeon may leave a drain (a piece of cloth or rubber) in the abscess cavity to prevent it from closing before all the pus has drained out. Alternative treatment If an abscess is directly beneath the skin, it will be slowly working its way through the skin as it is more rapidly working its way elsewhere. Since chemicals work faster at higher temperatures, applications of hot compresses to the skin over the abscess will hasten the digestion of the skin and eventually result in its break down and spontaneous release of pus. This treatment is best reserved for smaller abscesses in less sensitive areas of the body such as limbs, trunk, and back of the neck. It is also useful for all superficial abscesses in their very early stages. It will “ripen” them. Contrast hydrotherapy, alternating hot and cold compresses, can also help assist the body in resorption of the abscess. There are two homeopathic remedies that work to rebalance the body in relation to abscess formation, Silica and Hepar sulphuris. In cases of septic abscesses, bentonite clay packs (bentonite clay and a small amount of Hydrastis powder) can be used to draw an infection from the area.

Prognosis Once an abscess is properly drained, the prognosis is excellent for the condition itself. The reason for the abscess (other diseases an individual has) will determine the overall outcome. If, on the other hand, an abscess ruptures into neighboring areas or permits the infectious agent to spill into the bloodstream, serious or fatal consequences are likely. Abscesses in and around the nasal sinuses, face, ears, and scalp may work their way into the brain. Abscesses within an abdominal organ such as the liver may rupture into the abdominal cavity. In either case, the result is life threatening. Blood poisoning is a term commonly used to describe an infection that has spilled into the blood stream and spread throughout the body from a localized origin. Blood poisoning, known to physicians as septicemia, is also life threatening.

An amoebic abscess caused by Entameoba histolytica. (Phototake NYC. Reproduced by permission.)

Of special note, abscesses in the hand are more serious than they might appear. Due to the intricate structure and the overriding importance of the hand, any hand infection must be treated promptly and competently.

Health care team roles First aid providers may unknowingly initiate an abscess by using inappropriate or incorrect techniques. A physician, surgeon, physician’s assistant, or nurse practitioner usually diagnoses the presence of an abscess. Radiologists and laboratory personnel may assist in the process of establishing a diagnosis. A physician, surgeon, physician’s assistant, or nurse practitioner usually drains an abscess. Nurses provide supportive care, dress the wound, and educate patients about caring for the resulting wound. Occasionally, a physical therapist may be needed to recover lost function.

Prevention Infections that are treated early with heat (if superficial) or antibiotics will often resolve without the formation of an abscess. It is even better to avoid infections altogether by taking prompt care of open injuries, particularly puncture wounds. Bites are the most dangerous of all, even more so because they often occur on the hand. Resources BOOKS

Balistreri, William. “Liver abscess.” In Nelson Textbook of Pediatrics, 16th ed., edited by Richard E. Behrman et al., Philadelphia, Saunders, 2000, 1212. Chesney, Russell W. “Brain abscess.” In Nelson Textbook of Pediatrics, 16th ed., edited by Richard E. Behrman et al., Philadelphia, Saunders, 2000, 1857-1858.

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Finegold, Sydney M. “Lung abscess.” In Cecil Textbook of Medicine, 21st ed., edited by Goldman, Lee and Bennett, J. Claude. Philadelphia: W.B. Saunders, 2000, 439-442. Herendeen, Neil E and Szilagy, Peter G. “Peritonsillar abscess.” In Nelson Textbook of Pediatrics, 16th ed., edited by Richard E. Behrman et al., Philadelphia, Saunders, 2000, 1266-1267. Scheld, W. Michael. “Bacterial meningitis, brain abscess, and other suppurative intracranial infections.” In Harrison’s Principles of Internal Medicine, 14th ed., edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 2419-2434. Schwartz, Seymour, Shires, Tom and Spencer, Frank C.Principles of Surgery, 7th ed. New York, McGraw Hill, 1998. Stern, Robert C. “Pulmonary abscess.” In Nelson Textbook of Pediatrics, 16th ed., edited by Richard E. Behrman et al., Philadelphia, Saunders, 2000, 1309-1310. Townsend, Courtney M. Sabiston Textbook of Surgery: The Biological Basis of Modern Surgical Practice, 16th ed. Philadelphia, Saunders, 2001. PERIODICALS

Balatsouras DG, Kloutsos GM, Protopapas D, Korres S, Economou C. “Submasseteric abscess.” Journal of Laryngology and Otology 115, no. 1 (2001): 68-70. Chua, F. “Clinical picture: paravertebral abscess.” Lancet 357, no. 9251 (2001): 168-70. Rockwell PG. “Acute and chronic paronychia.” American Family Physician 63, no. 6 (2001): 1113-6. Struk DW, Munk PL, Lee MJ, Ho SG, Worsley DF. “Imaging of soft tissue infections.” Radiology Clinics of North America 39, no. 2 (2001): 277-303. Taiwo B. “Psoas abscess: a primer for the internist.” Southern Medical Journal 94, no. 1 (2001): 2-5. ORGANIZATIONS

American Academy of Family Physicians, 11400 Tomahawk Creek Parkway, Leawood, KS 66211-2672. (913) 9066000. . [email protected]. American Society of Clinical Pathologists, 2100 West Harrison Street, Chicago IL 60612. (312) 738-1336. . [email protected]. College of American Pathologists, 325 Waukegan Road, Northfield, IL 60093. (800) 323-4040. . OTHER

American Society of Colon and Rectal Surgeons. . Merck Manual. . South Bank University. . Tuberculosis.Net. . University of Bristol. . 8

University of California-San Diego: . University of Kansas Medical Center. .

L. Fleming Fallon, Jr., MD, DrPH

Achromatopsia see Color blindness

Acid-base balance Definition Acid-base balance can be defined as homeostasis of the body fluids at a normal arterial blood pH ranging between 7.37 and 7.43.

Description An acid is a substance that acts as a proton donor. In contrast, a base, also known as an alkali, is frequently defined as a substance that combines with a proton to form a chemical bond. Acid solutions have a sour taste and produce a burning sensation with skin contact. A base is any chemical compound that produces hydroxide ions when dissolved in water. Base solutions have a bitter taste and a slippery feel. Despite variations in metabolism, diet, and environmental factors, the body’s acidbase balance, fluid volume, and electrolyte concentration are maintained within a narrow range.

Function Many naturally occurring acids are necessary for life. For example, hydrochloric acid is secreted by the stomach to assist with digestion. The chemical composition of food in the diet can have an effect on the body’s acid-base production. Components that affect acid-base balance include protein, chloride, phosphorus, sodium, potassium, calcium, and magnesium. In addition, the rate at which nutrients are absorbed in the intestine will alter acid-base balance. Cells and body fluids contain acid-base buffers, which help prevent rapid changes in body fluid pH over short periods of time, until the kidneys pulmonary systems can make appropriate adjustments. The kidneys and pulmonary system then work to maintain acid-base balance through excretion in the urine or respiration. The partial pressure of carbon dioxide gas (PCO2) in the pulmonary system can be measured with a blood sample and

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Role in human health Production of CO2 is a result of normal body metabolism. Exercise or serious infections will increase the production of CO2 through increased respiration in the lungs. When oxygen (O2) is inhaled and CO2 is exhaled, the blood transports these gases to the lungs and body tissues. The body’s metabolism produces acids that are buffered and then excreted by the lungs and kidneys to maintain body fluids at a neutral pH. Disruptions in CO2 levels and HCO3- create acid-base imbalances. When acid-base imbalances occur, the disturbances can be broadly divided into either acidosis (excess acid) or alkalosis (excess base/alkali).

Common diseases and disorders Acid-base metabolism imbalances are often characterized in terms of the HCO3-/CO2 buffer system. Acidbase imbalances result primarily from metabolic or respiratory failures. An increase in HCO3- is called metabolic alkalosis, while a decrease in the same substance is called metabolic acidosis. An increase in PCO2, on the other hand, is known as respiratory acidosis, and a decrease in the same substance is called respiratory alkalosis. Acidosis Acidosis is a condition resulting from higher than normal acid levels in the body fluids. It is not a disease, but may be an indicator of disease. Metabolic acidosis is related to processes that transform food into energy and body tissues. Conditions such as diabetes, kidney failure, severe diarrhea, and poisoning can result in metabolic acidosis. Mild acidosis is often compensated by the body in a number of ways. However, prolonged acidosis can result in heavy or rapid breathing, weakness, and headache. Acidemia (arterial pH < 7.35) is an accumulation of acids in the bloodstream that may occur with severe acidosis when the acid load exceeds respiratory capacity. This condition can sometimes result in coma

Acid-base balance

correlates with blood carbon dioxide (CO2) levels. PCO2 can then be used as an indicator of the concentration of acid in the body. The concentration of base in the body can be determined by measuring plasma bicarbonate (HCO3-) concentration. When the acid-base balance is disturbed, the respiratory system can alter PCO2 quickly, thus changing the blood pH and correcting imbalances. Excess acid or base is then excreted in the urine by the renal system to control plasma bicarbonate concentration. Changes in respiration occur primarily in minutes to hours, while renal function works to alter blood pH within several days.

KEY TERMS Acid—(a) Any ionic or molecular substance that can act as a proton donor; (b) A sour-tasting substance, like vinegar; (c) A chemical compound that can react with a base to form a salt. Acidosis—A dangerous condition where the blood and body tissues are less alkaline (or more acidic) than normal. Alkalosis—Excessive alkalinity of the blood and body tissue. Alkalemia—Abnormal blood alkalinity. Base—(a) Any ionic or molecular substance that can act as a proton acceptor; (b) A bitter-tasting substance which has a soapy feel; (c) A chemical compound that can react with an acid to form a salt. A base can also be called an alkali. Bicarbonate—A salt of carbonic acid produced by neutralizing a hydrogen ion. Diabetic ketoacidosis—A condition characterized by excessive thirst and urination. Other symptoms may include appetite loss, nausea, vomiting, and rapid deep breathing. Diuretic—An agent or drug that eliminates excessive water in the body by increasing the flow of urine. Electrolyte—A substance such as an acid, bases, or salt. An electrolyte’s water solution will conduct an electric current and ionizes. Acids, bases, and salts are electrolytes. Homeostasis—An organism’s regulation of body processes to maintain internal equilibrium in temperature and fluid content. Hypochloremic chloride.

alkalosis—A

large

loss

of

Hypokalemic alkalosis—Low plasma potassium. pH—The negative logarithm of H+ (hydrogen) concentration.

and, if the pH falls below 6.80, it will lead to death. Diabetic ketoacidosis is a condition where excessive glucagon and a lack of insulin contribute to the production of ketoacids in the liver. This condition can be caused by chronic alcoholism and poor carbohydrate utilization. Respiratory acidosis is caused by the lungs’s failure to remove excess carbon dioxide from the body, reducing

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Acid-base disturbances, causes, and compensatory mechanisms Acid-base disturbance

Common cause

Mode of compensation

Respiratory acidosis

Respiratory depression (drugs, central nervous system trauma) Pulmonary disease (pneumonia, chronic obstructive pulmonary disease, respiratory underventilation)

Kidneys will retain increased amounts of HCO3– to increase pH

Respiratory alkalosis

Hyperventilation (emotions, pain, respirator overventilation) Diabetes, shock, renal failure, intestinal fistula

Kidneys will excrete increased amounts of HCO3– to lower pH

Sodium bicarbonate overdose, prolonged vomiting, nasogastric drainage

Lungs retain CO2 to lower pH

Metabolic acidosis Metabolic alkalosis SOURCE:

Pagana, K.D. and T.J. Pagana. Mosby’s Diagnostic and Laboratory Test Reference. 3rd ed. St. Louis: Mosby, 1997.

the pH in the body. Several conditions, including chest injury, blockage of the upper air passages, and severe lung disease, may lead to respiratory acidosis. Blockage of the air passages may be caused by bronchitis, asthma, or airway obstruction, resulting in mild or severe acidosis. Regular, consistent retention of carbon dioxide in the lungs is referred to as chronic respiratory acidosis. This disorder results in only mild acidosis because it is balanced by increased bicarbonate production. The predominant symptoms of acidosis are sometimes difficult to distinguish from symptoms of an underlying disease or disorder. Mild conditions of acidosis may be asymptomatic or may be accompanied by weakness or listlessness, nausea, and vomiting. Most often, severe metabolic acidosis (pH < 7.20) is associated with increased respiration to compensate for a shortage of HCO3-. This is followed by a secondary decrease in PCO2 that occurs as part of respiratory compensation process. Treatment options for acidosis typically require correction of the underlying condition by venous administration of sodium bicarbonate or another alkaline substance. Alkalosis Alkalosis is a condition resulting from a higher than normal level of base/alkali in the body fluids. An excessive loss of HCO3- in the blood causes metabolic alkalosis. The body can compensate for mild alkalinity, but prolonged alkalosis can result in convulsions, muscular weakness, and even death if the pH rises above 7.80. Alkalosis can be caused by drugs or disorders that upset the normal acid-base balance. Prolonged vomiting and hyperventilation (abnormally fast, deep breathing) can result in alkalosis. The predominant symptoms of alkalosis are neuromuscular hyperexcitability and irritability. Alkalemia (abnormal blood alkalinity) increases protein binding of ionized calcium even though plasma total calcium does not change. Severe cases may induce hypocalcemia (a 10

Lungs “blow off” CO2 to raise pH

low level of plasma calcium). Low plasma potassium leads to a condition called hypokalemic alkalosis. It is frequently accompanied by metabolic alkalosis, resulting in cramping, muscle weakness, polyuria, and ileus (obstruction of the intestines). Diuretic medications may cause hypokalemic alkalosis. Prolonged vomiting may induce hypochloremic alkalosis (a large loss of chloride). The kidneys may conserve bicarbonate in order to compensate for the chloride reduction. Compensated alkalosis results when the body has partially compensated for alkalosis, and has restored normal acid-base balances. However, in compensated alkalosis, abnormal bicarbonate and carbon dioxide levels persist. Alkalosis requires correction of the underlying condition and may involve venous administration of a weak acid to restore normal balance. If the source of alkalosis is excessive drug intake, it may be appropriate to reduce intake to restore the normal acid-base balance. Respiratory alkalosis results from decreased CO2 levels caused by conditions such as hyperventilation (a faster breathing rate), anxiety, and fever. The pH is elevated in the body. Hyperventilation causes the body to lose excess carbon dioxide in expired air and can be triggered by altitude or a disease that reduces the amount of oxygen in the blood. Symptoms of respiratory alkalosis may include dizziness, lightheadedness, and numbing of the hands and feet. Treatments include breathing into a paper bag or a mask that induces rebreathing of carbon dioxide. Resources BOOKS

Shaw, Patricia, ed. Fluids & Electrolytes Made Incredibly Easy! Springhouse, PA: Springhouse Publishing Co., 1997. PERIODICALS

Remer, T. “Influence of diet on acid-base balance.” Seminars in Dialysis 13, no. 4 (2000): 221–226.

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Special safety precautions

Bookallil, Michael. “pH of the blood: acid-base balance.” . Grogono, Alan. “Acid-base tutorial.” .

Crystal Heather Kaczkowski, MSc.

Acid-fast culture Definition The term acid-fast refers to a type of organism not readily decolorized by acid after staining. An acid-fast culture is the microbiological analysis of such an organism. An acid-fast culture refers to the process of detection, growth, isolation, identification, and antibiotic susceptibility testing of mycobacteria that cause pulmonary tuberculosis and other infections such as skin, abdominal, and disseminated (widely spread throughout many organs).

Purpose The acid-fast culture is used to isolate Mycobacterium tuberculosis when tuberculosis (TB) is suspected. More recently the test has become important for the identification of other acid-fast organisms including Mycobacterium avium complex (MAC), Mycobacterium bovis, and Mycobacterium africanum responsible for causing tuberculosis in AIDS patients and other immunosuppressed persons. Antibiotic sensitivity testing performed when cultures are positive or when patients are known to have tuberculosis determines the appropriate drugs for treatment. This is essential because of the emergence of tuberculosis strains that are resistant to many of the antibiotics that were once effective in treating this disease. The test is also used to differentiate tuberculosis from carcinoma and bronchiectasis that may appear similar on x ray.

Precautions Antibiotics and some sulfonamides may interfere with test results, causing the results to be falsely negative. Sufficient organisms may not be recovered to diagnose infection when a single culture sample is collected. Therefore, sputum cultures should be collected on three consecutive mornings.

Health care workers involved with collection and handling of specimens from patients suspected of having tuberculosis or other mycobacterial infections should observe universal precautions for the prevention of transmission of bloodborne pathogens. In addition, health care personnel working with patients and handling specimens from patients suspected of having tuberculosis must be given a skin test (e.g. Mantoux or PPD test) on a regular basis. Precautions must be followed closely when handling mycobacterial specimens. The laboratory personnel who process and handle the infectious material from the patient are at greatest risk (about three times higher than other laboratory personnel) for tuberculosis infection or skin test positivity. The hazard of working in a laboratory that handles mycobacterial specimens is greatly reduced if the personnel follow proper procedures when handling and processing the specimens. All processing should take place in a biologic safety cabinet (BSC). The biologic safety cabinets used in the clinical mycobacterial laboratory are of two types: Class I, or negative-pressure cabinets, and Class II, or vertical-laminar-flow cabinets. Correct operation of these safety devices along with proper maintenance and testing of the air flow are essential to their performance. Yearly inspection of the cabinets by trained individuals is required. Processing specimens, testing organisms, and transferring viable cultures must be carried out within the BSC. After processing specimens or working under the BSC, the area inside the cabinet is disinfected and a UV (ultraviolet) light located within the cabinet is turned on to kill any organisms on the surface of the work area as well as any airborne bacteria. After performing a procedure, the work area must be decontaminated with a disinfectant solution (e.g., the use of a phenol-soap mixture containing orthophenol or phenolic derivitives with an effective contact time of 10-30 minutes). Protective clothing including gloves, fluid-proof gowns, goggles, and face mask or respirator is recommended for laboratory personnel working in the mycobacterial laboratory. Incinerators (no bunsen burners) are used within the BSC to reduce aerosoling of bacteria from infectious material while processing and culturing.

Description Tuberculosis is an infection caused by Mycobacterium tuberculosis, a disease which is a major health problem worldwide. Mycobacterium tuberculosis is a rod-shaped bacterium characterized by acid-fastness. It is commonly transmitted via the air to the lungs, where it thrives, causing fever, cough, and hemoptysis (coughing up blood-tainted secretions). Tuberculosis is highly con-

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OTHER

Acid-fast culture

KEY TERMS Bronchiectasis—The formation of dilated, enlarged bronchi that results from lower respiratory tract infection. Granuloma—Encapsulation of infected tissue caused by phagocytic cells that surround the foci of infection. Nosocomial—An infection acquired in a hospital setting.

tagious. Disease is spread when persons cough, releasing an aerosol of organisms that are easily inhaled by others. Although deaths from tuberculosis in the United States had declined since the 1950s, recently there has been a resurgence of the disease, with the higher incidence of infection seen in certain races, in poor socioeconomic conditions, among new immigrants, in prison inmates, and in persons infected with the human immunodeficiency virus. Because it takes several weeks for most Mycobacteria to grow in a culture, the laboratory performs an acid-fast smear first to aid in early diagnosis; however, the acid-fast smear should not be used in place of culture, as a culture is far more sensitive. An acid-fast culture can detect as few as 10 to 100 CFU/mL of sputum. The smear can provide a presumptive diagnosis of mycobacterial disease; confirm that cultures growing on media are acidfast; and demonstrate that antibiotic treatment is effective pending follow-up culture results. The genus Mycobacterium includes organisms that are obligate parasites, saprophytes (i.e., organisms that live off dead tissue), and opportunistic pathogens. Mycobacteria cause tuberculosis as well as non-tuberculous clinical conditions; therefore, mycobacteria are divided into two major groups based upon whether they cause tuberculosis (M. tuberculosis complex) or nontuberculous infections (NTM). The principle pathogen causing tuberculosis in humans is Mycobacterium tuberculosis. It is estimated that about one third of the world’s population is infected with M. tuberculosis. The World Health Organization reports an estimated eight million new cases and three million deaths attributable to tuberculosis each year. Tuberculosis is a leading cause of death in developing countries. Other organisms causing human tuberculosis that are included in the M. tuberculosis complex are: M. bovis (the cause of tuberculosis in cattle and humans, as well as other carnivores); M. bovis BCG (a strain used as a vaccine against tuberculosis in many parts of the world); and 12

M. africanum (the cause of human tuberculosis in tropical Africa). Mycobacterium tuberculosis causes an infection that may mimic other diseases such as pneumonia, neoplasm, or fungal infections. Patients may be symptomatic or asymptomatic with signs of pulmonary and other organ involvement. Symptoms include night sweats, low-grade fever, anorexia, fatigue, weight loss, and a productive cough or coughing of blood in pulmonary tuberculosis infections. Patients with HIV are more likely to develop active tuberculosis. It is necessary to identify the tuberculosis-causing mycobacteria by species and determine the antibiotic sensitivity or resistance-pattern for epidemiologic and public health information as well as for the effective treatment of infected persons. As stated earlier, about one-third of the world’s population (1.7 billion persons) are infected with M. tuberculosis. Therefore, it is of great concern that the emergence of epidemic multidrug-resistant strains of M. tuberculosis has increased at the same time as the increase in HIV infections in the United States. The primary routes of transmission for the M. tuberculosis complex are via inhalation of airborne droplets from an infected person; through infectious aerosols produced when processing clinical specimens for the recovery of Mycobacteria spp.; and by ingestion of contaminated milk from cows (or goats) infected with M. bovis. M. africanum is also transmitted by the inhalation of droplets containing infecting organisms. In all cases, close contact with infected individuals leads to the acquisition of tuberculosis infection. The nontuberculous mycobacteria (NTM) group, which are not transmitted by person to person contact as is the M. tuberculosis complex, are differentiated by rate of growth (slow-growing or rapid-growing) as well as color pigmentation (the ability or inability of the colonies to change color when exposed to light). Growth patterns are divided into two main groups: slow-growers and rapid growers. Slow growers take more than seven days to grow and form colonies on solid media; rapid-growers produce colonies on solid media within three to five days. This method of classification for the NTM, by growth patterns and exposure to light, is referred to as the Runyon Classification. Some organisms in this group are considered pathogenic, and others are potentially pathogenic or non-pathogenic. One of the most often recovered mycobacterium species in the United States belongs to the NTM group and is referred to as the Mycobacterium avium complex (MAC). The MAC group consists of two main species, M. avium and M. intracellulare. These two mycobacteria are very similar and are differentiated by DNA tests. The

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Pulmonary disease in AIDS patients due to MAC cannot be distinguished clinically or by x ray from those caused by M. tuberculosis. Infections caused by disseminated MAC organisms in AIDS patients usually occur about one year after the diagnosis of AIDS. Also, nonAIDS patients who are white males, 45-60 years of age, typically heavy smokers, or alcohol abusers with preexisting lung disease are good candidates for a tuberculosis-like disease also caused by MAC organisms. An NTM, which will not grow in vitro (non-cultivatable), is M. leprae. Mycobacterium leprae is the cause of leprosy, or Hansen’s disease. This organism causes a chronic, debilitating, and disfiguring disease involving the skin, mucous membranes, and nerve tissue. There is often extensive damage to the skin (lesions) and nerves. Infectivity is low and transmission can occur from person to person through contact with infected skin; however, inhalation of nasal secretions from the infected person (close contact) appears to be the predominant mode of transmission. Leprosy in North America is rare, and most of the cases are acquired from exposure to the organism while in a tropical country. Mycobacterium leprae cannot be cultured on solid or liquid media in vitro; therefore, it is diagnosed by DNA amplification tests such as the polymerase chain reaction (PCR) using infected tissue, or mucous membrane secretions, and by observing acidfast bacilli (using acid-fast staining procedures) in the tissue preps or skin biopsies of infected patients.

losis as well as cervical lymphadenitis and cutaneous diseases; tap water is the main reservoir for humans. • Mycobacterium haemophilum: A slow grower, causing skin nodules and disseminated disease in immunosuppressed patients with AIDS, Hodgkins’s disease, and kidney and bone marrow transplants, as well as cervical lymphadenitis in children. • Mycobacterium marinum: A slow grower, causing cutaneous infections such as “swimming pool granuloma” and “fish tank granuloma” with its natural reservoir being fresh and salt water from infected fish and other marine life. • Mycobacterium ulcerans: A slow grower, infecting the skin (usually after some trauma) causing nodules and ulcers to form; infection occurs mainly in tropical and temperate climates (Africa and Australia) and is rare in the United States. • Mycobacterium xenopi: A slow grower, causing pulmonary infections in adults (resembling MTB complex and MAC complex). The infection is considered nosocomial, since it is recovered from hospital water storage systems and hot and cold taps quite often. • Mycobacterium scrofulaceum: A slow grower responsible for cervical adenitis in children, recovered from raw milk, soil, water, and dairy products. • Mycobacterium szulgai: A slow grower causing pulmonary disease similar to M. tuberculosis. • Mycobacterium fortuitum complex: Rapid growing microorganisms which include M. fortuitum, M. abscessus, and M. chelonae causing infections involving surgical wounds, post-traumatic wound infection, otitis media, and chronic pulmonary disease. Mycobacterium gordonae is the non-pathogenic mycobacterium most commonly recovered from patient specimens. It is found in the environment and is called the “tap water bacillus.” It is only rarely implicated as a cause of human infection. Specimen collection

Several other NTM (non-tuberculous mycobacteria) organisms are considered potential pathogens for humans while others are rarely implicated in disease. The following NTM are considered potential pathogens and should be identified especially if recovered from immunocompromised patients:

Specimens to be processed for the recovery of mycobacteria are obtained and handled using specific guidelines to ensure successful growth, isolation, and identification of the causative organism. Containers must be sterile, leak-proof, and labeled properly. After collection, if the specimen cannot be processed within one hour, refrigeration is required but no longer than overnight. However, blood samples must be placed in the proper media and incubated immediately at 35-37°C.

• Mycobacterium kansasii: A slow grower, causing a chronic pulmonary disease resembling classic tubercu-

The most often requested specimens are pulmonary specimens (secretions) which must be obtained before

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MAC organisms are frequently isolated from immunocompromised patients, such as patients infected with HIV and patients with pre-existing pulmonary disease. MAC infections have been found to be the most common cause of NTM (nontuberculous mycobacteria) infections in humans. The NTM organisms are found in the environment (frequently recovered from water, soil, house dust, and plants) and are sometimes found colonized in the respiratory or gastrointestinal tract of healthy individuals. In AIDS patients, MAC infections may be focal or disseminated. It is theorized that the MAC organisms, acquired from the environment, colonize the respiratory tract or gastrointestinal tract before disseminating in an HIV-positive patient. Sputum and stool samples from HIV infected patients often contain MAC organisms.

Acid-fast culture

any treatment (antibiotic therapy) is given. Pulmonary specimens may be obtained in several ways: spontaneously produced (expectorated) sputum; aerosolinduced sputum; bronchioscopic aspirations, washings and brushings; gastric aspirates, and lavages (washings) from patients who have swallowed sputum through the night. Saliva is not acceptable as a specimen for the recovery of mycobacteria and is usually rejected as a contaminated specimen. A series of early morning sputum specimens are recommended over a three-day period. The ideal amount of sputum specimen for processing and recovery of mycobacteria is 5-10 mL of sputum. Upon rising in the morning, the patient is instructed to cough deeply to produce sputum (expectorated sputum). A patient who is unable to bring up any sputum is given an aerosol treatment (aerosol-induced sputum) by a respiratory therapist in order to recover a sufficient amount of sputum for culture. Other specimens requested for culture and recovery of mycobacteria are early morning, voided urine specimens; fecal specimens; tissue and body fluids (pleural, pericardial and peritoneal fluids), cerebrospinal fluid (CSF), bone marrow aspirates, and blood. Blood and stool specimens are usually cultured from AIDS patients. These specimens reveal numerous mycobacteria when infection is present in these patients. Wound or skin lesions (abscesses) require a technique using aspiration of the specimen into a syringe rather than the use of a swab to obtain the specimen. Specimens not suitable for culture and usually rejected are 24-hour urine specimens, pooled sputum, saliva, and swabs containing pulmonary secretions. The high rate of contamination as well as the reduced rate of mycobacteria recovery in these specimens renders them unsuitable. Specimen processing Decontamination and digestion of sputum specimens is necessary to recover mycobacteria for culture and identification. The process of decontamination (removing unwanted bacteria) and digestion (breaking down mucous and protein) of sputum specimens is necessary to release the mycobacteria that may be present but are trapped in the mucous, and also to kill the unwanted bacteria (normal flora). Specimens from sterile body sites (blood, tissue, and body fluids, etc.) do not need the process of decontamination and digestion as do sputum samples. If the process of decontamination and digestion is not done or done improperly, recovery of mycobacteria from sputum samples is inhibited causing a false-negative report. Mucous, cells, and normal bacterial flora (from the oral cavity) entrap and enmesh the 14

mycobacteria in sputum. A common decontaminant is sodium hydroxide (4%) which is also used as a mucolytic agent (for liquifaction or digestion of mucous). A combination is often used which consists of N-acetyl-Lcysteine (NALC) and a lower concentration (2%) of sodium hydroxide. This combination gives a better recovery rate when used together as a mucolytic-decontaminant. Liquifaction of the thick mucous in sputum is necessary to free the mycobateria trapped in it without harming the mycobacteria, and decontamination kills the normal flora (bacteria from the mouth, throat and oral cavity) which interfere with the recovery of mycobacteria. The final product is reduced (concentrated) from the original 5-10 mL volume, and a portion of the resulting specimen is transferred by sterile technique to either sterile solid, tube or plate media, and liquid media, while another portion is used to make several smears on glass slides for staining. Acid fast and fluorescent staining The smears made after the process of decontamination and digestion of sputum are stained using either an acid-fast staining procedure or a fluorochrome stain. Mycobacteria do not stain well with the Gram staining procedure used routinely in the microbiology laboratory. Specimens obtained from sterile sites (bone marrow, tissue, etc.) do not need processing and smears are made directly from the specimen onto glass microscope slides. Mycobacteria are slightly curved or straight bacilli, about 0.2 to 0.6 by 1.0 to 10 micrometers in size. The cell wall of mycobacteria contains a high lipid content, and is made up of long-chain, multiply cross-linked fatty acids (mycolic acids). In the acid-fast staining procedure, a basic dye, carbolfuchsin stain, is used to stain the cell wall. The long-chain mycolic acids and waxes in the mycbacteria cell wall serve to complex the carbolfuchsin. The Ziehl-Neelsen acid fast stain for mycobacteria uses heat to fix the dye in the cell wall, while the Kinyoun staining method uses an increased concentration of basic fuchsin and phenol eliminating the heat requirement. In the Ziehl-Neelsen procedure, the carbolfuchsin stain is left on the smear for five minutes while heat is applied under the slide by a bunsen burner or a hot plate. The carbolfuchsin dye penetrates the cell wall and the excess stain is washed off with a 3% acid-alcohol mixture (95% ethanol and 3% hydrochloric acid). The mycobacteria cell wall retains the dye (a red-purple color) and will not be decolorized (washed out) by the acid-alcohol, thus the term acid-fast. A second dye, methylene blue, is used to stain any background material including any other bacteria that may be present. This dye results in a light background providing good contrast to the red-purple stain of the carbolfuchsin dye, thus aid-

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Another staining method used for the detection of mycobacteria is the auramine-rhodamine fluorochrome stain. This method requires a fluorescent microscope. Smears are scanned at a lower magnification (250 X to 400 X). The fluorochrome dyes used in this procedure complex to the mycolic acids in acid-fast cell walls. The fluorescing mycobacteria are seen as bright yelloworange bacilli against a dark background. Fluorescent stained smears can be read more rapidly than acid-fast stains, but there are drawbacks. Mycobacteria spp. that are rapid-growers may not appear fluorescent with these stains; artifacts may fluoresce; material on the oil objective may have floated off a previous positive smear causing a false-positive reading for the next smear examined. All positive smears from the auramine-rhodamine fluorochrome method should be confirmed using the ZiehlNeelsen method for acid-fast bacilli. Acid-fast bacillus (AFB) smear report Laboratories performing staining procedures and reporting smear results must adhere to guidelines from the U.S. Department of Health and Human Services (Public Health Service, Centers for Disease Control, Atlanta). The rule for reporting acid-fast smears for mycobacteria requires scanning the smear for a minimum of 15 minutes (at least 300 oil immersion fields) before calling the slide negative for acid-fast bacilli or “No AFB seen.” The following are recommended interpretations and ways to report smear results: • A request for another specimen or a doubtful report is the result of seeing AFB of 1-2/300 fields for the ZiehlNeelsen (Z-N) stain and AFB of 1-2/70 fields for the auramine-rhodamine (fluorochrome) stain. • A “1+” report for AFB seen = 1-9/100 fields for the ZN method and 2-18/50 fields for the fluorochrome stain. • A “2+” report for AFB seen = 1-9/10 fields for the Z-N method and 4-36/10 fields for the fluorochrome stain. • A “3+” report for AFB seen = 1-9/field for the Z-N method and 4-36/field for the fluorochrome stain. • A “4+” report for AFB seen = less than 9/field for the Z-N method and less than 36/field for the fluorochrome stain.

Culture media and isolation methods Several types of media are used for the cultivation of mycobacteria, and each facility determines which ones are most appropriate for use. A combination of culture media is often used to optimize recovery of mycobacteria as well as inhibit the growth of contaminants. Mycobacteria require a pH of 6.5-6.8 for growth and grow best at higher humidity. Commercially prepared solid culture media (in tubes with screw-top caps) consist of bovine serum albumin agar-based media (Middle-brook 7H10 and 7H11) and egg-based media (Lowenstein-Jensen). Liquid media (Middlebrook 7H9) is used to subculture stock strains or as part of a system (e.g., BACTEC 12B medium, Septi-Chek AFB) to cultivate and detect growth of acid-fast bacilli. Mycobacterium spp. grow more rapidly in liquid media; solid media takes approximately 17 days for the isolation of acid-fast bacilli whereas liquid media takes only about 10 days. The following are descriptions of three general types of media that are most often used. • Lowenstein-Jensen media (L-J) is an egg-potato base solid media containing malachite green (an inhibitory agent). The use of L-J media is excellent for the recovery of M. tuberculosis from sterile-site specimens as well as decontaminated-digested sputum specimens. • Petragnani media is an egg-milk-potato solid medium also containing malachite green. It is primarily used for specimens from highly contaminated areas (e.g., fecal material). • Middlebrook 7H10 media is a liquid based media containing salts, vitamins, cofactors, oleic acid, albumin, catalase, glycerol, and glucose. This media enhances the recovery of MAC organisms (Mycobacteria avium complex). Each culture medium described above represents a nonselective formulation, but selective formulations are also used which contain antibiotics to enhance the growth of mycobacteria and suppress the growth of contaminating bacteria. The enhanced formulas are used for specimens that are highly contaminated. All culture tubes are incubated in an atmosphere of 5-10% CO2 (for growth enhancement) even though mycobacteria are strict aerobes. The tubed media are kept in a high humidity incubator at 35°C in the dark in a slanted position with the caps loosened (in order for CO2 to enter the tubes and excess fluid to evaporate). For specimens obtained from skin or superficial lesions, a lower temperature (25-30°C) is required for the recovery of M. marinum and M. ulcerans. A nutritional requirement of hemin and a temperature of 30°C are needed for the recovery of M. haemophilum (cultured from skin

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ing in the detection of acid-fast bacilli. If mycobacteria are present in the smear, the appearance of red-purple short or long bacilli are observed at 1000 X magnification. Some species of mycobacteria appear “beaded” while others may appear pleomorphic (a mixture of coccoid and rod shapes), or filamentous (branching of the bacillus).

Acid-fast culture

nodule specimens). If M. xenopi is suspected, a temperature of 42-45°C is required (cultured from hospital hot water tanks). AFB cultures are held for six to eight weeks before reporting “No growth of AFB.” Cultures are observed daily for the first two weeks, checking for any growth or colony formation. Rapid-growing mycobacteria usually appear on non-selective media in two to three days at temperatures between 20 to 40°C. The slow-growing mycobacteria associated with disease require four to six weeks of incubation on selective media. Since the use of liquid media allows mycobacteria to grow more rapidly and is considered the most sensitive primary isolation media, the Becton Dickinson Diagnostic Instrument Systems developed the BACTEC System. The BACTEC System utilizes Liquid Middlebrook 7H12 and 7H13 in an automated radiometric culture system. The broth is placed in commercially prepared vials containing a 14Clabeled substrate (palmitic acid) used by mycobacteria, liberating radioactive carbon dioxide (14C02) into the upper part of the vial. The 14 C02 liberated is detected by the BACTEC 460 (instrument) and is recorded as a “growth index” denoting growth of mycobacteria in the vial of broth. This method of growth significantly improves the isolation rate of mycobacteria compared with conventional isolation using solid tubed media. The BACTEC vials must be checked within four days of inoculation. This method detects Mycobacteria spp. growth in clinical specimens in less than two weeks compared to four to six weeks for conventional methods. Non-radiometric automated systems are also available for the detection of growth and recovery of mycobacteria from clinical specimens. An example is the Septi-Chek AFB system (BBL-Becton Dickinson Microbiology Systems) that detects, isolates, rapidly identifies, and performs antibiotic susceptibility testing. This is a biphasic media system (a bottle containing liquid media and solid media) that uses growth enhancing factors and antimicrobial agents in the liquid and three different solid media on a paddle inserted in the top of the vial. This system rapidly grows, isolates, and presumptively identifies M. tuberculosis (i.e., differentiates it from other mycobacteria). Identification Based on the volume of specimens submitted, the ability of performance, and the expertise of the clinical laboratory personnel, the American Thoracic Society (ATS) and the College of American Pathologists (CAP) have recommended levels of service for clinical laboratories testing of mycobacteria. The ATS recommends 16

four levels of testing while the CAP lists three levels. The three levels of service recommended by CAP are: • Level I. Specimen collection only; no identification procedures performed with all specimens sent to other qualified laboratories. • Level II. Perform microscopy; isolate and identify and sometimes perform susceptibility tests for M. tuberculosis. • Level III. Perform microscopy; isolate, identify, and perform susceptibility testing for all species of Mycobacterium. Identification of Mycobacteria spp. by qualified clinical laboratories entails several of the following: • Confirmation that the isolate recovered in broth or on solid media is an acid-fast organism. • Categorize (presumptively) the isolate by phenotypic characteristics, such as colony morphology, photoreactivity, growth rate, and optimum growth temperature. • Identification through tests based on enzyme systems of the organism, metabolic by-products, and inhibition of growth by exposure to selected biochemicals. • Chromatographic detection of mycolic acid. • Identification by DNA hybridization (e.g., Gen-ProbeSan Diego, Calif.) • Identification by PCR (polymerse chain reaction) tests. The biochemical tests most often utilized are niacin accumulation, nitrate reduction, TCH (inhibition of growth when exposed to thiophene-2-carboxylic acid hydrazide), growth in 5% NaCl, tellurite reduction, growth on MacConkey agar, catalase, hydrolysis of Tween 80, iron uptake, and tests for the enzymes arylsulfatase, urease, and pyrazinamidase. Biochemical testing is time consuming and may take several weeks to obtain results. Molecular methods (DNA and PCR) are becoming increasingly available commercially and allow for identification and detection of mycobacteria faster, with less cost and more specificity. Antibiotic susceptibility testing for tuberculosis The susceptibility testing for Mycobacteria tuberculosis is done on a pure culture which may take two to three weeks to prepare after the initial culture has grown. Thus, a total of five to seven weeks is not uncommon before the physician finally receives an antibiotic susceptibility report for a patient with a positive MTB culture. However, rapid testing systems mentioned previously may be used for susceptibility testing, which reduces the time considerably.

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The methods used for susceptibility testing are: radiometric (BACTEC System); proportional; resistance ratio (agar dilution and disk elution); and absolute concentration methods. It is important to isolate and determine the susceptibility pattern for M. tuberculosis because of the increase in multidrug-resistant cases in the United States.

Preparation Prior to breakfast, the patient will be asked to provide a 5-10 mL specimen of sputum delivered into a sterile cup with a screw top lid. Obtaining an appropriate sample will require that the patient cough deeply several times to bring up the sputum. Failure to do so will result in a specimen containing saliva or post-nasal drip, which are both considered sample contaminants.

Aftercare There are not specific requirements for care after obtaining the specimen.

cates one of three conditions for each drug: sensitive, equivocal, or resistant.

Health care team roles A physician orders and interprets the report for an acid-fast culture. A nurse, physician assistant, or respiratory therapist assists in sputum or sample collection. A clinical laboratory scientist/medical technologist who is specially trained in mycobacteriology performs the microbiological testing. Resources BOOKS

Chernecky, Cynthia C, and Berger, Barbara J. Laboratory Tests and Diagnostic Procedures. 3rd ed. Philadelphia, PA: W. B. Saunders Company, 2001. Fischback, Francis. A Manual of Laboratory and Diagnostic Tests, 5th Edition. Philadelphia: J. B. Lippincott Company, 1996, p.327 335. Forbes, BA, Sahm, DF, and Weissfeld, AS. Baily and Scott’s Diagnostic Microbiology. 10th Edition. Mosby, St. Louis, 1998. Kee, Joyce LeFever. Handbook of Laboratory and Diagnostic Tests. 4th ed. Upper Saddle River, NJ: Prentice Hall, 2001. Metchock, BG, Nolte, FS, and Wallace RJ. “Mycobacterium.” In Manual of clinical Microbiology. 7th ed. Murray, P, Baron EJ, Pfaller, MA, et. al. Editors. Washington, D.C.: American Society for Microbiology, 1999. Vossler JL. “Mycobacterium tuberculosis and other nontuberculous mycobacteria.” In Textbook of Diagnostic Microbiology. 2nd ed. Mahon, CR, Manuselis, G, Editors. Philadelphia: Saunders, 2000. OTHER

Center for Disease Control. .

Pamella A. Phillips Victoria E. DeMoranville

Complications There are no complications associated with this test.

Results The acid-fast smear report will indicate “no AFB seen” if results are negative. If positive, the report should be documented as described above. For cultures, “no growth of AFB” on any medium after eight weeks is considered a negative test. Growth on any medium is tested for acid-fastness and if positive, a preliminary report of a positive culture for Mycobacterium spp. is submitted. A final report of the mycobacterium species identified and antibiotic susceptibility is submitted as soon as results are available. The antibiotic susceptibility report indi-

Acquired immunodeficiency syndrome see AIDS

Activities of daily living evaluation Definition An activities of daily living (ADL) evaluation is an assessment of an individual’s physical and sometimes

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Once the physician receives the initial smear report (i.e., positive AFB on smear) and the initial culture report (presumptive M. tuberculosis isolated), the patient is given two or more primary drugs (first-line drugs) to initiate treatment that may require six to nine months of drug therapy. The first line (primary drugs) drugs tested in vitro include isoniazid (INH), rifampin, pyrazinamide, ethambutol, and streptomycin. After three months of therapy, patients are again cultured. If the cultures are still positive, re-testing of different or secondary drugs is done. The second-line drugs include ethionamide, capreomycin, cycloserine, kanamycin, pyrazinamide, amikacin, ciprofloxacin, ofloxacin, rifabutin, and paraaminosalicylic acid.

Activities of daily living

KEY TERMS Adaptation—Altering a tool used in performing a task so that the patient is better able to function independently or with minimal assistance. Dressing stick—A long rod with a hook attached to the end that a patient uses in place of the hands. Typically a dressing rod would be used to pull on a pair of pants or socks. Home modification—Altering the physical environment of the home so as to remove hazards and provide an environment that is more functional for the patient. Examples of home modification include installing grab bars and no-slip foot mats in the bathroom to prevent falls.

mental skills. In the area of physical or occupational therapy, it reflects how well a disabled patient or someone recovering from disease or accident can function in daily life. It is also used to determine how well patients relate to and participate in their environment.

Purpose ADL evaluations help practitioners determine how independent patients are and what skills they can accomplish on their own, as well as to gauge how independent each individual can become after intervention by a health professional. The goal of practitioners performing ADL evaluations is to help patients become as independent as possible, using appropriate adaptations if needed.

Description Many ADL indexes exist, such as the Katz Index, Revised Kenny Self-Care Evaluation, and the Barthel Index. These indexes typically evaluate patients on their self-care skills and rate each individual according to how functional they are. Scoring is based on how independently a task can be performed and whether supervision or assistance is needed in performing the task. Basic ADL versus Instrumental ADL Basic activities of daily living are those skills needed in typical daily self care. An evaluation would, in part, consist of bathing, dressing, feeding, and toileting. The evaluator would examine various activities in each category to determine the patient’s skill. Afterward it can be determined what, if any, changes will be necessary to allow the patient to function as independently as possible. 18

Instrumental activities of daily living refer to skills beyond basic self care that evaluate how individuals function within their homes, workplaces, and social environments. Instrumental ADLs may include typical domestic tasks, such as driving, cleaning, cooking, and shopping, as well as other less physically demanding tasks such as operating electronic appliances and handling budgets. In the work environment, an ADL evaluation assesses the qualities necessary to perform a job, such as strength, endurance, manual dexterity, and pain management. If a person is being treated following an injury or disorder diagnosis, whether an intervention is needed depends upon how severe his or her functional ability has been affected. If an individual’s ADL function is not restored, a health care professional will perform an intervention, which entails helping the individual adapt to permanent dysfunction or regain meaningful function. How well an individual must be able to perform these tasks depends upon the living setting he or she is returning to, whether it is a full custodial facility, assisted living community, or living at home on his or her own.

Complications Returning a client to full meaningful function can be problematic for individuals who do not have the motivation to do so. A holistic approach to treatment is most important in cases such as these, and physical and occupation therapists are trained to evaluate not only the physical disability or dysfunction of an individual, but also the person’s mental health and well-being. Occupational therapists can address mental health issues resulting from injury or disorder diagnosis, such as depression. However, in cases where a patient has sustained a permanent cognitive disability and is learningimpaired, it is more effective and appropriate for the occupational therapist to teach family members or a caretaker how to perform daily tasks for the patient.

Results Interventions implemented to increase function include adaptations and home modification. Adaptations are devices that can enhance the usability of everyday items for individuals who have a limited range of motion. Home modification involves the process of making one’s living environment more functional for ADL. Adaptations There are several ways that adaptations can be used to make common household items more functional. For example, patients commonly have a weakened grasp that is insufficient to hold heavy or small objects, so enhance-

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Acupressure Definition Acupressure is a form of touch therapy that utilizes the principles of acupuncture and Chinese medicine. In acupressure, the same points on the body are used as in acupuncture, but are stimulated with finger pressure instead of with the insertion of needles. Acupressure is used to relieve a variety of symptoms and pain.

Home modifications Home modification has become a major area for occupational therapists to practice. In order for patients to return home or go to a group setting, the physical environment of the house or facility may have to be altered to make ADL function better. Common examples of home modifications include the installation of grab bars in the shower, toilet area and hallways; lower kitchen counters for easier access to wheelchair-bound individuals; and the elimination of potential trip points, such as loose throw rugs and slight changes in floor elevation.

Health care team roles Occupational therapists and physical therapists are the two primary disciplines most qualified to assess ADL function and recommend the appropriate intervention and modifications in one’s home and work environment. Physical therapists might focus primarily on a patient’s mobility and ambulation, while the occupational therapist might focus on more specific tasks described above. Resources BOOKS

Eisenberg, Myron G. Dictionary of Rehabilitation. New York: Springer Publishing Company, Inc., 1995. Neistadt, Maureen E. and Elizabeth Blesedell Crepeau. Williard & Spackman’s Occupational Therapy. Philadelphia: Lippincott-Raven Publishers, 1998. Reed, Kathlyn L. and Sharon Nelson Sanderson. Concepts of Occupational Therapy Practice Baltimore: Lippincott Williams & Wilkins, 1999. Trombly, Catherine A., ed. Occupational Therapy for Physical Dysfunction Baltimore: Williams & Wilkins, 1995. ORGANIZATIONS

The American Occupational Therapy Association. 4720 Montgomery Lane, Bethesda, MD 20824-1220. (301) 652-2682. . The American Physical Therapy Association. 1111 North Fairfax Street, Alexandria, VA 22314-1488. (703) 6842782. .

Meghan M. Gourley

Origins One of the oldest text of Chinese medicine is the Huang Di, The Yellow Emperor’s Classic of Internal Medicine, which may be at least 2,000 years old. Chinese medicine has developed acupuncture, acupressure, herbal remedies, diet, exercise, lifestyle changes, and other remedies as part of its healing methods. Nearly all of the forms of Oriental medicine that are used in the West today, including acupuncture, acupressure, shiatsu, and Chinese herbal medicine, have their roots in Chinese medicine. One legend has it that acupuncture and acupressure evolved as early Chinese healers studied the puncture wounds of Chinese warriors, noting that certain points on the body created interesting results when stimulated. The oldest known text specifically on acupuncture points, the Systematic Classic of Acupuncture, dates back to 282 A.D. Acupressure is the non-invasive form of acupuncture, as Chinese physicians determined that stimulating points on the body with massage and pressure could be effective for treating certain problems. Outside of Asian-American communities, Chinese medicine remained virtually unknown in the United States until the 1970s, when Richard Nixon became the first U.S. president to visit China. On Nixon’s trip, journalists were amazed to observe major operations being performed on patients without the use of anesthetics. Instead, wide-awake patients were being operated on, with only acupuncture needles inserted into them to control pain. At that time, a famous columnist for the New York Times, James Reston, had to undergo surgery and elected to use acupuncture for anesthesia. Later, he wrote some convincing stories on its effectiveness. Despite being neglected by mainstream medicine and the American Medical Association (AMA), acupuncture and Chinese medicine became a central to alternative medicine practitioners in the United States. Today, there are millions of patients who attest to its effectiveness, and nearly 9,000 practitioners in all 50 states. Acupressure is practiced as a treatment by Chinese medicine practitioners and acupuncturists, as well as by massage therapists. Most massage schools in American

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ments such as easily gripped handles could be added to small objects, such as eating utensils or personal grooming items. Other adaptations may involve the use of unique tools to facilitate tasks, such as using a long rod with a hook at one end, known as a dressing stick, to pull on pants or socks. Adaptations may involve altering the environment to aid in other tasks, such as providing adequate lighting or magnifying lenses to compensate for a vision impairment.

Acupressure Therapist working acupressure points on a woman’s shoulder. (Photo Researchers, Inc. Reproduced by permission.)

include acupressure techniques as part of their bodywork programs. Shiatsu massage is very closely related to acupressure, working with the same points on the body and the same general principles, although it was developed over centuries in Japan rather than in China. Reflexology is a form of bodywork based on acupressure concepts. Jin Shin Do is a bodywork technique with an increasing number of practitioners in America that combines acupressure and shiatsu principles with qigong, Reichian theory, and meditation.

Benefits Acupressure massage performed by a therapist can be very effective both as prevention and as a treatment for many health conditions, including headaches, general aches and pains, colds and flu, arthritis, allergies, asthma, nervous tension, menstrual cramps, sinus problems, sprains, tennis elbow, and toothaches, among others. Unlike acupuncture which requires a visit to a professional, acupressure can be performed by a layperson. Acupressure techniques are fairly easy to learn, and have been used to provide quick, cost-free, and effective relief from many symptoms. Acupressure points can also be stimulated to increase energy and feelings of well-being, 20

reduce stress, stimulate the immune system, and alleviate sexual dysfunction.

Description Acupressure and Chinese medicine Chinese medicine views the body as a small part of the universe, subject to laws and principles of harmony and balance. Chinese medicine does not make as sharp a destinction as Western medicine does between mind and body. The Chinese system believes that emotions and mental states are every bit as influential on disease as purely physical mechanisms, and considers factors like work, environment, and relationships as fundamental to a patient’s health. Chinese medicine also uses very different symbols and ideas to discuss the body and health. While Western medicine typically describes health as mainly physical processes composed of chemical equations and reactions, the Chinese use ideas like yin and yang, chi, and the organ system to describe health and the body. Everything in the universe has properties of yin and yang. Yin is associated with cold, female, passive, downward, inward, dark, wet. Yang can be described as hot,

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Chi (pronounced chee, also spelled qi or ki in Japanese shiatsu) is the fundamental life energy. It is found in food, air, water, and sunlight, and it travels through the body in channels called meridians. There are 12 major meridians in the body that transport chi, corresponding to the 12 main organs categorized by Chinese medicine. Disease is viewed as an imbalance of the organs and chi in the body. Chinese medicine has developed intricate systems of how organs are related to physical and mental symptoms, and it has devised corresponding treatments using the meridian and pressure point networks that are classified and numbered. The goal of acupressure, and acupuncture, is to stimulate and unblock the circulation of chi, by activating very specific points, called pressure points or acupoints. Acupressure seeks to stimulate the points on the chi meridians that pass close to the skin, as these are easiest to unblock and manipulate with finger pressure. Acupressure can be used as part of a Chinese physician’s prescription, as a session of massage therapy, or as a self-treatment for common aches and illnesses. A Chinese medicine practitioner examines a patient very thoroughly, looking at physical, mental, and emotional activity, taking the pulse usually at the wrists, examining the tongue and complexion, and observing the patient’s demeanor and attitude, to get a complete diagnosis of which organs and meridian points are out of balance. When the imbalance is located, the physician will recommend specific pressure points for acupuncture or acupressure. If acupressure is recommended, the patient might opt for a series of treatments from a massage therapist. In massage therapy, acupressurists will evaluate a patient’s symptoms and overall health, but a massage therapist’s diagnostic training isn’t as extensive as a Chinese physician’s. In a massage therapy treatment, a person usually lies down on a table or mat, with thin clothing on. The acupressurist will gently feel and palpate the abdomen and other parts of the body to determine energy imbalances. Then, the therapist will work with different meridians throughout the body, depending on which organs are imbalanced in the abdomen. The therapist will use different types of finger movements and pressure on different acupoints, depending on whether the chi needs to be increased or dispersed at different points. The therapist observes and guides the energy flow through the patient’s body throughout the session.

Sometimes, special herbs (Artemesia vulgaris or moxa) may be placed on a point to warm it, a process called moxibustion. A session of acupressure is generally a very pleasant experience, and some people experience great benefit immediately. For more chronic conditions, several sessions may be necessary to relieve and improve conditions. Acupressure massage usually costs from $30–70 per hour session. A visit to a Chinese medicine physician or acupuncturist can be more expensive, comparable to a visit to an allopathic physician if the practitioner is an MD. Insurance reimbursement varies widely, and consumers should be aware if their policies cover alternative treatment, acupuncture, or massage therapy. Self-treatment Acupressure is easy to learn, and there are many good books that illustrate the position of acupoints and meridians on the body. It is also very versatile, as it can be done anywhere, and it’s a good form of treatment for spouses and partners to give to each other and for parents to perform on children for minor conditions. While giving self-treatment or performing acupressure on another, a mental attitude of calmness and attention is important, as one person’s energy can be used to help another’s. Loose, thin clothing is recommended. There are three general techniques for stimulating a pressure point. • Tonifying is meant to strengthen weak chi, and is done by pressing the thumb or finger into an acupoint with a firm, steady pressure, holding it for up to two minutes. • Dispersing is meant to move stagnant or blocked chi, and the finger or thumb is moved in a circular motion or slightly in and out of the point for two minutes. • Calming the chi in a pressure point utilizes the palm to cover the point and gently stroke the area for about two minutes. There are many pressure points that are easily found and memorized to treat common ailments from headaches to colds. • For headaches, toothaches, sinus problems, and pain in the upper body, the “LI4” point is recommended. It is located in the web between the thumb and index finger, on the back of the hand. Using the thumb and index finger of the other hand, apply a pinching pressure until the point is felt, and hold it for two minutes. Pregnant women should never press this point. • To calm the nerves and stimulate digestion, find the “CV12” point that is four thumb widths above the navel

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male, active, upward, outward, light, dry, and so on. Nothing is either completely yin or yang. These two principles always interact and affect each other, although the body and its organs can become imbalanced by having either too much or too little of either.

Acupressure

invisible energy of the body, and the idea that pressing on certain points can alleviate certain conditions seems sometimes too simple for scientists to believe.

KEY TERMS Acupoint—A pressure point stimulated in acupressure. Chi—Basic life energy. Meridian—A channel through which chi travels in the body. Moxibustion—An acupuncture technique that burns the herb moxa or mugwort. Shiatsu—Japanese form of acupressure massage. Yin/yang—Universal characteristics used to describe aspects of the natural world.

in the center of the abdomen. Calm the point with the palm, using gentle stroking for several minutes. • To stimulate the immune system, find the “TH5” point on the back of the forearm two thumb widths above the wrist. Use a dispersing technique, or circular pressure with the thumb or finger, for two minutes on each arm. • For headaches, sinus congestion, and tension, locate the “GB20” points at the base of the skull in the back of the head, just behind the bones in back of the ears. Disperse these points for two minutes with the fingers or thumbs. Also find the “yintang” point, which is in the middle of the forehead between the eyebrows. Disperse it with gentle pressure for two minutes to clear the mind and to relieve headaches.

Precautions Acupressure is a safe technique, but it is not meant to replace professional health care. A physician should always be consulted when there are doubts about medical conditions. If a condition is chronic, a professional should be consulted; purely symptomatic treatment can exacerbate chronic conditions. Acupressure should not be applied to open wounds, or where there is swelling and inflammation. Areas of scar tissue, blisters, boils, rashes, or varicose veins should be avoided. Finally, certain acupressure points should not be stimulated on people with high or low blood pressure and on pregnant women.

Research and general acceptance In general, Chinese medicine has been slow to gain acceptance in the West, mainly because it rests on ideas very foreign to the scientific model. For instance, Western scientists have trouble with the idea of chi, the 22

Western scientists, in trying to account for the action of acupressure, have theorized that chi is actually part of the neuroendocrine system of the body. Celebrated orthopedic surgeon Robert O. Becker, who was twice nominated for the Nobel Prize, wrote a book on the subject called Cross Currents: The Promise of Electromedicine; The Perils of Electropollution. By using precise electrical measuring devices, Becker and his colleagues showed that the body has a complex web of electromagnetic energy, and that traditional acupressure meridians and points contained amounts of energy that non-acupressure points did not. The mechanisms of acupuncture and acupressure remain difficult to document in terms of the biochemical processes involved; numerous testimonials are the primary evidence backing up the effectiveness of acupressure and acupuncture. However, a body of research is growing that verifies the effectiveness in acupressure and acupuncture techniques in treating many problems and in controlling pain.

Training and certification There are two routes to becoming trained in the skill of acupressure. The first is training in traditional acupuncture and Chinese medicine, which has many schools and certifying bodies around the country. The majority of acupressure practitioners are trained as certified massage therapists, either as acupressure or shiatsu specialists. The Acupressure Institute provides certification and resources for acupressure practitioners. Address: 1533 Shattuck Ave., Berkeley, CA 94709, phone (510) 8451059, website: www.acupressure.com. The American Oriental Bodywork Therapy Association (AOBTA) certifies acupressure practitioners and has over 1,400 members. It also provides a list of schools and training programs. Address: 1010 Haddonfield-Berlin Road, Suite 408, Voorhees, NJ 08043, phone (856) 782-1616, email: AOBTA @prodigy.net. The Jin Shin Do Foundation for Body/Mind Acupressure is an international network of teachers and practitioners. Address: 1084G San Miguel Canyon Road, Royal Oaks, CA 95076, phone (408) 763-7702. The largest organization that certifies massage therapists, with over 40,000 members worldwide, is the American Massage Therapy Association. It also has a

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times be reversed, leaving no permanent or serious damage to the kidneys.

Causes and symptoms

BOOKS

Jarmey, Chris and John Tindall. Acupressure for Common Ailments. London: Gaia, 1991. Kakptchuk, Ted. The Web That Has No Weaver: Understanding Chinese Medicine. New York: Congdon and Weed, 1983. Warren, Frank Z., MD. Freedom From Pain Through Acupressure. New York: Fell, 1976. PERIODICALS

Massage Therapy Journal. 820 Davis Street, Suite 100, Evanston, IL 60201-4444. OTHER

American Association of Oriental Medicine. (December 28, 2000). National Acupuncture and Oriental Medicine Alliance. (December 28, 2000).

Douglas Dupler

Acute kidney failure appears most frequently as a complication of serious illness, like heart and/or liver failure, serious infection, dehydration, severe burns, and excessive bleeding (hemorrhage). It may also be caused by an obstruction to the urinary tract or as a direct result of kidney disease, injury, or an adverse reaction to medicine. These conditions divide AKF into three main categories: prerenal, postrenal, and intrinsic (inside) conditions. Prerenal AKF does not damage the kidney, but can cause diminished kidney function and significantly decreased renal (kidney) blood flow. It is the most common type of acute renal failure, and is often the result of: • dehydration • extracellular fluid (ECF) volume depletion (or other acute fluid loss from the gastrointestinal tract, kidneys, or skin) • drugs (NSAIDS, cyclosporine, radiopaque contrast materials, or any substance toxic to the kidneys) • hemorrhage

Acute kidney failure Definition Acute kidney failure (AKF) occurs when there is a sudden reduction in kidney function that results in nitrogenous wastes accumulating in the blood (azotemia).

Description The kidneys are the body’s natural filtration system. They perform the critical task of processing approximately 200 quarts of fluid in the bloodstream every 24 hours. Waste products like urea and toxins, along with excess fluids, are removed from the bloodstream in the form of urine. Kidney (or renal) failure occurs when kidney functioning becomes impaired somehow. Fluids and toxins begin to accumulate in the bloodstream. As fluids build up in the bloodstream, the patient with AKF may become puffy and swollen (edematous) in the face, hands, and feet. Their blood pressure typically begins to rise, and they may experience fatigue and nausea. Often urine output decreases drastically or is not produced at all. Unlike chronic kidney failure, which is long term and irreversible, acute kidney failure is often a temporary condition. With proper and timely treatment, it can many

• septicemia, or sepsis • congestive heart failure (CHF) • liver failure • burns • decreased intravascular volume (referred to as third spacing, also found in the presence of pancreatitis, post surgical patients, and patients with a nephrotic syndrome) Postrenal AKF is the result of an obstruction of some kind somewhere in the urinary tract, often in the bladder or ureters (the tubes leading from the kidney to the bladder). The kidneys compensate to such a degree that one kidney can be completely obstructed and the other will maintain nearly normal kidney function for the body. The conditions that often cause postrenal AKF are: • inflammation of the prostate gland in men (prostatitis) • enlargement of the prostate gland (benign prostatic hypertrophy) • bladder or pelvic tumors • kidney stones (calculi) Intrinsic AKF involves a type of kidney disease or direct injury to the kidneys. This type of AKF accounts

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member directory and lists of training programs. Website: www.amtamassage.org.

Acute kidney failure

for 20-30% of AKF reported among hospitalized patients. Intrinsic AKF can result from: • lack of blood supply to the kidneys (ischemia) • use of radiocontrast agents in patients with kidney problems • drug abuse or overdose • long-term use of nephrotoxic medications, like certain pain medicines • acute inflammation of the glomeruli, or filters, of the kidney (glomerulonephritis) • kidney infections (pyelitis or pyelonephritis) • infiltration by lymphoma, leukemia, or sarcoid carcinomas Common symptoms of AKF include: • Anemia. The kidneys are responsible for producing erythropoietin (EPO), a hormone that stimulates red blood cell production. If kidney disease causes shrinking of the kidney, red blood cell production is reduced, leading to anemia. • Bad breath or bad taste in mouth. Urea in the saliva may cause an ammonia-like taste in the mouth. • Bone and joint problems. The kidneys produce vitamin D, which helps the body absorb calcium and keeps bones strong. For patients with kidney failure, bones may become brittle. In children, normal growth may be stunted. Joint pain may also occur as a result of high phosphate levels in the blood. Retention of uric acid may cause gout. • Edema. Puffiness or swelling in the arms, hands, feet, and around the eyes. • Frequent urination. • Foamy or bloody urine. Protein in the urine may cause it to foam significantly. Blood in the urine may indicate bleeding from diseased or obstructed kidneys, bladder, or ureters. • Cola-colored urine followed by oliguria (decreased urine output) or anuria (no urine output) • Headaches. High blood pressure may trigger headaches. • Hypertension, or high blood pressure. The retention of fluids and wastes causes blood volume to increase. This makes blood pressure rise. • Increased fatigue. Toxic substances in the blood and the presence of anemia may cause the patient to feel exhausted. • Itching. Phosphorus, normally eliminated in the urine, accumulates in the blood of patients with kidney fail24

ure. An increased phosphorus level may cause the skin to itch. • Lower back pain. Patients suffering from certain kidney problems (like kidney stones and other obstructions) may have pain where the kidneys are located, in the small of the back below the ribs. • Nausea. Urea in the gastric juices may cause upset stomach.

Diagnosis Kidney failure is diagnosed by a doctor, whether the patient is in the hospital or seen as an outpatient. He or she will take a complete medical history and make a thorough review of the patient’s medical record, looking for exposure to nephrotoxic (medicines that can be hard on the kidneys) drugs or other clues to the patient’s condition. The physician will then conduct a thorough physical examination, making a careful assessment of the patient’s ECF volume and effective circulating blood volume (EBV). A nephrologist, a doctor that specializes in the kidney, may be consulted to confirm the diagnosis and recommend treatment options. He or she will look for a recent history of changes in body weight and try and determine whether the patient is taking in much more fluid than he or she is excreting. Capillary wedge pressure and cardiac output values are also effective tools in pinpointing the cause and extent of the AKF. The patient that is suspected of having AKF will have blood and urine tests to determine the level of kidney function. A blood test will assess the levels of creatinine, blood urea nitrogen (BUN), uric acid, phosphate, sodium, and potassium. The kidney regulates these agents in the blood. Urine samples will also be collected, usually over a 24-hour period, to assess protein loss and/or creatinine clearance. Determining the cause of kidney failure is critical to proper treatment. Prerenal or obstructive causes are often looked into first because they are the quickest types of AKF to treat. A full assessment of the kidneys is necessary to determine if the underlying disease is treatable and if the kidney failure is chronic or acute. X rays, magnetic resonance imaging (MRI), computed tomography scan (CT), ultrasound, renal biopsy, and/or arteriogram of the kidneys may be used to determine the cause of kidney failure and level of remaining kidney function. X rays and ultrasound of the bladder and/or ureters may also be needed.

Treatment Treatment for AKF varies, since it is directed to the underlying, primary medical condition that triggered the

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Frequently, patients in AKF require hemodialysis, hemofiltration, or peritoneal dialysis to filter fluids and wastes from the bloodstream until the primary medical condition can be controlled. Hemodialysis Hemodialysis involves circulating the patient’s blood outside of the body through an extracorporeal circuit (ECC), or dialysis circuit. The ECC is made up of plastic blood tubing, a filter known as a dialyzer (or artificial kidney), and a dialysis machine that monitors and maintains blood flow and administers dialysate. Dialysate is a sterile chemical solution that is used to draw waste products out of the blood. The patient’s blood leaves the body through the vein and travels through the ECC and the dialyzer, where fluid removal takes place. During dialysis, waste products in the bloodstream are carried out of the body. At the same time, electrolytes and other chemicals are added to the blood. The purified, chemically-balanced blood is then returned to the body. A dialysis “run” typically lasts three to four hours, depending on the type of dialyzer used and the physical condition of the patient. Dialysis is used several times a week until AKF has resolved. Blood pressure changes associated with hemodialysis may pose a risk for patients with heart problems. Peritoneal dialysis may be the preferred treatment option in these cases. Hemofiltration Hemofiltration, also called continuous renal replacement therapy (CRRT), is a slow, continuous blood filtration therapy used to control acute kidney failure in critically ill patients. These patients are typically very sick and may have heart problems or circulatory problems. They cannot endure the rapid filtration rates of hemodialysis. They also frequently need antibiotics, nutrition, vasopressors, and other fluids given through a vein to treat their primary condition. Because hemofiltration is continuous, prescription fluids can be given to patients in kidney failure without the risk of fluid overload. Like hemodialysis, hemofiltration uses an ECC. A hollow fiber hemofilter is used instead of a dialyzer to remove fluids and toxins. Instead of a dialysis machine, a blood pump makes the blood flow through the ECC. The volume of blood circulating through the ECC in

hemofiltration is less than that in hemodialysis. Filtration rates are slower and gentler on the circulatory system. Hemofiltration treatment will generally be used until kidney failure is reversed. Peritoneal dialysis Peritoneal dialysis may be used if the patient in AKF is stable and not in immediate crisis. In peritoneal dialysis (PD), the lining of the patient’s abdomen, the peritoneum, acts as a blood filter. A flexible tube-like instrument (catheter) is surgically inserted into the patient’s abdomen. During treatment, the catheter is used to fill the abdominal cavity with dialysate. Waste products and excess fluids move from the patient’s bloodstream into the dialysate solution. After a certain time period, the waste-filled dialysate is drained from the abdomen, and replaced with clean dialysate. There are three types of peritoneal dialysis, which vary according to treatment time and administration method. Peritoneal dialysis is often the best treatment option for infants and children. Their small size can make vein access difficult to maintain. It is not recommended for patients with abdominal adhesions or other abdominal defects (like a hernia) that might reduce the efficiency of the treatment. It is also not recommended for patients who suffer frequent bouts of an inflammation of the small pouches in the intestinal tract (diverticulitis).

Prognosis Because many of the illnesses and underlying conditions that often trigger AKF are critical, the prognosis for these patients many times is not good. Studies have estimated overall death rates for AKF at 42-88%. Many people, however, die because of the primary disease that has caused the kidney failure. These figures may also be misleading because patients who experience kidney failure as a result of less serious illnesses (like kidney stones or dehydration) have an excellent chance of complete recovery. Early recognition and prompt, appropriate treatment are key to patient recovery. Survival statistics also depend on the type of AKF the patient has, age at time of onset, and general health. If the patient has prerenal AKF, there is a good recovery prognosis, but the mortality rate is higher among those who fail to respond to diuretics and vasodilator therapy. Since 1980, age has become a risk factor that increased mortality in patients with acute tubular necrosis (ATN), an intrinsic form of AKF. Up to 10% of patients who experience AKF will suffer irreversible kidney damage. They will eventually go on to develop chronic kidney failure or end-stage renal

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kidney failure. Prerenal conditions may be treated with replacement fluids given through a vein, diuretics, blood transfusion, restricted salt intake, or medications. Postrenal conditions and intrarenal conditions may require surgery and/or medication.

Acute kidney failure

KEY TERMS Anuria—When the body ceases to make urine entirely or falls below 100 mls.

Glomeruli—The tiny structures that perform the actual mechanical filtering in the kidney.

Azotemia—Too many nitrogenous compounds in the blood caused by the kidneys’ failure to remove urea from the blood.

Gout—A condition caused by error in uric acid metabolism.

Blood urea nitrogen (BUN)—A waste product that is formed in the liver and collects in the bloodstream; patients with kidney failure have high BUN levels.

Intravascular volume—The volume of fluid inside a blood vessel.

Capillary wedge pressure—The blood pressure inside of a capillary. Cardiac output—The volume of blood pushed out by the ventricles. Creatinine—A protein produced by muscle that healthy kidneys filter out. Edema—The abnormal accumulation of fluid in the interstitial spaces of tissue. Electrolytes—An element or a compound that can break into ions and conduct electrical current when melted or dissolved in water.

Interstitial—The space between cells.

Intrinsic—Starting from or situated inside an organ or tissue. Ischemia—A lack of blood supply to an organ or tissue. Lymphoma—Cancer of the lymph tissue. Nephritis—Inflammation and abnormal functioning of the kidney. Nephrologist—A physician who specializes in treating diseases of the kidney. Nephrotoxic—Toxic, or damaging, to the kidney. NSAIDS—Non-steroidal, antiinflammatory drug. Oliguria—Abnormally low urine production.

Erythropoietin (EPO)—A glycoprotein hormone made in the kidneys.

Radiocontrast agents—Dyes administered to a patient for the purposes of a radiologic study.

Extracellular fluid (ECF)—That part of body fluid made of interstitial fluid and blood plasma.

Sepsis—A bacterial infection of the bloodstream.

Extracorporeal—Outside of, or unrelated to, the body.

Vasopressors—Medications that constrict the blood vessels.

disease. These patients will require long-term dialysis or kidney transplantation to replace their lost renal functioning.

Health care team roles The patient who suffers from AKF will come in contact with a number of different health care professionals during both the diagnosis and treatment phase of the illness. Patients will require (according to the type and severity of their condition) laboratory work, diagnostic radiology services, pharmaceutical and nutritional interventions, dialysis (in some cases), nursing care, and disease management by a nephrologist. The medical history, taken by a physician in the emergency room, the patient’s family doctor, a fellow nurse practitioner, physician’s assistant (PA), or a nephrologist is the most essential tool in determining the 26

Urea—A systemic diuretic.

cause and type of AKF. The admitting physician or nephrologist will conduct a thorough physical, looking at the following areas for specific clues. Skin. Checking the patient for areas of small, purple or red spots (petechiae), hemorrhage beneath the skin (purpura), and bluish discoloration of a fairly large area of the skin (ecchymosis) can lead to a diagnosis of an inflammatory or vascular cause for the AKF. Eyes. Certain conditions in the eyes can point to a diagnosis of interstitial nephritis (inflammation between the cells and tissues of the kidney) or necrotizing vasculitis (inflammed blood vessels). Cardiovascular and volume status. Evaluating the condition of the heart and the rest of the circulatory system plus volume status (fluid balance) is the most important part of diagnosing and managing AKF. Nurses and nurses’ aides will measure and chart daily intake and

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Abdomen. The physician will feel for signs of urinary tract obstruction by palpating (pressing) on the bladder and the upper corners of the abdomen that may reveal an obstruction in the ureter (tube between the kidney and the bladder) somewhere. If the entire abdomen is unusually swollen and filled with fluid (ascites), the AKF may be the result of liver failure. Arms and legs (extremities). The physican and nursing staff will check the patients arms and legs for edema at the time of diagnosis and throughout treatment. Edema in the arms and legs is a sign of a decrease in oxygenated blood (ischemia), muscle tenderness from rhabdomyolysis (disease of the skeletal muscle), or arthritis. The presence and degree of edema is helpful in pinpointing the cause of AKF and in measuring the patient’s progress with treatment. Nervous system. The physician will assess the patient’s degree of mental clarity and nerve responses, as abnormalities in these areas of the nervous system are often common symptoms of AKF. The nursing staff also monitors the patient’s mental status during the course of treatment. Laboratory personnel will draw blood and collect urine samples to help diagnose AKF and later, to evaluate treatment. Increases in BUN (blood urea nitrogen) and creatinine (substance formed from the metabolism of creatine) are indicators of AKF. The urinalysis is the most important test run in the early stage of AKF evaluation. Significant color changes point to an intrinsic cause for AKF. Urine dipstick tests that prove positive for proteinuria (too much protein) and blood are helpful in diagnosing many causes of AKF. The different types of sediment readings from spun urine samples can further help to distinguish the cause and type of AKF. Urine electrolytes indicate how well the tubules (part of the kidney’s nephron) are working. Nurses and nurses’ aides will keep track of fluids the patient takes in (intake) and eliminates (output) to help determine the type of AKF the patient is in and to help the physician manage the patient’s course of treatment.

Fluid management is critical in the patient with AKF, regardless of the cause. Patients in AKF may undergo further evaluation in the Radiology Department to determine the cause of their disease and to plan an appropriate plan of treatment. They may undergo an ultrasound examination, doppler scan, nuclear scan, MRI, renal angiography, or a renal biopsy. The ultrasound, doppler scan, and MRI are the least invasive of the procedures. Contrast material is injected for the angiogram and the renal biopsy requires taking tissue samples from the kidney itself. These procedures are performed by trained and licensed radiologic technologists and radiologists. Nutrition is crucial to the effective management of the patient in AKF. The dietician will work closely with the patient, physician, nursing staff, and pharmacist to ensure proper electrolyte balance, whether the patient eats regular foods or is nourished by total parenteral nutrition (TPN, nutrients mixed and fed through a tube). Some patients will require kidney dialysis that will be performed by nurses and technicians from the renal or urology department. Since many different medications are eliminated through the kidneys, the physician works closely with the pharmacist to modify dosing and minimize the use of medications that are toxic to the kidneys.

Prevention Since AKF can be caused by many things, prevention is difficult. Medications that may impair kidney function should be given cautiously. Patients with preexisting kidney conditions who are hospitalized for other illnesses or injuries should be carefully monitored for kidney failure complications. Treatments and procedures that may put them at risk for kidney failure (like diagnostic tests requiring radiocontrast agents or dyes) should be used with extreme caution. Resources BOOKS

Anderson, Kenneth N., Anderson, Lois, E., and Glanze, Walter D., eds. Mosby’s Medical, Nursing, & Allied Health Dictionary, 5th edition. New York: Mosby, 1998. Beers, Mark H., M.D., and Berkow, Robert M.D., eds. The Merck Manual, 17th edition. New Jersey: Merck Research Laboratories, 1999. Faubert, Pierre F., and Porush, Jerome G. Renal Disease in the Elderly. New York: Marcel Dekker, Inc., 1999. Gennari, F. John, ed. Medical Management of Kidney and Electrolyte Disorders. New York: Marcel Dekker, Inc., 2001.

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output (measuring how much fluid the patient takes in and how much he or she excretes in a 24-hour period of time). This is one of the best ways to get a good estimate of volume status. The pulse rate and blood pressure will be taken by the physician, nurses, and nurses’ aides often in both the upright (standing or sitting on the side of the bed with legs dangling down) and supine (lying down) positions. The physician will also check the pulse in the neck, examine the heart and lungs, and check for edema (fluid buildup) in the arms and legs. Different combinations of the results of these assessments point to different causes for and types of AKF.

Administration of medication

Greenberg, Arthur, Cheung, Alfred K., Coffmann, Thomas M., Falk, Ronald J., and J. Charles, Jeanette, eds. Primer on Kidney Diseases, Second Edition - National Kidney Foundation. New York: Academic Press, 1999. PERIODICALS

Description

Andreucci, M., Federico, S., and Andreucci, V.E. “Edema and Acute Renal Failure.” Seminars in Nephrology 21, 3(May 2001): 251-6. Forbes, J.M., Hewitson, T.D., Becker, G.J., and Jones, C.L. “Simultaneous Blockade of Endothelin A and B Receptors in Ischemic Acute Renal Failure is Detrimental to Long-term Kidney Function.” Kidney International 59, 4(April 2001): 1333-41. Gruberg, L., Mehran, R., Dangas, G., Mintz, G.S., Waksman, R., Kent, K.M., Pichard, A.D., Satler, L.F., Wu, H., and Leon, M.B. “Acute Renal Failure Requiring Dialysis After Percutaneous Coronary Interventions.” Catheter Cardiovascular Interventions 59, 4(April 2001): 409-16. Knoll, T., Schult, S., Birck, R., Braun, C., Michel, M.S., Bross, S., Juenemann, K.P., Kirchengast, M., and Rohmeiss, P. “Therapeutic Administration of an Endothelin-A Receptor Antagonist After Acute Ischemic Renal Failure Dose-Dependently Improves Recovery of Renal Function.” Journal of Cardiovascular Pharmacology 37, 4(April 2001): 483-8. Rana, A., Sathyanarayana, P., and Lieberthal, W. “Role of Apoptosis of Renal Tubular Cells in Acute Renal Failure: Therapeutic Implications.” Apoptosis 6,1-2(FebruaryApril 2001): 83-102. ORGANIZATIONS

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Natcher Building, 6AS-13K, 45 Center Dr., Bethesda, MD 20892-6600. . National Kidney Foundation (NKF). 30 East 33rd St., New York, NY 10016. (800) 622-9020. .

Susan Joanne Cadwallader

Acute leukemias see Leukemias, acute ADA see Americans with Disabilities Act ADL evaluation see Activities of daily living evaluation

Administration of medication Purpose The administration of medication is often a chief responsibility of the nurse. The practice of administering 28

medication involves providing the patient with a substance prescribed and intended for the diagnosis, treatment, or prevention of a medical illness or condition.

The central action of medication administration involves actual and complete conveyance of a medication to the patient. However, there is a wider set of practices required to achieve safe, effective patient outcomes and to prepare for and evaluate the outcome of medication administration. Laws regarding medication administration vary from state to state. Doctors, physicians, physician assistants, nurse practitioners, and nurses are generally trained and authorized to administer medication, while other medical disciplines may have a limited responsibility in this area. In certain circumstances, unlicensed personnel may be trained and authorized to administer medication in residential care settings. State and federal laws also restrict the distribution of and access to medications that can be abused (called controlled substances). Responsibility for controlled substances includes accountability for any discarded substances, double-locked storage, and counting of medication supply at regular intervals by clinician teams. Preparation for medication administration begins with the order for medication, in most circumstances written by the physician. Nurse practitioners and physician assistants are also often authorized to write prescriptions. State laws vary regarding these privileges. A record of orders for medication and other treatments is kept in the medical chart. Universally accepted safe clinical practice guidelines and state laws govern the components of medication orders in order to ensure consistency and patient safety. All orders should contain the patient’s name, the date and time when the order is written, and the signature of the ordering clinician. Caregivers administering medication are responsible for checking that these components are present and clear. The name of the medication is accompanied by the dosage, or how much of the drug should be given; the route of administration, or how the medication should be given (ie, intramuscular injection); and frequency, or how often the drug is to be given. Common routes of administration are discussed below. The most common route of administration is the oral route, or swallowing of medication. This is the easiest and safest route. The physical position and swallowing abilities of the patient should be evaluated to avoid choking. Patients may also receive medication by the buccal route (through the inner cheek or gum) or the sublingual route (under the tongue).

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Medication can also be instilled via the mucous membranes. Asepsis must be used to avoid introduction of infection. Rectal or vaginal medications are most often given in suppository form and must be introduced gently to avoid tearing or bleeding of tissue. Nasal medications are often instilled via spray or drops and often involve closing one nostril and asking the patient to inhale gently. The head should be tilted back to avoid aspiration. Ear or otic medications are given in liquid form. The patient’s head is tilted to the side. Instruments should never enter the ear. If the medication is not instilled correctly, the patient may experience nausea or vertigo. Eye or ophthalmic medications may be given via drops or ointment. The container for the medication should not touch the eye, and drops are introduced into the inner canthus or corner of the eye. Inhalational medications are inhaled via the respiratory tract, most often to treat respiratory conditions. Metered dose inhalers (MDI) are often used. MDIs involve pressing a specially designed canister to release a mist.

Administration of medication

Administration involving a needle or syringe occurs with several drug routes. These routes are referred to as parenteral. Care must be taken to maintain asepsis with all injections and injection sites. Intramuscular medications are injected into the muscle. A special injection technique called Z-track can be used when administering intramuscular medications that can be damaging to the tissue. All intramuscular injections involve the practice of landmarking, or identifying anatomical markers that indicate the correct injection site and avoid damage to bone or nerves. Subcutaneous injections are administered under the skin. Insulin is a common medication that is usually given subcutaneously. Intradermal medications are used much less frequently than subcutaneous or intramuscular injections. They are injected into the skin. Intravenous medications are given through an intravenous line into the vein. These medications may be mixed with a large amount of solution that is being infused, given in a small solution through a port in the intravenous tubing (bolus), or attached in smaller infusion containers to the larger infusion (piggyback). In all cases of administration with a needle or syringe, rotation of injection sites is required to prevent damage to tissue. It is also important that the size of the needle is selected based on the thickness of the medication to be given and the depth of the injection, while maximizing the patients level of comfort during insertion. Needle sticks with contaminated needles are a hazard to both health professional and patient. Care is taken to dispose of needles and syringes rapidly in impervious containers. Protective systems that sheath the needle after use are commonly used to prevent inadvertent needle sticks.

An anesthesiologist administers drugs to a patient in surgery. (Photograph by Michelle del Guercio. Science Source/Photo Researchers. Reproduced by permission.)

Topical medications are applied to the surface of the skin. The skin needs to be cleansed and assessed for breaks before administering topical medications. Topical patches that gradually release medication need to be labeled with date and time in case a second patch is inadvertently applied without removal of the first. Ointments are applied evenly. The clinician should avoid touching the topical medication, as medications that are absorbed into the system via the skin, such as nitroglycerin paste, may affect the clinician. As with all medication techniques, asepsis must be maintained to avoid introduction of microorganisms. Frequency of administration is most often ordered on a repeating schedule (ie, every 8 hours). At times the order may be written as a STAT (give right away) order, a one-time order (give just once) or a prn (give as needed) order. Standing orders are routine hospital orders that doctors in specialized areas prescribe on admission.

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Many abbreviations are used in writing medication orders. Other common abbreviations include:

• toxic effects: dangerous effects that often occur due to build up of drug in body or impaired metabolism

• p.o.: by mouth

• tolerance: certain drugs require increasing doses over time to achieve the same effect

• IM: intramuscular injection

• physiological variables: sex, age, size, and physical condition may alter how a drug is processed in the body

• SC: subcutaneous injection • IV: intravenous

• diet: certain foods, liquids, or nutritional states may alter the drug’s effect on the body

• PR: per rectum • h.s.: at hour of sleep (bedtime) • ac: before meals • pc: after meals • q: every, ie, q 8 h means every 8 hours • q.d.: every day • b.i.d.: twice/day • t.i.d.: three times/day • q.i.d.: four times/day • q.o.d.: every other day Some examples of medication orders using these abbreviations are: • digoxin 0.25 mg p.o. q.d. • diphenhydramine 25 mg p.o. q h.s. prn. If orders are illegible, ambiguous, or confusing, the author of the order should be consulted to clarify the order before any medication administration occurs. When the order is clear, it often needs to be transcribed to another document reserved for recording administration of medications. Health care institutions have specific policies regarding methods with which to check medication orders and ensure proper transcription. Policies also dictate parameters for order renewal or medication discontinuation. Poor penmanship, misunderstanding of penmanship, and errors in transcription often contribute to medication errors. It is increasingly common for medical facilities to use a computerized system that lowers the risk of error by reducing steps in the process and validating information automatically. Once the order has been read and verified, the caregiver needs to evaluate the order in the context of the individual patient. Some factors to consider include: • pharmacodynamics: how the drug works in the body • interactions: possible effects of other medication or food on the ordered medication • allergies: patient history of hypersensitivity to drug or drug class • contraindications: medical conditions that preclude the use of the ordered drug • side effects: potential adverse reactions to the drug 30

Due to the large number of medications available and the large body of information required for appropriate drug administration, it is important to have access to a current medication reference such as the Physician’s Desk Reference or other reference handbooks about medication. The package insert that comes with every medication is also a good resource. Pharmacists are knowledgeable resources and can answer many questions regarding medication. It is important to be familiar with the medication ordered before attempting to administer it. Procedural manuals by the institution or medical reference publishers detail the step-by-step techniques for administering various types of medication. The patient should be notified of the order for the drug and provided with education about the medication they are to receive. Before administration, five factors often referred to as the “five rights” should be addressed. Medication records should be on hand at time of administration to ensure safe administration. Right patient. Identify patient by name badge or bracelet. Avoid simply asking patient’s name or checking the name on the door as miscommunications can sometimes occur. Right drug. Check record for name of drug and compare with drug on hand. As many drugs have similar spellings, this needs to be checked carefully. For prevention of error, it is often recommended that three checks of the drug to be administered are made: when reaching for the package that contains the drug, when opening the drug, and when returning the packaging to its storage area. It is also recommended that clinicians only administer drugs that they have prepared, versus those prepared by another clinician. Right route. Check medication record for how to administer the drug and check labeling of drug to ensure it matches prescribed route. Right dose. Compare ordered dose to dose on hand. At times, calculations may need to be performed to ascertain the correct dose. For example, a scored tablet, or one that is designed and intended for dividing, may need to be halved or quartered in order to administer the correct oral dose. This requires simple division. Common situations requiring calculation include calculation of intravenous

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The formula for this calculation can be applied to many situations: • dose ordered/dose on hand x amount on hand = amount to administer Using the above medication question, 25 mg /100 mg x 2 ml = 0.5 ml (amount to administer) Intravenous medications also require frequent calculation. For example, an intravenous anticoagulant such as heparin may be ordered as “1000 units per hour,” and the clinician may need to calculate how many drops are needed per minute or hour based on how the intravenous solution is prepared. These calculations may vary according to the infusion equipment used, for example, varying drop factor ratings or use of a device called a buretrol that carefully measures infused medication. Often a mechanical pump is used to control intravenous infusion rates. Right time. Verify that frequency or time ordered matches current time. All medications should be handled to ensure that they do not come into contact with potentially contaminated objects or surfaces. Medications of any sort should not be left unattended, and patients should be observed taking the medication. This avoids the disposal, hoarding, abuse, or misuse of the medication, and assures the safety of the patient. Documentation of medication administration is an important responsibility. The medication record tells the story of what substances the patient has received and when. Like other health care records, it is also a legal document. Various institutions have policies and procedures regarding documentation. The initials of the administering nurse or other health care provider and the time and date should be documented on the record next to the appropriate order. Other information may be required, such as location and severity of pain when administering a pain medicine (analgesic) or pulse rate when administering certain heart medications (i.e., digoxin). Patient refusals of medication also need to be documented, and the prescribing clinician should be informed. Medication errors need to be documented as well. The prescribing clinician should be notified of errors. Institutional policies usually require filing a separate form to document errors. Errors can include administering the wrong drug, wrong dose, at the wrong time, or via the wrong route. Omissions of medication are also considered errors.

It is important to evaluate the patient following medication administration and document effect. For example, many hospitals dictate that a note be written regarding pain relief within several hours after analgesic administration. Any adverse effects from medication should be reported.

Preparation Preparation for safe medication administration requires a background of education and hands-on training. New nurses and other professionals should be supervised until they demonstrate an appropriate level of knowledge and competent skills for independent medication administration.

Aftercare The patient should be monitored to make sure the medication has had the desired effect.

Health care team roles In addition to the clinician who administers medication, other members of the health care team play vital roles surrounding the medication administration process. Doctors or other prescribing clinicians are responsible for writing clear, legible orders and for monitoring the response of the patient to medication. They are also responsible for responding to potential adverse effects and concerns by the patient or other clinicians. Pharmacists are responsible for evaluating the medication order for potential problems, correctly filling the order, and monitoring the medication supply. All health care professionals are responsible for complying with medication-related policies designed to protect the patient and/or staff and for maintaining current knowledge regarding medication and medication administration. Resources BOOKS

Potter, Patricia A., and Anne Griffin Perry. Fundamentals of Nursing: Concepts, Process, and Practice, 4th ed. St Louis: Mosby-Year Book, Inc., 1997. Taylor, Carol, Carol Lillis, and Priscilla LeMone. Fundamentals of Nursing: The Art of Science of Nursing, 3rd ed. Philadelphia: Lippincott-Raven Publishers, 1997.

Katherine Hauswirth, APRN

Administering medicine to the ear see Ear instillation

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infusion rates and the conversion of measurement units, for example, determining how many milliliters (mL) are required to give the ordered number of milligrams.

Adolescent nutrition

Administering medicine to the eye see Eyedrop instillation

Description

Administering medicine to the nose see Nasal instillation Administering medicine to the rectum see Rectal medication administration Administering medicine to the vagina see Vaginal medicine administration Administering medicine under the tongue see Sublingual and buccal medication administration

Adolescent nutrition Definition Adolescence is a time of increased growth and development, in which a greater need for nutrients coincides with a change in food habits that also influences nutritional needs. Due to differences in body type, physical activity, and rate of growth, every adolescent has different nutritional needs.

Purpose It is important to meet such needs during adolescence or ramifications may extend into adulthood. For instance, because bone mass is accumulated through young adulthood and slows dramatically thereafter, inadequate calcium intake may lead to weaker bones throughout life.

Precautions During adolescence, bodies are rapidly changing and growing, which often causes teens to feel uncomfortable with themselves, especially if they are different from their peers. Teenagers are more likely to miss meals. Emotional distress may cause them to either eat too much or too little and use diet pills or supplements. Such patterns can lead to the development of eating disorders, which are characterized by unhealthy eating behaviors including starvation, induced vomiting, overusing laxatives, and overeating. Eating disorders usually begin between ages 14 and 20 and are estimated to be the third most common chronic disorder among adolescents. It is important to provide early intervention to avoid serious long-term complications. 32

Due to variation in physical activity, metabolism, and growth rate, the nutritional needs of adolescents vary from person to person, and should be based on individual needs. However, general recommendations for adolescents can provide guidance. Caloric needs are usually based on the growth rate and level of exercise and should average between 2,200 and 3,000 calories per day. Protein needs are based on height. To determine individual needs, divide the RDA total of protein by the individual’s height in centimeters. The average is about 0.3 gm/cm of height. Mineral needs increase during adolescence, especially for calcium and iron. Recommended intake of calcium is 1,300 milligrams (mg) per day; iron requirements are about 10-12 mg for males and 15 mg for females. Zinc, which is needed for growth and sexual development, is also needed in adequate amounts. Requirements for zinc are 15 mg for males and 12 mg for females. Vitamin needs increase during adolescence and the need for supplementation can be avoided by providing a well-balanced diet.

Complications Adolescents may also have special needs, such as chronic illness, substance abuse problems, and pregnancy. Drug abuse often interferes with adequate food choices, but the effects of drugs greatly depends on the substance, amount, and the nutritional status of the adolescent. Adolescents with chronic illness may have increased or decreased needs based on individual circumstances. Pregnant teenagers have increased needs, because they are still growing and developing themselves.

Results Poor nutrition in adolescence can have important health consequences in adulthood. Obesity and excessive fat intake increases the likelihood of being an overweight adult and puts the individual at risk for cardiovascular disease and other health problems. Substituting sodas and fruit juices for milk at this time of rapid growth and bone-building may lead to osteoporosis and bone fractures during later years. Too much sugar in the diet causes cavities. A diet heavily dependent on fast food results in decreased energy intake, excess fat and sodium, and a deficiency of calcium, riblofloavin, vitamin A, folic acid, and fiber. A healthy diet in adolescence promotes adequate growth and sexual maturity. A decreased risk of cavities, as well as hypertension and hyperlipidemias in older years, is closely correlated with adequate nutrition during adolescence.

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Adrenal glands

Health care team roles Dietitians play an important role in educating teenagers about eating well-balanced diets to receive the proper amounts of all the nutrients. When complications such as eating disorders are present, dietitians can also provide the nutritional information necessary to treat the disorder. However, psychologists and other mental health professionals should be consulted to assess the mental and emotional status of the individual. Resources BOOKS

Mahan, Kathleen L. and Sylvia-Escott Stump. Krause’s Food, Nutrition, and Diet Therapy. Philadelphia: W.B. Saunders Company, 2000. Worthington-Roberts, Bonnie S. and Sue Rodwell Williams. Nutrition Throughout the Life Cycle, 4th Edition. Boston: McGraw-Hill Companies, Inc., 2000.

Lisa M. Gourley

Adrenal glands Definition Adrenal glands produce and release several different hormones that maintain internal fluid levels, maintain sodium and potassium levels, and mediate the stress response.

Description The human body contains two adrenal glands, one on top of each kidney. The gland is triangular in shape and yellowish in appearance. Subdivisions include the adrenal cortex and the medulla. The cortex is the outer layer and is responsible for the production of steroid hormones called glucocorticoids, mineralcorticoids, and androgens. The medulla forms the inner layer of the adrenal glands and releases norepinephrine and epinephrine (known commonly as noradrenaline and adrenaline) directly into the bloodstream. The adrenal cortex and medulla serve very different functions in the human body because of the different hormones that they produce and release.

Function The adrenal cortex converts cholesterol into glucocorticoids, mineralcorticoids, and androgens. The glucocorticoids are so named due to their role in regulating body glucose levels. The major glucocorticoid produced

Cross section of human adrenal gland (triangular shape). (Photograph by Martin M. Rotker. Phototake NYC. Reproduced by permission.)

by the adrenal is cortisol. Cortisol is also known as the stress hormone because the body releases cortisol in order to help cope with stressful situations. The immediate effects of cortisol are to increase levels of fatty acids, proteins, and glucose in the blood. Cortisol causes these increases by taking protein from muscles, fatty acids from fatty tissues, increasing gluconeogenesis (the process of making glucose), and decreasing the body’s uses of glucose. Thus, in Cushing’s syndrome (hypercortisolism), patients may experience muscle wasting (too much protein is taken from the muscles). Paradoxically, although cortisol increases the levels of free fatty acids, patients with too much cortisol over a long period of time experience an increase in fat on the upper body. Cortisol and other glucocorticoids are also potent inhibitors of the immune system. Thus, it is not too surprising that synthetic glucocorticoids, like prednisone, are used to treat autoimmune diseases and allergies— diseases in which the immune system is too active. The release of cortisol is under the control of the anterior pituitary. The anterior pituitary accomplishes this by releasing the peptide hormone, adrenocorticotropin (ACTH) onto the adrenal gland. The mineralcorticoids are so named due to their role in establishing mineral and water levels in the body. The major mineralcorticoid produced by the adrenal gland is aldosterone (although the glucocorticoid cortisol has some mineralcorticoid activity). The primary role of aldosterone is to regulate the balance of potassium, sodium, and water by affecting the absorption of all three in the kidney. Briefly, aldosterone causes the kidney to reabsorb more water and sodium, while causing potassium to be excreted in exchange for the sodium. When too much aldosterone is produced by the adrenal glands, as in primary aldosteronism, the level of potassium in the

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Adrenal glands

KEY TERMS Adrenal cortex—Outer layer of the adrenal gland that produces steroid hormones. Adrenal medulla—Inner layer of the adrenal gland that releases adrenaline. Androgens—Male sex hormones. Hyperkalemia—An abnormally high level of potassium in the blood. Hypokalemia—An abnormally low level of potassium in the blood. Hypovolemia—An abnormally low volume of blood. Glucocorticoid—A steroid hormone, like cortisol, that affects fat, carbohydrate, and protein levels in the blood as well as regulating the immune response. Mineralcorticoid—A steroid hormone, like aldosterone, that regulates the excretion of salt, potassium, and water.

blood is low (hypokalemia) and the retention of sodium and water is high. Patients can experience hypertension and muscle weakness. When there is too little aldosterone, potassium levels are high and there are extreme water and sodium losses. The loss of water and increased potassium levels can lead to extremely low blood pressure and death. A disease that might result in a loss of mineralcorticoid function is Addison’s disease. In Addison’s disease, the adrenals are usually at least 90% decimated before symptoms arise. The peptide, angiotensin II, and potassium levels are the main control for the release of aldosterone from the adrenals. The adrenal glands also secrete small amounts of androgens such as testosterone. However, in the adult, that amount of androgens produced from a normally functioning adrenal gland is so small that it is unlikely to have a major effect. Nevertheless, pathology of the adrenals may result in abnormally high levels of androgens being secreted. The androgens may cause masculinization in males or females. The adrenal medulla is really an extension of the sympathetic division of the autonomic nervous system. The sympathetic nervous system mediates “fight or flight” responses to environmental stimuli. Sympathetic nerves that originate in the spinal cord release the neu34

rotransmitter, acetylcholine, onto the adrenal glands. The adrenal glands respond by releasing dopamine, norepinephrine, and epinephrine directly into the bloodstream. Norepinephrine and epinephrine are commonly referred to as noradrenaline and adrenaline, respectively. Epinephrine makes up the majority of the substance secreted by the adrenal medulla. Circulating norepinephrine and epinephrine can increase heart rate, constrict blood vessels, dilate eye pupils, inhibit motility and digestion in the stomach and intestines, increase sweating, increase metabolism, and increase breathing. The adrenal medulla is stimulated to release norepinephrine and epinephrine under stressful situations such as exercise or emotional distress.

Role in human health Thus, the adrenal glands play a significant role in mental and physical health. Not only are the adrenal glands vital for maintaining a proper balance of sodium and potassium, they mediate the body’s response to stress, both short-term and long-term. In response to immediate stress, the adrenal glands produce epinephrine, norepinephrine, and the hormone cortisol. The body is prepared for flight or fight, and energy is made available for instant use. In the long term, the adrenal glands may have a negative impact on human health. Prolonged stress can produce undesirable changes in the body that range from immune system depression to fertility complications.

Diseases and disorders Addison’s disease Addison’s disease arises from a hypoactive adrenal cortex. The adrenal cortex fails to produce adequate amounts of the glucocorticoid cortisol, and sometimes the mineralcorticoid aldosterone. A lack of aldosterone causes the kidneys to excrete excess sodium and water while retaining potassium. This can lead to hyperkalemia (high levels of potassium), hypovolemia (low blood volume), and hypotension (low blood pressure). Hyperkalemia may cause fatal heart arrhythmias, and (severe) hypovolemia can lead to shock and kidney failure. Common symptoms include frequent urination, dehydration, fatigue, dizziness, skin discoloration, nausea, vomiting, weakness, and cold intolerance. Treatment includes oral or intravenous glucocorticoids such as prednisone, and, if necessary, administration of the oral mineralcorticoid fludrocortisone acetate to replace aldosterone. The cause of Addison’s disease is not known, but in 80% of the cases there is a wasting or atrophy of the adrenal cortex.

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Conn’s syndrome is also known as primary aldosteronism. In this disease, too much of the mineralcorticoid, aldosterone, is made by the adrenal glands. The increased levels of aldosterone cause excessive potassium excretion while promoting excessive sodium and water retention. This leads to hypertension (high blood pressure) and hypokalemia (low serum potassium). Hypokalemia is an important diagnostic clue in the process of differentiating primary aldosteronism from other similar disorders. In some cases, Conn’s syndrome is due to an adrenal tumor, in which case it may be surgically removed. In other cases, the diuretic drugs, spironalactone or amiloride, are given to block the effects of aldosterone. Cushing’s syndrome The adrenal cortex is overactive in Cushing’s syndrome. The adrenal cortex overproduces glucocorticoids, which can lead to high blood sugar levels and high blood pressure. Symptoms include obesity, muscle wasting, fatigue, irritability, excessive hair growth in women, irregular menstrual cycles, and decreased male fertility. A tumor of the adrenal gland, or an overproduction of ACTH by the pituitary, may cause Cushing’s syndrome. Treatment may include chemotherapy or hormoneinhibiting medications. Pheochromocytoma Pheochromocytomas are tumors of the adrenal glands that secrete large quantities of norepinephrine and epinephrine. The most common symptom is extremely high blood pressure. Treatment is usually surgical removal of the tumor. Resources BOOKS

Guyton A.C. and J.E. Hall. Medical Physiology, 10th edition, Philadelphia, PA: W.B. Saunders Company, 2000. Guyton A.C. Medical Physiology. 8th edition. Philadelphia, PA: W.B. Saunders Company, 1991. PERIODICALS

Hostetter T.H., Rosenber M.E., Ibrahim H.N., and Juknevicius I. “Aldosterone in renal disease.” Current Opinion in Nephrology Hypertension (10 January 2001): 105-110. ORGANIZATIONS

National Adrenal Diseases Foundation. 505 Northern Blvd, Great Neck, NY 11021. (516) 487-4992. .

Susan M Mockus, Ph.D.

Adrenocortical hormone tests Definition Adrenocortical hormone tests measure levels of aldosterone and cortisol (also known as hydrocortisone) in blood and urine. These hormones are synthesized from cholesterol by the action of several enzymes. The cells responsible are located in the outer part (cortex) of the adrenal glands, two small organs, one sitting just above each kidney. As steroid hormones, they are an important part of the body’s endocrine system and help to regulate body functions. The adrenal cortex also produces many other steroid hormones including androgens, primarily dehydroepiandrosterone (DHEA) and androstenedione, that are converted to testosterone and dihydrotestosterone. Aldosterone, a mineralcorticoid, helps regulate the amounts of sodium and potassium in the blood and, because fluid follows sodium, helps maintain fluid balance and blood volume, which, in turn, affect blood pressure. Cortisol, a glucocorticoid, helps regulate the metabolism of proteins, fats, and carbohydrates, especially glucose (sugar). Specifically, cortisol helps convert amino acids (subunits of proteins) into glucose within the liver. It raises blood sugar levels by stimulating the release of glucose from cellular glucose stores and simultaneously acts to inhibit insulin, which moderates glucose transport into the cells. Cortisol also has a number of anti-inflammatory effects, including suppressing the immune system and reducing fever.

Purpose Aldosterone measurement is used to detect aldosteronism (hyperaldosteronism), which is the excess secretion of the hormone by the adrenal glands. It is also used to detect those cases of hypoaldosteronism that occur in the absence of a low cortisol. The cortisol test is performed on patients who are suspected to have malfunctioning adrenal glands. It is considered to be the best indicator of adrenal activity. Blood and urine cortisol measurements, together with the determination of ACTH levels, are the three most important tests in the investigation of Cushing’s syndrome (overproduction of cortisol) and Addison’s disease (underproduction of cortisol). Additional tests called simulation and suppression tests may be needed to detect disease in difficult cases, or to distinguish between the causes.

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Adrenocortical hormone tests

Primary aldosteronism

Adrenocortical hormone tests

Precautions Adrenocorticol function tests may be done on serum or urine. The nurse or phletotomist performing venipuncture should observe universal precautions for the prevention of transmission of bloodborne pathogens. Cortisol levels in blood are subject to diurnal variation. Test results must be evaluated with regard to the time of day the blood was collected. Physicians will determine if patients whose fluid balance may already be compromised by illness can undergo 24-hour urine tests. Physicians will also determine if patients can discontinue taking drugs that control sodium and potassium levels and fluid balance prior to testing. These tests are sometimes performed by a method called radioimmunoassay (RIA) that tags test reagents with radioactive iodide. RIA based tests may be contraindicated for patients who have had recent procedures using radiation or who have had radioactive drugs administered, because results may be altered and unreliable.

Description Aldosterone Aldosterone is produced by the outer area of the adrenal cortex called the zona glomerulosa. Aldosteronism, an increased secretion of aldosterone, can be primary (a malfunction in the adrenal glands or in aldosterone secretion itself) or secondary (caused by another condition). Excessive aldosterone production results in the retention of sodium, and subsequently in fluid retention and high blood pressure (hypertension). Because potassium can be lost in this process, muscle weakness is also a frequent symptom. Primary aldosteronism is most often caused by an adrenal tumor (adenoma) a condition referred to as Conn’s syndrome. Primary aldosteronism can also be idiopathic (of unknown origin) or congenital. Secondary aldosteronism is more common and occurs as a consequence of non-adrenal conditions characterized by severe imbalances in sodium and potassium with resulting fluid imbalance, such as congestive heart failure, cirrhosis (liver disease) with fluid in the abdominal cavity (ascites), certain kidney diseases, excess potassium (hyperkalemia), a sodium-depleted diet, and the toxemia of pregnancy. To differentiate primary aldosteronism from secondary aldosteronism, a plasma renin test should be performed at the same time as the aldosterone assay. Renin, an enzyme produced in the kidneys, is typically elevated in secondary aldosteronism and reduced in primary aldosteronism. Hypoaldosteronism is characterized by low serum sodium, dehydration, and high serum potassium (hyperkalemia). Hypoaldosteronism can occur in Addison’s dis36

ease, which usually is caused by autoimmune damage to the adrenal cortex. Addison’s disease is marked by decreased glucocorticoids and is detected by tests for deficient cortisol production. However, hypoaldosteronism may also occur in the absence of low glucocorticoids. This condition may result from decreased renin production by the kidney, heparin treatment, and a deficiency of an enzyme needed to produce aldosterone. In such cases, serum aldosterone and plasma renin activity must be measured to establish the diagnosis. Cortisol Cortisol and the other glucocorticoid hormones are produced in the zona fasciculata and reticularis of the cortex. Overproduction of glucocorticoids (cortisol) by the adrenal cortex is called Cushing’s syndrome. Excessive cortisol production leads to high blood glucose levels, sodium retention, obesity, and excessive hair growth. Because cortisol production can suppress the immune system, excess levels may also cause chronic infection in some patients. The release of cortisol is controlled by circulating levels of a pituitary hormone, adrenocorticotropic hormone (ACTH). In a complex process, the hypothalamus manufactures corticotropin-releasing hormone (CRH), which, in turn, stimulates the pituitary gland to produce ACTH. While ACTH stimulates the adrenal glands to produce cortisol, rising levels of cortisol act by negative feedback to inhibit further production of CRH and ACTH. Disturbances in this elaborate feedback mechanism can be caused by certain types of stress, such as physical trauma, infection, extreme heat or cold, exhaustion from strenuous exercise, and extreme anxiety. When normal feedback becomes uncoordinated as a result of one of these conditions, excessive amounts of ACTH and, in turn, cortisol will be released. For this reason, cortisol levels in blood can vary considerably with time, a phenomenon called pulse variation. Cushing’s syndrome has four causes. The majority of cases result from the use of cortisol and related compounds for immunosuppression and treatment of inflammatory diseases. This is called iatrogenic hypercortisolism. The next most prevalent cause is Cushing’s disease, also called pituitary Cushing’s. This results from adenomas of the pituitary gland that secrete ACTH. Less commonly, Cushing’s syndrome is caused by adrenal adenoma or carcinoma or by ACTH secreting tumors located outside the pituitary (ectopic ACTH). Primary Addison’s disease results from damage to the adrenal cortex. The most common causes are autoimmune disease and infection. Secondary Addison’s disease is caused by a pituitary deficiency of ACTH. These two

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Measurement Cortisol is routinely measured by most laboratories. The most common method used is enzyme immunoassay. Aldosterone levels are far lower and require a more sensitive method, typically chemiluminescent immunoassay or radioimmunoassay. Measurement of cortisol intermediates such as 11-dexoycortisol and 17-hydroxyprogesterone are used in conjunction with cortisol for the diagnosis of congenital adrenal hyperplasia. In this condition, an enzyme deficiency in the synthetic pathway of cortisol leads to low cortisol and accumulation of one or more steroid intermediates above the block. These compounds are measured by RIA. ACTH is typically measured by RIA because of its low concentration in plasma. Plasma renin is usually measured by determining the activity of the enzyme (renin activity) rather than by immunoassay of the hormone mass because the latter method measures both the active and inactive forms. In the assay, renin acts on angiotensinogen to produce angiotensin I, which is then measured by RIA. Adrenocortical hormone tests are typically performed on blood plasma or 24-hour urine samples. When performed on blood, physicians may request that tests be performed on two samples, each drawn at a different time, to account for fluctuations in hormone levels at different times during the day (diurnal variation). Tests for aldosterone are performed on blood plasma or on a 24-hour urine specimen. Levels of aldosterone peak in early morning and are at half that level by afternoon, making the time of drawing a blood sample significant. To help ensure a more reliable evaluation, two samples may be drawn for testing, one in early morning (8 AM) and one mid-afternoon (4 PM). Diet and posture (upright or lying down) may also cause aldosterone levels to fluctuate, so that a single blood sample may miss increased or decreased levels and may not accurately reflect hormone production. Because a 24-hour urine specimen reflects hormone production over an entire day, it will usually provide a more reliable aldosterone measurement. Elevated blood levels should ideally be confirmed with a 24-hour urine test. Since posture and body position affect aldosterone production, hospitalized patients should remain in an upright position (at least sitting) for two hours before blood is drawn. Occasionally blood will be drawn before

Normal findings for aldosterone assay Blood test Supine Upright Adult female Adult male Newborn 1 week–1 year 1–3 years 3–5 years 5–7 years 7–11 years 11–15 years 24-hour urine test

3–10 ng/dl (0.08–0.30 nmol/L) 5–30 ng/dl (0.14–0.80 nmol/L) 6–22 ng/dl (0.17–0.61 nmol/L) 5–60 ng/dl 1–160 ng dl 5–60 ng/dl 1:160, and in 25% of patients with chronic hepatic cirrhosis. Positive samples should be screened by EIA for antibodies specific to the M2 antigen to confirm the diagnosis of PBC. Antiphospholipid antibody test Reference levels will be dependent on the type of commercial EIA kit used and should be independently established in each laboratory. Antiphospholipid antibodies occur with a prevalence of 40% in patients with SLE. Over 75% of patients presenting with spontaneous abortions were positive for only IgG antibodies, while patients with thromboses had mainly IgM antibodies. IgG and IgM antibodies were found simultaneously in 31% of patients with Sjögren’s syndrome. Cryoglobulin test The percent cryoprecipitation is reported (cryocrit). Although there is considerable overlap, Type I and Type II cyroglobulins, positive in Waldenström’s macroglobulinaemia and in chronic lymphocytic leukemia, are often present in relatively high concentrations, with cryocrits usually > 5%, sometimes as high as 20–40%, especially with Type I cyroglobulins. Type III cryoglobulins generally give a cryocrit of < 1% and are associated with autoimmune diseases, including systemic lupus erythematosus (SLE), rheumatoid arthritis, scleroderma, and Sjögren’s syndrome. Cold agglutinins test A normal titre for cold agglutinins is less than 1:64. Cold agglutinin disease associated with autoimmune hemolytic anemia usually produces titres between 1,000100,000. Higher titers are alwo seen in about 60% of persons with Mycoplasma pneumoniae infections and other acute infectious diseases such as infectious mononucleosis. In cold autoimmune hemolytic anemia, the peripheral blood smear may show red blood cells present in clumps caused by their reaction with cold agglutinins. Some cases of chronic cold agglutinin disease occur in association with Waldenström’s macroglobulinemia. 234

Rheumatoid factor test Normal rheumatoid factor titer for adults is < 1:80 (by particle agglutination) or 60 U/ml (by nephelometry). A positive test may result with chronic hepatitis, chronic viral infection, dermatomyositis, infectious mononucleosis, leukemia, rheumatoid arthritis, scleroderma, or SLE. Adult Still’s disease, chronic infection, juvenile rheumatoid arthritis, nephrotic syndrome, and Sjögren’s syndrome may also give positive results. Reference levels with commercial EIA kits will be dependent on the type of kit used and should be independently established in each laboratory. IgM-type rheumatoid factors are present in 75% of patients with chronic polyarthritis (CP), in 50–65% of patients with interstitial pulmonary fibrosis, in only 30% of patients with mixed connective tissue disease (SLE, Sjögren’s syndrome), and with a prevalence of 10–20% in viral hepatitis, liver cirrhosis, sarcoidosis, and tuberculosis. IgA-class rheumatoid factors can be an early finding in severe rheumatic disease and are also found in SLE patients. Specific determination of IgG class rheumatoid factors, mainly present as immune complexes, have been described in both juvenile and chronic polyarthritis.

Health care team roles A nurse or phlebotomist usually collects the blood sample by venipuncture and sees to the timely and appropriate transport to the laboratory for analysis. A member of the health care team should observe the patient to ensure that bleeding from the puncture site is stopped. Autoimmunity tests are performed by a clinical laboratory scientist/medical technologist. For immunofluorescence assays the technologist will usually have advanced training in fluorescent microscopy and the interpretation of immunofluorescence patterns. A physician interprets the autoantibody test results and uses them in combination with a complete medical history and thorough physical examination to reach a diagnosis. The physicians, nurses, and other caregivers should instruct the patient that diagnosis of an autoimmune disorder is a difficult process that may take considerable time and strive to allay the patient’s feelings of frustration and anxiety. Resources BOOKS

Spickett, Gavin. Oxford Handbook of Clinical Immunology. Oxford, UK: Oxford University Press, 1999.

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Byk-Sangtec Diagnostica GmbH and Co. von Hevesy-Str. 3, D-63128 Dietzenbach, Germany, +49 (0) 6074/401-0. MyLifePath, Blue Shield of California, 2001. . Systemic Lupus Erythematosus. National Arthritis and Musculoskeletal and Skin Diseases Information Clearinghouse, NIAMS/National Institutes of Health, 1 AMS Circle, Bethesda, MD 20892-3675, 1 (301) 4954484. . OTHER

Cryoglobulin - serum. UCSD Medical Center Laboratory Reference website, 2001. . General Health Encyclopedia. HealthCentral.com, 6001 Shellmound St., Suite 800, Emeryville, CA 94608, and adam.com, 2001. . Mellors, Robert C. Autoimmunity and Autoimmune Disease. Immunopathology website. Cornell University Medical College, 2001. . Reeves, Glenn and Maree Gleeson. Cryoglobulins Hunter Immunology Unit website, 1998. .

Patricia L. Bounds, Ph.D.

ent tissues. The disease recurs periodically and is seen mainly in young and middle-aged women. • Rheumatoid arthritis. Occurs when the immune system attacks and destroys the tissues that line bone joints and cartilage. The disease occurs throughout the body, although some joints may be more affected than others. • Goodpasture’s syndrome. Occurs when antibodies are deposited in the membranes of both the lung and kidneys, causing both inflammation of kidney glomerulus (glomerulonephritis) and lung bleeding. It is typically a disease of young males. • Grave’s disease. Triggered by an antibody that binds to specific cells in the thyroid gland, causing them to make excessive amounts of thyroid hormone. • Hashimoto’s thyroiditis. Also referred to as autoimmune thyroiditis and chronic lymphocytic thyroiditis; a chronic inflammatory glandular autoimmune disease. It is caused by an antibody that binds to cells in the thyroid gland. Unlike in Grave’s disease, however, this antibody’s action results in less thyroid hormone being made. • Pemphigus vulgaris. A group of autoimmune disorders that affect the skin. • Myasthenia gravis. A condition in which the immune system attacks a receptor on the surface of muscle cells, preventing the muscle from receiving nerve impulses and resulting in severe muscle weakness. • Scleroderma. Also called CREST syndrome or progressive systemic sclerosis, scleroderma affects the connective tissue.

Autoimmune disorders Definition Autoimmune disorders are conditions in which a person’s immune system attacks the body’s own cells, causing tissue destruction.

Description Autoimmunity is accepted as the cause of a wide range of disorders and suspected to be responsible for many more. Autoimmune diseases are classified as either general (the autoimmune reaction takes place simultaneously in a number of tissues) or organ specific (the autoimmune reaction targets a single organ). Autoimmune disorders include the following: • Systemic lupus erythematosus. A general autoimmune disease in which antibodies attack a number of differ-

• Autoimmune hemolytic anemia. Occurs when the body produces antibodies that coat red blood cells. • Autoimmune thrombocytopenic purpura. Disorder in which the immune system targets and destroys blood platelets. • Polymyositis and dermatomyositis. Immune disorders that affect the neuromuscular system. • Pernicious anemia. Disorder in which the immune system attacks the lining of the stomach in such a way that the body cannot metabolize vitamin B12. • Sjögren’s syndrome. Occurs when the exocrine glands are attacked by the immune system, resulting in excessive dryness. • Ankylosing spondylitis. Immune-system induced degeneration of the joints and soft tissue of the spine. • Vasculitis. A group of autoimmune disorders in which the immune system attacks and destroys blood vessels.

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ORGANIZATIONS

Autoimmune disorders

• Type I diabetes mellitus. May be caused by an antibody that attacks and destroys the islet cells of the pancreas that produce insulin.

Causes and symptoms The symptoms of the above disorders include: • Systemic lupus erythematosus. Symptoms include fever, chills, fatigue, weight loss, skin rashes (particularly the classic “butterfly” rash on the face), vasculitis, polyarthralgia, patchy hair loss, sores in the mouth or nose, lymph-node enlargement, gastric problems, and, in women, irregular periods. About half of those who suffer from lupus develop cardiopulmonary problems, and some may also develop urinary problems. Lupus can also effect the central nervous system, causing seizures, depression, and psychosis. • Rheumatoid arthritis. Initially may be characterized by a low-grade fever, loss of appetite, weight loss, and a generalized pain in the joints. The joint pain then becomes more specific, usually beginning in the fingers, then spreading to other areas, such as the wrists, elbows, knees, and ankles. As the disease progresses, joint function diminishes sharply and deformities occur, particularly the characteristic “swan’s neck” curling of the fingers. • Goodpasture’s syndrome. Symptoms are similar to that of iron deficiency anemia, including fatigue and pallor. Symptoms involving the lungs may range from a cough that produces bloody sputum to outright hemorrhaging. Symptoms involving the urinary system include blood in the urine and/or swelling. • Grave’s disease. This disease is characterized by an enlarged thyroid gland, weight loss without loss of appetite, sweating, heart palpitations, nervousness, and an inability to tolerate heat. • Hashimoto’s thyroiditis. This disorder generally displays no symptoms. If symptoms do occur, it is most often weight gain, intolerance to cold, fatigue, enlarged neck or goiter, and constipation. About 25% of patients may be subject for developing pernicious anemia, diabetes, adrenal insufficiency, or other autoimmune diseases. • Pemphigus vulgaris. This disease is characterized by blisters and deep lesions on the skin. It is associated with other autoimmune diseases, such as systemic lupus and myasthenia gravis. • Myasthenia gravis. Characterized by fatigue and muscle weakness that at first may be confined to certain muscle groups, but then may progress to the point of paralysis. Myasthenia gravis patients often have 236

expressionless faces as well as difficulty chewing and swallowing. If the disease progresses to the respiratory system, artificial respiration may be required. • Scleroderma. Disorder is usually preceded by Raynaud’s phenomenon. Symptoms that follow include pain, swelling, and stiffness of the joints, and the skin takes on a tight, shiny appearance. The digestive system also becomes involved, resulting in weight loss, appetite loss, diarrhea, constipation, and distention of the abdomen. As the disease progresses the heart, lungs, and kidneys become involved, and malignant hypertension causes death in approximately 30% of cases. • Autoimmune hemolytic anemia. May be acute or chronic. Symptoms include fatigue and abdominal tenderness due to an enlarged spleen. • Autoimmune thrombocytopenic purpura. Characterized by pinhead-size red dots on the skin, unexplained bruises, bleeding from the nose and gums, and blood in the stool. • Polymyositis and dermatomyositis. In polymyositis, symptoms include muscle weakness, particularly in the shoulders or pelvis, that prevents the patient from performing everyday activities. In dermatomyositis, the same muscle weakness is accompanied by a rash that appears on the upper body, arms, and fingertips. A rash may also appear on the eyelids, and the area around the eyes may become swollen. • Pernicious anemia. Signs of pernicious anemia include weakness, sore tongue, bleeding gums, and tingling in the extremities. Because the disease causes a decrease in stomach acid, nausea, vomiting, loss of appetite, weight loss, diarrhea, and constipation are possible. Also, because vitamin B12 is essential for the nervous system function, the deficiency of it brought on by the disease can result in a host of neurological problems, including weakness, lack of coordination, blurred vision, loss of fine motor skills, loss of the sense of taste, ringing in the ears, and loss of bladder control. • Sjögren’s syndrome. Characterized by excessive dryness and itching of the eyes and dry mouth. Difficulty swallowing, hoarseness, loss of taste, and severe dental caries may also occur. Other symptoms are fatigue, joint pain, and swelling of the glands. • Ankylosing spondylitis. Generally begins with lower back pain that progresses up the spine. The pain may eventually become crippling. • Vasculitis. Symptoms depend upon the group of veins affected and can range greatly. Some forms of vasculitis may be caused by allergy or hypersensitivity to medications such as sulfa or penicillin, other drugs, toxins, and other inhaled environmental irritants. Other forms

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• Type I diabetes mellitus. Characterized by fatigue and an abnormally high level of glucose in the blood (hyperglycemia). To further understand autoimmune disorders, it is helpful to understand the workings of the immune system. The purpose of the immune system is to defend the body against attack by infectious microbes (germs) and foreign objects. When the immune system attacks an invader, it is very specific—a particular immune system cell will only recognize and target one type of invader. To function properly, the immune system must not only develop this specialized knowledge of individual invaders, but it must also learn how to recognize and not destroy cells that belong to the body itself. Every cell carries protein markers on its surface that identifies it in one of two ways: what kind of cell it is (i.e., nerve cell, muscle cell, blood cell, etc.) and to whom that cell belongs. These markers are called major histocompatability complexes (MHCs). When functioning properly, cells of the immune system will not attack any other cell with markers identifying it as belonging to the body. Conversely, if the immune system cells do not recognize the cell as “self,” they attach themselves to it and put out a signal that the body has been invaded, that in turn stimulates the production of substances such as antibodies that engulf and destroy the foreign particles. In case of autoimmune disorders, the immune system cannot distinguish between “self” cells and invader cells. As a result, the same destructive operation is carried out on the body’s own cells that would normally be carried out on bacteria, viruses, and other such harmful entities. The reasons why the immune systems become dysfunctional in this way is not well understood. However, most researchers agree that a combination of genetic, environmental, and hormonal factors play into autoimmunity. Researchers also speculate that certain mechanisms may trigger autoimmunity. First, a substance that is normally restricted to one part of the body, and therefore not usually exposed to the immune system, is released into other areas where it is attacked. Second, the immune system may mistake a component of the body for a similar foreign component. Third, cells of the body may be altered in some way, either by drugs, infection, or some other environmental factor, so that they are no longer recognizable as “self” to the immune system. Fourth, the immune system itself may be damaged, such as by a genetic mutation, and therefore cannot function properly.

KEY TERMS Autoantibody—An antibody made by a person that reacts with their own tissues. Autoimmune disease—A broad category of related diseases in which the person’s immune system attacks his or her own tissue.

Diagnosis A number of tests that can help diagnose autoimmune diseases; however the principle tool used by doctors is antibody testing. Such tests involve measuring the level of antibodies found in the blood and determining if they react with specific antigens that would give rise to an autoimmune reaction. An elevated amount of antibodies indicates that a humoral immune reaction is occurring. Elevated antibody levels are also seen in common infections. These must be ruled out as the cause for the increased antibody levels. The antibodies can also be typed by class. There are five classes of antibodies and they can be separated in the laboratory. The class IgG is usually associated with autoimmune diseases. Unfortunately, IgG class antibodies are also the main class of antibody seen in normal immune responses. The most useful antibody tests involve introducing the patient’s antibodies to samples of his or her own tissue— if antibodies bind to the tissue it is diagnostic for an autoimmune disorder. Antibodies from a person without an autoimmune disorder would not reacting to “self” tissue. The tissues used most frequently in this type of testing are thyroid, stomach, liver, and kidney.

Treatment Treatment of autoimmune diseases is specific to the disease, and usually concentrates on correction of any major deficiencies. For example, if a gland involved in an autoimmune reaction is not producing a hormone such as insulin, administration of that hormone is required. Administration of a hormone, however, will not restore the function of the gland damaged by the autoimmune disease. The other aspect of treatment is controlling the inflammatory and proliferative nature of the immune response. This is generally accomplished with two types of drugs. Steroid compounds are used to control inflammation. There are many different steroids, each having side effects. The proliferative nature of the immune response is controlled with immunosuppressive drugs. These drugs work by inhibiting the replication of cells

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may be due to infection, parasites, or viral infections. These causes need to be ruled out before considering an underlying autoimmune disorder.

Autopsy

and, therefore, also suppress non-immune cells leading to side effects such as anemia.

Autonomic nervous system see Nervous system, autonomic

Prognosis Prognosis depends upon the pathology of each autoimmune disease, as well as early detection and the ability to put the disease process into remission.

Definition

Health care team roles Health care teams should help patients to understand their illness and treatment plan. With any autoimmune disorder, communication between the patient and doctor is critical, so health care teams should be available to answer questions about the patient’s particular condition, especially what changes and symptoms to expect.

Prevention To date, prevention of many autoimmune disorders is unavailable since the exact causes of the disease are not understood in many cases. Genetic screening of an unborn fetus may be the only method of preventing some autoimmune disorders. Resources BOOKS

Benjamini, Eli, Richard Coico, and Geoffrey Sunshine. Immunology: A Short Course. 4th ed. New York: John Wiley & Sons, 2000. Kendall, Marion D. Dying to Live: How Our Bodies Fight Disease. Cambridge, UK: Cambridge University Press, 1998. Ravicz, Simone, Ph.D. Thriving With Your Autoimmune Disorder: A Woman’s Mind-Body Guide. Oakland, CA: New Harbinger Publications, 2000. Sompayrac, Lauren M. How the Immune System Works. Oxford: Blackwell Science Inc., 1999. PERIODICALS

Weetman, A. P. “Medical Progress: Graves’ Disease.” New England Journal of Medicine 343 (2000): 1236-1248. ORGANIZATIONS

American Autoimmune Related Diseases Association, Inc. National Office. 22100 Gratiot Ave., Eastpointe, MI 48021. (810) 776-3900. .

Crystal Heather Kaczkowski, MSc.

Automatic implantable cardioverter-defibrillator see Implantable cardioverterdefibrillator 238

Autopsy An autopsy is a postmortem assessment or examination of a body to determine the cause of death. An autopsy is performed by a physician educated in pathology. Often this physician also has forensic training.

Purpose Most autopsies advance medical knowledge or provide evidence for legal action. Medically, autopsies may determine the exact cause and circumstances of death, discover the pathway of a disease, and/or provide valuable information to be used in the care of the living. When foul play is suspected, a government coroner or medical examiner performs an autopsy to collect data for legal investigation. This branch of medical study is called forensic medicine. Forensic specialists investigate deaths resulting from violence or occurring under suspicious circumstances. Benefits of research from autopsies include the discovery of new medical information on diseases such as toxic shock syndrome, acquired immunodeficiency syndrome (AIDS), and Alzheimer’s disease.

Precautions When performed for medical reasons, autopsies require formal permission (written consent), from family members or a legal guardian. Autopsies required for legal reasons when foul play is suspected require authorization from a coroner or medical examiner. Such autopsies do not need the consent of next of kin. During the autopsy, very concise notes and documentation must be made for both medical and legal reasons. Some religious groups prohibit autopsies, although special waivers apply where suspicious death occurs.

Description An autopsy is the examination of a deceased human body with a detailed investigation of the person’s remains. This procedure dates back to the Roman era when few human dissections were performed. Autopsies were utilized, however, to determine the cause of death in criminal cases.

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Autopsy A pathologist fills out an autopsy report during an autopsy. (Photograph by Glauberman. Science Source/Photo Researchers. Reproduced by permission.)

At the beginning of the procedure, the exterior body is examined and the internal organs are removed and studied. Some pathologists argue that more autopsies are performed than necessary. However, recent studies show that autopsies can detect major findings about a person’s condition which were not suspected when the person was alive. The growing awareness of the influence of genetic factors in disease has also emphasized the importance of autopsies. Despite the usefulness of autopsies, fewer autopsies have been performed in the United States during the past 10 to 20 years. A possible reason for this decline is concern about malpractice suits on the part of the attending physician, although there are other reasons. Hospitals are performing fewer autopsies because of the expense. Modern technology, such as CT scans and magnetic resonance imaging (MRI), can often provide sufficient diagnostic information. Nonetheless, federal regulators and pathology groups have begun to establish new guidelines designed to increase the number and quality of autopsies being performed. Many experts are concerned that if the number of autopsies increases, hospitals may be forced to charge families a fee for the procedure as autopsies are not normally covered by insurance companies or Medicare. However,

according to several pathologists, the benefits of the procedure for families and doctors justify the cost. In medical autopsies, physicians remain cautious, examining only as much of the body as necessary, taking into account the wishes of the family. It is important to note that in certain circumstances, autopsies can provide peace of mind for a bereaved family.

Preparation If a medical autopsy is being performed, written permission is secured from the family member of record of the deceased.

Aftercare After an autopsy has been completed, the body is prepared for final arrangements according to the family’s wishes, or the funeral director’s instructions.

Complications There is some risk of disease transmission from the deceased. In fact, some physicians may refuse to do autopsies on specific persons because of a fear of contracting diseases such as AIDS, hepatitis, or Creutzfeld-Jakob disease.

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KEY TERMS Acquired immunodeficiency syndrome (AIDS)— A group of diseases resulting from infection with the human immunodeficiency virus (HIV). A person infected with HIV gradually loses immune function, becoming less able to resist immunerelated diseases and cancers, resulting in death. Computed tomography scan (CT scan)—The technique used in diagnostic studies of internal bodily structures in the detection of tumors or dysfunction. This diagnostic test consists of a computer analysis of a series of cross-sectional scans made along a single axis of a bodily structure or tissue that is used to construct a three-dimensional digital image of that structure. Creutzfeld-Jakob disease—A rare, often fatal disease of the brain, characterized by gradual dementia and loss of muscle control that occurs most often in middle age and is caused by a slowacting virus. Hepatitis—Inflammation of the liver, caused by infectious or toxic agents and characterized by jaundice, fever, liver enlargement, and abdominal pain, with abnormal blood chemistry readings. Magnetic resonance imaging (MRI)—A diagnostic tool that utilizes nuclear magnetic energy in the production of digital images of specific atoms and molecular structures in solids, especially human cells, tissues, and organs. Postmortem—After death.

Results In most situations, the cause of death is determined from the autopsy without any transmission of disease. Results of tests performed on samples of tissue and bodily fluids provide information about the cause and mechanism of death. Abnormal results include inconclusive results from the autopsy and transmission of infectious disease during the autopsy. By following proper procedures, these are both highly unusual.

Health care team roles Bodies of persons dying in a hospital are taken to the morgue by hospital attendants. Bodies of persons from any other location are transported by funeral home personnel, coroners, or their assistants. An autopsy is conducted by a physician, usually by one trained in patholo240

gy or forensic science. In some states, a coroner can legally carry out an autopsy. Laboratory personnel process any specimens or samples obtained during an autopsy. Once completed, funeral home personnel transport the remains to another location for burial preparation. Resources BOOKS

Burgess, Samuel B. Understanding Autopsy. Burnsville, NC: Celo Valley Books, 1993. Dix, Jay. Forensic Pathology: A Color Atlas. Boca Raton, FL: CRC Press, 1999. Finkbeiner, J. Autopsy: A Manual & Atlas. Philadelphia: W.B. Saunders, 2001. Iserson, Kenneth B. Death to Dust: What Happens to Dead Bodies? Tucson, AZ: Galen Press Ltd, 2001. Sheaff, Michael T., and Deborah J. Hopster. Post Mortem Technique Handbook. New York: Springer Verlag, 2001. PERIODICALS

Burnett, B.R. “A Shot Through the Window.” Journal of Forensic Science 46(2001): 379-385. Houston, K., K. Hawton, and R. Sheppherd. “Suicide in Young People Aged 15-24: A Psychological Autopsy Study.” Journal of Affective Disorders 63(2001): 159-170. Roger, V.L., et al. “Time Trends in the Prevalence of Atherosclerosis: A Population-based Autopsy Study.” American Journal of Medicine 110(2001): 267-273. Targonski, P., et al. “Referral to Autopsy: Effect of Antemortem Cardiovascular Disease. A Population-based Study in Olmsted County, Minnesota.” Annals of Epidemiology 11(2001):264-270. ORGANIZATIONS

American Academy of Family Physicians, 11400 Tomahawk Creek Parkway, Leawood, KS 66211-2672. (913) 9066000. <www.aafp.org>. American Medical Association, 515 N. State Street, Chicago, IL 60610. (312) 464-5000. <www.ama-assn.org>. American Society of Clinical Pathologists, 2100 West Harrison Street, Chicago IL 60612. (312) 738-1336. <www.ascp.org/index.asp>. College of American Pathologists, 325 Waukegan Road, Northfield, IL 60093. (800) 323-4040. <www.cap.org>. OTHER

American Academy of Forensic Sciences website. <www.aafs.org/>. International Association of Forensic Nursing website. <www.forensicnurse.org>. Johns Hopkins Autopsy Resource. <www.med.jhu.edu/ pathology/iad.html>. Leicester University Virtual Autopsy. <www.le.ac.uk/ pathology/teach/VA/>.

L. Fleming Fallon, Jr., MD, DrPH

Avulsions see Wounds

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B B-cell count see Flow cytometry analysis

Back and neck pain, physical therapy for Definition Physical therapy for back and neck pain is the treatment of this pain using professionally accepted techniques and procedures carried out by a physical therapist.

Purpose The ultimate purpose of physical therapy is to restore normal function to the patient. Such a goal may not be possible, since the persons most likely to experience back pain in the future are those patients who have experienced back pain in the past. Regardless, the physical therapist will seek to ameliorate pain and improve musculoskeletal function to the best of their ability. To reach this goal, the physical therapist may apply various types of therapy to assist in the healing process, ranging from education to electrostimulation therapy to physical manipulation of the spine. Due to the less invasive nature of physical therapy, it may be indicated as an alternative to surgery on the back or neck. Physical therapy may also be prescribed after surgery, either because the surgery did not completely ameliorate the pain, or to ensure the patient achieves maximum benefit from the surgery.

Precautions There are a number of symptoms in patients with low back pain that may require immediate medical attention. These symptoms may indicate that back or neck pain is related to potentially serious non-mechanical or mechanical disease. Non-mechanical disorders that are neurological or organic in nature can cause symptoms of

back pain, but in these cases treatment needs to be directed at the disease, not merely the associated pain. Bowel, bladder, kidney, or gall bladder diseases, some types of cancer, cauda equina syndrome, and other neurological disorders are among the serious conditions that should be screened for and treated directly. If a patient has numbness in the area roughly corresponding to where a person would sit in a saddle (basically, the buttocks) with or without problems urinating, that patient should seek immediate medical attention (these symptoms may be an indication of cauda equina syndromea). Fever, confusion, back pain that occurs mostly at nighttime or when lying down, or problems with urination, bowel movements, or sexual function are other symptoms implicating non-mechanical disease that may also require immediate medical attention. Although the following symptoms may or may not be caused by mechanical disease, patients with sudden severe or increasing weakness, numbness, or tingling should seek immediate medical attention. Other symptoms in conjunction with back pain may also require immediate attention. If any unusual symptoms arise, even should they seem unrelated to back pain, a physician should be consulted. Regardless of the severity of these symptoms, all of them should at the very least be brought to the attention of a physician. Other precautions and contraindications will vary according to the cause of pain, the therapy used, and the presence of other diseases or conditions. Some conditions either related to or coexisting with the pain, such as severe cardiac disturbances or bone weakness due to osteoporosis or other conditions, may contraindicate exercise. Modalities, such as electrical stimulation techniques and thermal modalities, have their own sets of precautions. Conditions that may contraindicate the use of electrical stimuli include thrombophlebitis, cardiac demand pacemaker, disturbances in cardiac rhythm, local inflammation or infection, and cancer. The use of heat may not

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be indicated immediately after an injury, and should always be used with special caution to prevent burns. Electrical, heat, and cold therapies may all be contraindicated for use on sensory-impaired areas. Ultrasound should not be used on tissues with metal implants, because of its deep heating properties. Manipulation techniques can aggravate disk problems, or cause compression fractures in patients with osteoporosis. The physical therapist needs to be familiar with any risks involved with each condition and modality. A doctor’s diagnosis is often recommended prior to beginning treatment, and the physical therapist needs to make a careful diagnosis in order to make appropriate treatment choices.

Description Physical therapy treatment, also called physiotherapy, is performed by, or under the supervision of, a physical therapist. A physical therapist may have a baccalaureate, masters, or doctoral degree in physical therapy, and is required to pass a national licensure exam. Physical therapy treatment includes a wide range of exercises, procedures and modalities. However, patient education is also an extremely important part of the practice of physical therapy. According to an American Physical Therapy Association (APTA) patient education brochure on back pain, “the patient is the most important participant in the healing and prevention process.” The physical therapist can instruct correct posture and safe ways of performing activities of daily living (ADLs) and other tasks. Additionally the physical therapist can show the patient various kinds of exercise that promote relaxation, relieve pain, and improve the condition of the muscles and other tissues surrounding the spine. Patient education may extend the benefits of treatment by helping the patient to self-manage pain and avoid re-injury or recurrence of acute pain and injury. Avoiding re-injury is a goal of special importance, since most people who have one episode of back pain are likely to have another. Before treatment begins, the patient’s problem must be evaluated. Very often, a physician will have referred a patient to physical therapy. Physical therapy may be the lone method of treatment, or may be used in combination with medication, surgery, or other types of treatments. After the role of physical therapy is determined, the patient will be evaluated by the physical therapist. Evaluation includes an interview with the patient to assess the patient’s medical history, and activities that affect the condition. After the interview, the therapist will proceed with a musculoskeletal exam to assess the patient’s spinal movements, posture, muscular strength, and response to repeated movements. Any additional 242

tests considered necessary for a diagnosis will be performed. The physical therapist will then provide a diagnosis of the condition and a prognosis. The prognosis includes the predicted level of improvement, goals, and the time needed to achieve them. Then an individualized treatment plan will be designed and implemented. Treatment plans may vary widely from physical therapist to physical therapist for the same patient. Patients may wish to seek advice from a different therapist if their condition does not improve under the first therapist’s care. Back and neck pain can have many causes, such as: injury caused by accident or misuse, disease, general strain, postural problems, or just simple wrong movement. Specific causes of back or neck pain can include sprained ligaments, muscle strain, disk problems, joint irritation, arthritis, congenital disorders, psychological stress, spinal stenosis, osteoporosis, compression fractures, and various other conditions (non-mechanical causes of back pain have been discussed briefly in “Precautions”). Due to the large number of causes for back pain, it should not come as a surprise that there are a large number of therapies that address back and neck pain. Exercise is generally considered an essential part of the physical therapy regime. Different kinds of exercise are used according to the condition and the stage of recovery. Some controversy surrounds what types of exercise to use, perhaps depending on the cause of the back pain as well as other factors. Individual exercises may seek to increase one or more of the following: flexibility, range of motion, overall aerobic conditioning, and muscle strength. According to recent guidelines suggested by Malanga and Nadler, tolerable exercise is superior to bed rest for back pain. Bed rest and inactivity have been shown to weaken muscles and bones (a phenomenon known as deconditioning), and may prolong or interfere with recovery. Exercise, in general, increases strength and flexibility of the muscles and aids in healing by increasing blood flow to the affected area. Aquatic therapy is among the exercise options available to physical therapy patients. This form of exercise has the benefits of being low-impact and gentle on joints. As a supplement to whatever forms of guided exercise are chosen by the therapist and patient, the patient is also likely to be given a home exercise program to perform independently. Another type of treatment the physical therapist may use is manual therapy. Manual therapy is defined in the APTA’s Guide to Physical Therapist Practice, Second Edition as “skilled hand movements intended to improve tissue extensibility; increase range of motion; induce

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Although mobilization and manipulation have changed from the time of Hippocrates (460–355BC), they remain important techniques today (along with other forms of manual therapy). There are a large number of manipulation and mobilization techniques available to physical therapists, based on a number of different “schools of thought.” Many of these therapies have scientific evidence supporting their efficacy, and many do not. In part because there are so many different types of manipulation, the techniques, and the level of familiarity with different techniques, can vary widely from one physical therapist to the next. The most well-known forms of manipulation are those performed by chiropractors. Although physical therapists can be trained to perform the same manipulations as chiropractors, historically, physical therapists sought to use terminology such as mobilization to differentiate themselves from the chiropractic community. Part of this impetus was based on the bias against chiropractors found in allopathic physicians. However, the APTA has recently moved toward reclaiming the term manipulation as part of the physical therapy lexicon.

that much of the force being applied to the patient would be absorbed by non-spinal structures (e.g. the hips). Most importantly, patients who receive this kind of traction do not improve compared to those who do not receive this kind of therapy. IMT seeks to avoid these complications by applying intermittent (occasional) force a few times a week directly to the area of interest. A hip belt or a neck harness, and the immobilization of the upper body allow force to be applied more directly. The intermittent nature of the force prevents excessive muscle spasm, and the patient is spared the potentially harmful effects of bed rest. Modalities, or passive physical therapies, do not require the patient to participate. These methods usually employ some special equipment that can apply heat, cold, electricity, or other elements or forms of stimulation to the patient. One such modality would be applications of cold using ice packs or a cryo-stimulation device. Heat can be applied using diathermy (for dry heat), hydrocollator packs (for moist heat) or a heating pad. Ultrasound uses sound waves to create a deep heating effect. Electrical muscle stimulation (EMS) is used to exercise and strengthen specific muscle groups, while TENS (transcutaneous electrical nerve stimulation) units provide therapeutic nerve stimulation to reduce pain. Physical therapy services are often covered by medical insurance. The patient may want to ask the physical therapist to check with the insurance company to see what services and how many treatments are covered. Physical therapy is generally a cost-effective form of treatment, and if can be used to avoid surgery, then the expense of surgery and a hospital stay is also avoided.

Traction has also advanced since the time of Hippocrates. In the modern era, traction to the neck or low back may be applied as steady traction, or as intermittent motorized traction (IMT). The goal of traction in both cases is to correct physical deformities of the spine. Some modern traction practitioners speculate the benefit from traction is derived from pulling the intervertebral disk back into the intervertebral space (due to the force exerted on the spine).

The patient should provide all appropriate medical records for the physical therapist to review. The patient may also wish to keep a journal before attending physical therapy, detailing times and activities that cause pain.

In steady traction (for the low back) weights are applied to the ankles and patients are required to remain in bed, flat on their backs, for a significant period of time (weeks). The constant nature of the traction, and the way in which it was applied, led to a number of important disadvantages. First, bed rest is not recommended for general back health (as previously discussed). Second, the patient’s muscles might spasm, which would cause less force to be applied to the spine, the structure of interest. Third, the apparatus and the position of the patient means

Since physical therapy focuses on patient education, the patient may be better equipped after the physical therapy program to pursue self-care through proper posture and performance of activities, and by continuing a home exercise program. According to an APTA patient education guide, the goal of physical therapy is to help the patient return to normal activities as soon as possible and to teach the skills needed to avoid re-injury. The patient will not necessarily require additional episodes of therapeutic care.

Preparation

Aftercare

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relaxation; mobilize or manipulate soft tissue and joints; modulate pain; and reduce soft tissue swelling, inflammation, or restriction.” Manual therapy techniques include various forms of massage, manual traction, mobilization and manipulation of the soft tissues and joints, and passive range of motion movements. Manual therapy has a long and storied history. The first mention of manual therapy in Western culture can be traced to Hippocrates, who wrote several treatises on joint manipulation and traction (traction, in the context of back and neck physical therapy, is the extension of the spine using force).

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Results

KEY TERMS Co-morbidity—A disease or condition that coexists with the disease or condition for which the patient is being primarily treated. Disk (disc)—Soft, flexible, shock-absorbing material between each vertebra. Modalities—Passive physical therapies that are done to the patient rather than requiring their active involvement. These may not require constant attendance by the physical therapist. Soft tissue/joint mobilization—Application of specific stretching techniques to the body’s soft tissues and joints. Spinal stenosis—A condition caused by the narrowing of the spinal canal leading to compression of nerves in the back. Ultrasound—A treatment modality that uses high frequency sound waves to effect deep heating of soft tissue.

Complications

Health care team roles Physical therapists may work together with physical therapist assistants and aides, physicians, nurses, social workers, occupational therapists, or other health care professionals. Doctors may provide a diagnosis and prescription for physical therapy and recommend duration or types of therapy. The physical therapist assistant, under the physical therapist’s direction and supervision, may undertake various aspects of the patient’s treatment. Occupational therapists and social workers may also work with the patient to supplement physical therapy’s role in the patient’s return to normal life and work or adaptation to disability. Resources

Possible complications related to physical therapy treatments for back and neck pain depend on the cause of pain, other conditions present, and the type of interventions used. In general, physical therapy is a safe, gentle treatment option designed to work in harmony with the body’s natural structure and movement mechanisms. Severe complications are not common, as long as the diagnosis and plan of care are accurate and carefully made. The therapist should be aware of possible complications related to exercise in general, as well as those involved with various primary and co-existing conditions, and with any of the modalities used. Some forms of manipulation can lead to injury in the case of bone weakness or other pathological conditions. Patients whose conditions cause excessive fatigue should be monitored closely during exercise. If the precautions or contraindications relating to the patient’s condition, evaluation, medical history, and diagnosis are properly attended to and procedures used are observed, the risk of complications will be minimized. The patient may feel some additional pain or soreness when beginning exercise, but this should be mild and temporary. In rare cases, the patient may have an allergic reaction to gels and creams used in ultrasound or massage. 244

Results vary widely based on the cause of the dysfunction, the therapy used, and the skill of the therapist. The goal of returning patients to their original level of function may not occur. However, since physical therapy focuses on patient education, the patient may be better equipped after the physical therapy program to pursue self-care through proper posture and performance of activities, and by continuing a home exercise program.

BOOKS

APTA. Guide to Physical Therapist Practice, Second Edition. American Physical Therapy Association, 2001. Paris, S.V., and P.V. Loubert. Foundations of Clinical Orthopedics Seminar Manual, Institute Press, 1999. PERIODICALS

Lewis, Carol. “What to Do When Your Back Is in Pain.”FDA Consumer (March/April 1998). Malanga, G.A., and Nadler S.F. “Nonoperative treatment of low back pain.” Mayo Clinic Proceedings 74 no. 11 (November 1999): 1135-1148. ORGANIZATIONS

Academy of Orthopaedic Surgeons. 6300 North River Road. Rosemont, Illinois 60018-4262. (800) 346-AAOS. . American Physical Therapy Association (APTA). 1111 North Fairfax Street. Alexandria, VA 22314. (703) 684-2782. (800) 999-2782. . McKenzie Institute USA. 600 E. Genesee St., Ste. 124. Syracuse, NY 13202. [email protected]. (800) 635-8380. www.mckenziemdt.org. OTHER

The Agency for Health Care Policy and Research. Acute low back problems in adults. .

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Agency for Health Care Research and Quality. Care for Acute Low Back Pain. . Campo, Marc MS, PT, Cert. MDT. The McKenzie System. . Cluett, Jonathan, M.D. Back Pain: Information About Common Causes of Back Pain. . How a physical therapist can help with exercise. . Mayo clinic web-site. . National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) Web page. . Poesnecker. Traction-motorized. .

Bacillus

Tetrads

Diplobacillus

Sarcinae

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Vibrios

Staphylococcus Spirilla

Diane Fanucchi, C.M.T., C.C.R.A.

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Spirochete

Morphology and arrangement of bacterial cells. (Delmar Publishers, Inc. Reproduced by permission.)

Definition Bacteria are prokaryotes (unicellular organisms with no membrane-enclosed nucleus) with simple structures that typically range in size from about 0.5 to 20 micrometers.

Description Classification Bacteria are named according to the binomial (twoname) system of nomenclature first used by Swedish botanist Carolus Linnaeus in the eighteenth century. The first name, or generic name, indicates the genus of the bacteria (a group of closely related species). The second name, or specific name, indicates the species (a group of bacteria that share a number of characteristics). Examples of generic names include Staphylococcus and Esherichia; aureus and coli are examples of specific names.

various shape and complexity. Acetobacter aceti, for example, excretes a substance called cellulose that surrounds the cells to form a skinlike layer. Staphylococcus aureus forms grapelike clusters of cells. Many groups of bacteria have a cell wall, a structure surrounding the cell. Peptidoglycan (a chemical composed of carbohydrates and proteins) is a major component of the cell wall, although the exact composition of peptidoglycan varies according to bacteria group. Grampositive organisms have a relatively thick layer of peptidoglycan and stain violet when applied with certain dyes; gram-negative organisms have a thin layer of peptidoglycan covered by an outer membrane and stain red under the same application of dyes. Gram staining is therefore an important method for identifying bacteria.

The genus and species names of bacteria often reflect their shape; for example, the Bacillus family of bacteria are bacilli- or rod-shaped. Others are named for their founders (e.g. Yersinia pestis, the causative agent of bubonic plague, is named for Alexandre Yersin) or for their preferred habitat (e.g., Thermoplasma prefer temperatures up to 149°F, or 65°C).

Bacteria may be classified by their biochemical composition, and analysis of the protein and lipid content of an organism is often a means of identification. Growth requirements are often used as a means of classification: Mycobacterium tuberculosis, for example, is an obligate aerobe and therefore requires oxygen for growth, while the presence of oxygen is toxic to the anaerobe Clostridium tetani.

Under a microscope, different families of bacteria have different shapes. Typical cell shapes are straight rods (bacilli), spheres (cocci), bent or curved rods (vibrios), spirals (spirochetes), or thin filaments. Some bacteria exist as single cells, while others form clusters of

The most precise method of classification, however, is genetic analysis. Each species of bacteria has a unique genetic makeup, and therefore a unique sequence of deoxyribonucleic acid (DNA) bases. Some sequences remain constant by genus or species, while others vary

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considerably. These distinguishing factors are used to trace genetic relatedness and are often used for identification of unknown organisms. Bacterial structure Although prokaryotic organisms such as bacteria are considered to be “simple” in structure, each cell is equipped with all of the structures and macromolecules necessary for growth and survival. Complex functions such as energy production, synthesis of biomolecules, and assembly of new structures take place in a highly organized manner. The genetic material of bacteria is carried on doublestranded molecules of DNA (deoxyribonucleic acid), which is arranged into a circular structure called the chromosome. The region of the cytoplasm where the chromosome is located is called the nucleoid and is not enclosed by a membrane, as in eukaryotic cells. Many bacteria carry additional genetic information (often required for survival in specific environments) on structures called plasmids, smaller circular strands of DNA that are independent of the chromosome. Also found in the cytoplasm are ribosomes, small cellular components important in the process of translating genetic information into proteins. The total collection of genes is called the bacterial genome. Directly bordering the cytoplasm of the bacteria is the cytoplasmic membrane, which is important for various functions such as energy production and transport of materials in and out of the cell. The cell wall surrounds the cytoplasmic membrane of most bacteria. In gram-negative organisms, the cell wall is composed of a thin layer of peptidoglycan enclosed by an outer membrane. Lipopolysaccharide (LPS; also called endotoxin) is a major constituent of the outer membrane. The cell wall of gram-positive bacteria is distinctly different. Multiple peptidoglycan layers envelop the cytoplasmic membrane, and no outer membrane is present. The peptidoglycan layers form a meshlike shell around the cell that is important for maintaining structure, for replication, and for protection in extreme or toxic conditions. Proteins, lipids, and polysaccharides may also be found in the cell wall. Many bacteria have additional means of protection in hostile conditions. Some have the ability to form a capsule, layers of polysaccharides and proteins attached to the cell wall, that provides protection against toxic substances and helps inhibit host immune response. Spores are made by some gram-positive bacteria. Under favorable conditions, the cells exist in a vegetative state; but when introduced to a hostile environment, the cells convert to a spore state and become dormant, awaiting conditions in which they may once again prosper. 246

The flagellum is a filamentous structure attached to many prokaryotes that provides motility. With flagella, bacteria may move toward food and away from toxins, a process called chemotaxis. Pili are hairlike structures shorter than flagella found on many bacteria; they are used for adherence to other bacteria and surfaces such as host cells.

Function Energy requirements for growth All living organisms must find in their environment a source of energy to fuel cellular processes. Bacteria are no different. Phototrophs are organisms that use light as an energy source; those that require organic carbon are called heterotrophs. Autotrophs use carbon dioxide. Lithotrophs oxidize inorganic compounds such as hydrogen or ammonia for energy. Many bacteria have structures and processes that allow them to adapt to hostile environments, and they can exist under an enormous range of conditions. Those that require oxygen for growth are called obligate aerobes. In contrast, obligate anaerobes will not grow in the presence of oxygen. Acidophiles are bacteria that grow optimally under acidic conditions (pH of less than 7.0), while alkaphiles prefer alkaline or basic conditions (pH of greater than 7.0). Organisms that require a temperature near 99°F (37°C) (the body temperature of warmblooded animals) for growth are called mesophiles; those that grow at temperatures above 113°F (45°C) are called thermophiles; and psychrophiles are able to grow at temperatures near 32°F (0°C). Halophiles require sodium chloride (salt) for growth; osmophiles are able to grow in environments high in sugar; and xerophiles grow under dry conditions. Binary fission and the growth curve Bacteria grow and replicate in a process known as binary fission. In this process, one parent cell divides to produce two daughter cells. The process begins with the growth of the parent cell; the chromosome unwinds and replicates, each copy moving to opposite ends of the cell. The cell is then partitioned in half by the production of a dividing wall (called the septum). The cell is cleaved at the septum, and the two daughter cells are freed. The daughter cells then go on to reproduce as parent cells (i.e., if necessary nutrients and energy sources are present). The dynamics of a population of bacteria change during binary fission. The doubling time, or time required for one parent cell to produce two daughter cells, varies by bacteria species and strain and also by the

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environmental conditions. All bacteria exhibit a characteristic pattern of growth when introduced to a new medium; this is known as the growth curve. There are four phases of the growth curve: • During the lag phase, bacteria are adapting to the medium and begin to produce the cellular components necessary for cell division. There is no increase in cell population during the lag phase. • Cell division occurs at a maximal rate during the log or exponential phase. The doubling time remains constant, so the number of cells increases exponentially. • Cells stop growing exponentially and therefore remain constant during the stationary phase. This occurs when the medium begins to run out of the nutrients necessary for growth or when toxic products accumulate. • The number of cells begins to decrease during the death phase as cells begin to die, usually due to toxic conditions or lack of nutrients.

Role in human health Normal flora Only a small percentage of the vast population of bacteria is pathogenic (disease-causing) to humans. Many species of bacteria colonize the human body and are called the normal flora. Organisms of the normal flora are normally found on surface tissues (i.e., the skin, mucous membranes, and the gastrointestinal system). It is when bacteria enter normally sterile areas of the body (e.g., the brain, blood, muscle, etc.) that disease may result. Some organisms of the normal flora neither harm nor provide benefit to the human body; this relationship is called commensalism. Normal commensals are bacteria that can always be found on or in healthy individuals and rarely cause disease. Bacteria that occasionally colonize the human body without causing disease are called occasional commensals. Although a human fetus is sterile in utero, colonization with normal flora bacteria begins with birth when the baby comes into contact with the mother’s vaginal bacteria; this continues with breastfeeding and subsequent contact with the environment. Many other types of bacteria interact with the human body in a relationship called mutualism, from which both organisms benefit. There are a number of ways that bacteria benefit the human host: • Normal flora bacteria on the skin such as Staphylococcus epidermidis protect against colonization by path ogenic bacteria, through a process called microbial competition.

Transmission electron micrograph (TEM) of a Group A Streptococcus bacterium. (Custom Medical Stock Photo, Inc. Reproduced by permission.)

• Bacteria in the vagina (e.g., Lactobacillus acidophilus) help to establish an acidic environment that inhibits colonization of pathogenic bacteria and yeast. • The normal flora in the gastrointestinal (GI) tract (e.g., Escherichia coli) secrete vitamins such as K and B12 that are essential for humans. The development of some GI tissues is stimulated by normal flora bacteria. • Ruminants (animals with a four-chambered stomach) rely on enzymes secreted by bacteria such as Ruminococcus albus to digest cellulose (a major component of plant cell walls). Pathogenic bacteria Although normal flora bacteria are not normally pathogenic, disease may result from invasion of normal flora into normally sterile areas or if the host immune system is deficient. When bacteria that normally reside in the GI tract (such as E. coli) are introduced to the urinary tract, for example, a urinary-tract infection may result. This is considered an endogenous infection. Exogenous infections result from invasion of noncommensal organisms (i.e., those not normally found on the human body). Transmission of exogenous bacteria may occur by various routes, including inhalation of aerosolized organisms, ingestion (e.g., contaminated food or utensils), or direct contact of a wound or mucous membrane with organisms. When bacteria first enter the body, local inflammation may be the first sign of infection. Physical symptoms such as pain, erythema (redness), edema (swelling), or pus formation result from the response of the immune system against the invading bacteria. If the bacteria spread to the bloodstream (bacteremia), they may disseminate to and colonize at various sites in the body.

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KEY TERMS Antibiotics—Chemicals produced by microorganisms that inhibit bacterial growth or kill bacterial cells. Binary fission—The process by which a single parent cell divides to produce two identical daughter cells. Flagellum—A filamentous structure attached to some bacteria that provides motility. Gram-negative—A class of bacteria that have a cell wall composed of a thin layer of peptidoglycan surrounded by an outer membrane made of polysaccharides and proteins. Gram-positive—A class of bacteria that have a cell wall composed of a thick layer of peptidoglycan. Growth curve—A characteristic growth pattern of bacteria when introduced into a new medium; it includes four phases (lag, log, stationary, and death). Normal flora—Species of bacteria that colonize the human body and do not normally cause disease. Nucleoid—Cytosolic region of a bacterial cell in which the chromosome is located. Pathogen—A disease-causing microbe. Peptidoglycan—A chemical composed of carbohydrates and proteins that is a major component of the bacterial cell wall. Prokaryote—A unicellular organism lacking a membrane-enclosed nucleus. Ribosome—A cytosolic structure important in the translating of genetic information into proteins. Toxins—Proteins produced by bacteria that are toxic to host cells. Endotoxin is a component of the cell wall of gram-negative bacteria; exotoxin is secreted by both gram-negative and gram-positive bacteria.

• Bacterial growth. The byproducts of normal bacterial growth may cause tissue destruction if colonization has occurred in a normally sterile site. For example, Clostridium perfringens is a normal flora bacteria of the GI tract but may cause gas gangrene if it infects a wound or trauma site. • Release of toxins. Some pathogenic bacteria produce proteins (toxins) that are inevitably toxic to the host. An endotoxin is composed of lipopolysaccharides found in the outer membrane of gram-negative bacteria. Exotoxins are proteins produced intracellularly and secreted by either gram-negative or gram-positive bacteria. • Capsule formation. The polysaccharide layers of a capsule form a protective shield around a bacteria and help the cell to evade immune response. • Internalization. Some bacteria are able to escape intracellular killing when internalized by phagosomes and go on to survive in the cytoplasm (e.g., Mycobacterium tuberculosis). In this way they are protected from antibody-mediated immune responses. • Granuloma formation. A granuloma is a lesion formed in response to infection by some intracellular pathogens. Viable bacteria are walled off in the granuloma and thus prevented from further colonization. • Antigenic mimicry. A bacterial cell may be able to trick the immune system by presenting antigens (molecules recognized by antibodies) that are similar to host antigens. Immunological cells therefore have difficulty distinguishing between the bacterium and a host cell. Antibiotic resistance The emergence of bacterial strains that are resistant to treatment by current antibiotics is an important public-health concern. Antibiotics are chemical substances produced by microorganisms that inhibit bacterial growth or kill bacterial cells. Narrow-spectrum antibiotics target only a limited variety of bacteria, while broad-spectrum antibiotics have the ability to inhibit or kill a wide variety of bacteria. Bacteria can resist the action of antibiotics using one or more of four basic mechanisms: • inactivation or modification of the drug • modifying the drug’s target binding site

VIRULENCE FACTORS. Bacteria have developed

numerous mechanisms that allow them to invade a host and colonize an otherwise inhospitable site to cause disease. Many of these mechanisms enhance their ability to cause disease in humans; such traits are called virulence factors. Some common virulence factors include: 248

• decreasing uptake of the drug into the cell • altering the biochemical pathway that the drug is targeting In many developing countries, antibiotics are freely distributed as over-the-counter drugs, leading to their

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Common diseases and disorders The following list describes some of the most common bacteria that are pathogenic to humans. • Staphylococcus. Staphylococci are gram-positive bacteria found as part of the normal flora of most individuals. S. aureus is the causative agent of many infections, including toxic shock syndrome (TSS), staphylococcal food poisoning, impetigo, and furuncles (boils). S. saprophyticus causes urinary-tract infections in sexually active women. S. epidermidis may infect damaged or artificial heart valves and cause a condition called endocarditis. • Streptococcus. Streptococci are gram-positive bacteria that commonly colonize the oropharynx (the area of the throat at the back of the mouth). Example syndromes include pharyngitis (sore throat), scarlet fever, necrotizing fasciitis (streptococci are popularly known as the “flesh-eating bacteria”), and rheumatic fever. S. pneumoniae is a common cause of bacterial pneumonia and meningitis. • Neisseria. N. gonorrhoeae is the causative agent of gonorrhea, a leading sexually transmitted disease (STD). N. meningitidis is a leading cause of adult meningitis. • Escherichia. E. coli is the most commonly encountered species of this genus. The bacteria is a common cause of gastroenteritis (inflammation of the lining of the stomach and intestines) but also causes urinary-tract infections and neonatal meningitis. • Salmonella. Most Salmonella infections result from ingestion of contaminated food and lead to enteritis. The febrile (fever-inducing) illness typhoid fever is caused by S. typhi. • Vibrio. The most commonly known Vibrio infection is cholera, caused by V. cholerae. Spread by ingestion of contaminated food or water, cholera infection is an important cause of diarrheal disease in developing countries. • Clostridium. C. perfringens causes a variety of human diseases, including myonecrosis (gas gangrene), clostridial food poisoning, and soft-tissue infections (cellulitis and fasciitis). Tetanus (also known as lockjaw) is caused by C. tetani; C. botulinum causes foodborne botulism.

• Mycobacterium. Tuberculosis, caused by infection with M. tuberculosis, is a highly prevalent pulmonary disease. Hansen’s disease (also known as leprosy) is caused by M. leprae. • Chlamydia. Chlamydiae, once thought to be viruses because of their small size, cause numerous human diseases. C. trachomatis is the causative agent of conjunctivitis (inflammation of the outer surface of the eye), infant pneumonia, and urogenital chlamydia. Bronchitis, pneumonia, and sinusitis are often caused by C. pneumoniae. Resources BOOKS

Bergquist, L. M., and B. Pogosian. Microbiology Principles and Health Science Applications. Philadelphia: W. B. Saunders, 2000. Lengeler, J. W., G. Drews, and H. G. Schlegel, editors. Biology of the Prokaryotes. Malden, MA: Blackwell Science, 1999. Murray, P. R., K. S. Rosenthal, G. S. Kobayashi, and M. A. Pfaller. Medical Microbiology. St. Louis: Mosby, 1998. Williams, P., J. Ketley, and G. Salmond, editors. Bacterial Pathogenesis. San Diego: Academic Press, 1998. PERIODICALS

Hawkey, P. M. “The Origins and Molecular Basis of Antibiotic Resistance.” British Medical Journal (September 5, 1998): 657-660. Mitchell, T. J. “Molecular Basis of Virulence.” Archives of Diseases in Childhood (March 1998): 197-199. ORGANIZATIONS

American Society for Microbiology. 1752 N Street NW, Washington, DC 20036. (202) 737-3600. .

Stéphanie Islane Dionne

Bacterial meningitis see Meningitis

Balance and coordination tests Definition Balance is the ability to maintain the center of gravity over the base of support, usually while in an upright position. Coordination is the capacity to move through a complex set of movements that requires rhythm, muscle tension, posture, and equilibrium. Balance and coordination depend on the interaction of multiple body organs and

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widespread use for viral or noninfectious illnesses. This practice, coupled with the overuse of antibiotics in veterinary medicine, farming, and plant culture, has contributed to the spread of antibiotic-resistant bacteria.

Balance and coordination tests

practitioner should first evaluate the patient’s static and dynamic balance before leaving the patient unattended.

Description Assessment of balance and coordination can include discussion of the patient’s medical history and a complete physical examination including evaluation of the heart, head, eyes, and ears. A slow pulse or heart rate, or very low blood pressure may indicate a circulatory system problem, which can cause dizziness or fainting. During the examination, the patient may be asked to rotate the head from side to side while sitting up or while lying down with the head and neck extended over the edge of the examination table. If these tests produce dizziness or a rapid twitching of the eyeballs (nystagmus), the patient may have a disorder of the inner ear, which is responsible for maintaining balance. An examination of the eyes and ears may also provide clues to episodes of dizziness or incoordination. The patient may be asked to focus on a light or on a distant point or object, and to look up, down, left, and right moving only the eyes while the eyes are examined. Problems with vision may, in themselves, contribute to balance and coordination disturbances, or may indicate more serious problems of the nervous system or brain function. Hearing loss, fluid in the inner ear, or ear infection might indicate the cause of balance and coordination problems. A patient sits on a ball, working on his balance. He wears a belt so that the physical therapist can catch him if he loses balance. (Custom Medical Stock Photo. Reproduced by permission.)

systems including the eyes, ears, brain and nervous system, cardiovascular system, and muscles. Tests or examination of any or all of these organs or systems may be necessary to determine the causes of loss of balance, dizziness, or the inability to coordinate movement or activities.

Purpose Tests of balance and coordination, and the examination of the organs and systems that influence balance and coordination, can help to identify causes of dizziness, fainting, falling, or incoordination.

Precautions Tests for balance and coordination should be conducted in a safe and controlled area where patients will not experience injury if they become dizzy or fall. The 250

Various physical tests may also be used. A patient may be asked to walk a straight line, stand on one foot, or touch a finger to the nose to help assess balance. The patient may be asked to squeeze or push against the doctor’s hands, to squat down, to bend over, or stand on tiptoes or heels. Important aspects of these tests include holding positions for a certain number of seconds, successfully repeating movements a certain number of times, and repeating the test accurately with eyes closed. The patient’s reflexes may also be tested. For example, the doctor may tap on the knees, ankles, and elbows with a small rubber mallet to test nervous system functioning. These tests may reveal muscle weakness or nervous system problems that could contribute to incoordination. As ergonomics becomes a major emerging practice area in occupational therapy, balance and coordination is increasingly analyzed in workplace evaluations. Good balance and coordination, such as finger dexterity, may be needed for a worker to properly complete a specific task in his or her job. Assessments used to determine coordination include the Crawford Small Parts Dexterity Test, Bennettt Hand-Tool Dexterity Test, Purdue Pegboard, and the Minnesota Rate of Manipulation Test.

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Test Alternate heel to knee and heel to toe Alternate nose to finger

Drawing a circle Finger to finger Finger to nose

Finger opposition Finger to therapist’s finger

Fixation or position holding Mass grasp Pronation/supination

Rebound test

Tapping

SOURCE:

Description While lying down, the patient is asked to touch his or her knee and big toe alternately with the heel of the opposite extremity. The patient alternately touches the tip of his or her nose and the tip of the therapist’s finger with the index finger. The therapist may move his or her finger during testing to assess ability to change distance, direction, and force of movement. While sitting, standing, or lying down, the patient alternately draws an imaginary circle in the air, or on a table or floor, with either upper or lower extremity. Instead of a circle, a figure-eight pattern may be used. With both shoulders abducted to 90° and the elbows extended, the patient is asked to bring both hands toward the midline and approximate the index fingers from opposing hands. With the shoulder abducted to 90° and the elbow extended, the patient is asked to bring the tip of the index finger to the tip of the nose. The initial starting position may be changed to assess performance from different planes of motion. The patient touches the tip of the thumb to the tip of each finger in sequence. Speed may be gradually increased. The patient and therapist sit opposite each other. The therapist holds his or her index finger in front of the patient, and the patient is asked to touch the tip of the index finger to the therapist’s index finger. The position of the therapist’s finger may be altered during testing to assess ability to change distance, direction, and force of movement. Upper extremity: The patient holds arms horizontally in front. Lower extremity: The patient holds the knee in an extended position. The patient alternately opens and closes the fist (finger flexion to full extension). Speed may be gradually increased. With elbows flexed to 90° and held close to body, the patient alternately turns his or her palms up and down. This test also may be performed with shoulders flexed to 90° and elbows extended. Speed may be gradually increased. The ability to reverse movements between opposing muscle groups can be assessed at many joints, including the knee, ankle, elbow, fingers, etc. The patient is positioned with the elbow flexed. The therapist applies sufficient manual resistance to produce contraction of biceps. Normally when resistance is suddenly released, the opposing muscle group (triceps) will contract and “check” movement of the limb. Many other muscle groups can be tested for this phenomenon, such as the shoulder abductors or flexors, and elbow extensors. Foot: The patient is asked to “tap” the ball of one foot on the floor without raising the knee; heel maintains contact with floor. Hand: With the elbow flexed and the forearm pronated, the patient is asked to “tap” his or her hand on the knee.

O’Sullivan, S.B. and T.J. Schmitz. Physical Rehabilitation: Assessment and Treatment. 3rd ed. Philadelphia: F.A. Davis Co., 1994.

Standardized tests that evaluate gross motor coordination include the Bruinlinks-Oseretsky Test of Motor Proficiency, which evaluates gross and fine motor coordination, muscle strength, balance, and visual motor control; the Devereux Test of Extremity Coordination, which assesses static balance, motor attention span, and sequential motor activity; the Lincoln-Oseretsky Motor Development Scale, which assesses motor tasks such as walking backwards and one-foot standing; and the Miller Assessment for Preschoolers, which assesses gross motor function in young children. Balance testing instruments The Berg Balance Scale. This widely-used instrument identifies balance impairment. Functional activities such as reaching, bending, transferring, and standing are used as items on the test to measure balance. The test items are graded on a five-point scale to determine extent of impairment. Clinical Test of Sensory Interaction and Balance (CTSIB). This test, also known as the Sensory Organization Test, assesses static balance under six combinations of sensory conditions. For example, visual conditions vary by testing while the eyes are closed, open,

and also when peripheral vision is restricted. The test also includes having the subject balance while standing on a hard floor and while standing on foam. The effect on posture and balance is graded and scored. Functional Reach Test. This test measures a person’s stability while leaning forward and reaching as far as possible with arm outstretched and parallel to the floor in front of the body. A normal reach is at least six inches, measured from the distance the fist has traveled during the reach. The Tinetti Balance Test of the PerformanceOriented Assessment of Mobility Problems. This test measures balance and gait while performing typical daily activities. The activities are graded as normal, adaptive, or abnormal to determine the severity of balance impairment. The Timed Up and Go Test. This test measures the time it takes a person to rise from a standard armchair and stand, walk three meters, turn around, and walk back to the chair and sit down. The Physical Performance Test. This test evaluates a person’s physical functional capabilities. The person performs nine separate activities, such as feeding and writ-

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Coordination tests

Balance and coordination tests

KEY TERMS Incoordination—Uneven, inaccurate movement. Meniere’s disease—An abnormality of the inner ear that causes dizziness, ringing in the ears, and hearing loss.

ing, and is scored on each of the activities based on speed from 0-4.

Neistadt, Maureen E. and Elizabeth Blesedell Crepeau. Willard & Spackman’s Occupational Therapy. Philadelphia: Lippincott-Raven Publishers, 1998. Reed, Kathlyn L. and Sharon Nelson Sanderson. Concepts of Occupational Therapy. Baltimore: Lippincott Williams & Wilkins, 1999. Shaw, M. “Ears and Hearing.” In Everything You Need to Know About Medical Tests. Springhouse, Pennsylvania: Springhouse Publishing Corporation, 1996, 254-262. Williams, Pedretti, Lorraine and Mary Beth Early. Occupational Therapy, Practice Skills for Physical Dysfunction, 5th ed. St. Louis: Mosby, 2001. PERIODICALS

Preparation No special preparation is required prior to administration of balance and coordination tests. The patient may be asked to disrobe and put on an examination gown to make it easier for the doctor to observe muscles and reflex responses.

Aftercare No special aftercare is generally required. However, some of the tests may cause episodes of dizziness or incoordination. Patients may need to use caution in returning to normal activities if they are experiencing any symptoms of dizziness, lightheadedness, or weakness.

Risks These simple tests of balance and coordination are generally harmless.

Results These tests do not normally cause dizziness, loss of balance, or incoordination. The presence of dizziness, lightheadedness, loss of coordination, unusual eye movements, muscle weakness, or impaired reflexes are abnormal results and may indicate the problem causing the loss of balance or incoordination. In some cases, additional testing may be needed to diagnose the cause of balance or coordination problems. Resources BOOKS

Blakley, B.W., and M.E. Siegel. “Finding the Cause of Dizziness and Vertigo.” In Feeling Dizzy: Understanding and Treating Dizziness, Vertigo, and Other Balancing Disorders. New York: Macmillan Publishing, 1995, 43-82. “Clinical Evaluation of Complaints Referable to the Ears.” In The Merck Manual, 16th ed., edited by Robert Berkow. Rahway, NJ: Merck & Co., Inc., 1992, 2318-2319.

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Abbott, Andrea, and Doreen Bartlett. “The Relationship Between the Home Environment and Early Motor Development.” Physical & Occupational Therapy in Pediatrics 19(1999): 43–57. Bowen, J. “Dizziness: A Diagnostic Puzzle.” Hospital Medicine 34 (1) (1998): 39-44. Lesensky, Sheila, and Lillian Kaplan. “Occupational Therapy and Motor Learning.” OT Practice (25 September 2000): 13–6. Martini, Rose, and Helene J. Polatajko. “Verbal Self-Guidance as a Treatment Approach for Children with Developmental Coordination Disorder: A Systematic Replication Study.” The Occupational Therapy Journal of Research (Fall 1998): 157–81. Missiuna, Cheryl. “Development of ‘All About Me,’ a Scale that measures Children’s Perceived Motor Competence.” The Occupational Therapy Journal of Research (Spring 1998): 85–108. Whitney, Susan L., Janet L. Poole, and Stephen P. Cass. “A Review of Balance Instruments for Older Adults.” The American Journal of Occupational Therapy (September 1998): 666–71. Wilson, Brenda N., Bonnie J. Kaplan, Susan G. Crawford, Anne Campbell, and Deborah Dewey. “Reliability and Validity of a Parent Questionnaire on Childhood Motor Skills.” American Journal of Occupational Therapy 54(September/October 2000): 484–93. ORGANIZATIONS

American Academy of Otolaryngology-Head and Neck Surgery. One Prince Street, Alexandria, VA 22314. (703) 836-4444. Ear Foundation. 2000 Church Street, Box 111, Nashville, TN 37236. (615) 329-7807 or (800) 545-HEAR. Vestibular Disorders Association (VEDA). P.O. Box 4467, Portland, OR 97208-4467. (800) 837-8428 or (503) 2297705. Fax: (503) 229-8064.

Meghan Gourley

Balance assessment see Gait and balance assessment

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Ball and socket joint

Balance impairments see Gait and balance problems

Ball and socket joint Definition Ball and socket joints are multiaxial, synovial joints. They are lubricated by a clear, sticky fluid called synovia.

Description Also called spheroidal joints, the ball and socket joints are formed by the rounded or “ball-shaped” head of one bone fitting into the cup-like cavity of another bone. The articulating bone fits into the cavity and allows the distal bone to move around. The hip and shoulder joints are examples of the ball and socket joint.

Function The purpose of joints is to provide movement for the body. Different types of joints move in different ways. The ball and socket joint is fully mobile under the control of muscles, ligaments, and tendons. The ends of the bones are covered with tough cartilage and are lined with the synovial membrane. Each joint contains a small amount of synovial fluid which lubricates it. Synovial fluid provides protection for the ball and socket joint and allows for stress-free movement. The ball and socket joint provides swinging and rotating movements. The articulating bone is received into the cavity of another bone, allowing the distal bone to move around three main axes with a common center. The joint has stabilizing ligaments that limit the directions and extent to which the bones can be moved. However, the ball and socket joint is the most mobile in the body.

Role in human health Ball and socket joints are the most mobile and intricate of all the joints. They are also the most prone to disease and prone to require medical intervention. Hip or shoulder replacements are common forms of surgical intervention that restore a patient’s quality of life by replacing worn ball and socket joints with prosthetic ones.

The shoulder joint is supported by the scapula (shoulder blade) and the clavicle (collar bone). The humerus (upperarm bone) articulates with the glenoid cavity in a ball and socket type joint. (David Gifford. Science Source/Photo Researchers. Reproduced by permission.)

Common diseases and disorders There are many disorders and diseases that can afflict the synovial joints, making the ball and socket joint vulnerable to pain and discomfort. Degenerative or inflammatory diseases, conditions involving the membranes around the joints, generalized and congenital disorders, and dislocations and fractures can all cause damage to ball and socket joints. Arthritis is one of the conditions that causes pain and dysfunction in the ball and socket joint. There are several types of arthritis, but osteoarthritis and rheumatoid arthritis are the most common. Osteoarthritis is a degenerative disease that affects the cartilage in the joints, and it can cause inflammation in the tissues surrounding the affected joint or joints. Degeneration is commonly thought to be caused by stress

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KEY TERMS Axis/axes—A central or principal structure about which something turns or is arranged. The cuplike structure of the ball and socket joint is the axis where the distal bone rotates. Dysplasia—Dislocation of a bone from its proper place. Hip or shoulder displacement are two of the best-known types of dysplasia. Multiaxial—Having more than one axis. The ball and socket joint has at least three axes on which it rotates. Synovial fluid—A transparent, viscous fluid found in the synovial joints. It lubricates the ball and socket joint for easier movement.

on the joints or by injury to the joint lining. Osteoarthritis can affect all joints, but it is usually found in the fingers, feet, hips, spine, and knees. It causes joint stiffness and pain. Symptoms of osteoarthritis can be treated, but the disease is irreversible. Rheumatoid arthritis is an inflammatory disease that involves the muscles and the membrane linings of cartilage and joints. The areas commonly affected are the hands, hips, knees, legs, and joints. The symptoms include low-grade fever, stiffness in the morning, and redness, pain, warmth, and tenderness in the affected joints. Rheumatoid arthritis can cause crippling pain and deformities of the hands and causes painful swelling of the joints. Hip dysplasia is a dislocation of the hip joint that can be caused either by a congenital condition or by an accident. Dysplasia occurs when the thighbone (femur) does not fit correctly into or pops out of the cup-shaped socket at the hipbone (acetabulum). If hip dysplasia is caused by a congenital condition, the acetabulum is too shallow to hold the head of the femur. Physical therapy can help remedy the problem by deepening the cavity of the socket. Accidental hip dislocation is usually caused by a hip fracture. Resources BOOKS

Irons-George, Tracy. Magill’s Medical Guide. Vols. 1, 2, 3. Pasadena, CA: Salem Press, 1998. OTHER

“Ball-and-Socket Joints.” .

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“UCI Medicine for the New Millennium: Hip/Joint Replacements at UCI Medical Center.” . “WebMD—Joint.” .

Peggy E. Browning

Balloon angioplasty see Angioplasty

Balloon valvuloplasty Definition Balloon valvuloplasty is a minimally invasive procedure performed by an interventional radiologist and/or an interventional cardiologist in which a stenotic (narrowed) heart valve is stretched open using a special catheter with an inflatable balloon at its tip. The procedure is much less invasive than open heart surgery.

Purpose There are four valves in the heart: the aortic valve, pulmonary valve, mitral valve, and tricuspid valve. The valves open and close to regulate the blood flow from one chamber to the next. They are vital to the efficient functioning of the heart. Balloon valvuloplasty is performed on children and adults with stenosis (narrowing of the valves) to improve valve function and blood flow. The balloon stretches the thin muscular leaves of flaps of the valve, enlarging the valve opening. It is a treatment for aortic, mitral, and pulmonary stenosis. Balloon valvuloplasty is effective treatment for narrowed pulmonary valves, and results with mitral valve stenosis are generally good. For stenosis of the aortic valve, the procedure is more difficult to perform and less successful as a treatment.

Description During balloon valvuloplasty, a contrast medium (dye) is administered to the patient to make the process visible. Then a catheter (thin tube) with a small deflated balloon at the tip is inserted in the groin area. It is then threaded back up to the heart, passing through the vessels leading to the chamber adjacent to the stenotic valve. The balloon is then inflated, which stretches the leaves of the valve open. The procedure repairs some valve obstructions quite successfully.

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Preparation For at least six hours before balloon valvuloplasty, the patient is instructed to take nothing by mouth. An intravenous line is inserted in the arm as a medication administration route. The patient’s groin area is shaved and scrubbed with an antiseptic solution.

KEY TERMS Aortic valve—One of several valves in the heart that regulate blood flow. Cardiac catheterization—The process of running a catheter—a long, thin, hollow tube—into the area of the heart for a variety of medical treatments. Hematoma—Blood that has escaped from blood vessels and collected below the surface of the skin or under the surface of an organ. Also known as a blood blister or bruise. Pulmonary valve—Any of several valves regulating blood flow to the lungs. Stenosis—The narrowing of any valve, especially one of the heart valves or the opening into the pulmonary artery from the right ventricle. Valve—Tissue in the passageways between the heart’s upper and lower chambers that controls passage of blood and prevents regurgitation. Valve leaflets—The tissues that form the moveable parts of a valve. Valvuloplasty—Widening or forcing open the valves of the circulatory system, usually with a catheter equipped with a balloon.

Aftercare After balloon valvuloplasty, the patient is sent to the recovery room for several hours, where vital signs and heart rhythms are monitored. A 12-lead ECG (electrocardiogram) is performed. The leg in which the catheter is inserted is temporarily immobilized, and the catheter itself is secured so that it cannot come out. The insertion site is covered by a sterile dressing, on top of which is a sandbag to maintain pressure. The site is observed for bleeding until the catheter is removed. Intravenous fluids are administered to help eliminate (flush) the contrast medium; intravenous anticoagulants (blood thinners) or other medications to dilate the coronary arteries may be given. Pain medication is available. For at least 30 minutes after removal of the catheter, direct pressure (in the form of a sand bag) is applied to the dressing at the groin where the catheter was inserted; after this, a pressure dressing is applied. Following discharge from the hospital, the patient can usually resume normal activities. After balloon valvuloplasty, lifelong followup monitoring is necessary because valve leaflets sometimes degenerate or stenosis recurs, requiring more invasive surgery.

Complications Balloon valvuloplasty may have serious complications, such as cerebral or pulmonary embolism, in which pieces of the valve break off and travel to the brain or the lungs. Another complication is the potential for the valve opening to become distended so that it does not close completely. This condition is known as valvular incompetence. This condition permits blood backflow (regurgitation) and reduces the amount of blood pumped by the chamber through the valve, into the circulation. If the procedure causes severe damage to the valve leaflets, immediate surgery is required. Less frequent complications are bleeding and hematoma (a “bruise,” or local collection of clotted blood) at the catheter insertion site, abnormal heart rhythms, reduced blood flow, myocardial infarction, cardiac rupture, infection, and circulatory problems.

Health care team roles Balloon valvuloplasty is performed by interventional cardiologists in the cardiac catheterization laboratory. Clinical specialist nurses, radiology and laboratory tech-

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The procedure is performed in the cardiac catheterization laboratory and may take as long as four hours. About an hour before the procedure, the patient is given an oral sedative such as diazepam (Valium). The patient is also sedated intravenously, but is usually awake, and local anesthesia is administered to block pain sensation at the area of catheter insertion. After the insertion site is prepared and anesthetized, the cardiologist inserts a catheter, then passes a balloon-tipped catheter through the lumen (opening) of the first catheter. Guided by a video monitor and fluroscopy, the physician slowly threads the catheter into the heart. The deflated balloon is positioned in the valve opening, and inflated repeatedly. The inflated balloon widens the valve’s opening by splitting the valve leaflets apart. Once the valve is widened, the balloon is deflated, and the balloon-tipped catheter is removed by sliding it back out the entry route. The other catheter remains in place for six to 12 hours because in some cases the procedure must be repeated.

Bandages and dressings

nologists, and technicians assist during the procedures and provide pre- and postoperative education, monitoring, and supportive care. Resources BOOKS

“Balloon Valvuloplasty.” In Mayo Clinic Practice of Cardiology, 3rd ed., edited by Emilio R. Giuliani, et al. St. Louis: Mosby, 1996, pp. 393-94. Texas Heart Institute. “Congenital Heart Disease” and “Diseases of the Heart Valves.” In Texas Heart Institute’s Heart Owner’s Handbook. New York, NY: John Wiley & Sons, 1996, pp. 267-268; 299. “Valvular Heart Disease” and “Pulmonary Stenosis.” In Current Medical Diagnosis & Treatment, 36th ed., edited by Lawrence M. Tierney, Stephen J. McPhee, and Mazine A. Papadakis. Stamford, CT: Appleton & Lange, 1997, pp. 331-36; 327.

Purpose The purposes served by dressings include protecting wounds; promoting healing; and providing, retaining, or removing moisture. Bandages can be used to hold dressings in place, and also to relieve pain and generally make the patient comfortable. Elastic bandages are useful to provide ongoing pressure on varicose veins, fractured ribs, swollen joints, etc.

Description

PERIODICALS

Cowley, C. G., M. Dietrich, R. S. Mosca, E. L. Bove, A. P. Rocchini, and T. R. Lloyd. “Balloon valvuloplasty versus transventricular dilation for neonatal critical aortic stenosis.” American Journal of Cardiology 87, no. 9 (May 1, 2001): 1125-1127. Yates, L. A., R. E. Peverill, R. W. Harper, and J. J. Smolich. “Usefulness of short-term symptomatic status as a predictor of mid- and long-term outcome after balloon mitral valvuloplasty.” American Journal of Cardiology 87, no. 7 (April 1, 2001): 912-916. Zaki, A., M. Salama, M. El Masry, M. Abou-Freikha, D. Abou-Ammo, M. Sweelum, E. Mashhour, and A. Elhendy. “Immediate effect of balloon valvuloplasty on hemostatic changes in mitral stenosis.” American Journal of Cardiology 85, no. 3 (February 1, 2000): 370-375. ORGANIZATIONS

American College of Cardiology, Heart House, 9111 Old Georgetown Rd., Bethesda, MD 20814-1699. (800) 2534636 or (301) 897-5400. Fax: (301) 897-9745. . American Heart Association. National Center. 7272 Greenville Avenue, Dallas, TX 75231-4596. (214) 373-6300. .

Barbara Wexler

There have been tremendous advances made in the design and composition of dressings and bandages in recent years. The field is becoming increasingly complex, and there are numerous reports of health care workers applying inappropriate products. Wound-care materials come in a wide variety of product classes, including the following: • Alginate dressings. These are derived from brown seaweed, and contain calcium alginate, which turns into a sodium alginate gel when it comes in contact with wound fluid. Alginate dressings are available as pads or ropes. • Biosynthetic dressings. Composites of biological (often animal-derived) and synthetic materials such as polymers. • Collagen dressings. Made from collagen, a protein obtained from cowhide, cattle tendons, or birds. They are available as particles or gels. • Composite dressings. These look like Band-Aids, and include an adhesive border, a nonadhesive or semiadhesive surface that is applied to the wound, an absorbent layer, and a bacterial barrier. • Contact layers. A low-adherent layer of perforated or woven polymer material, designed to stop a secondary absorbent dressing from sticking to the wound surface.

Balneology see Hydrotherapy

• Gauze. This woven fabric of absorbent cotton is available in a number of formats and materials, including cotton or synthetic, nonimpregnated, and impregnated with water, saline, or other substances. Gauze is sold as surgical swabs, sheets, rolls, pads, sponges, and ribbon.

Bandages and dressings Definition Bandages and dressings are both used in wound management. A bandage is a piece of cloth or other mate256

rial used to bind or wrap a diseased or injured part of the body. Usually shaped as a strip or pad, bandages are either placed directly against the wound or used to bind a dressing to the wound. A dressing can consist of a wide range of materials, sometimes containing medication, placed against the wound.

• Growth factors. These short-chain proteins affect specific target cells. They exist naturally in humans. They

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Bandages and dressings

can be transplanted from one part of the body to another, or manufactured outside the body. • Hydrocolloid dressings. Used for leg ulcers, minor burns, pressure sores, and traumatic injuries, these self-adhesive dressings form a gel as they absorb fluid from the wound. They consist of materials such as sodium carboxymethylcellulose (an absorbent), pectin, and gelatin, attached to a foam sheet or a thin polyurethane film. • Hydrofibers. Similar in appearance to cotton, carboxymethylcellulose fibers turn into a gel when they are brought into contact with wound fluid. They are available as ribbons or pads, and are highly absorbent. • Hydrogels. These are sold as sheets and in gel form, and are primarily used to supply moisture to wounds. Depending on the state of the tissue, they can either absorb fluid or moisten the wound. An electrically conductive aloe vera gel is available to provide electrotherapy to wounds. • Hydropolymers. These foamed-gel products consist of multiple layers. The surface layer is designed to expand to fill the wound’s contours, at the same time drawing away fluids. • Leg compression/wrapping products. Designed to apply external pressure to improve blood flow and resolve chronic edema in the feet and legs. Available in a broad range of formats including stockings, compression bandages, or pneumatic pump. • Polyurethane foam dressings. These are sheets of foamed polymer solutions with small open chambers that draw fluids away from the wound. Some, but not all, of these foam products offer adhesive surfaces. They are available as sheets and rolls, as well as in various other formats suitable for packing wounds. • Skin substitutes. Also known as allografts or skin equivalents, these are obtained from human cells cultured and expanded in vitro from neonatal foreskins. • Superabsorbents. These are particles, hydropolymers, or foams that act like the material inside diapers, with a high capacity for rapid absorption. • Transparent films. These consist of a thin, clear polyurethane sheet that, on one side, has a special adhesive that does not stick to moist surfaces like those found on a wound. They prevent bacteria and fluids from entering the wound through the dressing, but allow limited circulation of oxygen. • Wound fillers. These can be bought as powders or pastes, or in strands or beads. They are used to fill wounds and also absorb wound fluid.

Dressings are used to protect wounds and promote healing. They are often held to the wound with bandages. (Custom Medical Stock Photo. Reproduced by permission.)

• Wound pouches. Equipped with a special collection system for wounds that have a high flow of secretion. Designed to contain odors, and to be easily drained. • Other assorted wound-care products. These include adhesive bandages, surgical tapes, adhesive skin closures, surgical swabs, paste bandages, specialty absorptive dressings, support bandages, retention bandages, elasticized tubular bandages, lightweight elasticized tubular bandages, foam-padded elasticized tubular bandages, and plain stockinettes.

Operation Just as there is a large selection of bandage and dressing products to choose from, there is also a broad range of applications for these products: • Alginate dressings are used on wounds that exude moderate to heavy amounts of fluid. They are useful for packing wounds, although strip-packing gauze may be preferable for deeper wounds because it is easier to retrieve. Common applications of alginate dressings include treatment of acute surgical wounds, leg ulcers, sinuses, and pressure sores. These dressings should not be used on third-degree burns. Neither are they advisable for wounds that are dry or are secreting only small amounts of fluid, because their powerful absorbing capability may dry out the wound. These are primary dressings that need be covered by a secondary dressing. • Biosynthetic dressings are used on burns and other wounds. Another application is as a temporary dressing for skin autograft sites. Some patients may be allergic to these dressing materials. • Collagen dressings are believed to hasten wound repair and are often used on stubborn wounds. They are most effective on wounds that contain no dead tissue.

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KEY TERMS Edema—Swelling of body tissues, caused by collection of excess fluid. Electrotherapy—The treatment of body tissues by passing electrical currents through them, stimulating the nerves and muscles. Sinus—In the context of wound management, a narrow hollow in the body extending from an infected area to the skin’s surface. Stockinette—A soft elastic material used for bandages and clothing for infants.

Collagen dressings should not be used in dry wounds, third-degree burns, or on any patient who is sensitive to bovine (cow) products. • Composite dressings are sometimes used alone, sometimes in combination with other dressings. Deep wounds should first be packed with wound filler material. These dressings should not be cut, and are not recommended for use of third-degree burns. • Contact layers are designed for use in clean wounds that contain no dead tissue. They are not recommended for infected, shallow, dry, or infected wounds, or on third-degree burns. • Gauze is used to pack wounds, and also for debridement and wicking. It is especially desirable for packing deep wounds. When using gauze to pack wounds, a loose packing technique is preferred. • Growth factors. These have highly specific applications against such conditions as diabetic foot ulcers involving disease of the peripheral nerves. Growth factors are heat sensitive and often require refrigeration. Not recommended for patients with tumors, either benign or malignant. • Hydrocolloid dressings are used for leg ulcers, minor burns, pressure sores, and traumatic injuries. Because they are not painful to remove, hydrocolloid dressings are often employed in pediatric wound management. Because of their absorbent capabilities, they are used on wounds that are secreting light to moderate amounts of fluid. • Hydrofibers are highly absorbent, so they are particularly useful for wounds that are draining heavily. For this reason, they are not recommended for dry wounds or wounds with little secretion, because they may result in dehydration. Hydrofibers should not be used as surgical sponges or on third-degree burns. 258

• Hydrogels are often used on wounds that contain dead tissue, infected surgical wounds, and on painful wounds. They should not be used on wounds with moderate to heavy secretions. As with all dressings, it is important to check the manufacturer’s directions. In the case of hydrogels, directions on some products indicate they are not to be used on third-degree burns. • Hydropolymers are typically used on wounds with minimal to moderate drainage. They are not indicated for dry wounds or third-degree burns. • Leg compression/wrapping products are used to increase blood flow and reduce edema in the lower extremities of the body. A medical doctor should be consulted before using these products on patients with edema. In many cases, topical dressings are used underneath these products. • Polyurethane foam dressings are very absorbent and are typically used on wounds with moderate to heavy secretions. They should not be used on third-degree burns, or wounds that are not draining or have sinuses or tunneling. • Skin substitutes are a relatively new product category, approved for treating venous leg ulcers. It is often advisable to cut slits in the artificial skin, so that wound secretions underneath do not lift the newly applied skin. • Superabsorbents are employed on wounds that are secreting heavily, or in applications requiring extended wear. A packing material is commonly employed under this product. Superabsorbents should not be used on third-degree burns or wounds that are either dry or have minimal secretions. • Transparent films are often employed as a secondary cover for another, primary dressing. They are used on superficial wounds, and on intact skin at risk of infection. It is important to remove transparent films very carefully, to avoid damaging fragile skin. • Wound fillers are primary dressings that are usually used in conjunction with other, secondary dressings. Wound fillers are considered appropriate for shallow wounds with little or moderate secretions. They are not appropriate for use in third-degree burns, or in dry wounds. They are similarly not recommended for wounds with tunnels or sinuses. • Wound pouches are useful in treating wounds with high volumes of secretion. They are not suitable for dry wounds.

Maintenance Recommended intervals between dressing changes varies widely between product classes. Some dressings

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Health care team roles Wound-care nursing is a demanding field that can require its practitioners to also be administrators, educators, clinical experts, and researchers. Nurses are the front-line workers in wound care, often working as part of a multidisciplinary team of colleagues from other professions and disciplines. This approach is considered necessary because of the multifaceted nature of wounds. Its importance is especially noticeable in acute care, where 5.4% of hospital patients develop a stage one ulcer. Across the United States, such ulcers in acute care cost more than $839 million a year. Other members of the wound-care team may come from home care, administration, nutrition, geriatrics, vascular surgery, plastic surgery, biomedical, general nursing, pharmacy, materials management, infection control, purchasing, quality assurance, and physical and occupational therapy. Numerous ad hoc members and consultants may also be involved, including representatives from dermatology, trauma, podiatry, risk management, staff development, orthotic specialists, rehabilitation, diabetology, and social services. To be successful, multidisciplinary wound-care teams must establish ongoing communication with primary-care physicians. Nurses are intensively involved in the initial assessment of tissue damage, a responsibility that demands both accuracy and consistency. Other responsibilities may include cleansing and dressing wounds, removal of non-viable tissue, pain management, patient education, nutritional counseling, statistical analysis, and helping the patient cope with the psychological effects of serious or disfiguring wounds. Determining the cause of wounds is often very important, especially the cause of chronic wounds such as skin ulcers. A physician should be advised of any signs of infection or other changes in the wound.

Training Wound-care nursing is a rapidly advancing field that requires considerable training, clinical experience, and judgment, causing some observers to predict that it will eventually develop into advanced practice nursing or a specialty-based practice. Increasingly, the demands on wound-care nurses are expected to require that they undertake graduate studies. For all nurses working in the field, ongoing education is a must, to keep up with new knowledge, technologies, and techniques. Numerous organizations and institutions offer continuing education courses in wound care management. The Wound,

Ostomy and Continence Nurses Society is one such organization. It offers a variety of resident programs at several U.S. centers and also has distance-learning options. Resources BOOKS

Bryant, Ruth A. Acute & Chronic Wounds, 2nd ed. St. Louis, MO: Mosby, 2000. ORGANIZATIONS

The Wound, Ostomy, and Continence Nurses Society. 1550 South Coast Highway, Suite #201, Laguna Beach, CA, 92651. (888) 224-WOCN (toll-free). .

David L. Helwig

Barium enema Definition A barium enema (or BE), also known as a lower GI (gastrointestinal) series, is a radiographic exam used to view the large intestine. There are two types of barium enemas: the single-contrast technique where just barium sulfate is injected into the rectum to outline the large intestine; and the double-contrast (or “air contrast”) technique in which barium and air are injected into the rectum.

Purpose The purpose of a barium enema is to demonstrate the anatomy and morphology of the large intestine. The large intestine frames the abdomen and is divided into six sections. These include the rectum, sigmoid colon, descending colon, transverse colon, ascending colon, and cecum. A barium enema may be performed for a variety of reasons, including abdominal pain or a change in bowel habits such as diarrhea or constipation, as well as a change in the caliber (size) of the stools. This exam is also requested when parasites, blood, mucus, or pus are found in the stools. Occult (hidden) blood found in the stools and anemia may be an indication of intestinal bleeding due to ulcers, inflammatory disease, or a cancerous lesion. Doctors may also order this exam as a screening tool for patients with a history of polyps (precancerous growths extending outward from a mucous membrane) or a family history of colorectal cancer. A barium enema may also be requested when the large intestine was not completely visualized during a

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are designed to be changed several times a day. Others can remain in place for one week. The manufacturer’s directions should be consulted and followed.

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technologist may take one preliminary view of the abdomen to determine how well the patient’s bowel has been cleansed. Any retained fecal material can create false filling defects and mucosal abnormalities on the films. A single-contrast enema would usually be done on patients with a poor bowel preparation. After the films are taken and the patient has evacuated as much of the barium as possible air may be introduced into the large intestine and further films taken. This method takes longer and gives more radiation to the patient. The patient will be instructed to lie on the left side on the x-ray table, and the radiography technologist will insert a lubricated enema tip into the rectum. The enema tips contain a small balloon which may be inflated to help the patient retain the barium. The patient may remain on their left side or turned prone (face-down) depending on the procedure and routine of the radiologist.

A barium enema exam allows any obstructions or tumors to be seen on a monitor. (Photo Researchers, Inc. Reproduced by permission.)

colonoscopy (examination of the large intestine with a fiber-optic tube) or when a sigmoidoscopy is done, which only partially visualizes the colon. Sometimes a barium enema may be used as a treatment for intussusception (telescoping of one section of the bowel into another causing obstruction). This is a rare disorder occuring most often in young children, but when it occurs immediate action must be taken. A barium enema may also be done to evaluate the remaining colon on colostomy patients. The barium is injected into the stoma (external drainage opening in the abdominal wall) instead of the rectum. A barium enema may be done if obstruction, perforation, or fistula formation is suspected.

Precautions As with any radiographic procedure there is the risk of radiation. The x-ray technologist must always make sure there is no risk of pregnancy and that the least amount of films as possible are done. No lead shielding can be used since all the abdominal area must be visualized on the films.

Description All patients must be changed into a hospital gown. All clothing is removed, including shoes and socks, since some leakage of the barium mixture can occur. In some departments disposable slippers are supplied. The x-ray 260

For a single-contrast barium enema, the barium sulphate solution is a thinner consistency but a larger amount is needed to completely fill the large intestine. High kilovoltage (100-125kvp) is used to get a good penetration of the barium filled colon, and it is important to take the films as quickly as possible since the patients are very uncomfortable when the bowel is completely distended. Routine films for a single contrast study include a supine and prone abdomen film as well as both obliques to see the hepatic and spenic flexures of the large bowel. The patient will completely evacuate the bowel and one more film, the post-evacuation film (PE) usually done AP (anteroposterior, or front–to–back) supine, will be taken. In a double-contrast barium enema, a fine coating of thick barium is needed to outline the mucosal lining of the bowel. The patient will be placed prone so that gravity can assist the air in distributing the liquid around the large bowel. The patient is asked to turn over 360 degrees a few times during the exam to aid in the coating of the bowel. The patient is then placed upright, and more air is injected into the bowel so gravity again can assist in visualizing the large intestine. Patients may develop spasms of the bowel during this exam, so the radiologist may give the patient a glucagon injection to relax the large bowel. This injection should not be given to patients with a history of glaucoma and can cause temporary doublevision in these patients. The radiologist will take spot-films under fluoroscopy of each segment of the bowel but most of the films will be made following the procedure by the x-ray technologist. Since less barium is used along with some air, less kilovoltage (90-100kvp) is needed to achieve a high contrast x-ray of the large intestine. The usual AP and PA (posteroanterior) abdomen films will be done as well as the two oblique views of the abdomen. An

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Preparation In order to conduct the most accurate barium enema test, the patient must follow a prescribed diet and bowel preparation prior to the test. This includes a diet of tea, coffee (black), clear soups, and gelatin 24-48 hours before the barium enema. Laxatives and cathartics such as magnesium citrate (X-Prep) or Dulcolax tablets may also be required as part of the bowel preparation. Each radiology department has their own specific requirements. A rectal suppository or cleansing enema may also be necessary on the morning before the exam. Patients must drink as much fluids as possible to prevent dehydration. Patients with heart disease, diabetes, or kidney disorders should consult their physician for an alternate bowel preparation. Children are usually placed on a clear liquid diet on the day before their examination. A barium enema may be done in a hospital or a certified x-ray clinic and will take 30 minutes to one hour depending on what type of exam has been ordered and the physical ability of the patient.

Aftercare Patients should follow several steps immediately after undergoing a barium enema, including: • Drinking plenty of fluids to help counteract the dehydrating effects of the bowel preparation. • Taking time to rest. A barium enema and the bowel preparation taken before it can be exhausting. • A cleansing enema or laxative may be given to eliminate any remaining barium. White stools containing barium are normal for two or three days following a barium enema.

Complications While a barium enema is considered a safe screening test used on a routine basis, it can cause complica-

tions in certain patients. The following contraindications should be kept in mind before a barium enema is performed: • Those who have a rapid heart rate, severe ulcerative colitis, toxic megacolon, or a presumed perforation in the intestine should not undergo a barium enema. • The test can be cautiously performed if the patient has a blocked intestine. Gastrograffin, an iodine-based contrast, will be used instead of the barium in case emergency surgery is needed following the barium enema.

Results A normal result indicates no structural or filling defects of the large intestine. Radiologists look for any enlargement or narrowing of the large bowel as well as variations in the mucosal lining. The walls of the intestine should collapse normally after the post-evacuation film, and the bowel should have normal haustral markings (undulations of the colon wall). Abnormal results may include colorectal polyps, diverticulosis (multiple abnormal sacs bulging through the intestinal wall), ulcerative colitis, abscesses, or tumors visualized on the walls or adjacent to the large intestine. Further evaluation such as a biopsy or CT scan may be necessary to determine the extent of any positive findings.

Health care team roles It is the resposibility of the radiography technologist to prepare the barium, insert the enema tip, and take the overhead films after the radiologist has filled the entire colon with either the barium or a combination of barium and air. In some departments an interventional radiology technologist will perform the complete exam. He or she will have had additional education and training by the radiologists to complete this duty. The x-ray technologist must work closely with the nurses to make sure all hospital patients follow the bowel preparation. Since the preparation is physically exhausting for the patient, care is taken to complete the exam as soon as possible so the patient may resume a normal diet. Patient education Since a good preparation is the most important step in a barium enema, all patients should receive detailed information on the reasons and requirements for the cleansing treatment. The x-ray technologist must explain the procedure in detail before starting the exam. The patient must be informed that the barium enema can sometimes cause cramps and that the urge to have a

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upright film may be done as well depending on the routine of the radiologist. The most important films for the double-contrast exam are the two lateral decubitus films. The patient is placed on a large cushion or sponge and turned completely onto one side. A stationary grid is placed next to the patient and the x-ray tube is turned 90 degees. This film allows the air to rise to the upper surface of the abdomen so that the air along with the thin coating of barium creates a detailed visualization of the intestinal lining. This is extremely important when looking for small polyps, cancers, and ulcerations of the bowel. Films of both sides are always taken.

Beds and bed preparation techniques

Resources

KEY TERMS

BOOKS

Barium sulfate—A barium compound used during a barium enema to block the passage of x rays during the exam,allowing visualization of the intestinal lining. Colonoscopy—An examination of the large colon performed with a colonoscope. Diverticula (plural of diverticulum)—A sac or pouch in the colon walls which is usually asymptomatic (without symptoms) but may cause difficulty if it becomes inflamed.

Eisenberg, Ronald. Clinical Imaging: An Atlas of Differential Diagnosis, 3rd Ed. Philadelphia: Lippincott, Williams & Wilkins, 1996. Segen, Joseph C., and Joseph Stauffer. “Barium Enema (lower GI series).” In The Patient’s Guide To Medical Tests: Everything You Need To Know About The Tests Your Doctor Prescribes. New York, NY: Facts On File, Inc., 1998, pp. 44-45. PERIODICALS

Friedenberg, Richard M.D. “The supertechnologist.” Radiology Review (June 2000): 630-633.

Diverticulitis—A condition of the diverticula of the intestinal tract, especially in the colon, where inflammation may cause and pain.

ORGANIZATIONS

Diverticulosis—A condition of the colon characterized by the presence of diverticula.

OTHER

Glaucoma—A disease of the eye characterized by increased ocular pressure resulting in damage to the retina and optic nerve if not treated. Sigmoidoscopy—A visual examination of the rectum and sigmoid colon using a fiberoptic sigmoidoscope.

American Cancer Society. 1599 Clifton Road NE, Atlanta, GA 30329-4251. (800) ACS-2345. .

Health Discovery.

Lorraine K. Ehresman

Barium swallow see Upper GI exam

Ulcerative colitis—An ulceration or erosion of the mucosa of the colon.

bowel movement is completely normal. Some leakage of the barium may occur and the patient should not feel embarrassed if this happens because it occurs fairly often, especially in elderly patients. Care should be taken when inserting the enema tip because the rectum is already irritated, due to the multiple bowel movements during the preparation. The x-ray technologist must take note of any history of glaucoma in case an injection of glucagon is needed. Patients should be completely covered at all times and care taken when placing the patient in the upright position since many patients are weak after undergoing the bowel preparation. The x-ray technologist should also explain to the patient the need to drink plenty of fluids after the barium enema and that white stools following a barium enema are normal. All radiography technologists must be certified, having completed a two to four year program depending on where the course was completed. All x-ray technologists must be registered with the A.S.R.T. and earn continuing education credits to remain registered. 262

Beds and bed preparation techniques Definition A hospital bed is the piece of equipment most frequently used by the hospitalized patient. Hospital beds are also found in long-term-care facilities, as well as patients’ homes. The ideal hospital bed should be selected for its impact on patients’ comfort, safety, medical condition, and ability to change positions.

Purpose The purpose of a well-made hospital bed, as well as an appropriately chosen mattress, is to provide a safe, comfortable place for the patient, where repositioning is more easily achieved, and pressure ulcers are prevented.

Precautions When selecting a bed, the nurse should consider the patient’s mobility, overall medical condition, and risk for pressure ulcer development. Safety factors should also be considered. Unless a patient is accompanied by a

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Another precaution to take, especially for weak or bed-bound patients, or for those with altered mental status, is to elevate the side rails. However, health care professionals should be aware of a safety alert issued by the Food and Drug Administration (FDA) in 1995 concerning the use of hospital beds’ side rails. Because of a number of injuries and deaths related to side rail entrapment, the FDA recommends the following actions to prevent potential deaths and injuries related to side rail entrapment:

Beds and bed preparation techniques

health care professional or other caregiver, the bed should always be placed in its lowest position to reduce the risk of injury from a possible fall.

Two nurses change bedsheets with the patient in the bed. (Photograph by Cliff Moore. Science Source/Photo Researchers. Reproduced by permission.)

• All hospital bed frames, side rails, and mattresses should be inspected regularly to identify potential areas of entrapment. The alignment of the bed frame, side rail, and mattress should leave no gap that is wide enough to entrap a patient’s head or any other part of the body.

Various safety features are present on hospital beds. These features include:

• Be alert for side rails or mattresses that have been replaced. Not all of these are interchangeable, and may increase the potential for entrapment.

• Side rails: They help to protect patients from accidentally falling out of bed, as well as provide support to the upper extremities as the patient gets out of bed.

• Check side rails for proper installation.

• Removable headboard: This feature is important during emergency situations, especially during cardiopulmonary resuscitation.

• Consider additional safety measures for those patients at high risk for entrapment. Side rail protective barriers may be used to close off open spaces. • Do not use side rails as a substitute for patient protective restraints.

Description The usual hospital bed consists of a mattress on a metal frame that can be raised or lowered horizontally. The frame is separated into three sections so the head and foot of the bed can be raised and lowered, in addition to inclining the entire bed with the headboard up or down. The majority of hospital beds are powered by electrical motors, but some are run manually (using a crank) or by hydraulic methods. The bed’s position is typically changed by using electrical controls that may be located on the side or foot of the bed, in a bedside table, or on a pendant. The electrical controls enable patients to reposition the bed with very little effort. Patients should be instructed how to use the bed controls. They should also be cautioned against raising the bed to a position that may contribute to injuries or falls. At its lowest level, a hospital bed is usually about 26–28 inches (65–70 cm) above the floor.

• Wheel locks: These should be used whenever the bed is stationary.

Most hospital beds have water-repellent mattresses. However, a number of specially designed beds, frames, and mattresses have been created to aid in caring for bedbound patients. Some of these beds help to turn the immobile patient, and may make it easier for nurses to lift or reposition the patient. The major categories of specialized beds are: • Air-fluidized beds: These are also known as bead beds, sand beds, and high-air-loss beds. Air is circulated via silicone microspheres, creating a fluid-like state. • Low-air-loss beds. These beds have interconnected air cells with a minimum depth of five inches (12–13 cm). They allow air to escape from the surface of the bed. There are also a variety of support surfaces that can be placed on top of the existing mattress, or specialized mattresses that can reduce the risk of pressure ulcer formation. These surfaces and mattresses include: • static air-filled overlays • alternating air-filled mattress overlays • gel- or water-filled mattress overlays • foam mattresses • low-air-loss replacement mattresses

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linens are being changed. The nurse should perform the following when making the occupied bed:

KEY TERMS Draw sheet—A sheet placed over the bottom sheet to help lift or move a patient and to protect the bottom sheet from soiling. Fowler’s position—A bed position where the head of the bed is raised to an angle of 45° or more; a semisitting position. Trendelenburg—A bed position where the entire frame of the bed is tilted with the head of the bed down.

The rotokinetic bed is used primarily for severely immobilized patients or patients with spinal cord injuries. The bed can rotate a patient up to 270°. Bariatric beds are available for especially obese patients.

Preparation The nurse normally makes the bed in the morning after a patient’s bath, or when the patient is out of the room for tests. The nurse should straighten the linens throughout the day, making certain they are neither loose nor wrinkled. Any sheets that become wet or soiled should be changed promptly. When changing bed linen, the nurse should keep the soiled linen away from the uniform, and place it in the appropriate linen bag or other designated container. Never fan or shake linens, which can spread microorganisms and, if any of the sheets touch the floor, they should be replaced.

• Raise the bed to a comfortable working height. Loosen the top linens, and help the patient assume a side-lying position. • Roll the bottom linens toward the patient. • Place the bottom sheet on the mattress, seam side down, and cover the mattress. Miter the corners of any non-fitted sheets. • Place waterproof pads and/or a draw sheet on the bed. • Tuck in the remaining half of the clean sheets as close to the patient as possible. • Assist the patient to roll over the linen. Raise the side rail, and go to the other side of the bed. • Remove the dirty linen and dispose of appropriately. • Slide the clean sheets over and secure. Pull all sheets straight and taut. • Place the clean top sheets over the patient and remove the used top sheet and blanket. Miter the corners of the top linens at the foot of the bed. Loosen the linens at the foot of the bed for the patient’s comfort. • Change the pillowcase. • Return the patient’s bed to the appropriate position, at its lowest level. The nurse also needs to place the bed into one of the following positions, considering the particular needs of each patient:

The bed can be made in a variety of ways, depending on the particular patient situation. The categories of unoccupied bed making include:

• Fowler’s: The head of the bed is raised to an angle of 45° or more; a semisitting position. This position is appropriate when the patient is eating. It is also used during nasotracheal suctioning or during nasagrastic tube placement.

• Open unoccupied: In an open bed, the top covers are folded back so the patient can easily get back into the bed.

• Semi-Fowler’s: In this position, the head of the bed is raised about 30°. This position helps to promote adequate lung expansion.

• Closed unoccupied: In a closed bed, the top sheet, blanket, and bedspread are pulled up to the head of the mattress and beneath the pillows. A closed bed is done in a hospital bed prior to the admission of a new patient.

• Trendelenburg: The entire bed frame is tilted with the head of the bed down. This helps to promote postural drainage or to promote venous return in patients with poor peripheral circulation.

• Surgical, recovery, or postoperative: These techniques are similar to the open unoccupied bed. The top bed linens are placed so that the surgical patient can transfer easily from the stretcher to the bed. The top sheets and bedspread are folded lengthwise or crosswise at the foot of the bed.

• Reverse Trendelenburg: The entire bedframe is tilted with the foot of the bed down. This position is not frequently used, though it may help to prevent esophogeal reflux.

The other method of making a hospital bed is an occupied bed, where the patient is in the bed while the 264

• Flat: Keeping the bed flat is appropriate for some patients with spinal injuries, and for those in cervical traction. It may also be used for patients with hypotension. It is a position preferred by many for sleeping.

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After preparing the hospital bed, the patient should be assessed for comfort and safety.

Health care team roles Selecting and preparing a bed for the patient are important responsibilities for the nurse. The nurse or nursing assistant normally makes up the bed, but it is important that all health care professionals be aware of the positive impact an appropriate, well-made bed has on a patient’s care, safety, and sense of comfort. Resources BOOKS

Potter, Patricia A., and Anne G. Perry. Fundamentals of Nursing, 5th ed.St. Louis, MO: Mosby, 2001. PERIODICALS

Warren, Joseph B., et al. “Development of a decision tree for support surfaces: a tool for nursing.” Medical-Surgical Nursing 8 (August 1999): 239. ORGANIZATIONS

The Hospital Bed Safety Work Group. .

Deanna M. Swartout-Corbeil, R.N.

Bedside monitors see Cardiac monitor Bedsores see Pressure ulcer

Behavioral optometry Definition Behavioral optometry is a system of eye care that emphasizes visual training as a way to improve the way a patient uses his or her eyes. Rather than simply prescribe lenses to compensate for eyesight weaknesses, behavioral optometrists attempt to train the patient to see better across a range of different circumstances.

Origins Behavioral optometry traces its roots to the writings of Dr. William H. Bates, a New York City ophthalmologist. Bates began writing in the 1920s about alternatives to the use of corrective lenses. He believed that many physical and emotional stresses caused vision problems, and that alleviating these stresses could improve vision. He noted that modern humans spend an inordinate

amount of time doing close work such as reading, while the human eye may have been originally adapted for distance vision. Bates devised a program of eye training that allowed patients to gradually improve their vision without glasses. The English novelist Aldous Huxley recovered from near-blindness using Bates’s system, and wrote a book about his experience. Other optometrists built on Bates’s insights, supplementing his research and ideas. Some researchers focused on the fact that the need for corrective lenses rises in proportion to a person’s level of education. They concluded that the stress of reading was probably responsible for poor eyesight. Others noted that vision problems increase as cultures become increasingly industrialized and developed. Practitioners of behavioral optometry who built on and extended Bates’s ideas include Dr. Raymond L. Gottlieb and Dr. Jacob Liberman, both influential authors and teachers. Behavioral optometrists are distinctly a minority in the field of optometry, but they can be found across the United States and worldwide.

Benefits Behavioral optometrists promise many benefits from this way of treating vision problems. Perhaps the foremost is that people can learn to live without the discomfort and bother of wearing eyeglasses or contact lenses. Behavioral optometry also focuses on children, particularly those with learning difficulties. These children can benefit from learning to train their eyes and so overcome reading problems due to inability to concentrate or inability to keep the eyes in place on the page. Behavioral optometry also tries to help patients deal with stress, so that vision training can lead to a more relaxed and healthy lifestyle. In addition, behavioral optometry has been used to develop the special visual acuity that is needed for sports, and some practitioners are trained to treat patients who have suffered vision trauma such as stroke, or to work with autistic or disabled children.

Description Behavioral optometry aims to treat the whole patient, not just correct his or her vision. The first step in an examination may be a wide-ranging series of tests and questions, geared to determine the patient’s overall visual abilities. This term means not just how well the eyes read letters on a chart, but such broader areas of visual perception as hand-eye coordination and color perception. Behavioral optometrists will prescribe corrective lenses, but these are usually somewhat different from traditional glasses. The lenses are designed to relieve the stress caused by such close-focus work as reading or working at a computer. But for distance seeing, the lens-

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Aftercare

Bioelectricity

KEY TERMS Ophthalmologist—A physician who specializes in treating diseases and disorders of the eye. Optometrist—A professional who examines the eyes for vision defects in order to fit the patient with corrective lenses or prescribe other appropriate treatment.

es may not be as accurate as traditional lenses, since the behavioral optometrist seeks to teach the eyes to relearn distance vision skills that have atrophied. Many behavioral optometrists prescribe lenses that include a series of small prisms, which are supposed to help the eyes develop better vision patterns. Behavioral optometrists also practice vision therapy, in which the optometrist works closely with the patient in step-by-step exercises to help the eyes relax and relearn lost skills. These are not merely eye exercises, because exercising the muscles around the eye can fatigue them instead of strengthen them. The therapy might involve learning new skills such as juggling, drawing, dancing, or ball games, as well as relaxation techniques. The optometrist may also work with the patient to alter diet, sleep patterns, and lifestyle stress.

Research and general acceptance Though behavioral optometrists are definitely a minority within the field of optometry, a body of research supports their methods. This can be found in professional journals such as Journal of Behavioral Optometry and Journal of Optometric Vision Development. Bates’s method has been in use since the 1920s, and much anecdotal evidence attests to its efficacy, including the dramatic case of writer Aldous Huxley. Other patients and practitioners have written of their ability to function without glasses and overcome learning disabilities through behavioral optometry. And one of the major contentions of behavioral optometry is that conventional optometry does not cure the eye conditions it treats. Myopic patients are given glasses, and then a stronger pair of glasses, and then a stronger, as vision gradually worsens. Behavioral optometrists use this development as evidence that conventional optometry fails its patients.

Training and certification In the United States, there are three major training institutions for behavioral optometry. The College of Optometrists and Vision Development offers courses and examinations leading to an international certificate in 266

behavioral optometry. Clinical education workshops are offered by the Optometric Extension Program Foundation in Santa Ana, California. The Baltimore Academy of Behavioral Optometry offers in-depth coursework in behavioral optometry to qualified optometrists. Only people who already have a degree in optometry can take these courses. Technicians also work with behavioral optometrists. These technicians need have no specific educational background, but to become certified, they must work for 2,000 hours under a certified behavioral optometrist and pass a written and oral examination. Resources BOOKS

Bates, William. The Bates Method for Better Eyesight Without Glasses. New York: Henry Holt & Co., 1981. Liberman, Jacob. Take Off Your Glasses and See. New York: Crown Publishers, 1995. ORGANIZATIONS

Baltimore Academy of Behavioral Optometry. 16 Greenmeadow Drive, Suite 103. Timonium, MD 21093. (800) 447-0370. College of Optometrists in Vision Development. 353 H. Street, Suite C. Chula Vista, CA 91910. (888) 268-3770. Optometric Extension Program Foundation. 2912 South Daimler Street, Suite 100. Santa Ana, CA 92705. (949) 250-8070.

Angela Woodward

Bends see Decompression sickness Beta-carotene see Vitamin A Bicarbonate test see Electrolyte tests Bilirubin test see Liver function tests

Bioelectricity Definition Bioelectricity refers to electrical potentials and currents occurring within or produced by living organisms. It results from the conversion of chemical energy into electrical energy. Bioelectric potentials are generated by a number of different biological processes, and are used by cells to govern metabolism, to conduct impulses along nerve fibers, and to regulate muscular contraction. In most organisms bioelectric potentials vary in strength from one to several hundred millivolts. The most impor-

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Description Historical background Prior to the eighteenth century, European physicians and philosophers generally believed that nervous impulses were conducted to the brain via an organic fluid of some kind. The experiments of two Italians, the physician Luigi Galvani and the physicist Alessandro Volta, demonstrated that the true explanation of nervous conduction is bioelectricity. Impulses within the nervous system are carried by electricity generated directly by organic tissue. In the nineteenth century, such researchers as Emil du Bois-Reymond invented and refined instruments that were capable of measuring the very small electrical potentials and currents generated by living tissue. One of du Bois-Reymond’s students, a German scientist named Julius Bernstein, is generally credited with the hypothesis that nerve and muscle fibers are normally polarized, with positive ions on the outside and negative ions on the inside; and that the current that can be measured results from the reversal of this polarization. In the early part of the twentieth century, several British scientists identified the chemical substances involved in the transfer of information between the nerves and muscles. Cell membrane potential Bioelectricity begins with the fact that all animal cells have electrical properties derived from the ability of the cell membrane to maintain unequal charges inside and outside the cell. The cell membrane is semipermeable, which means that it forms a selective barrier to ions, which are electrically charged atoms or atom groups. The semipermeability of the cell membrane allows the cell to maintain concentrations of ions in the cytosol (the fluid portion of cell cytoplasm) that differ from those in the fluid outside the cell. Potassium and chloride ions can diffuse through the membrane relatively easily, while sodium ions cannot diffuse into the cell at all. Because of the semipermeability of the cell membrane, the concentration of sodium in the fluid outside the cell is higher than in the cytosol; the concentration of potassium is higher inside the cell than outside, and the concentration of chloride is higher outside the cell than

inside. There are thus two forms of energy stored across the cell membrane—a chemical force (the differences in ion concentration) and an electrical force. This bioelectric potential across the cell membrane is called the resting potential. In most cells the resting potential is about 50 millivolts. Diffusion The most important ions in bioelectrical phenomena are sodium (Na+), potassium (K+), calcium (Ca2+), and chloride (Cl-). The first three types of ions carry a positive charge while the chloride ion carries a negative charge. Ions can move across the cell membrane in two ways. First, they can move through pores called ion channels. Most ion channels are specific to a particular ion or group of ions. In addition, most ion channels are gated, which means that they require a stimulus to open them. Because ions move passively through the channels, the only direction they can travel via channels is from areas of high concentration to areas of low concentration. This movement from areas of higher to areas of lower concentration is called diffusion. Active transport A second kind of transport, which moves ions across the cell membrane against the electrochemical gradient is called active transport. Active transport involves an ion pump, which is sometimes called a sodium/potassium pump. Ion pumps differ from ion channels in that the pumps require energy to move the ions. The energy is derived from adenosine triphosphate, or ATP, which is a nucleotide that is the primary source of energy in all living cells. The sodium/potassium pump controls the volume of the cell and creates the electrical potential across the cell membrane. For example, the concentration of Na+ is approximately 10 times higher outside the cell compared to the inside, and the concentration of K+ is about 20 times higher on the inside of the cell. This difference is maintained by the action of the cell’s ion pumps, which pump three sodium ions outside the cell for every two potassium ions that are pumped inside, consuming one molecule of ATP in the process. Because ions are charged molecules, a difference in chemical concentration establishes a difference in electrical charge as well. The ion channels and the ion pump work together to maintain this charge difference across the cellular membrane.

Bioelectrical functions Synapses and synaptic transmission A neuron, or nerve cell, consists of dendrites (receiving portions), a cell body, an axon, and the axon terminal.

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tant difference between bioelectric currents in living organisms and the type of electric current used to produce light, heat, or power is that a bioelectrical current is a flow of ions (atoms or molecules carrying an electric charge), while standard electricity is a movement of electrons.

Bioelectricity

KEY TERMS Acetylcholine—A short-acting neurotransmitter involved in the process of muscle contraction. Action potential—The change in electrical potential that occurs between the inside and outside of a nerve or muscle fiber when it is stimulated. Active transport—The movement of ions across the cellular membrane against the electrochemical gradient by means of the sodium/potassium pump. Adenosine triphosphate (ATP)—A nucleotide that is the primary source of energy in living tissue. It fuels the sodium/potassium pump. Axon—The appendage of a neuron that transmits impulses away from the cell body. Cytosol—The fluid portion of cell protoplasm. Depolarization—Movement of the resting potential of a cell membrane back toward zero. Diffusion—The movement of ions across the cell membrane from areas of higher concentration to areas of lower concentration. Ion—An atom or atom group that acquires an electrical charge by the loss or gain of electrons. Ion channel—A passive means of moving ions from one side of the cell membrane to another by diffusion. Myosin—A protein found in muscle tissue that interacts with another protein called actin during muscle contraction. Neurotransmitter—A chemical released by nerve endings that helps to transmit information from one nerve cell to another nerve cell, or from a nerve to a muscle. Resting potential—A steady-state condition with no net flow of ions across the cell membrane. The resting potential can be observed on unstimulated nerve or muscle tissue. Sodium/potassium pump—The mechanism of active transport that moves potassium ions into the cell and sodium ions out, consuming ATP in the process. Synapse—A region in which nerve impulses are transmitted across a gap from an axon terminal to another axon or the end plate of a muscle.

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The axon is a long appendage that conducts information in the form of action potentials away from the cell body. The site of contact between two neurons is called a synapse. The presynaptic neuron releases a chemical called a neurotransmitter into the synaptic cleft between the two neurons. The neurotransmitter passes on information to the postsynaptic neuron. Although most forms of communication between neurons are mediated by chemicals, some neurons also transmit information by direct electrical communication. Neurons may connect to other neurons, to muscles, or to receptor cells in the skin and other sensory organs. Chemical or electrochemical stimulation of a neuron results in a temporary change in the permeability of the cell membrane. The membrane becomes more permeable to sodium and potassium ions. The sodium ions enter the cell because of their concentration and electrical gradient, while the potassium ions leave the cell because of their chemical gradient. The result is a depolarization (loss of electrical charge) of the cell. The nerve impulse, or action potential, can be defined as a localized region of depolarization that travels down the nerve fiber with the membrane potential being immediately restored behind it. Transmission of nerve impulses to muscle Muscle contraction is the end result of a process similar to the transmission of action potentials from one neuron to another. The neurotransmitter that is released from the presynaptic neuron is a chemical called acetylcholine. The postsynaptic cells on the muscle cell membrane receive the acetylcholine, which increases the permeability of the muscle cell membrane to sodium and potassium ions. As the sodium ions enter the cell, the potassium ions leave, producing a net depolarization of the cell membrane.This electrical signal travels along the muscle fibers. The muscle action potential is conveyed through the movement of calcium ions into actual muscle contraction through the interaction of two types of proteins, actin and myosin.

Role in human health Bioelectricity is one of the fundamental forms of energy in the human body. In the form of moving action potentials, it is the basis for such central bodily functions as conduction of motor, autonomic, or sensory messages along the nerves; muscle contraction; and brain function. Specifically, motor nerve signals result in muscle contractions. Autonomic nervous signals control such basic functions of the body as breathing and heartbeat. Sensory nerve signals collect input from the outside world, including warnings of damage to the body in the form of pain.

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There are three types of electrical signals in human beings, two of which are routinely monitored or analyzed for diagnostic purposes. The first is the electroencephalogram, which is a relatively weak, fluctuating signal that originates in the brain. The second is the electrocardiogram, which is about 100 times stronger than the electroencephalogram, and is produced by the contractions of the heart muscle. The third type of electrical signal in humans, the surface electrical potential, is about as strong as the electrocardiogram but changes more slowly over time. The origin and significance of the surface electrical potential in humans are not yet known.

Common diseases and disorders A large number of diseases and disorders are related to disturbances of the bioelectrical system. These conditions can be classified according to the component of the nerve cell/muscle cell group, or motor unit, that is affected. The motor unit can be divided into the motor neuron, the nerve root (paired bundles of nerves coming from the spinal cord), the nerve plexus (bundles of nerves further removed from the spinal cord), the peripheral nerve, the neuro-muscular junction, and the muscle fiber. Defects in any of these components may disrupt bioelectrical signals. Defects in the motor neuron can be inherited, such as spinal muscular atrophies; or acquired, such as poliomyelitis or amyotrophic lateral sclerosis (Lou Gehrig’s disease). Nerve root problems may result from herniated disks in the spine, metastatic cancer, neurofibroma, or trauma. Diseases of the plexus include acute brachial neuritis (inflammation of the nerves of the arm), damage caused by diabetes mellitus, blood clots, metastatic cancer, and trauma. The peripheral nerves may be damaged through hereditary, infectious, inflammatory, and metabolic causes. Examples of some hereditary conditions include hereditary motor and sensory neuropathy (HMSN) and some autonomic neuropathies. Infection with diphtheria, herpes, HIV, leprosy, and Lyme disease can all cause types of peripheral neuropathies. Some inflammatory causes of peripheral neuropathy include chronic inflammatory demyelinating polyneuropathy (CIDP), GuillainBarrë syndrome, and vasculitis. Metabolic causes of peripheral nerve damage include amyloidosis, diabetes mellitus, dysproteinemic neuropathy, excessive ethanol intake (alcoholic neuropathy), and renal failure. Disorders of the neuromuscular junction can result from botulism (severe food poisoning caused by ingesting the neurotoxin made by Clostridium botulinum), congenitial myasthenic syndrome, Eaton-Lambert syn-

drome, myasthenia gravis, and toxic neuromuscular junction disorders. Muscle fiber problems can be divided into dystrophies, channelopathies, and congenital, endocrine, and metabolic defects. Dystrophies are diseases characterized by progressive muscular weakness. Channelopathies are diseases caused by defects in the ion channels that control the membrane conduction system. These include familial periodic paralysis and Thomsen’s disease. Central core disease, centronuclear myopathy, and nemaline myopathy are three examples of congenital muscle fiber damage. Endocrine disorders that may disrupt electrical signals to muscle tissue include acromegaly, Cushing’s syndrome, hypothyroidism, and thyrotoxic myopathy. Metabolic causes of muscle fiber damage include glycogen storage disease and lipid storage disease. Resources BOOKS

Cooper, Geoffrey M. The Cell. Washington, DC: ASM Press, 1997. Martin, John H., PhD. Neuroanatomy: Text and Atlas, 2nd ed. Norwalk, CT: Appleton & Lange, 1996. Senneff, John A. Numb Toes and Aching Soles: Coping with Peripheral Neuropathy. San Antonio, TX: MedPress, 1999. PERIODICALS

Zangaro, George. “Diabetic Neuropathy: Pathophysiology and Prevention of Foot Ulcers.” Clinical Nurse Specialist 13 (March 1999): 57. ORGANIZATIONS

The ALS Association, 27001 Agoura Road, Suite 150, Calabasas Hills, CA, 91301-5104. (888) 949-2577. <www.alsa.org>. The Neuropathy Association, 60 E. 42nd St., Suite 942, New York, NY, 10165-5714. (800) 247-6968. <www. neuropathy.org>. OTHER

“Excitable Cells.”Kimball’s Biology Pages January 13, 2001. (May 21, 2001).

Michelle L. Johnson, M.S., J.D.

Bioethics Definition Bioethics is the study of moral issues in the fields of biology and health.

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Bioelectrical signals in humans

Bioethics

KEY TERMS Cloning—The production of an organism that is genetically identical to its parent. Deoxyribonucleic acid (DNA)—The genetic material of all cellular organisms and most viruses. DNA carries the information needed to direct proteins. Each molecule of DNA consists of two twisted strands, called a double helix. Embryo—The initial developmental stage of human offspring following conception. After the eighth week an embryo is classified as a fetus. Gene—The basic unit of heredity found in the cells of all living organisms, from bacteria to humans. Genes determine the physical characteristics that an organism inherits, such as hair and eye color. Genetic engineering—Altering the genetic structure of an organism to provide it with traits deemed useful or desirable. Hippocratic Oath—An oath taken by physicians to observe the ethical standards of their profession. Human Genome Project—An international scientific collaboration that seeks to understand the entire human genetic blueprint. In vitro fertilization—Fertilization of an ovum by sperm outside the body, and subsequent implantation in the womb. Patent—A grant issued in the name of the United States under the seal of the Patent and Trademark Office, that gives the applicant exclusive rights related to ownership. Stem cell—An undifferentiated cell from which specialized cells develop.

Description Always complex and controversial, the field of bioethics has grown even more so with the advent of advanced technologies and treatments. The mechanical respirator and the heart-lung machine have blurred the line between life and death. The legalization of morningafter pills and the abortion drug RU-486, approved for use in the United States in 2000, have intensified the already volatile abortion debate. In vitro fertilization techniques to help infertile couples conceive raise a host of ethical issues including how couples should choose sperm or egg 270

donors, and what to do with fertilized eggs not implanted. Ethicists are also concerned with how scarce and expensive advanced treatments, such as in vitro fertilization, organ transplants, and the antiretroviral AIDS treatments should be distributed throughout society. The rapidly evolving field of genetic engineering in particular, is introducing some of the greatest challenges ever faced in bioethics, as humans develop the ability to affect changes to living matter that were beyond imagining in the past decade or two. Current areas in experimental genetics of interest to bioethicists include: • Cloning. The year 1997 marked the birth of the first clone, a sheep named Dolly produced from a cell of an adult female sheep. Since then hundreds of animals have been cloned, including bulls, cows, mice, monkeys, and pigs. Even clones of clones have been produced. The cloning controversy is multifaceted, with much of the controversy centered on the potential technical feasibility of cloning humans, although animal rights activists and others are also concerned that a substantial majority of cloned animals surviving to birth have significant birth defects. Humans should never be exposed to such risks, argue opponents of human cloning research. Some opponents fear a future in which cloning technology is used by narcissistic parents to custom design their offspring, while proponents see human cloning as a potentially useful technique to treat infertility or avoid known hereditary traits for disease. Several U.S. states have banned human cloning. • Stem cell research. Stem cells, which are undifferentiated cells that give rise to specialized cells throughout the body, are considered one of science’s best tools for finding cures for many diseases, as well as for developing bioartificial blood, skin, and organs that will not be rejected by the body. Stem cell research is currently hampered by the controversy surrounding the source of the cells, which are sometimes culled from aborted fetuses or from embryos left behind after fertility treatments, or are produced using cloning technology. Some religious groups such as the Roman Catholic Church condemn the use of human embryos for research, and Congress has passed restrictions on federal funding of embryonic stem cell research. • Gene patenting. Advances in genome research wrought by the Human Genome Project and others have led many individuals and institutions, public and private, to apply for patents on genes and gene combinations. Many fear the patenting of genes may make genetic testing of patients prohibitively expensive. Although it will be technically possible in the not-too-distant future to analyze patients’ genomes in the primary care en-

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• Genetic testing. Controversial genetic tests in use for several decades allow parents to learn about genetic diseases like sickle-cell anemia prior to birth. An experimental technique known as preimplantation genetic diagnosis gives couples even more control, enabling genetic analysis of embryos created through in vitro fertilization before they are implanted in the uterus. Many fear this technique may one day be used not just to pinpoint genetic diseases, but also to choose embryos with more desirable attributes. Other genetics tests that pinpoint flawed genes, and predict one’s drug responses and vulnerability to disease offer numerous potential benefits, but ethicists are concerned about how this information will be used. Employers or insurers may use such information to discriminate, for example.

Viewpoints A multitude of viewpoints exist regarding every area of health care influenced by bioethics. While some individuals believe bioethics results in legislation that unnecessarily impedes the progress of science (for example, it is costly and time consuming for researchers to comply with informed consent laws), most recognize the need for at least some bioethical guidelines (the costs of compliance pales in comparison to the safeguard of informed consent on human subjects). Some individuals believe the field of bioethics is increasingly important as research technologies develop with the potential to strip away human privacy, and even to alter the definition of human life. Private and public healthcare organizations have attempted to present ethical guidelines for practitioners. For example, the American Medical Association’s Council on Ethical and Judicial Affairs sets ethics policy for the American Medical Association (AMA), and AMA’s Institute for Ethics investigates how professional ethics can be integrated into health care. Other organizations such as the American Association of the Advancement of Science, take formal positions on various bioethical issues to guide health care practitioners and the general public. Also, the U.S. Department of Energy and the National Institutes of Health devoted 3% to 5% of their annual Human Genome Project budgets toward study of the bioethics of genetic information, making theirs the world’s largest bioethics program.

tremendous risks in addition to potent opportunities to predict and treat human diseases, there is a need for practitioners to main a bioethical framework in their use of these technologies, if they are to adhere to their professional oaths. Resources PERIODICALS

Lea, D. “A New World View of Genetics Service Models.” Online Journal of Issues in Nursing 5, no. 3 (2000). . ORGANIZATIONS

American Medical Association. The Council on Ethical and Judicial Affairs. 515 N. State Street, Chicago, IL 60610. (312) 464-4823. . ANA, American Nurses Association, 600 Maryland Avenue, SW, Suite 100 West, Washington, DC 20024. (800) 2744ANA. . American Society for Bioethics and Humanities. 4700 W. Lake, Glenview, Il 60025-1485. (847) 375-4745. Fax: (877) 734-9385. . The American Society of Human Genetics. 9650 Rockville Pike, Bethesda, Maryland 20814-3998. (301) 571-1825. . Center for Bioethics at the University of Pennsylvania, Suite 320, 3401 Market Street, Philadelphia, PA 19104-3308. (215) 898-7136. . National Bioethics Advisory Commission, 6705 Rockledge Drive, Suite 700, Rockville, Maryland 20892-7979. (301) 402-4242. . National Coalition for Health Professional Education in Genetics. (410) 583-0600. . NSNA, National Student Nurses Association, 555 West 57th Street, New York, NY 10019. (212) 581-2211. . The International Society of Nurses in Genetics. . OTHER

Human Genome Project Information. Ethical, Legal, and Social Issues. .

Ann Quigley

Biological rhythms Definition

Professional implications Because many of the current technologic advances in health care, including the advances in genetics, offer

A biological rhythm is one or more biological events or functions that reoccur in time in a repeated order and with a repeated interval between occurrences.

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vironment and provide them with information about their future disease risk, this technology will not be economically feasible if it requires payment of multiple license fees.

Biological rhythms

Description Biological rhythms are the ways that organisms adapt and live with the environmental rhythms around them, such as the spin of the earth, the movement of the earth around the sun, and movement of the moon around the earth. Often generated by “biological clocks” (the term for the internal physiological systems that track the environmental rhythms), biological rhythms allow an organism to harmonize successfully with its environment. Although biological rhythms have not been studied in every living thing, they have been found in every organism in which experiments were performed. Accordingly, scientists believe biological rhythms are ubiquitous. Generally, there are two types of biological rhythms, exogenous and endogenous. Exogenous biological rhythms are driven directly by the environment or another external influence. Another term for this type of biological rhythm is a direct effect. An example of an exogenous biological rhythm is the hopping of sparrows on a perch when a light is turned on. Such rhythms are said to have a geophysical counterpart; in this case, the presence of light. In contrast, endogenous biological rhythms are driven by internal biological clocks and are maintained even when environmental cues are removed. Some examples of endogenous biological rhythms are the wake-sleep cycle and the daily body temperature cycles. Sometimes it is difficult to determine whether the activity of an animal is due to a direct effect or that of an endogenous biological clock, because the two types of rhythms can mask each other. True biological clocks have four important characteristics. First, the clock is endogenous, meaning it gives the organism an innate ability to maintain periods of a particular length between biological functions. Experiments in space, with animals completely isolated from earthbound geophysical input, have supported the innate nature of the clocks. Second, the clock is temperature independent—a very unusual situation in biology but an essential characteristic to avoid biological rhythms being governed by the weather. Third, biological clocks have the ability to be reset in order to maintain a relationship with environmental cues. Finally, biological clocks are an internal continuous monitor of the passage of time, allowing the organism to keep track of duration biologically. Chronobiology, the study of biological rhythms, categorizes rhythms by the length of the cycle. The most studied type of biological rhythm are circadian rhythms, which fluctuate on a daily basis. Alertness, body temperature, and the circulating concentrations of growth hor272

mone, cortisol, and postassium are all examples of physiological functions that run on a circadian basis. Infradian cycles last about a month or longer. Menstruation in the human adult female is an example of an infradian biological rhythm. Circannual cycles last about a year; overwinter hibernation as a common example. The shortest cycles are ultradian, where the cycles are less than 24 hours. Heart rate and breathing are two examples of ultradian biological rhythms.

Function The function of biological clocks and the resulting biological rhythms involves two factors: the capacity of the biological clock to freerun (operate without external cues), and the ability of timing signals, known as Zeitgeber (German for “time-giver”), to synchronize the cycles to the environmental signals. Some common Zeitgebers include light, temperature, and social cues such as clocks, sound, or physical contact. A biological clock is said to be freerunning when these external cues are removed. Based on multi-day isolation experiments, the average freerun period for circadian rhythms in humans is 25 hours. Thus, if isolated from outside input, people tend to go to sleep one hour later each day, quickly becoming out of sync with the rest of the 24 hourbased human world. Entrainment is the process of aligning a biological rhythm with an environmental stimulus. There are limits to the time periods that biological rhythms can be entrained. For circadian rhythms in most animals, 18 hours is the shortest period tolerated, with an upper limit of about 28-30 hours. If Zeitgebers are provided for shorter or longer intervals, the organism reverts back to freerunning. A good example of entrainment is the acquisition of the 24-hour wake-sleep schedule by human infants after birth. Newborn circadian rhythms freerun, significantly disrupting the sleeping patterns of their parents. However, as they mature and become responsive to Zeitgebers such as light and dark, infants gradually adopt the 24-hour schedule of adults. Physiology of biological clocks The physiological location of biological clocks has been studied in a number of animal systems, including humans. In most vertebrates other than mammals—sparrows, for example—the primary biological clock has been located in the pineal gland. This gland is located at the base of the brain and is responsible for the production of melatonin, a hormone produced in high levels at night and low levels during the day. In mammals, additional cells responsible for biological clock functions were located in the hypothalamus, in

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The exact function of melatonin in mammals is not completely understood. Scientists believe this hormone is likely involved in many aspects of biology, including the wake-sleep cycle, body temperature control, and (particularly with mammals that have seasonal mating) sexual maturity and reproduction. Genetic control of biological clocks The molecular basis for the control of circadian rhythms has been studied extensively in the fruit fly insect model, where the first genetic mutants that affected circadian rhythms were discovered. Because homologs to the fruit fly genes (genes which have a similar structure, and therefore likely have a similar function) have been discovered in mammals, including mice and humans, scientists strongly suspect that similar control mechanisms have been conserved in mammals. In fruit flies, five genes are believed responsible for the baseline oscillation of the circadian rhythms: period (per), timeless (tim), clock (clk), cycle (cyc), and doubletime (dbt). The protein products of these genes work together to produce a negative feedback loop that allows the concentration of the period and timeless proteins to build in concentration slowly over the 12-hour day. Both clock and cycle are positive transcription elements. These proteins work together to result in the production of the period and timeless proteins. When the period protein is produced, the doubletime protein modifies it, marking it with a phosphate molecule for quick destruction by the cell if not paired with the timeless protein. Thus, the period protein will be degraded until the concentration of timeless protein is high enough so that period and timeless dimers form. The destruction resulting from the phosphate modification delays the formation of the dimers, stretching out the process over the 12-hour evening. Eventually, dimers of period and timeless are present in high enough concentrations to interact with clock and cycle proteins to turn off production of both period and timeless proteins, closing the feedback loop. At dawn, the highly light-sensitive timeless protein is degraded, leaving the phosphorylated period protein unpaired and vulnerable to degradation as well. In this way, light resets

KEY TERMS Chronobiology—The study of biological rhythms. Circadian—A biological rhythm that happens about once a day. Dimer—A pair of proteins that noncovalently bond to each other during function. Entrainment—The synchronization of a biological rhythm and an environmental cue. Freerun—The length of the period of a biological rhythm in the absence of environmental cues. Homolog—A gene found in a particular species that is similar in sequence and often in function to another gene from another species. Zeitgeber—A cue from outside the body that resets the biological clock.

the feedback loop to start again, making it the Zeitgeber for this biological clock. In early 2001, studies of the molecular basis of biological rhythms were extended to humans, with the report of the first known human gene homologous to the fruit fly genes. The gene is called hPer2 and is homologous to the period gene. A mutation in this gene is present in a Utah family and results in an advanced sleep phase syndrome. The mutation maps to the location where the period gene is marked with a phosphate, suggesting that the mutant protein would be not be phosphorylated. The details of the mutation fit the proposed function of the protein and the problems seen by those having the mutation. Lack of phosphorylation would cause the mutant protein to be degraded more slowly, speeding up the circadian rhythms of the person having the mutation.

Role in human health The exact role of biological rhythms and biological clocks in human health is not fully understood. However, it is clear that humans are subject to biological clocks in a number of physiological areas, most notably hormone secretion and wake-sleep cycles. A well-functioning biological clock is important for falling asleep and getting enough of the various stages of normal sleep. This affects, in turn, alertness, job performance, interpersonal relationships, and day-to-day safety issues. Well-functioning circadian rhythms may also play a role in psychological health, particularly for persons living in areas with decreased light in the winter months.

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two clusters of nerve cells called the suprachiasmatic nuclei (SCN). Light receptors in the retina are connected by nerves to the SCN. The SCN and the mammalian pineal gland are linked, by both nervous connections and by the presence of melatonin receptors on SCN cells. Thus, light is detected by the eye, which passes this information on to the SCN, which in turn passes the information on to the pineal gland, controlling melatonin production.

Biomedical engineering

Common diseases and disorders The most common human disorders related to biological rhythms are due to disassociations of the endogenous biological clock and the external environmental cue. These displacements are called phase shifts and occur with rapid travel across time zones and shift work. The resulting disorientation produces the symptoms known as jet lag—sleep disturbances, fatigue, indigestion, and nausea. When occurring in the workplace these symptoms can have serious consequences. The Exxon Valdez, Chernobyl, and Challenger shuttle disasters all occurred on the night shift. Research is ongoing to develop methods of using melatonin and bright light exposure to help compensate. The role of biological rhythms in seasonal affective disorder (SAD), a form of depression with symptoms more severe in the winter months, is much less clear. Studies have been unable to find other evidence of circadian disorder in persons diagnosed with SAD. However, treatment with light therapy does bring significant improvement in the majority of patients. Resources BOOKS

Binkley, Sue. Biological Clocks: Your Owner’s Manual. Amsterdam, The Netherlands: Harwood Academic Publishers, 1997. Refinetti, Roberto. Circadian Physiology. Boca Raton, Florida: CRC Press, 1999. PERIODICALS

Toh, K.L. et al. “An hPer2 phosphorylation site mutation in familial advanced sleep phase syndrome.” Science 291 (February 2001): 1040–1043.

Biomedical engineering Definition Biomedical engineering, also known as bioengineering, is the application of engineering principles to the study of medical and biological problems. The goal of biomedical engineering is to use electrical, chemical, and mechanical engineering principles to conduct studies and develop tools that can aid in the biomedical care of patients. In 1997, the National Institutes of Health issued the following expansive definition of biomedical engineering/bioengineering: “Bioengineering integrates physical, chemical, or mathematical sciences and engineering principles for the study of biology, medicine, behavior, or health. It advances fundamental concepts, creates knowledge from the molecular to the organ systems levels, and develops innovative biologics, materials, implants, devices, and informatics approaches for the prevention, diagnosis, and treatment of disease, for patient rehabilitation, and for improving health.”

Description Biomedical engineering can trace its history to as far back as a hundred years ago, when the first x-ray machines and electrocardiographs dramatically illustrated how technology could be applied towards the diagnosis of disease. Today, the field of biomedical engineering is in full flower, propelled by the momentum of the postWorld War II technology boom and the latest molecular, genetic, and computational developments. Having gone beyond its roots in imaging and instrumentation, biomedical engineering now encompasses at least 13 specialties, according to the 2000 edition of The Biomedical Engineering Handbook. These specialties include

ORGANIZATIONS

National Science Foundation Center for Biological Timing, CBT Gilmer Plaza, University of Virginia, Charlottesville, VA (804) 982-4500. . OTHER

• biomechanics • prosthetic devices and artificial organs • transport phenomena • biomaterials • biomedical instrumentation

“Clockwork Genes Discoveries in Biological Time.” Howard Hughes Medical Institute Web Page. 2000. . (April 20, 2001). “Seasonal Affective Disorder” National Mental Health Association Web Page. .

• biosensors • medical and biologic analysis • medical imaging • physiologic modeling, simulation, and control • biotechnology

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• rehabilitation engineering

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• medical informatics Biomechanics, prosthetic devices and artificial organs, and transport phenomena Biomechanics is the application of classical mechanics (the study of how objects move in response to forces placed on them) to biomedical problems. Classical mechanics provides general principles for understanding (for example) how fluids move, how objects become deformed under various forces, and how levers and forces move objects. Biomechanics uses these principles to understand how blood moves throughout the body, how injuries affect the shape and mechanics of body parts, and the mechanics of body movement (e.g. how an arm is lifted, or how a person walks). Biomechanics has contributed to an understanding of the mechanical function of the bones, cartilage, and soft tissue in the musculoskeletal system, as well as an understanding of other major organ systems, such as the heart, lungs, and blood vessels. Some of the technologies coming from biomechanics include artificial hearts and heart valves, and artificial joints such as prosthetic hip and knee replacements. These types of technologies have spawned another specialty in biomedical engineering, prosthetic devices and artificial organs. Another closely affiliated specialty is transport phenomena. This subfield concerns itself with the processes of fluid flow and heat transfer in biological systems.

systems to monitor the body’s physiologic status. Many of the physiologic changes that occur in the body are mediated by electrical signals. Different ions (charged elements or molecules) are allowed to flow into and out of cells at different times, depending on cellular and systemic demands. Biomedical instrumentation attempts to infer aspects of the body’s physiologic state by measuring and interpreting these electrical signals. Optical systems are used to measure the variable of interest indirectly; for example, because hemoglobin—the molecule that carries oxygen in the blood—changes its light absorptiveness according to whether it is attached to oxygen, changes in the oxygenation of blood can be inferred from the optical properties of blood and tissue. The specialty of biosensors focuses on the development and instrumentation of measurement systems. Technologies emerging from biomedical instrumentation generally, and biosensors specifically, include electrocardiographs (ECGs) and pulse oximeters that measure blood oxygenation. The associated specialty of medical and biologic analysis seeks to refine current understanding of the biomedical signals received by the instruments. It attempts to discern and amplify the signals of interest while diminishing noise and unrelated signals. In addition to biomedical measurement, the specialty of biomedical instrumentation includes the development of devices to control and guide biomedical processes through mechanical or electrical means, e.g., cardiac pacemakers and respirators.

Biomaterials Biomaterials are living and artificial materials that can be used in implantation. Whereas biomechanics focuses on the mechanical design of an implant, biomaterials science focuses on the body’s biochemical interactions with the material from which an implant is made. A biomaterial for an implant should be chemically inert, non-toxic, and non-carcinogenic. It should also be resilient enough to endure a lifetime of chemical and mechanical forces. Biomedical engineers in the specialty of biomaterials test and study materials possibly suited for implantation. Biomaterials science has contributed to the use and understanding of currently used implant materials, such as ceramics, polymers, metal alloys, and composite materials. Biomaterials science is also leading research into the use of living tissue as implant material with the goal of minimizing implant rejection and simulating the body’s original biomechanical environment. Biomedical instrumentation, biosensors, medical and biologic analysis Biomedical instrumentation, or bioinstrumentation, uses mechanical, electrical, and optical principles and

Medical imaging Medical imaging uses energy phenomena and physics principles, in conjunction with high-speed data processing, to produce images of the body that reflect its anatomic structure and physiologic function. Developments in medical imaging include x-ray applications (mammography, angiography), ultrasound, computer tomography (CT), magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), and positron emission tomography (PET). Each of these technologies is based on exploiting an understanding of electromagnetic or sound energy patterns to provide images of not readily observable aspects of body structure and function. Physiologic modeling, simulation, and control Physiologic modeling, simulation, and control—also known as systems physiology—attempts to provide formal quantitative models of the various systems of the body, from micro-level systems (at the level of the cell) to macro-level systems (at the level of large organ systems and full-body interactions). Using experimental

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• clinical engineering

Biomedical engineering

data and mathematical models, system physiology relies on computer simulation to describe and understand human physiology. These models provide a basis for thinking about how the body functions in an integrated way. Systems physiology is the source of such models as cardiovascular models, respiratory models, neural network models, and biochemical metabolic models. Biotechnology Biotechnology, also known as cellular, tissue, and genetic engineering, is the study of how biological materials can be modified at a micro-level for useful ends. Biotechnology studies the biochemistry and physics of cells to develop beneficial interventions and biomedical research and diagnostic tools. A sprawling specialty, biotechnology developments have included the development of new diagnostic tests for diseases, the invention of miniature devices that can deliver therapeutic drugs to specific sites, and the production of synthetic vaccines and therapeutic proteins.

Work settings Biomedical engineers and biomedical engineering technologists work in a variety of private and public sector settings. In the private sector, biomedical engineers and technologists find employment in industry, such as at biomedical device firms and pharmaceutical companies, and in hospitals. In the public sector, biomedical engineers and technologists are employed at research facilities, universities, and government agencies. Depending on the specialty, biomedical engineers may work in a laboratory setting, a clinical setting, a software development setting, or a managerial/administrative environment. Because of their multidisciplinary training, biomedical engineers often serve in a liaison or coordinating role, interacting with both engineering and medical professionals.

Education and training

Rehabilitation engineering Rehabilitation engineering focuses on developing tools for cognitive and physical rehabilitation. Specifically, rehabilitation engineering is concerned with designing technologies that assist mobility and communication. These include the development of rehabilitation prosthetics, the design of living space modifications, the development of transportation alternatives, and the design of hardware and software to aid in communication and cognitive rehabilitation. Clinical engineering Clinical engineering focuses on how the latest biomedical technologies are used in a clinical setting. Aspects of this specialty include the adaptation of biomedical technologies to the needs of the hospital and clinicians, the management of medical instrumentation and equipment, and the purchase and use of current biomedical technologies. An important aspect of clinical engineering is the interface between the medical instrumentation and the clinical software that records data of interest to the hospital. Patient safety and progress are also important aspects of clinical engineering. Medical informatics Medical informatics is the study of how information is used and disseminated in health care settings. Medical informatics includes the study of health information systems, computer networks in clinical settings, and clinical decision systems. Tools used in medical informatics 276

include neural network models, artificial intelligence models, expert systems, and patient records and archives.

A four-year university degree in a biomedical engineering or bioengineering program is the minimum required for a biomedical engineer. The undergraduate program gives training in both biological and engineering aspects of the field, and specialization in a subfield may be required. The undergraduate degree program should be accredited by ABET, or the Accreditation Board for Engineering and Technology, Inc., which imposes strict requirements on curriculum design and quality. If a biomedical engineer wants to offer his/her services to the public, she or he must be registered as a Professional Engineer. To qualify for a license, an individual must (1) have graduated from a degree program approved by ABET, (2) have had a minimum of four years of engineering experience, and (3) pass the Professional Engineer exam offered by the National Council of Engineering Examiners. After a Professional Engineer license is issued, the license can be renewed every two years, contingent on satisfying the continuing education requirements. To become a biomedical engineering technologist (BMET), a two-year (associate) degree in biomedical equipment technology or electronics technology is the minimum education typically required. In this program, the BMET learns the basic biomedical principles and the instrumentation skills required to operate and maintain biomedical equipment. Certification for BMETs is given through the International Certification Commission (ICC) for Clinical Engineering and Biomedical Technology. To be eligible

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Because of the continuing interest in biomedical technology developments, demand for biomedical engineers in government and at research institutes will remain moderately strong. Resources

Advanced education and training To conduct research and develop designs in biomedical engineering, a PhD degree in biomedical engineering is required; in some cases, depending on the specialty, a master’s degree may be sufficient. Some biomedical engineers also have advanced degrees in other fields such as clinical medicine. BMETs are typically offered many opportunities for on-the-job training. In addition, continuing education is a requirement for the renewal of BMET certification.

Future outlook The occupational outlook for biomedical engineering is good, particularly for those engineers who elect to work in industry. According to the University of Cincinnati Center for Economic Education, the medical instruments and supplies industry grew by 27% during the period from 1987 to 1994. The biotechnology industry has been expanding at an even faster rate. Although the recent economic downturn has slowed the expansion in the biotechnology sector somewhat, the health care industry and allied industries are expected to maintain strong growth. The American Society for Engineering Education reports that, among biomedical engineering Ph.D. graduates who received their degrees during the academic year 1996–97, the average starting salary for those working in industry was $62,000. About 50% of Ph.D. biomedical engineering graduates surveyed chose to work at universities, and the average salary of this group of graduates was $48,000. The average salary of clinical engineers (who do not have PhDs) was also $48,000. For biomedical engineering technologists, particularly those who work at hospitals, the outlook is very bright. According to the Association for the Advancement of Medical Instrumentation, the high demand for and relative shortage of BMETs mean higher salaries and greater benefits for job candidates. According to the 2000 salary survey reported in the Journal of Clinical Engineering, the average salary for a BMET I position in 1999 was $31,600, while that of a BMET III position was $48,000. Overall, the occupational outlook for biomedical engineers and biomedical engineering technologists is very good, especially in hospitals and private industry.

BOOKS

Bronzino, Joseph D., ed. The Biomedical Engineering Handbook, Volumes I & II. Boca Raton, FL: CRC Press, 2000. Yarmush, Martin L., Kenneth R. Diller, and Mehmet Toner. Annual Review of Biomedical Engineering. Palo Alto, CA: Annual Reviews, 2000. ORGANIZATIONS

The Association for the Advancement of Medical Instrumentation. 110 N. Glebe Road, Suite 220, Arlington, VA 22201-4796. (703) 525-0890. . The Biomedical Engineering Society. 8401 Corporate Drive, Suite 110, Landover, MD 20785-2224. (301) 459-1999. . Engineering in Medicine and Biology Society of the Institute of Electrical and Electronic Engineers. 445 Hoes Lane, Piscataway, NJ 08855-1331. (732) 981 3451. . OTHER

The Biomedical Engineering Network of the Whitaker Foundation. .

Genevieve Pham-Kanter

Biomedical equipment technology Definition Biomedical equipment technology professionals are employed at jobs involving the repair, sale, calibration, installation, troubleshooting, and management of biomedical instrumentation and electronics technology in the health industry.

Description Biomedical equipment technology is a profession that requires broad knowledge of biomedical system instrumentation. Necessary knowledge includes system usage, maintenance responsibilities, and ways to obtain data on an extensive range of monitoring, diagnostic, therapeutic, and surgical instrumentation. Solutions to issues encountered while interacting with doctors, nurs-

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for certification, an individual must have either the appropriate associate’s degree and two years of full-time BMET work experience, or four years of full-time BMET work experience. The individual must also pass the biomedical equipment technician test given by the ICC.

Biomedical equipment technology

es, and other technicians who use biomedical instrumentation are often studied and realized by those in the profession. A biomedical equipment technologist must study electronics, electronics management, medical physiology, and computer applications. After graduating, he or she may opt to specialize in particular types of equipment used, generally in nuclear medicine, surgery, radiology, clinical laboratory, dialysis, or intensive care.

Work settings Graduates of biomedical equipment technology programs usually work • in hospitals • in medical clinics • at medical colleges • at medical research facilities • at computer and electronic instrumentation manufacturers • at companies as sales representatives or distributors • in United States government agencies

Upon graduation from an associate degree program, a graduate will be capable of performing a range of tasks. Erie Community College of western New York and the University of Florida (which adds the final four items) provide lists of what is expected of a typical graduate, reproduced below: • Be able to use the resistor color code and component recognition.

• in the U.S. Armed Forces

• Be proficient at electronic soldering and terminating wire connections using solderless-type connectors.

• in public health services • as field service technicians On the job, a biomedical equipment technologist may work with machines used to diagnose and treat diseases or disorders, or those used to assist in the role of vital organs (e.g. a respirator). They often work under the supervision of biomedical engineers, performing such tasks as the evaluation, inspection, repair, maintenance, and installation of diverse instrumentation, including electrosurgical equipment; ultrasound devices; chemical analyzers; defibrillators; centrifuges; x-ray instrumentation; spectrophotometers; infusion pumps; heart, lung, and kidney dialysis machines; pacemakers; infant incubators; respirators; blood pressure and heart rate monitors; and magnetic resonance imaging (MRI or NMR) machines.

• Use a curve tracer to check all types of diodes, bipolar transistors, and field effect transistors. • Demonstrate proficiency in using electronic test instrumentation dual trace scopes, frequency counters, and function generators. • Be proficient at troubleshooting half-wave, full-wave, and bridge power supplies. In addition, students should be able to troubleshoot and repair voltage doublers. • Demonstrate proficiency in using electronic instrumentation. • Prototype multi-stage analog and digital circuits. • Interact with computer systems. • Isolate data communications systems faults. • Isolate and repair computerized process devices.

Education and training Biomedical equipment technologists may be trained at vocational schools (which may lead to a job involving on-the-job training), technical colleges, community colleges, military training schools, or at various universities as part of a standard Bachelor of Science program. Education includes instruction in electronics, circuit theory, computer applications, bio-instrumentation, health and safety, and general knowledge of human anatomy, physiology, and terminology. Background knowledge of 278

physics and mathematics is essential and is expanded during coursework, especially involving applications of biomedical electronics. The technologist should possess solid communication skills, manual dexterity, and handeye coordination for labor on machine parts and electronic circuits. Education generally culminates in an associate’s degree (two years) or a bachelor’s degree (four years). Many programs associated with either degree sponsor extensive co-op or internship opportunities that provide ample occasion to sample some aspects of the field. Specialties are not commonly available during educational training, but one may choose to specialize upon graduation in a relevant type of instrumentation technology; it is possible to specialize in a specific instrument if the demand is great enough, or to specialize in education, repair, calibration, etc.

• Analyze system malfunctions by relating program execution to specific groups of circuits. • Perform routine safety checks on equipment including ground and leakage current tests. • Read and interpret instructions and maintenance manuals as well as blueprints, mechanical drawings, and schematic diagrams related to equipment serviced. • Install equipment and provide instruction on its use to physicians, nurses, physical therapists, and others.

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• Modify components to meet specific therapeutic or diagnostic requirements. • Maintain an inventory of parts and tools used in repair work.

Advanced education and training Technicians with an associate’s degree have advancement opportunities including progressing to senior technician or shop supervisor and becoming certified within five years (normally two years); graduation results in eligibility to take the certification exam to become a certified biomedical equipment technician (CBET). With more advanced education, technicians may become instructors, administrators, or research assistants in medical research facilities. One may also advance through specializing, becoming an expert, in a particular type of equipment. Technicians with a bachelor’s degree have all the options open to associate’s degree holders with additional alternatives. Qualified students may further their education in biomedical equipment technology with a masters or doctoral degree, usually in a field such as electrical engineering or biomedical engineering; however, these graduates are then not generally classified as biomedical equipment technologists, but as biomedical engineers or an equivalent. The International Certification Commission for Clinical Engineering and Biomedical Technology (ICC) is the group responsible for formally recognizing qualified biomedical equipment technicians (BMETs) through administration of written examinations. Certification is achieved by exhibiting high aptitude in both the theoretical aspects and practical applications of the central tenets of biomedical equipment technology. The exam board, which is overseen by the ICC and the United States Certification Commission (USCC), governs not only the CBET certification program, but also the programs of two specialties: radiology equipment specialists (CRES) and clinical laboratory equipment specialists (CLES). Each program requires a separate examination for certification and is entirely independent of the others. It is also possible to become certified by the Association for the Advancement of Medical Instrumentation (AAMI).

Future outlook Biomedical equipment technologists are employed throughout the world, and there is always a need for professionals who can understand, operate, and instruct other health professionals in the increasingly complex, rarefied business of biomedical instrumentation. The outlook for biomedical equipment technologists is better than average in the near future (as of 2001), through at least the year 2005. The field of biomedical equipment technology is still considered relatively new, so job opportunities abound as new types of jobs are found for professionals with a biomedical equipment technology education and related experience. The plethora of biomedical devices on the market and waiting to reach the market is still accelerating, and as such, requires the assistance of biomedical equipment technicians to install, calibrate, test, maintain, evaluate, assist with usage of, instruct doctors and other health professionals about, and to repair. As might be expected, however, jobs for biomedical equipment technicians tend to be significantly greater in larger cities that include more hospitals and comparable medical facilities. Resources BOOKS

Carr, Joseph J., and John M. Brown. Introduction to Biomedical Equipment Technology, 4th ed. Prentice Hall, 2001. ORGANIZATIONS

Association for the Advancement of Medical Instrumentation (AAMI). 1110 N. Glebe Road, Suite 220, Arlington, VA 22201-4795. (703)525-4890. Fax: (701)525-1424. . OTHER

Biomedical Equipment Technology Program. . Biomedical Equipment Technology Program. . Biomedical Equipment Technology Program. .

Bryan Ronain Smith

Biophysical profile see Fetal biophysical profile Biopsy see Lung biopsy Biorhythms see Biological rhythms

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• Inspect and calibrate equipment such as radiation monitors, blood gas analyzers, electrocardiographs, dialysis machines, and many others to insure safety and accuracy.

Biotin

plication of diabetes, and those with Duchenne muscular dystrophy, who suffer from metabolic deficiencies.

Biotin Description Biotin is a member of the B complex family, but is not actually a vitamin. It is a coenzyme that works with them. Also known as vitamin H and coenzyme R, it was first isolated and described in 1936. It is water soluble and very unstable; it can be destroyed by heat, cooking, exposure to light, soaking, and prolonged contact with water, baking soda, or any other alkaline element. The body obtains biotin from food and can also synthesize this nutrient from bacteria in the digestive tract.

General use Biotin is utilized by every cell in the body and contributes to the health of skin, hair, nerves, bone marrow, sex glands, and sebaceous glands. Apart from being a vital cofactor to several enzymes, biotin is essential in carbohydrate metabolism and the synthesis of fatty acids. It is also involved in the transformation of amino acids into protein. Biotin plays a role in cell growth and division through its role in the manufacture of DNA and RNA, the genetic components of cells. Adequate biotin is required for healthy nails and hair, and biotin deficiency is known to be a factor in balding and the premature graying of hair. It has been claimed that, as part of an orthomolecular regime, it can reverse the graying of hair. When PABA and biotin are taken together in adequate amounts they can restore hair color. Biotin supplements will also effectively treat weak, splitting nails. Biotin can be a valuable tool to combat yeast infections, which are notoriously difficult to eradicate. In their book The Yeast Syndrome, John Parks Trowbridge and Morton Walker describe how adequate levels of biotin can prevent Candida albicans from developing from its yeast-like state into fungal form, in which it sends out mycelium that further invade body organs. Seborrheic dermatitis, or Leiner’s disease, which is a non-itchy, red scaling rash affecting infants during the first three months of life, is also treated with biotin and other B complex vitamins. Biotin has been used in conjunction with other nutrients as part of weight loss programs, as it aids in the digestion and breakdown of fats. High doses of biotin are sometimes used by the allopathic medical profession to treat diabetes since it enhances sensitivity to insulin and effectively increases levels of enzymes involved in glucose metabolism. Biotin is also used to treat peripheral neuropathy, a com280

Biotin can be found in beans, breads, brewer’s yeast, cauliflower, chocolate, egg yolks, fish, kidney, legumes, liver, meat, molasses, dairy products, nuts, oatmeal, oysters, peanut butter, poultry, wheat germ, and whole grains.

Preparations The recommended daily allowance for adults in the United States is 30 mcg. Daily requirements are estimated at 30 mcg for adults and 35 mcg for women who are nursing. Supplementation ranges from 100–600 mcg per day, and can be obtained in the form of brewer’s yeast, which contains biotin as part of the B complex, or as an individual biotin supplement.

Precautions The body needs biotin on a daily basis since it is not stored to any great extent. Biotin requirements increase during pregnancy and lactation, and should be supplemented in anyone who is taking antibiotics. Certain individuals are at risk for biotin deficiency, including infants fed biotin-deficient formula or with inherited deficiency disorders, patients who are fed intravenously, and anyone who habitually eats a lot of raw egg whites, because they contain a protein called avidin, which prevents the absorption of biotin. Mild deficiency Because it is synthesized in the digestive tract, deficiency symptoms of biotin are rare. However, they may include weakness, lethargy, grayish skin color, eczema (which may include a scaly red rash around the nose, mouth and other orifices), hair loss, cradle cap in infants, muscle aches, impaired ability to digest fats, nausea, depression, loss of appetite, insomnia, high cholesterol levels, eye inflammations, sensitivity to touch, anemia, and tingling in the hands and feet. Extreme deficiency Symptoms of extreme biotin deficiency include elevation of cholesterol levels, heart problems, and paralysis. When extreme deficiency is a problem, the liver may not be able to detoxify the body efficiently, and depression may develop into hallucinations. Infants may exhibit developmental delay and lack of muscle tone. Biotin deficiency could result in a loss of immune function, since animal experiments have shown that biotin deficiency resulted in a decrease in white blood-

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OTHER

Coenzyme—A non-protein organic compound that plays an essential role in the action of particular enzymes.

“Vitamins, etc.” (August 1, 2000).

Lactobacillus—A bacteria present in the digestive tract of healthy people.

Patricia Skinner

Mycelium—Fine thread-like tendrils sent out by a fungus to seek nutrition, capable of invading body organs. Peripheral neuropathy—Weakness and numbness of the nerves in the fingers and toes, which may progress up the limb—often a complication of diabetes.

cell function. Because biotin is essential to the body’s metabolic functions, any deficiency could result in impaired metabolism as well. Overdose There have been no reports of effects of overdose of biotin, even at very high doses, primarily because any excess is excreted in the urine.

Side effects There are no side effects associated with biotin supplementation.

Interactions Biotin works in conjunction with all the B vitamins, which are synergistic, meaning they work best when all are available in adequate amounts. Raw egg white contains the protein avidin, which prevents absorption of biotin. Sulfa drugs, estrogen, and alcohol all increase the amount of biotin needed in the body. In addition, anticonvulsant drugs may lead to biotin deficiency. Long term use of antibiotics may prevent the synthesis of biotin in the digestive tract by killing off the bacteria which help the body produce biotin. Supplements of lactobacillus may help the body make sufficient amounts of biotin after long term antibiotic use. Resources BOOKS

Kenton, Leslie. The Joy of Beauty. Great Britain: Century Publishing Co Ltd., 1983.

Bipolar disorder Definition Bipolar, or manic-depressive disorder, is a mood disorder that causes radical emotional changes and mood swings, from manic highs to depressive lows. The majority of bipolar individuals experience alternating episodes of mania and depression. The switch between highs and lows often comes without warning. For instance, a “high” mood can quickly deteriorate into a “low,” which causes the sufferer exceptional stress.

Description An estimate by the National Institute of Mental Health states that more than two million American adults—about 1% of the population age 18 and over in any given year—have bipolar disorder. Bipolar disorder typically develops in late adolescence or early adulthood. However, some people have their first symptoms during childhood, while others develop them late in life. Very often, bipolar disorder is not recognized as an illness. Many people suffer for years before it is properly diagnosed and treated. Like diabetes or heart disease, bipolar disorder is a long-term illness that must be carefully managed throughout a person’s life. An even grimmer survey by the National Depressive and Manic Depressive Association (NDMDA) estimates that over 17.4 million adults in the United States suffer with an affective disorder each year (one in seven people). Women are twice as likely as men to experience major depression, while manic depression occurs on an even percentage between the sexes. Onset of major or manic depression can occur at any age, however it most commonly develops between the ages of 25 and 44. The problem is compounded by inaccurate or no diagnoses in the early stages. A survey taken by the NDMDA reports that half of respondents reported visiting three or more professionals before receiving a correct

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KEY TERMS

Trowbridge, John Parks, and Morton Walker. The Yeast Syndrome. New York: Bantam Books, 1986.

Bipolar disorder

diagnosis, and over one-third reported a wait of 10 years or more before they were correctly diagnosed. The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR), the diagnostic standard for mental health professionals in the United States, defines four separate categories of bipolar disorder: bipolar I, bipolar II, cyclothymia, and bipolar not-otherwise-specified (NOS). Bipolar I disorder is characterized by manic episodes, the “high” of the manic-depressive cycle. A bipolar patient experiencing mania often has feelings of self-importance, elation, talkativeness, increased sociability, and a desire to embark on goal-oriented activities, coupled with the characteristics of irritability, impatience, impulsiveness, hyperactivity, and a decreased need for sleep. Usually this manic period is followed by a period of depression, although a few bipolar I individuals may not experience a major depressive episode. However, these individuals are usually characterized as mild, moderate, or severe without psychotic features. Mixed states, where both manic or hypomanic symptoms and depressive symptoms occur at the same time, also occur frequently with bipolar I patients (for example, depression with the racing thoughts of mania). Also, dysphoric mania is common (mania characterized by anger and irritability). Catatonic features occasionally occur. Two of the following must be present for the bipolar I diagnosis to move into bipolar I with catatonic features: 1. motor immobility; 2. excessive, purposeless motor activity that is not caused by external stimuli; 3. extreme negativity or mutism; 4. inappropriate or bizarre postures, movements, mannerisms, or grimaces; 5. repetitive or echoing speech patterns. Bipolar II disorder is characterized by major depressive episodes alternating with episodes of hypomania, a milder form of mania. At least one hypomanic instance must occur before the bipolar II criteria are met. Bipolar depression may be difficult to distinguish from a unipolar major depressive episode. Patients with bipolar depression tend to have extremely low energy, retarded mental and physical processes, and more profound fatigue (for example, hypersomnia; a sleep disorder marked by a need for excessive sleep or sleepiness when awake) than unipolar depressives. Catatonic features may also be present in bipolar II disorder. Cyclothymia refers to the cycling of hypomanic episodes with depression that does not reach major depressive proportions. For this diagnosis, symptoms must be present for at least two years for adults and one year for children and adolescents. During the one and two year diagnosis-gathering period, patients may not be symptomfree for more than a two-month consecutive period. After 282

the initial diagnostic periods, there may be superimposed mixed or manic episodes. In these instances, bipolar I and cyclothymic disorder may be diagnosed simultaneously. A third of patients with cyclothymia will develop bipolar I or II disorder later in life. A phenomenon known as rapid cycling occurs in up to 20% of bipolar I and II patients. In rapid cycling, manic and depressive episodes must alternate frequently—at least four times in 12 months—to meet the diagnostic definition. In some cases of “ultra-rapid cycling,” the patient may bounce between manic and depressive states several times within a 24-hour period. This condition is very hard to distinguish from mixed states. Bipolar NOS is a category for bipolar states that do not clearly fit into the bipolar I, II, or cyclothymia diagnoses. Examples include: • Very rapid transitions (a matter of days) between manic and depressed symptoms; • Recurrent hypomanic episodes without depressive symptoms; • Manic or mixed episodes that are superimposed on delusional disorder, residual schizophrenia, or psychotic disorder NOS; • Hypomanic episodes that alternate with depression, but are not frequent enough to qualify for a diagnosis of cyclothymia; • Situations where it has been assumed that a bipolar condition exists, but a determination cannot be made as to whether it is the primary diagnosis, is substanceinduced, or comes from another medical condition.

Causes and symptoms The source of bipolar disorder has not been clearly defined. Because two-thirds of bipolar patients have a family history of affective or emotional disorders, researchers have searched for a genetic link to the disorder. Studies have uncovered a number of possible genetic connections to the predisposition for bipolar disorder. Another possible biological cause under investigation is the presence of an excessive calcium buildup in the cells of bipolar patients. Also, dopamine and other neurochemical transmitters appear to be implicated in bipolar disorder and these are under intense investigation. Over half of patients diagnosed with bipolar disorder have a history of substance abuse. There is a high rate of association between cocaine abuse and bipolar disorder. Some studies have shown that up to 30% of abusers meet the criteria for bipolar disorder. The emotional and physical highs and lows of cocaine use correspond to the

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For some bipolar patients, manic and depressive episodes coincide with seasonal changes. Depressive episodes are typical during winter and fall, and manic episodes are more probable in the spring and summer months. Symptoms of bipolar depressive episodes include low energy levels, feelings of despair, difficulty concentrating, extreme fatigue, and psychomotor retardation (slowed mental and physical capabilities). Manic episodes are characterized by feelings of euphoria, lack of inhibitions, racing thoughts, diminished need for sleep, talkativeness, risk taking, and irritability. In extreme cases, mania can induce hallucinations and other psychotic symptoms such as grandiose illusions.

Diagnosis Bipolar disorder is usually diagnosed and treated by a psychiatrist and/or a psychologist with medical assistance. In addition to an interview, several clinical inventories or scales may be used to assess the patient’s mental status and determine the presence of bipolar symptoms. These include the Millon Clinical Multiaxial Inventory III (MCMI-III), Minnesota Multiphasic Personality Inventory II (MMPI-2), the Internal State Scale (ISS), the Self-Report Manic Inventory (SRMI), and the Young Mania Rating Scale (YMRS). The tests are verbal and/or written and are administered in both hospital and outpatient settings. Psychologists and psychiatrists typically use the criteria listed in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSMIV-TR) as a guideline for diagnosing this disorder and other mental illnesses. DSM-IV-TR describes a manic episode as an abnormally elevated or irritable mood lasting a period of at least one week that is distinguished by at least three of the mania symptoms: inflated selfesteem, decreased need for sleep, talkativeness, racing thoughts, distractibility, increase in goal-directed activity, or excessive involvement in pleasurable activities that have a high potential for painful consequences. If the mood of the patient is irritable and not elevated, four of the symptoms are required. Although many clinicians find the criteria too rigid, a hypomanic diagnosis requires a duration of at least four days with at least three of the symptoms indicated for manic episodes (four if mood is irritable and not elevated). DSM-IV-TR notes that unlike manic episodes, hypomanic episodes do not cause a marked impairment in social or occupational functioning, do not require hospi-

talization, and do not have psychotic features. In addition, because hypomanic episodes are characterized by high energy and goal directed activities and often result in a positive outcome, or are perceived in a positive manner by the patient, bipolar II disorder can go undiagnosed. Bipolar symptoms often present differently in children and adolescents. Manic episodes in these age groups are typically characterized by more psychotic features than in adults, which may lead to a misdiagnosis of schizophrenia. Children and adolescents also tend toward irritability and aggressiveness instead of elation. Further, symptoms tend to be chronic, or ongoing, rather than acute, or episodic. Bipolar children are easily distracted, impulsive, and hyperactive, which can lead to a misdiagnosis of attention deficit hyperactivity disorder (ADHD). Furthermore, their aggression often leads to violence, which may be misdiagnosed as a conduct disorder. Substance abuse, thyroid disease, and use of prescription or over-the-counter medication can mask or mimic the presence of bipolar disorder. In cases of substance abuse, the patient must ordinarily undergo a period of detoxification and abstinence before a mood disorder is diagnosed and treatment begins.

Treatment Treatment of bipolar disorder is usually involves medication. A combination of mood stabilizing agents with antidepressants, antipsychotics, and anticonvulsants is used to regulate manic and depressive episodes. Mood stabilizing agents such as lithium, carbamazepine, and valproate are prescribed to regulate the manic highs and lows of bipolar disorder. Lithium (Cibalith-S, Eskalith, Lithane, Lithobid, Lithonate, Lithotabs) is one of the oldest and most frequently prescribed drugs available for the treatment of bipolar mania and depression. Because the drug takes 4–10 days to reach a therapeutic level in the bloodstream, it is sometimes prescribed in conjunction with neuroleptics and/or benzodiazepines to provide more immediate relief of a manic episode. Lithium has also been shown to be effective in regulating bipolar depression, but is not recommended for mixed mania. Lithium may not be an effective long-term treatment option for rapid cyclers, who typically develop a tolerance for it, or may not respond to it. Possible side effects of the drug include weight gain, thirst, nausea, and hand tremors. Prolonged lithium use may also cause hyperthyroidism (a disease of the thryoid that is marked by heart palpitations, nervousness, the presence of goiter, sweating, and a wide array of other symptoms.)

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manic depression of the bipolar patient, making the disorder difficult to diagnose.

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Carbamazepine (Tegretol, Atretol) is an anticonvulsant drug usually prescribed in conjunction with other mood stabilizing agents. The drug is often used to treat bipolar patients who have not responded well to lithium therapy. Blurred vision and abnormal eye movement are two possible side effects of carbamazepine therapy. As of early 1998, carbamazepine did not have an FDAapproved indication for mania. Valproate (divalproex sodium or Depakote; valproic acid or Depakene) is one of the few drugs available that has been proven effective in treating rapid cycling bipolar and mixed states patients. Valproate is prescribed alone or in combination with carbamazepine and/or lithium. Stomach cramps, indigestion, diarrhea, hair loss, appetite loss, nausea, and unusual weight loss or gain are some of the common side effects of valproate. Note: valproate is also approved for the treatment of mania. Because antidepressants may stimulate manic episodes in some bipolar patients, their use is typically short-term. Selective serotonin reuptake inhibitors (SSRIs) or, less often, monoamine oxidase inhibitors (MAO inhibitors) are prescribed for episodes of bipolar depression. Tricyclic antidepressants used to treat unipolar depression may trigger rapid cycling in bipolar patients and are, therefore, not a preferred treatment option for bipolar depression. SSRIs, such as fluoxetine (Prozac), sertraline (Zoloft), and paroxetine (Paxil), treat depression by regulating levels of serotonin, a neurotransmitter. Anxiety, diarrhea, drowsiness, headache, sweating, nausea, sexual problems, and insomnia are all possible side effects of SSRIs. MAOIs, such as tranylcypromine (Parnate) and phenelzine (Nardil), block the action of monoamine oxidase (MAO), an enzyme in the central nervous system. Patients taking MAOIs must cut foods high in tyramine (found in aged cheeses and meats) out of their diet to avoid hypotensive side effects. Bupropion (Wellbutrin) is a heterocyclic antidepressant. The exact neurochemical mechanism of the drug is not known, but it has been effective in regulating bipolar depression in some patients. Side effects of bupropion include agitation, anxiety, confusion, tremor, dry mouth, fast or irregular heartbeat, headache, and insomnia. ECT, or electroconvulsive therapy, has a high success rate for treating both unipolar and bipolar depression, and mania. However, because of the convenience of drug treatment and the stigma sometimes attached to ECT therapy, ECT is usually employed after all pharmaceutical treatment options have been explored. ECT is given under anesthesia and patients are given a muscle 284

relaxant medication to prevent convulsions. The treatment consists of a series of electrical pulses that move into the brain through electrodes on the patient’s head. Although the exact mechanisms behind the success of ECT therapy are not known, it is believed that this electrical current alters the electrochemical processes of the brain, consequently relieving depression. Headaches, muscle soreness, nausea, and confusion are possible side effects immediately following an ECT procedure. Temporary memory loss has also been reported in ECT patients. In bipolar patients, ECT is often used in conjunction with drug therapy. Adjunct treatments are used in conjunction with a long-term pharmaceutical treatment plan. Long-acting benzodiazepines such as clonazepam (Klonapin) and alprazolam (Xanax) are used for rapid treatment of manic symptoms to calm and sedate patients until mania or hypomania have waned and mood stabilizing agents can take effect. Sedation is a common effect, and clumsiness, lightheadedness, and slurred speech are other possible side effects of benzodiazepines. Neuroleptics such as chlorpromazine (Thorazine) and haloperidol (Haldol) are also used to control mania while a mood stabilizer such as lithium or valproate takes effect. Because neuroleptic side effects can be severe (difficulty in speaking or swallowing, paralysis of the eyes, loss of balance control, muscle spasms, severe restlessness, stiffness of arms and legs, tremors in fingers and hands, twisting movements of body, and weakness of arms and legs), benzodiazepines are generally preferred over neuroleptics. Because bipolar disorder is thought to be biological in nature, therapy is recommended as a companion to, but not a substitute for, pharmaceutical treatment of the disease. Psychotherapy, such as cognitive-behavioral therapy, can be a useful tool in helping patients and their families adjust to the disorder, in encouraging compliance to a medication regimen, and in reducing the risk of suicide. Also, educative counseling is recommended for the patient and family. Calcium channel blockers (nimodipine or Nimotop), typically used to treat angina and hypotension, have been found effective in a few small studies for treating rapid cyclers. Calcium channel blockers stop the excess calcium build up in cells that is thought to be a cause of bipolar disorder. They are usually used in conjunction with other drug therapies such as carbamazepine or lithium. Clozapine (Clozaril) is an atypical antipsychotic medication used to control manic episodes in patients who have not responded to typical mood stabilizing agents. The drug has also been a useful prophylactic, or preventative treatment, in some bipolar patients.

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Risperidone (Risperdal) is another atypical antipsychotic medication that has been successful in controlling mania in several clinical trials when low doses were administered. The side effects of risperidone are mild compared to many other antipsychotics (constipation, coughing, diarrhea, dry mouth, headache, heartburn, increased length of sleep and dream activity, nausea, runny nose, sore throat, fatigue, and weight gain). Lamotrigine (Lamictal, or LTG), an anticonvulsant medication, was found to alleviate manic symptoms in a 1997 trial of 75 bipolar patients. The drug was used in conjunction with divalproex (divalproate) and/or lithium. Possible side effects of lamotrigine include skin rash, dizziness, drowsiness, headache, nausea, and vomiting. rTMS, or repeated transcranial magnetic stimulation is a new and still experimental treatment for the depressive phase of bipolar disorder. In rTMS, a large magnet is placed on the patient’s head and magnetic fields of different frequency are generated to stimulate the left front cortex of the brain. Unlike ECT, rTMS requires no anesthesia and does not induce seizures. Alternative treatment General recommendations include maintaining a calm environment, avoiding overstimulation, getting plenty of rest, regular exercise, and proper diet. Chinese herbs may soften mood swings. Biofeedback is effective in helping some patients control symptoms such as irritability, poor self-control, racing thoughts, and sleep problems. A diet low in vanadium (a mineral found in meats and other foods) and high in vitamin C may be helpful in reducing depression.

Prognosis While most patients will show some positive response to treatment, response varies widely, from full recovery to a complete lack of response to all drug and/or ECT therapy. Drug therapies frequently need adjustment to achieve the maximum benefit for the patient. Bipolar disorder is a chronic recurrent illness in over 90% of those afflicted, and one that requires lifelong observation and treatment after diagnosis. Patients with untreated or

KEY TERMS Affective disorder—An emotional disorder involving abnormal highs and/or lows in mood. Now termed mood disorder. Anticonvulsant medication—A drug used to prevent convulsions or seizures; often prescribed in the treatment of epilepsy. Several anticonvulsant medications have been found effective in the treatment of bipolar disorder. Antipsychotic medication—A drug used to treat psychotic symptoms, such as delusions or hallucinations, in which patients are unable to distinguish fantasy from reality. Benzodiazepines—A group of tranquilizers having sedative, hypnotic, antianxiety, amnestic, anticonvulsant, and muscle relaxant effects. DSM-IV—Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). This reference book, published by the American Psychiatric Association, is the diagnostic standard for most mental health professionals in the United States. ECT—Electroconvulsive therapy is sometimes used to treat depression or mania when pharmaceutical treatment fails. Hypomania—A milder form of mania which is characteristic of bipolar II disorder. Mixed mania/mixed state—A mental state in which symptoms of both depression and mania occur simultaneously. Mania—An elevated or euphoric mood, or irritable state that is characteristic of bipolar I disorder. Neurotransmitter—A chemical in the brain that transmits messages between neurons, or nerve cells. Changes in the levels of certain neurotransmitters, such as serotonin, norepinephrine, and dopamine, are thought to be related to bipolar disorder. Psychomotor retardation—Slowed mental and physical processes characteristic of a bipolar depressive episode.

inadequately treated bipolar disorder have a suicide rate of 15–25% and a nine-year decrease in life expectancy. With proper treatment, the life expectancy of the bipolar patient will increase by nearly seven years, with work productivity increasing by ten years.

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Common side effects of clozapine include tachycardia (rapid heart rate), hypotension, constipation, and weight gain. Agranulocytosis, a potentially serious but reversible condition in which the white blood cells that typically fight infection in the body are destroyed, is a possible side effect of clozapine. Patients treated with the drug should undergo weekly blood tests to monitor white blood cell counts.

Birth injuries

Prevention The ongoing medical management of bipolar disorder is critical in preventing relapse or recurrence of manic episodes. Even in carefully controlled treatment programs, bipolar patients may experience recurring episodes of the disorder. Patient education in the form of psychotherapy or self-help groups is crucial for training bipolar patients to recognize signs of mania and depression and to take an active part in their treatment program.

National Alliance for the Mentally Ill (NAMI). 200 North Glebe Road, Suite 1015, Arlington, VA 22203-3754. (800) 950-6264. . National Depressive and Manic-Depressive Association (NDMDA). 730 N. Franklin St., Suite 501, Chicago, IL 60610. (800) 826-3632. . National Institute of Mental Health (NIMH). 5600 Fishers Lane, Rm. 7C-02, Bethesda, MD 20857. (301) 443-4513. .

Jacqueline N. Martin, M.S.

Birth control see Contraception

Health care team roles The health care team roles are crucial to the proper treatment of bipolar disorder. Bipolar disorder requires lifelong care, and regular monitoring is essential so that the optimum treatment goals are achieved. A treatment team comprised of family members and caregivers, as well as professional staff, is advised to meet regularly to discuss progress and assess new needs. The treatment plan is based on input from a psychological or psychiatric evaluation, as well as input from the caregivers and the patient. This plan of care should be regularly updated and personalized to fit the patient’s individual needs. Periodic assessment will track the patient’s progress/ regression and will make use of current research. Resources BOOKS

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th ed. Washington, DC: American Psychiatric Press, Inc., 1994. Maxmen, Jerrold S., and Nicholas G. Ward. “Mood Disorders.” In Essential Psychopathology and Its Treatment, 2nd ed. New York: W.W. Norton, 1995, pp. 206-43. Whybrow, Peter C. A Mood Apart. New York: Harper Collins, 1997.

Birth injuries Definition A birth injury is defined by the Centers for Disease Control and Prevention (CDC) as an impairment of the neonate’s (a newborn; usually less than one-month old) body function or structure caused by adverse influences occurring at birth.

Description Birth injuries can occur during any birth. In the CDC’s April 1999 report on vital statistics, birth injuries were highest when mothers were 25 to 29 years of age and lowest when mothers were 40 to 54 years old. Birth injuries include: • asphyxia • shoulder dystocia • brachial plexus injury • fractures of the clavicle and humerus

PERIODICALS

• fractures of the long bones

Biederman, Joseph A. “Is There a Childhood Form of Bipolar Disorder?” Harvard Mental Health Letter, vol. 13, no. 9 (March 1997): 8. Bowden, Charles L. “Choosing the Appropriate Therapy for Bipolar Disorder.” Medscape Mental Health, vol. 2, no. 8 (1997). . Bowden, Charles L. “Update on Bipolar Disorder: Epidemiology, Etiology, Diagnosis, and Prognosis.” Medscape Mental Health, vol. 2, no. 6 (1997). .

• cerebral injury

ORGANIZATIONS

American Psychiatric Association (APA). Office of Public Affairs. 1400 K Street NW, Washington, DC 20005. (202) 682-6119. . 286

• cephalhematoma • facial nerve palsy

Causes and symptoms Infants of diabetic mothers are particularly at risk for birth injuries due to macrosomia (large body size). Macrosomia is a problem in about 33% of diabetic pregnancies, even with efforts for strong glycemic control. However, when glycemic control approximates normal blood glucose levels, injury rates are reduced. Macrosomia is also a problem associated with multipari-

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Diagnosis Asphyxia is defined as the presence of hypoxia and acidosis. Hypoxia is a decreased level of oxygen in the tissues. Acidosis is the increased concentration of hydrogen ions in the tissues, a metabolic imbalance. Asphyxia may occur in utero, due to umbilical cord compression, placenta previa, or placental abruption (a tearing away or detachment). It can also occur during birth and postpartum. Preterm infants are especially at risk for respiratory problems. Difficulty breathing can result in prolonged fetal circulation after birth because the ductus arteriosus fails to close. Meconium aspiration (inhalation by the newborn of its first intestinal discharges during labor and/or delivery) can also lead to impaired breathing. Deep suctioning may be required to rid the lungs of meconium. Meconium aspiration syndrome (MAS) is a serious condition in which the airway can become obstructed leading to respiratory distress, pneumonia, and even death. MAS is associated with hypoxia, pulmonary hypertension, and persistent fetal circulation. MAS occurs in only a small percentage of infants who aspirate meconium. Postdates infants (born later than the estimated date of delivery) are especially at risk for meconium aspiration, as are infants who suffered hypoxia in utero. Hypoxia leads to a relaxation of the anal sphincter muscles, allowing leakage of meconium into the amniotic (pertaining to the membrane around the fetus) fluid. MAS is eight times more likely to

occur in the postdates infant than in the term infant. Meconium release is also more likely with a breech delivery because of the pressure against the buttocks. Small for gestational age infants and preterm infants are a risk for asphyxia because of the increased risk of hypoxia and because their underdeveloped chest muscles lead to ineffective respiration. Infants born by cesarian section are also at risk for respiratory distress. This is because they avoid delivery through the birth canal which causes thoracic compression and its accompanying expulsion of lung fluid. The incidence of shoulder dystocia is increasing along with the rise in birth weight, although 40-50% of infants with shoulder dystocia have a birth weight under 4,000 grams. A large infant or cephalopelvic (size of the fetal head compared to the mother’s pelvis) disproportion may not be diagnosed prior to birth. During delivery, the head can be born, but the shoulders become stuck. Danger to the mother arises with prolonged labor and delivery, the risk of cervical or vaginal tears, and postpartal hemorrhage. Fetal risks include cord compression, fractured clavicle, and brachial plexus (spinal nerve network in neck-shoulder region) injury. Shoulder dystocia should be suspected with prolonged labor and in a condition called turtle sign. In turtle sign the fetal head is born then partially retracts, looking like a turtle with its head partially pulled back into its shell. Brachial plexus injury is the most common of the nerve injuries seen in neonates. Injury can arise from traction to the head and neck during a vertex (crown of the head) vaginal delivery, or during shoulder traction in a breech delivery. In Erb’s palsy (paralysis of the upper arm) the C5 and C6 nerves are affected, and the arm on the affected side is limp with the affected shoulder drawn toward or past the body’s median axis. The arm is internally rotated, with the elbow extended. The forearm is pronated (palms facing backwards), with wrist flexion. When eliciting the Moro reflex (primitive reflex that disappears a few months after birth), an assymetrical response is noted. The grasp reflex should remain intact. Klumpke’s palsy results from an injury to the C8 and T1 nerves. Diagnosis is suspected if the hand appears paralyzed, with a limp wrist and absence of the grasp reflex. Diaphragmatic paralysis or respiratory compromise can occur with injury to other cervical nerves. Not all brachial plexus injuries occur during birth. They may have occurred earlier during the pregnancy. Care should be taken during immobilization of the affected area to avoid contractures. Treatment may be followed by physical therapy. Full recovery in seen four months for 88% of cases, with 93% resolving within two years. Periodic neurologic evaluation can help avoid long-term impairment.

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ty (at least two births of a large infant by the same woman) because, with each pregnancy, the developing infant tends to be larger than its predecessor. A post-due date infant can also result in a large infant. When gestational age fetuses are large, they stretch the uterus, which can result in dysfunction during labor or delivery and increase the risk for postpartum hemorrhage. Larger infants have a 15% perinatal mortality rate versus the 4% mortality rate of appropriately sized neonates. Large infants born vaginally also have a higher than normal risk of shoulder dystocia, resulting in nerve injuries or fractured clavicle. In general, birth injuries are more likely to occur during a difficult vaginal birth, with prolonged labor, use of instrumentation such as forceps or vacuum extractor, with cephalopelvic disproportion, with fetal malpresentation, or during a Caesarian delivery. The injury may occur during labor, delivery, or neonatal resuscitation. Infants born preterm are especially at risk for birth injuries. One reason for this is the relationship between prenatal infections and preterm birth. Prenatal infection appears to play a significant role in premature delivery.

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may be associated with anemia or jaundice. Usually no treatment is undertaken unless it appears infected.

KEY TERMS Adduction—The limb is drawn in towards the body. Apgar score—The results of an evaluation of a newborn’s physical status, including heart rate, respiratory effort, muscle tone, response to stimulation, and color of skin. Macrosomia—A condition in which the neonate is large for gestational age with a high body weight. The condition is particularly associated with infants of diabetic mothers, especially if the diabetes is not well controlled. The circulating hyperglycemia encourages rapid growth and weight gain. Meconium aspiration—When a newborn inhales its first fecal discharges during labor or delivery. Pronation—The palm of the hand faces backwards.

A fractured clavicle may result from a difficult breech birth and also from shoulder dystocia. The clavicle should be straight, but if fractured a lump may be felt. At the time of the fracture, a cracking sound may be heard. A fracture should be suspected with decreased or lack of movement of the affected arm, swelling, skin discoloration, localized pain or tenderness, and lack of symmetry of the Moro reflex. The condition may also be asymptomatic. Injury can be confirmed by imaging. Treatment usually involves immobilizing the affected arm and shoulder for seven to ten days. Fractured long bones are usually caused by arm or leg rotation during a breech birth. It should be suspected with pain, swelling, and lack of movement on the affected side. The affected side may appear shorter. Imaging can confirm the diagnosis. Treatment usually involves casting the affected limb, with complete healing taking place in a month. Cephalhematoma is subcutaneous swelling caused by accumulation of blood from ruptured blood vessels located in the back of the neonatal skull underneath the scalp. It starts forming after trauma, perhaps as a result of the use of forceps or vacuum extractor, and increases in size over the next few days after birth. The swollen area may be black and blue due to the pooled coagulated blood. Cephalhematoma may resolve in a few days or take several months. The cephalhematoma is located on one or both sides and does not cross the suture lines. It 288

Facial nerve palsy is the paralysis of a facial nerve following injury. It can occur as a result of the use of forceps, or because of pressure on the nerve due to fetal position against the mother’s pelvic bones during birth or during the pregnancy. Lack of symmetry is most obvious when the infant cries. The affected side of the face looks smooth and the corner of the mouth droops. If the affected eye stays open it is necessary to use ophthalmic drops to avoid injury to the cornea. It usually resolves in a few days to weeks.

Treatment Treatment of asphyxia involves rapid recognition of a neonate in respiratory distress. A rapid respiratory may be the first warning sign of distress. Other signs include cyanosis, sternal retractions, and lack of respiratory effort. The Apgar evaluation (a physical assessment of newborns) scores respiratory rate at one and five minutes after birth. Should the infant appear in immediate distress, intervention and/or resuscitation is begun before the one-minute time period. Some infants have periods of apnea, or temporary stoppage of breathing. For some, stimulation of the soles of the feet may be enough to remind them to continue breathing. Others may need swift intervention. Cerebral palsy (CP) is associated with lack of oxygenation in utero, during birth, or shortly afterwards. However, some studies indicate that only 9% of cerebral palsy cases are directly caused by birth asphyxia. CP is also associated with maternal infection, a significant cause of preterm birth, and low birth weight and small for gestational age infants. Newborn infections such as meningitis or encephalitis can also result in cerebral palsy. Kernicterus (a severe form of jaundice) resulting from hyperbilirubinemia (a large amount of red bile pigment, or bilirubin, in the blood) can also lead to cerebral palsy. CP is also associated with premature rupture of membranes (PROM) due to the increased risk of infection and cord compression associated with PROM. Damage to the neonate can occur with the traction and rotation that accompanies delivery of the infant with shoulder dystocia. Asking the mother to perform the McRobert’s maneuver, or the sharp flexing of her thighs against her abdomen, can widen the pelvic outlet and facilitate delivery. Cesarian delivery does not avoid all cases of brachial plexus injuries because compression can occur in utero, not just with birth.

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The prognosis for birth injuries depends on many factors. Most of the injuries related to shoulder dystocia or fractured bones tend to heal completely, although some may require physical therapy or surgical intervention. About 10% of nerve injuries are permanent. Complications resulting from compromised oxygenation have a poorer outcome the longer the oxygen deficit has occurred. Cephalhematoma rarely requires intervention, but may when associated with anemia or hyperbilirubinemia. Degree of organ development at the time of birth is a significant factor in prognosis.

Resources BOOKS

Creasy, Robert K. and Robert Resnik. Maternal-Fetal Medicine, 4th Edition. Philadelphia: W. B. Saunders Company, 1999. Pillitteri, Adele. Maternal & Child Health Nursing: Care of the Childbearing and Childrearing Family. Philadelphia: Lippincott, 1999. Scott, James. Danforth’s Obstetrics and Gynecology, Eighth Edition. Philadelphia: Lippincott Williams & Wilkins, 1999.

Esther Csapo Rastegari, R.N., B.S.N., Ed.M.

Health care team roles Physicians, nurses, and respiratory therapists all play an important role in neonatal resuscitation. Physical therapists and nurses may have ongoing interactions with infants with cerebral palsy, or who need rehabilitation after injury from shoulder dystocia. Radiology technicians play an important role in gestational dating with ultrasound. Accurate dating and identification of small or large for gestational age infants can facilitate appropriate interventions.

Bites and stings Definition People can be injured by the bites or stings of many animals, including mammals such as dogs, cats, and fellow humans; arthropods such as spiders, bees, and wasps; snakes; and marine animals such as jellyfish and stingrays.

Prevention Many birth injuries cannot be prevented, as they occur in utero. Although having a member of a neonatal resuscitation team at every birth can facilitate swift intervention by specially trained individuals, it would be difficult to provide such services for all births, especially in small rural hospitals. The earlier intervention occurs, the better the prognosis. Respiratory distress is decreased with proper thermal regulation of the neonate. Drying the newborn under a radiant heater, changing the wet blankets for heated dry ones, and using a cap facilitates neonatal thermoregulation. Poor temperature control of the newborn increases respiratory effort. This is especially true in the preterm infant who has a decreased amount of brown fat. Ultrasonography assists in the diagnosis of placental problems, as well as in measuring fetal size. However, even with such technology, not all potential problems will be diagnosed prior to birth. Careful fetal monitoring during labor can often recognize fetal distress before permanent damage takes place. Close monitoring of the postdates fetus can decrease risk of placental insufficiency and cord compression due to insufficient amniotic fluid volume. The use of corticosteroids given to the mother before the delivery of a preterm infant can also decrease the risk of cerebral palsy.

Description Mammals DOGS. In the United States, where the dog popula-

tion exceeds 50 million, dogs surpass all other mammals in the number of bites inflicted on humans. Most come from family pets or other dogs known to the victim. Fortunately, most dog-bite injuries are minor. A 1994 telephone survey of American households indicated that there were 3,737,000 dog bites that did not require medical attention in the United States during that year, and 757,000 that did. Men and boys are more likely to be bitten than girls or women; not surprisingly, children face a greater risk than adults. Each year, about 10–20 Americans, mostly children under 10 years of age, are killed by dogs. In the United States, dog bites send an estimated 340,000 people to the emergency room each year. Children under 10 are more likely than older people to need immediate medical treatment; this is especially true for boys between five and nine. Children under ten were also much more likely to be bitten on the face, neck, and head. Few of the injuries suffered by people seeking emergency treatment were serious; most patients were

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Prognosis

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treated and released without being admitted or referred to another facility. CATS. Although cats are found in nearly a third of American households, their bites are far less common than dog bites. According to one study, cats inflict perhaps 400,000 harmful bites in the United States each year. Cat bites typically cause less tissue damage, but they carry a higher risk of infection (30-40%) than dog bites (15-20%). Young girls are the most likely to be bitten by cats. HUMANS. There are approximately 70,000 human bites each year in the United States. They can be just as serious a medical problem as a bite from an animal. Because the human mouth contains a multitude of potentially harmful microorganisms, these tend to become have a higher infection rate than those inflicted by animals.

Arthropods Arthropods are invertebrates such as insects, arachnids, crustaceans, and other subgroups of the phylum Arthropoda—a group that encompasses more than 700,000 species. The list of arthropods that bite or sting is extensive and includes lice, bedbugs, fleas, mosquitoes, blackflies, ants, chiggers, ticks, centipedes, scorpions, and other creatures. Spiders, bees, and wasps are the three that people encounter most often. SPIDERS. In the United States, only two kinds of ven-

omous spider have a truly life-threatening bite: black widow spiders and brown recluse spiders. The black widow, which is found in every state but Alaska, is probably the most infamous widow spider. It prefers dark, dry places such as barns, garages, and outhouses, and also lives under rocks and logs. Disturbing a female black widow or her web may provoke a bite. Red widow spiders are far more rare, but can be found in parts of Florida; their sting is also quite venomous. Brown recluse spiders also prefer sheltered places, including clothing, and may bite if disturbed. BEES AND WASPS. Bees and wasps will sting to defend their nests or if they are disturbed. Species common to the United States include honeybees, bumblebees, yellow jackets, bald-faced hornets, brown hornets, and paper wasps. More than 50 Americans die each year after being stung by a bee, wasp, or fire ant. Almost all of those deaths are caused by allergic reactions to the venom, not by its toxicity.

Snakes There are 20 species of venomous snakes in the United States; they’re found in every state except Maine, 290

Alaska, and Hawaii. Each year about 8,000 Americans receive a venomous snakebite, but no more than about 15 die; most of the deaths are from rattlesnake bites. The venomous snakes of the United States are divided into two families: Crotalidae (pit vipers) and Elapidae. Pit vipers, which take their name from the small heatsensing pit that lies between each eye and nostril, are responsible for about 99% of the venomous snakebites suffered by Americans. The group includes rattlesnakes, copperheads, and cottonmouths (also called water moccasins). This type of snake delivers its venom through two long, hinged fangs in the upper jaw. Some pit vipers carry a potent, fast-acting venom that can damage the brain and spinal cord. The venom of others, such as the copperheads, is less harmful. The Elapidae include two kinds of venomous coral snakes indigenous to the southern and western states. Because coral snakes are bashful creatures that come out only at night, they almost never bite humans, and are responsible for only about 25 bites a year in the United States. Coral snakes also have short fangs and a small mouth, which lessens the risk of a bite actually forcing venom through the skin and subcutaneous tissues into muscles or veins. However, if ingested, their venom is quite poisonous. Marine animals Several varieties of marine animal bite or sting, including sharks, jellyfish, stingrays, anemones, and even a few types of coral. Although only a few have venom powerful enough to kill, they can inflict painful injuries. As with spider and bee stings, allergic individuals can also have anaphylactic reactions to these bites.

Causes and symptoms Mammals DOGS. A typical dog bite results in a laceration, puncture, or crush injury. Infected bites usually cause pain, cellulitis (inflammation of the connective tissues), and a pus-filled discharge at the wound site within 8–24 hours. Most infections are confined to the wound site, but microorganisms in dogs’ mouths can cause systemic and possibly life-threatening infections such as sepsis and meningitis, especially among people with compromised immune systems that decrease their resistance to infection. Rabies is rare among pet dogs in the United States, most of which have been vaccinated against the disease. Tetanus is also a rare complication. CATS. Cat scratches and bites can transmit the Bartonella henselae bacterium, which can lead to cat-

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Cat bites are mostly found on the arms and hands. Sharp cat teeth typically leave behind a deep puncture wound that can reach muscles, tendons, and bones, which are vulnerable to infection because of their comparatively poor blood supply. This is one reason why cat bites are much more likely than dog bites to become infected. People are also less inclined to give cat bites immediate medical attention, increasing the risk that infection will set in. Infected cat scratches on fingers or toes, in fact, have been known to spread inward to the bone, and result in the need for amputation of the digit. HUMANS. Although children often bite other children, these bites are hardly ever severe. Most humans bites that require medical attention result from fights (raising the possibility of domestic or child abuse), sexual activity, medical and dental treatment, and seizures. They can transmit a wide range of dangerous diseases, including hepatitis B, syphilis, tuberculosis, and HIV.

Human bites fall into two categories: occlusional (true) bites and clenched-fist injuries. The former present a low risk of infection. The latter, which are very infectious and can permanently damage the hand, usually result when a fist hits teeth during a fight. People often wait before seeking treatment for a clenched-fist injury, with the result that about half of such injuries are infected by the time they are seen by a medical professional. Arthropods SPIDERS. People do not always feel a black widow’s bite. The first (and possibly only) evidence that a person has been bitten may be a mild swelling of the injured area and two red puncture marks showing where the spider’s fangs entered the skin. Within a short time, however, some victims begin to experience severe muscle cramps and rigid abdominal muscles. Other possible symptoms include excessive sweating, nausea, vomiting, headaches, and vertigo as well as breathing, vision, and speech problems.

A brown recluse spider’s bite can lead to necrotic arachnidism, in which the tissue in an area of up to several inches around the bite becomes necrotic, producing an open sore that can take months or years to heal completely. About 40% of all bites are accompanied by more severe symptoms: fever, chills, edema, nausea, vomiting, dizziness, muscle and joint pain, and a measles-like rash. The bite becomes hard and inflamed, and may turn gangrenous. In most cases, fortunately, the bite simply

produces a hard, painful, itchy, and discolored area that heals without treatment in two to three days. BEES AND WASPS. The familiar symptoms of bee and wasp stings include pain, redness, swelling, and itchiness in the area of the sting. Multiple stings can have much more severe consequences. If an allergic reaction occurs, there can be life-threatening symptoms of facial swelling, throat closure, tongue swelling, and airway blockage within a very short time.

Snakes Many pit viper and coral snake bites (20–60%) fail to poison (envenom) their victims, or manage to introduce only a small amount of venom into the victim’s body. The wounds, however, can still become infected by the harmful microorganisms that snakes carry in their mouths. Venomous pit viper bites usually begin to swell within 10 minutes and are sometimes painful. Other symptoms include edema at the wound site, skin blisters, discoloration, weakness, sweating, nausea, faintness, dizziness, bruising, and tender lymph nodes. Symptoms of severe poisoning include tingling in the scalp, fingers, and toes, muscle contractions, an elevated heart rate, rapid breathing, large drops in body temperature and blood pressure, vomiting of blood, and coma. Coral snake bites are painful but may be hard to see. After some time has passed, a bitten person begins to experience the effects of the venom, which include tingling at the wound site, weakness, nausea, vomiting, excessive salivation, and irrational behavior. Nerves in the head and neck can become paralyzed for six to 14 days, causing double vision, difficulty swallowing and speaking, respiratory failure, and other problems. Six to eight weeks may be needed before normal muscular strength is regained. Marine animals JELLYFISH. Jellyfish venom is delivered by barbs called nematocysts that are located on the creature’s tentacles. They sting anyone who brushes up against them, causing a red lesion that is instantly painful and itchy. The pain can continue up to 48 hours. Severe cases may lead to necrosis, muscle spasms and cramps, vomiting, nausea, diarrhea, headaches, excessive sweating, and other symptoms. In rare instances, cardiorespiratory failure results. STINGRAYS. Stingrays carry their venom in their tail spines, which can inflict deep puncture wounds. If, as often happens, pieces of spine become embedded in the wound, an infection can result. Most people are injured

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scratch disease, an uncommon and unpleasant but not usually life-threatening illness. The mouths of cats and dogs contain many of the same microorganisms, and many of the same types of infections can result.

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by a stingray when they inadvertently step on one that’s resting, and are lashed in the ankle by its tail. Stingray venom produces immediate, excruciating pain that lasts several hours. Sometimes the victim suffers a severe reaction, including vomiting, diarrhea, hemorrhage, a drop in blood pressure, and cardiac arrhythmia.

Diagnosis Mammals DOGS. Gathering information on the circumstances

of a dog attack is a crucial part of bite treatment. Among other things, medical professionals need to know when the attack occurred (the chances of infection increase dramatically if the wound has been left untreated more than eight hours) and what led to the attack (unprovoked attacks are more likely to be associated with rabid animals). The patient’s general health must also be assessed, including tetanus immunization history and possible allergies to medication. A physical examination demands careful scrutiny of the wound, with special attention to possible bone, joint, ligament, muscle, tendon, nerve, or blood-vessel damage that may have been caused by deep punctures or severe crush injuries. Experts advise that serious hand injuries should be evaluated by a surgeon who specializes in such cases. Most of the time, laboratory tests to identify the microorganisms in bite wounds are ordered only if infection is present. X rays and other diagnostic procedures may also be necessary. CATS. The diagnostic procedures used for dog bites also apply to cat bites. HUMANS. Anyone who has received a human bite must be tested for hepatitis B and other diseases; ideally, the biter should be tested as well. Clenched-fist injuries require evaluation by a hand surgeon. Because many people will deny having been in a fight, medical professionals are advised to always consider lacerations over the fourth and fifth knuckle—a typical clenched-fist injury—to be evidence of a bite wound, no matter what an individual says. Medical professionals should also look for other indications of spousal or child abuse when evaluating human bites.

Arthropods SPIDERS. Spider bites always require medical attention, although victims are often not aware that they’ve been bitten. To make matters worse, unless the spider is seen biting the victim, identifying which species is responsible is difficult. If possible, the spider should be

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captured and taken to the emergency room or doctor’s office for identification. Snakes Diagnosis relies on a physical examination of the victim, information about the circumstances of the bite, and a look at the snake itself (if it can safely be brought in for identification). Blood tests and urinalysis supply important data on the victim’s condition. Chest x rays and EKG (electrocardiogram) may also be necessary.

Treatment Mammals DOGS. Minor dog bites can be treated at home. The American Academy of Family Physicians recommends gently washing the wound with soap and water and then applying pressure to the injured area with a clean towel to stop the bleeding. Next, apply antibiotic ointment and a sterile bandage to the wound. To reduce swelling and fend off infection, ice should be applied and the injured area kept elevated above the level of the heart. The wound should be cleaned and ointment reapplied twice a day until healing is complete.

Any dog bite that does not stop bleeding after 15 minutes of pressure must be seen by a medical professional. The same is true for bites that are deep or gaping; for bites to the head, hands, or feet; and for bites that may have broken a bone, damaged nerves, or caused a major injury of another kind. Bite victims must also watch for signs of infection: fever, redness, swelling, warmth, increased tenderness, and pus at the wound site. Diabetics, people with AIDS or cancer, individuals who have not had a tetanus shot in five years, and anyone else who has a medical problem that can increase susceptibility to infection should seek medical treatment no matter how minor the bite appears. Medical treatment of dog bites involves washing the wound with an anti-infective solution. Dead and/or damaged tissue may be need to be removed, and any person whose tetanus shots are not up to date should receive a booster. Some wounds are left open and allowed to heal on their own, from the inside out, while others require stitches (stitching may be delayed a few days if infection is a concern). Many emergency departments prescribe antibiotics for all people with dog bites, but some researchers suggest that antibiotics are usually unnecessary and should be limited to those whose injuries or other health problems make them likely candidates for infection. A follow-up visit after one or two days is gen-

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erally required for anyone who has received bite treatment. Other than death by trauma, the biggest threat from a dog bite is rabies (although no one in the United States has contracted rabies from a dog bite for many years). Dogs who bite people should be contained and tested for rabies, unless the owner can prove the animal has been immunized. If this is not possible, a rabies vaccine series for the victim is effective if administered within two days of the bite. CATS. Because of the high risk of infection, people who are bitten by a cat should always see a doctor. Cat scratches do not require professional medical treatment unless the wound appears infected or the victim has a weakened immune system. Cats, like dogs, can also transmit rabies, and cats that inflict a bite should be contained and tested for rabies, unless their immunization history is known.

promising antivenin has been developed, but it’s not yet available for clinical use.

Medical treatment for cat bites generally follows the procedures used for dog bites. Experts advise, however, that cat-bite wounds should always be left open (not stitched) to prevent infection. Persons bitten by cats are also more likely to receive antibiotics as a preventive measure.

Black widow spider bites also need a doctor’s care. Apply ice to the bite, then take the patient to an emergency room. If necessary, antivenin is administered. In less severe cases, the symptoms are treated with calcium and muscle relaxants for spasms, along with drugs to lower blood pressure.

HUMANS. Human bites should always be examined by a doctor. Such bites are usually treated with antibiotics and left open because of the high risk of infection. A person who has been bitten may also require immunization against hepatitis B and other diseases. A followup visit is required after an occlusional bite. Persons who are being treated for a clenched-fist injury will require a daily follow-up examination for three to five days.

BEES AND WASPS. Most stings can be treated at home. A stinger can be scraped off the skin with a razor blade, fingernail, credit card, or piece of paper; using tweezers may push more venom out of the venom sac and into the wound. The area should be cleaned and covered with an ice pack. Aspirin and other pain medications, oral antihistamines, and calamine lotion can relieve the pain, itching, and swelling.

Arthropods SPIDERS. Brown recluse spider bites require immediate medical attention. Put an antiseptic on the bite, apply ice to reduce swelling, then get the patient to a doctor as quickly as possible. Analgesics, antihistamines, and a tetanus shot are the standard course of treatment, along with erythromycin and other antibiotics to combat infection. If necrosis results, the affected areas may need debridement.

Experimental treatment includes steroids to combat the hemolysis that can result from the spider venom. Surgical excision of the bite once eschar has developed may be an effective way to remove the venom and prevent further tissue damage. Interestingly, the leprosy drug dapsone has shown some promise in this area, and may prevent the need for surgery. Hyperbaric oxygen treatments may also restore blood flow to dying tissue. A

A close-up view of lacerations on the shin of an adult woman, inflicted by a Rottweiler dog. (Custom Medical Stock Photo. Reproduced by permission.)

The biggest risk from a bee sting is anaphylactic reaction to bee or wasp venom. This requires immediate medical attention. The danger signs, which usually begin within minutes after a sting, (but may not appear for several hours) include nausea, chest pain, hives (both internal and external), abdominal cramps, diarrhea, and difficulty swallowing or breathing. These last symptoms can be life threatening if not treated immediately. Patients with a history of allergic response to stings are prescribed a self-injecting kit of adrenaline and antihistamine. Snakes Although most snakes are not venomous, any snakebite should immediately be examined at a hospital. While waiting for emergency help to arrive, the victim should wash the wound site with soap and water, and then keep the injured area still and at a level lower

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minutes to neutralize the venom. Afterwards, the wound should be examined by a doctor to ensure that no pieces of spine remain.

Alternative treatment Arthropods

An insect bite caused this person’s lower lip to swell. (Custom Medical Stock Photo. Reproduced by permission.)

than the heart. Ice should never be used on the wound, and no attempts should be made to extract the venom. Making a cut at the wound site is also dangerous. It is important to stay calm and wait for emergency medical aid. When a snakebite victim arrives at a hospital, the medical staff must determine, if they can, whether the bite was inflicted by a venomous snake and, if so, how much venom the person received. Careful monitoring helps resolve doubtful cases. Fortunately, the effects of some snakebites can be counteracted with antivenin. Minor rattlesnake envenomations can be successfully treated without antivenin, as can copperhead and water moccasin bites. However, coral snake and the more dangerous rattlesnake envenomations require antivenin. Other treatment measures include antibiotics to prevent infection and a tetanus booster injection. Marine animals JELLYFISH. To stop envenomation from tentacles that cling to skin, various substances should be applied, depending on the species that delivered the sting. Vinegar, baking soda, meat tenderizer (papain), and other substances will neutralize nematocysts. Applying the wrong substance, however, can cause the nematocysts to fire again, increasing the dose of venom and the degree of pain for the victim. Once the tentacles have been neutralized, they can be scraped off, saved, and given to medical personnel for identification and diagnosis. Ice, topical anesthetics, antihistamines, steroids, and a tetanus booster can prevent further complications. As with bee stings, allergic reactions may occur, requiring emergency medical care. STINGRAYS. Stingray wounds should be washed with

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Several alternative self-care approaches are used to treat bee, wasp, and other minor arthropod stings, including aromatherapy, ayurvedic medicine, flower remedies, herbs, homeopathy, and nutritional therapy. The efficacy of these treatments has not been proven, however, and if alternative therapy delays the administration of traditional medical attention for dangerous bites or stings the risk of severe consequences increases.

Prognosis Mammals It is important to realize that apparently even minor bites can have serious consequences, and that prompt treatment is the key to a good outcome. Infected bites may require hospitalization and can be fatal if neglected. Surgery may be needed for severe bites. Arthropods SPIDERS. Even without treatment, adults tend to recover from black widow bites after two to three days. The risk of death, though rare, is highest for very young children, the elderly, and people with high blood pressure. BEES AND WASPS. The pain and other symptoms of a bee or wasp sting normally fade after a few hours. People who are allergic to such stings, however, can experience a severe and occasionally fatal reaction.

Snakes A snakebite victim’s chances of survival are excellent if medical aid is rendered in time. Some bites, however, result in amputation, permanent deformity, or loss of function in the injured area. Marine animals STINGRAYS. Stingray venom only rarely kills its

human victims.

Health care team roles Persons trained in first aid provide initial support. Emergency medical technicians provide life support and transportation to medical facilities. Physicians

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Prevention Mammals DOGS. The risk of a dog bite can be reduced by avoiding sick or stray dogs, staying away from dogfights (people often get bitten when they try to separate the animals), and not provoking or upsetting dogs while they are sleeping, eating, or tending their puppies. Infants and young children must never be left alone with a dog. Pit bulls, rottweilers, and German shepherd dogs—breeds that caused nearly half of all fatal dog attacks in the United States between 1997 and 2000—are potentially dangerous pets in households where children live or visit. All dog breeds benefit from obedience training and spaying or neutering to lessen the chances of aggressive behavior. CATS. Warn children to stay away from strange cats

and to avoid rough play and other behavior that can anger cats and cause them to bite. Arthropods SPIDERS. Common-sense precautions include exercising caution when clearing webs out of garages, outhouses, and other places favored by venomous spiders; keeping one’s hands away from places where spiders may be lurking; and, when camping or vacationing, checking clothing, shoes, and sleeping areas. BEES AND WASPS. When outdoors, avoid bee and wasp nests, and don’t eat sweet food or wear bright clothing, perfumes, or fragranced cosmetics that attract bees and wasps.

Emergency medical kits containing self-injecting epinephrine to counter anaphylactic shock are available for people with a history of allergic response to insect stings; these should be carried with them at all times. People who suspect they are allergic should consult an allergist about immunotherapy shots that can build up resistance to bee and wasp venom. Snakes Mowing the lawn, trimming hedges, and removing brush from the yard discourages snakes from living close

to homes. Use tongs to move brush, lumber, and firewood in case snakes are lying beneath them. Similarly, golfers should never use their hands to retrieve golf balls from a water hole, since snakes can be hiding in the rocks and weeds. Caution is also necessary when walking through weedy or grassy areas, and children should be prevented from playing in weedy, vacant lots and other places where snakes may live. Leather boots and long pants offer hikers and campers some protection from bites. Approaching a snake, even a dead one, can be dangerous, for recently killed snakes can still inflict a venomous bite if there is contact with the fangs. Marine animals JELLYFISH. Obey posted warning signs at the beach. Also, since jellyfish tentacles are transparent and can be up to 120 ft (36.5 m) long, great caution must be exercised whenever a jellyfish is sighted nearby. STINGRAYS. Shuffling while walking through shal-

low areas that may be inhabited by stingrays will disturb the water, causing the animal to move before it can be stepped on. Resources BOOKS

Holve, Steve. “Envenomations.” In Cecil Textbook of Medicine, 21st ed., edited by Lee Goldman and Bennett, J. Claude. Philadelphia: W.B. Saunders, 2000, 21742178. Linden, Christopher H., and Frederick H. Lovejoy, “Disorders Caused by Reptile Bites and Marine Animal Evenomations.” In Harrison’s Principles of Internal Medicine, 14th ed., edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 2544-2548. Norris, Robert L., Scott Oslund, and Paul S. Auerbach. “Ectoparasite Infestations and Arthropod Bites and Stings.” In Harrison’s Principles of Internal Medicine, 14th ed., edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 2548-2554. Sutherland, Struan, and James Tibballs. Australian Animal Toxins, 2nd ed. New York: Oxford University Press, 2001. PERIODICALS

Graudins A., M. Padula, K. Broady, and G. M. Nicholson. “Red-back Spider (Latrodectus hasselti) Antivenom Prevents the Toxicity of Widow Spider Venoms. Annals of Emergency Medicine 37 no. 2 (2001): 154-160. Herman, Bruce E., and Elisabeth Guenther Skokan. “Bites That Poison: A Tale of Spiders, Snakes, and Scorpions.” Contemporary Pediatrics 16 no. 8 (1999): 41-65. Jarvis, R. M., M. V. Neufeld, and C. T. Westfall. “Brown Recluse Spider Bite to the Eyelid.” Ophthalmology 107, no. 8 (2000): 1492-1496.

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trained in emergency or environmental medicine supervise treatment of bite victims. Registered nurses support, treat, and care for patients in emergency rooms and other hospital departments. Surgeons debride and repair serious bite wounds. Laboratory technicians process fluid and tissue specimens. Pathologists interpret test results. Physical therapists provide therapeutic services during the recovery period.

Bladder ultrasound

KEY TERMS Antibiotics—Substances used to fight bacteria that cause infection. Antibodies—Substances in the blood created by the body to combat infection. Antihistamines—Drugs that treat allergic reactions by acting against a substance called histamine, which the body releases as part of its immune response. Antivenin—An antitoxin to a specific animal venom. Antivenin is extracted from the blood serum of horses (or other animals) that have been immunized against the toxin. Blood serum—The component of blood plasma that remains after coagulation. Debridement—Removal of dead and/or damaged tissue.

American Academy of Emergency Medicine. 611 East Wells Street, Milwaukee, WI 53202. (800) 884-2236. . American Academy of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211-2672. (913) 9066000. . American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. (847) 4344000. . American Association of Poison Control Centers. 3201 New Mexico Avenue NW, Washington, DC 20016. (202) 3627217. . American College of Occupational and Environmental Medicine. 55 West Seegers Road, Arlington Heights, IL 60005. (708) 228-6850. . OTHER

City of Phoenix, Arizona. “Bites and Stings.” . Tamkin, Gary W. “Emergency Management of Brown Recluse Spider Bites: A Review.” . University of Sydney, Australia. “Australian Spider and Insect Bites.” .

Edema—Excessive fluid buildup in a body tissue. L. Fleming Fallon, Jr., M.D., Ph.D.

Eschar—Sloughed off dead tissue. Hemolysis—Breakdown of red blood cells. Necrosis—Dead skin, muscle, bone, or other tissue in the body caused by insufficient blood flow. Pus—A thick yellowish or greenish fluid composed of the remains of dead white blood cells, pathogens, and decomposed cellular debris; a definite sign of infection. Sepsis—A serious systemic infection caused by bacteria that have entered the bloodstream through a wound. Kasdan, M. L., A. S. Kasdan, and D. L. Hamilton. “Lionfish Envenomation.” Plastic and Reconstructive Surgery 80, no. 4 (1987): 613-614. Metry, D. W. and A.A. Hebert. “Insect and Arachnid Stings, Bites, Infestations, and Repellents.” Pediatric Annals 29, no. 1 (2000): 39-48. Sams, H. H., C.A. Dunnick, M. L. Smith, and L. E. King. “Necrotic Arachnidism. Journal of the American Academy of Dermatology 44, no. 4 (2001): 561-573. Sams, H. H. “Nineteen Documented Cases of Loxosceles reclusa Envenomation.” Journal of the American Academy of Dermatology 44, no. 4 (2001): 603-608. ORGANIZATIONS

American Academy of Clinical Toxicology. 777 East Park Drive, PO Box 8820, Harrisburg, PA 17105-8820. (717) 558-7750. .

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Bladder tumor antigen test see Tumor marker tests

Bladder ultrasound Definition A noninvasive method of assessing bladder volume and other bladder conditions using ultrasonography to determine the amount of urine retention or post-void residual urine.

Purpose Bladder ultrasound is used in the acute care, rehabilitation, and long-term care environments. It is a noninvasive alternative to bladder palpation and intermittent catheterization used to assess bladder volume, urinary retention, and post-void residual volume in postoperative patients who may have decreased urine output; in patients with urinary tract infections (UTIs), urinary incontinence, enlarged prostate, urethral stricture, neurogenic bladder, and other lower urinary tract dysfunctions; or in patients with spinal cord injuries, stroke, diabetes, and mental handicaps that may reduce the sensation of bladder fullness, thereby interfering with appropriate

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Precautions There are no contraindications for bladder ultrasound. However, users should be aware of errors in measurement that may occur. For the most accurate results, patients should be in a relaxed, supine (lying down) position, and the ultrasound scanning head should not be moved during the scan if a portable device is used. Measurements may be distorted in patients with staples or sutures, an indwelling catheter, or scar tissue. Fluid in a pelvic cyst or tumor may be misinterpreted as bladder volume.

Description Bladder ultrasound is conducted using a portable, battery-operated ultrasound scanner that consists of a small, handheld unit and an attached ultrasound probe. It may also be performed with a conventional ultrasound unit. The probe, which is placed on the patient’s abdomen over the bladder, holds a motorized scanning head with an ultrasonic transducer that transmits sound waves in a fanlike array that are reflected back from the patient’s bladder to the transducer. Data from multiple cross-sectional scans of the bladder are then transmitted to a computer in the handheld unit, which automatically calculates bladder volume. The handheld unit also contains an integral digital screen and printer for displaying the bladder volume measurements. The entire scan only takes a minute or two, is noninvasive and painless, and eliminates the discomfort, embarrassment, and risks associated with catheterization. The bladder ultrasound procedure is also referred to as bladder scanning or the bladderscan, after the brand name of the most widely available portable bladder ultrasound device. A dedicated portable bladder ultrasound scanner ranges in cost from approximately $6,000 to $10,000. Although general-purpose ultrasound scanners, such as those used in the radiology department, can be used to measure bladder volume, they may be inconvenient for regular use at the patient’s bedside due to their size and are much more expensive than portable units. However, they are often used for bladder ultrasound if there is no portable unit in the facility.

KEY TERMS Post-void residual volume—The amount of urine remaining in the patient’s bladder after voiding. Transducer—The part in the ultrasound scanning head that transmits acoustic energy and converts it into electrical energy to produce image data. Ultrasonography—An imaging modality that uses sound waves to produce anatomical images and measurements.

Preparation Before scanning, the end of the transducer scanning head should be wiped with alcohol and allowed to dry. Ultrasound transmission gel should then be applied to the end of the scanning head. The portable bladder ultrasound device should be set to either male or female; the male setting should be used for a female patient who has had a hysterectomy. To begin scanning, the tip of the scanning head should be positioned approximately one inch (2.5 cm) superior to the symphysis pubis and pointing toward the bladder. During scanning, the scanning head should be held stationary when obtaining measurements. For obese or elderly patients, abdominal flesh may need to be gently moved to one side while scanning to obtain more accurate results.

Aftercare After scanning is completed, the ultrasound gel should be wiped from the patient’s skin and the scanning head. The scanning head should then be cleaned with alcohol. Bladder volume measurements can then be printed out and attached to the patient’s chart. Depending on the bladder volume measured, urethral catheterization is performed to relieve urine retention if the patient cannot void on his/her own. If the patient has an indwelling catheter, the bladder volume measurement may indicate a need for catheter irrigation or checking for catheter blockage. The bladder scan may need to be repeated, depending on the catheterized or voided urine volume obtained.

Complications There are no complications associated with the bladder ultrasound procedure.

Results In general, if the bladder volume measured is greater than 300 milliliters, urethral catheterization or patient

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voiding. Bladder ultrasound may be used in rehabilitation for bladder assessment and training. Bladder ultrasound is used to evaluate bladder function in nursing home residents to monitor for UTIs, urinary incontinence, urinary retention, and bladder dysfunction associated with other medical conditions (e.g., pelvic organ prolapse).

Bleeding disorders

voiding to relieve urine retention should be performed. Clinical studies have demonstrated that using the bladder ultrasound scan instead of intermittent catheterization to measure urine retention reduces the risk of urinary tract infections.

Catheterization on Postoperative Patient Outcomes. University of Iowa College of Nursing Gerontological Nursing Interventions Research Center. .

Jennifer E. Sisk, M.A.

Health care team roles In the acute care setting, the nurse and physician are responsible for monitoring urine output in postoperative patients. In the long-term care and rehabilitation settings, the primary responsibility for monitoring urine output and/or bladder function lies with the nursing staff. Device manufacturer representatives provide in-service training to nursing staff on using the bladder ultrasound scanner. Clinical and nurse managers may also implement bladder scanning protocols and results and outcomes tracking, particularly when bladder ultrasound replaces intermittent catheterization protocols with the goal of reducing catheterization-related costs and infections. Resources PERIODICALS

Phillips, JoAnne K. “Integrating Bladder Ultrasound into a Urinary Tract Infection-Reduction Project.” American Journal of Nursing 100, no. 3 (March 2000, Supplement).. Smith, Diane A. “Gauging Bladder Volume without a Catheter.” Nursing 29, no. 12 (December 1999):52-3. . Sulzbach-Hoke, Linda M.; Schanne, Linda C. “Using a Portable Ultrasound Bladder Scanner in the Cardiac Care Unit.” Critical Care Nurse 19, no. 6 (December 1999):35-9. Warner, Amy J.; Phillips, Susan; Riske, Karin; Haubert, MariKay; Lash, Nancy. “Postoperative Bladder Distention: Measurement with Bladder Ultrasonography.” Journal of PeriAnesthesia Nursing 15, no. 1 (February 2000):20-5. Wooldridge, Leslie. “Ultrasound Technology and Bladder Dysfunction.” American Journal of Nursing 100, no. 6 (June 2000, Supplement). . ORGANIZATIONS

American Urological Association. 1120 North Charles Street, Baltimore, MD 21201. (410) 727-1100. . Society of Urologic Nurses and Associates. East Holly Avenue Box 56, Pitman, NJ 08071-0056. (856) 256-2335. . OTHER

Neitzel, Jennifer; Frederickson, Martha; Miller, Elaine Hogan; Cassibo, Lori. The Effects of Bedside Ultrasound Assessment of Bladder Volume vs. Intermittent 298

Bleeding disorders Definition Bleeding disorders are disruptions in the body’s ability to control blood clotting. Patients with these conditions bleed easily for longer periods of time than normal.

Description Coagulation, or clotting, is a complex process involving at least 20 components of the blood, including various enzymes, messenger chemicals, and proteins. Under normal circumstances, the components necessary for coagulation circulate in the blood. When an injury occurs, they act together in a series of chain reactions to form a clot and prevent uncontrolled bleeding. Several disorders affect the blood’s clotting components and diminish normal clotting capability. For people with these disorders, even a small injury could make them bleed to death. Anatomy of a blood clot In healthy individuals, clots begins when fibrin, an insoluble protein that forms the skeleton of the clot, forms at the wound site from fibrinogen, a soluble protein present in plasma. This chemical change is made possible by thrombin, an enzyme that itself is only created from the compound prothrombin when an injury occurs. Once fibrin strands are formed at the wound site, they trap platelets that flow past them. Platelets then initiate the contraction of damaged blood vessels so that less blood is lost. They also help plug damaged blood vessels and work with plasma to accelerate blood clotting. Hemophilia A Hemophilia A, also known as classic hemophilia, is a genetic disorder carried by females but expressed almost exclusively in males. The disorder is characterized by a lack of factor VIII, a glycoprotein found in blood plasma that, like all coagulation factors, is essential for blood clotting. Hemophilia causes uncontrolled

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Hemophilia B This X-linked genetic disorder, sometimes called Christmas disease (after one of the first patients in whom it was recognized) is a deficiency of the blood clotting factor IX, or plasma thromboplastin component, which is normally produced by the liver. Like hemophilia A, patients with hemophilia B bleed uncontrollably when injured, and the disease is carried almost exclusively by females; males are almost exclusively afflicted. The degree of severity depends where on the gene the defect is found. Hemophilia B is relatively rare, occurring in at least 1:50,000 people; some estimates are 1:25,000. Hemophilia C Hemophilia C is extremely rare, occurring in about 1:100,00 people; it is the only type of hemophilia that can be expressed equally in either males or females. It is marked by a deficiency of the blood clotting factor XI, although, unlike hemophilia A and B, the level of factor XI does not correspond to the disease’s severity. Hemophilia C is especially prevalent (1:10,000) among Ashkenazi Jews; in Israel it is estimated to affect 8% of the population. Disseminated intravascular coagulation disorder (DIC) Unlike hemophilia, DIC, also known as consumption coagulopathy or defibrination syndrome, is neither hereditary nor common. It is almost always caused by another disease or condition, which in turn activates abnormal and uncontrolled clotting. This causes many small blood clots to form throughout the body, giving the disease its name. This overproduction of clots depletes the supply of clotting factors and platelets necessary to prevent hemorrhage when an injury (or surgery) occurs. Patients with DIC will bleed abnormally even though there is no history of coagulation disorder. Thrombocytopenia (TCP) Thrombocytopenia is a group of bleeding disorders characterized by severely diminished platelet counts, which cause internal bleeding. TCP can occur during pregnancy, as a reaction to certain medications, when the spleen and lymph produce antibodies against

platelets, or for no known reason, a type called idiopathic TCP. Other bleeding disorders Von Willebrand’s disease (vWD), also called pseudohemophilia B, vascular hemophilia, or angiohemophilia, is a hereditary disorder, that, like hemophilia, is connected with a factor VIII deficiency and causes uncontrolled bleeding. Unlike hemophilia, however, the true deficiency is the von Willebrand factor, a blood plasma protein that helps transport and protect factor VIII platelets and also helps platelets adhere to tissue at wound sites and also. A further distinction is that both males and females can be affected, making vWD the most common type of bleeding disorder. There are three types of the disease: the first two are mild; the third is the most severe, and must be inherited from both parents. Hypoprothrombinemia, or factor II deficiency, is a lack of prothrombin (or factor II) that can lead to hemorrhage. The genetic type of the disorder is very rare, and must be inherited from both parents to emerge. Acquired factor II deficiency can result from vitamin K deficiency, liver disease, and several types of gastrointestinal disorders. Factor VII deficiency, also called proconvertin deficiency or serum prothrombin conversion accelerator (SPCA) deficiency, can be either congenital or acquired through disease, use of anticoagulants, or malnutrition. The congenital form is often diagnosed when newborns react to the trauma of birth with intracranial bleeding. The disease is quite rare, with 1:500,000 people, both males and females, afflicted.

Causes and symptoms Hemophilia Hemophilia A is usually inherited through a complex genetic system that passes a recessive gene on the female chromosome. If a woman carries the hemophila gene, each of her male children has a 50% chance of having hemophilia; each female child has a 50% chance of carrying the gene. About a third of all hemophilia patients develop the disease with no known genetic risk; these cases, called sporadic hemophilia, are assumed to be the result of spontaneous genetic mutation. Hemophilia A is suspected with when patients exhibit numerous large, deep bruises along with painful and swollen joints caused by internal bleeding. Mild hemophilia may first be discovered when prolonged bleeding follows a surgical procedure. If this involves bleeding into the neck, head, or digestive tract, or of the bleeding

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bleeding, often internally, which is not only painful, but can permanently damage muscles and joints. The disease can be mild to severe, depending on how much (or little) factor VIII the body produces. Hemophilia A affects about 20,000 Americans, and is found worldwide in about 1:10,000 males; the most severe form is less common, appearing in 1:16,000 males.

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is caused by an injury, emergency measures may be required. Hemophilia B Hemophilia B is also hereditary but less common than hemophilia A. Its severity varies from mild to severe, although mild cases are more common. Hemophilia B symptoms are similar to those of hemophilia A, including numerous large and deep bruises and prolonged bleeding. The more dangerous symptoms are those that represent possible internal bleeding, such as swollen joints or bleeding into internal organs upon trauma. Hemophilia C Nearly 50% of patients with this disorder experience no symptoms, but others may notice blood in their urine, nosebleeds, or bruising. Although joint bleeding seldom occurs, some patients will experience bleeding long after an injury occurs. Some women will experience prolonged bleeding after childbirth. Disseminated intravascular coagulation DIC has a number of causes, and it is not thoroughly understood why or how they lead to the coagulation problem. It is known, however, that DIC’s underlying causes share factors that affect proteins, platelets, or other clotting factors and processes. For example, uterine tissue can enter the mother’s circulation during prolonged labor, thus introducing foreign proteins into the blood; the venom of some exotic snakes can activate one of the clotting factors; severe head trauma can expose blood to brain tissue. No matter the cause, the results are a malfunction of thrombin (an enzyme) and prothrombin (factor II), which activate the fibrinolytic system, releasing clotting factors in the blood. DIC can alternate from hemorrhage to thrombosis, and both can exist, which further complicates diagnosis and treatment. Symptoms may include minute hemorrhage spots on the skin, and purple patches or hematomas caused by bleeding in the skin. Patients may also bleed from surgery or intravenous injection (IV) sites. Related symptoms include vomiting, seizures, coma, shortness of breath, shock, severe pain in the back, muscles, abdomen, or chest. Thrombocytopenia Thrombocytopenia, a defective or decreased production of platelets (thrombocytes), may be acquired or congenital. The most common cause of acquired TCP is medication use—mainly heparin or chemotherapy agents (also some antibiotics). Symptoms include sudden onset 300

of petechia or purpura, or bleeding into mucous membranes (such as nosebleeds). The disorder may also be evident as blood in vomit or stools, or unusually heavy menstrual flow in women. Some patients show none of these symptoms, but complain of fatigue and general weakness. Thrombocytopenia has several causes, most of which are more commonly acquired as a result of another disorder. Common underlying disorders include leukemia, drug toxicity, or aplastic anemia, all of which lead to decreased or defective production of platelets in the bone marrow. Other diseases, such as severe infection, disseminated intravascular coagulation, and cirrhosis of the liver may destroy platelets outside the marrow. The idiopathic form most commonly occurs in children, and is most likely the result of production of antibodies in the spleen and liver that destroy platelets. Other bleeding disorders Von Willebrand’s disease is caused by a defect in the von Willebrand clotting factor, a blood chemical that regulates the production and availability of factor VIII. In rare cases, it may be acquired. Symptoms include easy bruising, bleeding in small cuts that stops and starts, abnormal bleeding after surgery, and abnormally heavy menstrual bleeding. Nosebleeds and blood in the stool with a black, tarlike appearance are also signs of von Willebrand’s disease. Hypoprothrombinemia is a very rare deficiency in prothrombin, or factor II, a glycoprotein formed and stored in the liver. Unlike hemophilia, both parents must be carriers for the disease to occur. Under normal conditions, prothrombin is converted to thrombin as part of the clotting cascade, which activates fibrin and begins the process of coagulation. Some patients may show no symptoms while others will suffer severe hemorrhaging. Patients may experience easy bruising, profuse nosebleeds, postpartum hemorrhage, excessively prolonged or heavy menstrual bleeding, and postsurgical hemorrhage. Hypoprothrombinemia may also be acquired rather than inherited, usually as a result of vitamin K deficiency caused by liver diseases, newborn hemorrhagic disease, or a number of other factors. Factor VII deficiency causes varying types and degrees of bleeding, depending on the severity of the disease. Patients may bleed from the gums or nose, within the skin, or into the joints, stomach, intestine, and urinary tract. Women may experience heavy menstrual bleeding.

Diagnosis There are hundreds of different tests to detect various bleeding disorders, each one geared to the hallmarks

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Hemophilia A Hemophilia A (factor VIII deficiency) will be diagnosed with laboratory tests detecting presence of clotting factor VIII, factor IX (to distinguish it from hemophilia B), and others, as well as the presence or absence of clotting factor inhibitors. Hemophilia B Tests for hemophilia B look for diminished levels of factor IX, along with analyses of prothrombin and thromboplastin. Hemophilia C Hemophilia C (factor XI deficiency) is diagnosed with a test to measure the amount of factor XI in the blood. Disseminated intravascular coagulation Disseminated intravascular coagulation can be diagnosed through a number of laboratory tests that measure the concentration of platelets and fibrinogen in the blood with normal counts and prolonged prothrombin time. Other supportive data include diminished levels of factors V, VIII, and fibrinogen, hemoglobin, and other chemicals. Since many of the test results also indicate other disorders, the physician may have to put together several results to reach a diagnosis of DIC. Serial tests may also be recommended, because a single examine at one moment in time may not reveal the process that is occurring. Thrombocytopenia Tests for thrombocytopenia include coagulation tests revealing a decreased platelet count, prolonged bleeding time, and others. If these tests indicate that platelet destruction is causing the disorder, the physician may order bone marrow examination. Other bleeding disorders Von Willebrand’s disease will be diagnosed with laboratory tests that show prolonged bleeding time, absent or reduced levels of factor VIII and von Willebrand factor, a normal platelet count, and others.

Hypothrombinemia is diagnosed by medical history and tests that measure deficiencies in vitamin K, prothrombin, and clotting factors V, VII, IX, and X. Factor VII deficiency can be diagnosed with blood tests that show a diminished level of factor VII in the blood, along with other blood tests showing a prolonged prothrombin time and normal partial thromboplastin time.

Treatment For mild bleeding disorders, treatment may involve drugs that help the body increase the amount of clotting factors available. In severe cases, however, bleeding may only stop if the missing clotting factor that is replaced through fresh frozen plasma or cryoprecipitate, the blood fraction containing factor VIII. Every care must be taken to ensure that these infusions are free of HIV and other contaminants. Unfortunately, for many patients, this was not always the case, and many hemophiliacs, like Ryan White, contracted AIDS. New bioengineered therapies that rely on recombinant DNA technology should prevent any possibility of transferring HIV/AIDS. Hemophilia A Mild-to-moderate forms of hemophilia A may be controlled with desmopressin acetate, a synthetic form of a pituitary hormone that rapidly increases that amount of available factor VIII and von Willebrand factor. This drug is called DDAVP in the injectable form, and Stimate when formulated as a nasal spray. Severe bleeding episodes will require transfusions of human blood clotting factors. Many hemophiliacs, however, have become resistant to this form of treatment and have developed antibodies against it. For these patients, a synthetic protein called factor VIIa (tradename NovoSeven) can increase coagulation or prevent bleeding episodes altogether. Factor VIIa is made with recombinant DNA technology. Fetal tissue implants and gene therapies are also being studied as possible treatments for hemophilia. Hemophilia B The treatment for hemophilia B is similar to that for hemophilia A, with the infusion of synthetic and human blood products, such as factor IX concentrate or factor IX complex (prothrombin) concentrate, to promote coagulation. Hemophilia C Hemophilia C is most often treated with plasma, since concentrates of factor XI are not universally available in the United States, due to the disease’s extreme rarity.

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of the specific disease. In addition to blood tests, physicians will compile a medical history and perform a physical examination. In the case of acquired blood coagulation disorders, information such as prior or current diseases and medications will be important in determining the cause of the bleeding disorder.

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obstetrical complications, nor should it be administered to patients with head injuries or central nervous system bleeding.

KEY TERMS Blood clot—A clump of blood that forms as a result of coagulation when a blood vessel is injured. Without this process a person would bleed to death from a relatively small wound. Coagulation—The blood’s change from a liquid to a semisolid state through chemical reaction. Clotting factor—Any of several components normally found in blood that are essential for clotting to occur. Enzyme—A substance that causes a chemical reaction, usually a protein. Enzymes are secreted by cells. Hemorrhage—Abnormal, uncontrolled bleeding from the blood vessels, usually internally. Heparin—An anticoagulant; a drug used to dissolve or prevent the formation of blood clots. Idiopathic—Refers to a disease of unknown cause. Petechiae—Small pinpoint bruises caused by bleeding under the skin. Platelets—Also called thrombocytes, these are small, colorless particles found in the only in mammalian blood that help form clots, keep various body chemicals in circulation, and devour foreign bodies, such as viruses. Purpura—Purplish discoloration of the skin caused by bleeding into the skin and mucous membranes. Thrombosis—Formation of a clot that either blocks or partially blocks a blood vessel. The thrombus may lead to infarction, or tissue death.

Disseminated intravascular coagulation Treatment for DIC depends on what other disease is causing it. If the patient is not yet actively bleeding, the underlying cause should be dealt with. This supportive treatment may eliminate the DIC and the need for emergency measures. In some instances, heparin, an anticoagulant, is used to dissolve the small clots throughout the body; given that DIC can result in hemorrhage, this therapy is controversial. If bleeding has begun, however, the patient may need infusions of blood, platelets, plasma, and other blood products. Heparin should not be used to treat DIC caused by heatstroke, snakebite, trauma, mismatched transfusions, and acute problems resulting from 302

Thrombocytopenia Secondary acquired thrombocytopenia is best alleviated by treating the underlying cause or disorder. Sometimes, no treatment is necessary; the condition will resolve by itself. If treatment is required, it will depend on the underlying cause. Platelet transfusions can help alleviate TCP caused by chemotherapy, for example. In other cases, corticosteroids or immune globulin may be given to improve platelet production. Other bleeding disorders Von Willebrand’s disease often requires no treatment because the bleeding is mild and controllable. DDAVP can help raise levels of the Von Willebrand factor and is the treatment of choice for many cases. However, if trauma or surgery is scheduled there are several methods that will reduce bleeding time and replace factor VIII, which will consequently replace the von Willebrand factor. This may include infusion of cryoprecipitate or plasma,. For severe bleeding, infusions of a viral inactivated factor VIII products such as Humane-P, Alphanate, and Koate DVI may be required. Hypoprothrombinemia may be treated with concentrates of prothrombin. Acquired cases are often treated with vitamin. In bleeding episodes, the patient may receive plasma products. Factor VII deficiency patients may be treated with normal plasma or concentrates containing factor VII or the biomedically engineered VIIa.

Prognosis The prognosis for patients with mild forms of bleeding disorders is good; many lead normal lives and enjoy a normal life expectancy. Untreated bleeding episodes, however, cause severe muscle and joint pain that eventually becomes permanent damage. Any incident that causes blood to collect in the head, neck, or digestive system can be fatal without immediate medical attention. The clots that form throughout the body with DIC can produce gangrene in the fingers, nose, or genitals, and can even cause strokes. The prognosis depends on early intervention and treatment of the underlying condition.

Health care team roles Patients must communicate with their health care providers before undergoing procedures or tests that

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Other health care providers, such as counselors, may help patients cope with their conditions or illnesses. Support groups can also be helpful in understanding the specific condition and in achieving goals for personal wellness.

National Hemophilia Foundation. 116 West 32nd St., 11th Floor, New York, NY 10001. 800-42-HANDI. . OTHER

Brochert, Adam. “Disseminated Intravascular Coagulation.” Discovery Health: Diseases and Conditions. . “What Is Hemophilia?” World Federation of Hemophilia. . “Hemophila A (Factor VIII Deficiency).” Bleeding Disorders Info Center. National Hemophila Foundation. .

Crystal Heather Kaczkowski, MSc.

Prevention It is not always possible to prevent bleeding disorders. Some acquired conditions may be prevented by preventing underlying diseases such as cirrhosis, or discontinuing medications whose side effects cause bleeding. Hereditary disorders can be predicted with prenatal testing and genetic counseling. severe bleeding episodes may be prevented by refraining from activities that could cause injury, such as contact sports. Resources BOOKS

Beutler, Ernest, M.D., et al. Williams Hematology. Sixth edition. New York: McGraw-Hill Professional Publishing, 2000. Carr, Jacqueline H., and Bernadette F. Rodak. Clinical Hematology Atlas. London: W. B. Saunders Co., 1999. Harmening, Denise, ed. Modern Blood Banking and Transfusion Practices. 4th ed. Philadelphia: F. A. Davis Co., 1999. Hoffman, Ronald, ed., et al. Hematology: Basic Principles and Practice. 3rd ed. Edinburgh: Churchill Livingstone, 2000. Shin, Linda M., and Karen Bellenir, eds. Blood and Circulatory Disorders Sourcebook: Basic Information About Blood and Its Components. Health Reference Series, vol 39. Detroit: Omnigraphics, Inc., 1998. PERIODICALS

Girelli D., et al. “Polymorphisms in the Factor VII Gene and the Risk of Myocardial Infarction in Patients with Coronary Artery Disease.” New England Journal of Medicine 343 (2000): 774–780. Meijers J., et al. “High Levels of Coagulation Factor XI as a Risk Factor for Venous Thrombosis.” New England Journal of Medicine 342 (2000): 696–701. ORGANIZATIONS

National Heart, Lung and Blood Institute. Building 31, Room 4A21, Bethesda, MD 20892. (301) 496-4236. .

Bleeding time test see Coagulation tests Blindness see Visual disorders

Blood Definition Blood is a liquid connective tissue that performs many functions in the body, including transport of oxygen, carbon dioxide, nutrients, waste products, and hormones; clotting; and defense against microorganisms. Blood consists blood cells suspended in plasma, a fluid that contains proteins, salts, and other substances. When a blood sample is placed in a test tube and spun rapidly (a process called centrifugation), the heavier blood cells sink to the bottom of the test tube, while the straw-colored plasma floats on top.

Description All vertebrates circulate blood within blood vessels. Because blood is enclosed within blood vessels, the circulatory systems of vertebrates are called closed circulatory systems. (Some invertebrates have open circulatory systems that do not contain blood vessels and circulate a blood-like fluid called hemolymph.) The human body contains about 4 to 6.3 qt (4 to 6 L) of blood. Men have more blood than women, due to the presence of higher levels of testosterone, a hormone that regulates sex characteristics and function and also stimulates red blood cell formation. Plasma makes up 55% of the blood, while the blood cells constitute the other 45%. The various types of blood cells are red blood cells (erythrocytes), white blood cells (leukocytes or leucocytes), and platelets.

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could cause bleeding. The best care is obtained when treatment is coordinated by a health care team with expertise in the field. The Centers for Disease Control and Prevention found that patients with severe or moderate hemophilia had 60% less mortality and morbidity when their treatment was coordinated by a comprehensive hemophilia treatment compared to those not seen by a comprehensive hemophilia treatment center.

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Other proteins that are present in plasma are immunoglobins and fibrinogen. Immunoglobins, also called antibodies, are proteins that function in the immune response. Antibodies attach to invading bacteria and other microorganisms, marking them for destruction by immune cells. Fibrinogen is a protein that functions in a complex series of reactions that leads to the formation of blood clots. Plasma (55% of total volume)

Formed elements (45% of total volume)

Erythrocytes

Thrombocytes (platelets)

Neutrophil

Monocyte

Leukocytes Test tube containing whole blood

Eosinophil

Lymphocyte

Basophil

The major components of blood. (Delmar Publishers, Inc. Reproduced by permission.)

Plasma Plasma contains mostly water, which accounts for 91.5% of the plasma content. The water acts as a solvent for carrying other substances. PLASMA PROTEINS. Proteins account for 7% of plasma. The higher concentration of protein in blood prevents water from moving from the blood into the interstitial fluid. Without this osmotic protection, water would move from the blood into the interstitial fluid, causing a rapid loss of blood volume.

The most abundant of the plasma proteins is albumin, a protein also found in egg white. Albumin concentration is four times higher in the blood than in the interstitial fluid (the watery fluid that bathes tissues, but is located outside and between cells). This high concentration of albumin in plasma serves an important osmotic function. 304

OTHER PLASMA COMPONENTS. The other components of plasma are salts, nutrients, enzymes, hormones, and nitrogenous waste products. Together, these substances account for 1.5% of plasma. The salts present in plasma include sodium, potassium, calcium, magnesium, chloride, and bicarbonate. These salts function in many important body processes. For instance, calcium functions in muscle contraction; sodium, chloride, and potassium function in nerve impulse transmission in nerve cells; and bicarbonate regulates pH. These salts are also called electrolytes. An imbalance of electrolytes, which can be caused by dehydration, can be a serious medical condition. Many gastrointestinal illnesses, such as cholera, cause a loss of electrolytes through severe diarrhea. When electrolytes are lost, they must be replaced with intravenous or oral solutions of water and salts.

The remaining substances present in plasma are elements that the plasma is transporting from one place to another. For instance, plasma contains nutrients that nourish tissues. The nutrients found in plasma include amino acids, the building blocks of proteins; glucose and other sugars; and fatty acids and glycerol, the components of lipids (fats). In addition to nutrients, plasma also contains enzymes, or small proteins that function in chemical reactions, and hormones, which are transported from glands to body tissues. Waste products from the breakdown of proteins are also found in plasma. These waste products include creatinine, uric acid, and ammonium salts. Blood transports these waste products from the body tissues to the kidneys, where they are filtered from the blood and excreted in the urine. Red blood cells The human body contains an estimated 25 trillion red blood cells; approximately 4.8 million to 5.4 million are found in every microliter of blood. The structure of a red blood cell is eminently suited to its primary function, the transport of oxygen from the lungs to body tissues. Red blood cells are very small (about 6 nanometers wide), shaped like a disk, and contain a small depression on either side. Their small size allows them to squeeze through the tiniest of blood vessels (capillaries). In addition, their size allows a greater diffusion of oxygen across

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TRANSPORT OF OXYGEN. Red blood cells are unusual in that they do not contain nuclei or mitochondria, the cellular organelles in which aerobic metabolism (the breakdown of nutrients that requires oxygen) is carried out. Instead, red blood cells acquire energy through metabolic processes that do not require oxygen. The lack of nuclei and mitochondria therefore allow the red blood cell to function without depleting its cargo of oxygen, leaving more oxygen for the body tissues.

The molecule that binds oxygen in red blood cells is called hemoglobin. Hemoglobin is a large, globular protein consisting of four protein chains surrounding an iron core. Hemoglobin is densely packed inside the red blood cell; in fact, hemoglobin accounts for a third of the weight of the entire red blood cell. Each red blood cell contains about 250 molecules of hemoglobin. In the lungs, oxygen diffuses across the red blood cell membrane and binds to hemoglobin. As blood circulates to the tissues, oxygen diffuses out of the red blood cells and enters tissues. The waste product of aerobic metabolism, carbon dioxide, then diffuses across red blood cells and binds to hemoglobin. Once circulated back to the lungs, the red blood cells discharge their load of carbon dioxide, which is then breathed out of the lungs. However, only 7% of carbon dioxide generated from metabolism is transported back to the lungs for exhalation by red blood cells; the majority is transported in the form of bicarbonate, a component of plasma. HEMOPOIESIS. Red blood cells are formed in red bone marrow from precursor cells called pluripotent stem cells. The process of red blood cell formation is called hemopoiesis (alternatively, hematopoiesis). In adults hemopoiesis takes place in the marrow of ribs, vertebrae, the breastbone, and the pelvis. On average, a red blood cell lives only three to four months. Constant wear and tear on the red blood cell membrane, caused by squeezing through tiny capillaries, contributes to the red blood cell’s short life span. Worn out red blood cells are destroyed by phagocytic cells (cells that engulf and digest other cells) in the liver. Parts of red blood cells are recycled for use in other red blood cells, such as the iron component of hemoglobin.

White blood cells White blood cells are less numerous than red blood cells in the human body; each microliter of blood con-

tains 5,000 to 10,000 white blood cells. The number of white blood cells increases, however, when the body is fighting off infection. Their numbers are maintained until the immune system detects the presence of a foreign invader. When the immune system is activated, chemicals called lymphokines stimulate the production of more white blood cells. White blood cells function in the body’s defense against invasion and are key components of the immune system. They usually do not circulate in the blood vessels, and are instead found in the interstitial fluid and in lymph nodes. Lymph nodes are composed of lymphatic tissue and are located at strategic places in the body. Blood filters through the lymph nodes, and the white cells present in the nodes attack and destroy any foreign invaders. TYPES OF WHITE BLOOD CELLS. The human body contains five types of white blood cells: monocytes, neutrophils, basophils, eosinophils, and lymphocytes. Each type of white blood cell plays a specific role in the body’s immune defense system.

Under a microscope, three kinds of white blood cells appear to contain granules within their cytoplasm. These three types are the neutrophils, basophils, and eosinophils. Together, these three types of white blood cells are called granulocytes. The granules are specific chemicals that are released during the immune response. The other two types of white blood cells, the monocytes and lymphocytes, do not contain granules. These types are known as the agranular leukocytes. Monocytes, which comprise 3% to 8% of the white blood cells, and neutrophils, which comprise 60% to 70% of white blood cells, are called phagocytes. They ingest and digest cells, including foreign microorganisms such as bacteria. Monocytes differentiate into cells called macrophages. Macrophages can be fixed in one place, such as in the brain and lymph nodes, or can “wander” to areas where they are needed, such as the site of an infection. Neutrophils have an additional defensive property: they release granules of lysozyme, an enzyme that destroys cells. Basophils comprise 0.5% to 1% of the total composition of white blood cells and function in the body’s inflammatory response. Allergies are caused by an inflammatory response to relatively harmless substances, such as pollen or dust, in sensitive individuals. When activated, basophils release various chemicals that cause the characteristic symptoms of allergies. Histamines, for instance, cause the runny nose and watery eyes associated with allergic reactions; heparin is an anticoagulant that slows blood clotting and encourages the flow of blood to the site of inflammation, inducing swelling.

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the blood cells’ plasma membranes than if the cells were larger—because blood contains so many of these small cells, their combined surface areas translate into an extremely large surface area for the diffusion of oxygen. The disk shape and the depressions on either side also contribute to a greater surface area.

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Injury to lining of vessels exposes collagen fibers; platelets adhere.

Platelet plug forms.

Fibrin clot with trapped cells.

Platelets

Collagen fibers Platelet releases chemicals that make nearby platelets "sticky." Clotting factors from:

Calcium and other factors in blood plasma

Platelets Damaged cells

Prothrombin

Thrombin

Fibrinogen

Fibrin

Illustration of blood clotting. (Illustration by Hans & Cassidy. Courtesy of Gale Group.)

Eosinophils, which comprise 2% to 4% of the total composition of white blood cells, are believed to counteract the effects of histamine and other inflammatory chemicals. They also phagocytize bacteria tagged by antibodies. Lymphocytes, which comprise 20% to 25% of the total composition of white blood cells, are divided into two types: B lymphocytes (also called B cells) and T lymphocytes (also called T cells). The names of these lymphocytes are derived from their origin. T lymphocytes are named for the thymus, an organ located in the upper chest region where these cells mature; and B lymphocytes are named for the bursa of Fabricus, an organ in birds where these cells were discovered. T lymphocytes play key roles in the immune response. One type of T lymphocyte, the helper T lymphocyte, activates the immune response when it encounters a macrophage that has ingested a foreign microorganism. Another kind of T lymphocyte, called a cytotoxic T lymphocyte, kills cells infected by foreign microorganisms. B lymphocytes, when activated by helper T lymphocytes, become plasma cells, which in turn secrete large amounts of antibodies.

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All white blood cells arise in the red bone marrow. However, the cells destined to become lymphocytes are first differentiated into lymphoid stem cells in the red bone marrow. These stem cells undergo further development and maturation in the spleen, tonsils, thymus, adenoids, and lymph nodes. Platelets Platelets are not cells; they are fragments of cells that function in blood clotting. Platelets number about 250,000 to 400,000 per liter of blood. Blood clotting is a complex process that involves a cascade of reactions that leads to the formation of a blood clot. Platelets contain chemicals called clotting factors. These clotting factors first combine with a protein called prothrombin. This reaction converts prothrombin to thrombin. Thrombin, in turn, converts fibrinogen (present in plasma) to fibrin. Fibrin is a thread-like protein that traps red blood cells as they leak out of a cut in the skin. As the clot hardens, it forms a seal over the cut. This process works for relatively small cuts in the skin. When a cut is large, or if an artery is severed, blood loss is so severe that the physical pressure of the blood

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Platelets have a short life span; they survive for only five to nine days before being replaced. Platelets are produced in red bone marrow and are broken off from other red blood cells.

Role in human health Blood substitutes Researchers hope to create synthetic blood substitutes to ease the burden of dwindling blood donations that are needed to meet the demand for surgeries, transfusions, and emergencies. Currently under development are blood substitutes that use perfluorocarbons or modified hemoglobin to carry oxygen to tissues. Perfluorocarbons are long, fatty hydrocarbon chains containing fluorine that have the ability to pick up oxygen in lungs and release it into tissues. The artificial blood is a mixture of perfluorocarbons with saline (physiological salt water) using surfactants, substances that allow the mixing of oil and water. The solution then can be administered to patients. Over time, as the artificial blood helps deliver oxygen to tissues, the perflourocarbon molecules are exhaled from the body. Hemoglobin solutions contain hemoglobin that has been isolated from red blood cells and chemically altered to increase its lifespan in the bloodstream and to ensure adequate oxygen-carrying capabilities. Strictly, these substances are not whole blood substitutes since they only have the ability to carry oxygen and cannot replace the other important functions of blood. However, they would be valuable in eliminating the risk of transmitting disease during transfusions as well as preventing accidental blood type mismatches. ABO BLOOD GROUPS. An interesting aspect of red blood cells is that they carry certain proteins, called antigens, on their plasma membranes. These antigens are responsible for the various blood groups known as A, B, AB, and O:

• A person with A antigens is type A and has antibodies to B antigens. • A person with B antigens is type B and has antibodies to A antigens. • A person with both antigens is type AB and does not have antibodies to either antigen.

• A person with none of the antigens is type O and has antibodies to both A and B antigens. These combinations are necessary to know when performing a blood transfusion. For instance, if a type A individual donates blood to a type B individual, the A antibodies in the recipient’s B blood will react with the A antigens of the donor’s A blood. This reaction, called the agglutination reaction, causes the blood cells to clump together. Agglutination can be fatal. Until blood typing was worked out early in this century, many deaths from blood transfusions occurred due to incompatibility of antigens and antibodies. HLA ANTIGEN GROUPS. Like red blood cells, the plasma membranes of white blood cells also contain antigens. These surface antigens are called the human leukocyte associated (HLA) antigens. Like the red blood cell types, these HLA antigens represent different white blood cell “groups.” When a person receives an organ transplanted from a donor, the recipient and the donor must have the same HLA antigen group for the transplant to be successful. If the donor and recipient are two different HLA antigen groups, the recipient’s body will “reject” the organ; in other words, the recipient’s immune system will be activated by the foreign cells of the organ and initiate an immune response against the organ.

Common diseases and disorders Sickle cell anemia Sickle cell anemia is an inherited disorder caused by a defect in one of hemoglobin’s four protein chains. The defective hemoglobin distorts the shape of the red blood cells and injuries the red blood cell membrane. Water and potassium leak from the cells, causing the red blood cells to become rigid and “sickle-shaped.” As a result of these changes, oxygen transport is severely interrupted and circulation of the blood through the blood vessels can become blocked. These irregular blood cells do not carry as much oxygen as their normally shaped counterparts. Although the prognosis for individuals with sickle cell anemia was historically poor, improvements in life expectancy and quality have been made due to early diagnosis and treatment. Hemophilia Hemophilia is hereditary group of bleeding disorders that results in insufficient clotting and excessive bleeding. Types are hemophilia A, hemophilia B, and von Willebrand’s disease. Hemophilia A is the most common type. It results from a deficiency in clotting factor VIII. Only males have this sex-linked disease, but women may be carriers. Uncontrolled bleeding, both internal and

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leaving the body prevents clots from forming. In addition, in the inherited disorder called hemophilia, one or more clotting factors are lacking in the platelets. This disorder causes severe bleeding from even the most minor cuts and bruises.

Blood

KEY TERMS Aerobic metabolism—Metabolic processes that require oxygen. Antibody—An immune protein that marks foreign microorganisms in the body for destruction by other immune cells. Antigen—A protein that is attached to a cell’s plasma membrane. Centrifugation—A laboratory procedure in which a test tube of blood or other liquid is spun at a high speed. Clotting factor—A set of substances released by platelets that function in the clotting mechanism. Electrolytes—The salts and other substances present in the plasma that function in crucial body processes. Fibrin—A protein that functions in the clotting mechanism; forms mesh-like threads that trap red blood cells. Fibrinogen—The inactive form of fibrin present in plasma; activated by clotting factors released by platelets. Hemoglobin—The protein found in red blood cells that binds oxygen; consists of four protein chains surrounding an iron core. Hemophilia—A genetic disorder in which one or more clotting factors are not released by the platelets; causes severe bleeding from even minor cuts and bruises. Hemopoiesis—The process of red blood cell formation in the bone marrow.

external, may be caused by the smallest of injuries. Treatment involves clotting factor supplementation, and tranfusions are common when blood is lost, or prophylactically. Human immunodeficiency virus Human immunodeficiency virus (HIV), the causative agent of acquired immune deficiency syndrome (AIDS), attacks and kills T lymphocytes. This disease cripples the immune system and leaves the body helpless to stave off infections. As AIDS progresses, the number of helper T lymphocytes drops from a normal 1,000 per cubic millimeter to below 200. 308

Histamine—A chemical released by basophils during the inflammatory response; causes blood vessels to dilate. Immunoglobin—An antibody. Inflammatory response—A type of non-specific immune response; involves the release of chemicals from basophils that increase blood circulation and white blood cell migration to the affected area. Interstitial fluid—The fluid that bathes cells. Lymph node—A small structure located at several points in the body; consists of lymphatic tissue that filters blood and removes microorganisms. Lymphocyte—A type of white blood cell; includes B and T lymphocytes. Lysozyme—An enzyme released by neutrophils that kills cells. Lymphoid stem cell—The cell from which B and T lymphocytes are derived. Phagocytize—To engulf and digest a cell. Plasma cell—The cell derived from the B lymphocyte, which secretes antibodies. Pluripotent stem cell—The type of stem cell from which red blood cells and more white blood cells are derived in the bone marrow. Sickle cell anemia—A genetic disorder caused by a defect in one of hemoglobin’s four protein chains; causes red blood cells to be sickle-shaped.

Resources BOOKS

Long, Michael W. and Max S. Wicha, eds. The Hematopoietic Microenvironment: The Functional and Structural Basis of Blood Cell Development. Baltimore: Johns Hopkins University Press, 1993. Shin, Linda, and Karen Belliner. Blood and Coagulation Disorders Sourcebook: Basic Information about Blood and Its Components. Omnigraphics, 1998. PERIODICALS

Creteur, Jacques, William Sibbald, and Jean-Louis Vincent. “Hemoglobin Solutions: Not just Red Blood Cell Substitutes.” Critical Care Medicine 28 (August 2000): 3025-34.

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Delves, P. J. and I. M. Roitt. “The Immune System: Second of Two Parts.” New England Journal of Medicine 343 (13 July 2000): 108-17. Tremper, Kevin K. “Perfluorochemical Blood Substitutes: Indications for an Oxygen-Carrying Colloid.” Anesthesiology 91 (November 1999): 1185. ORGANIZATIONS

American Sickle Cell Anemia Association. 10300 Carnegie Avenue, East Office Building (EEb18), Cleveland, OH 44106. (216) 229-8600. . America’s Blood Centers. 725 15th Street NW, Suite 700, Washington, DC 20005. (202) 393-5725. . National Hemophilia Foundation. 116 West 32nd Street, 11th Floor, New York, NY 10001. (800) 42-HANDI. . OTHER

“Blood Work: A Useful Tool for Monitoring HIV.” Project Inform Website. April 2001. 7 July 2001. . “Sickle Cell Anemia.” KidsHealth Website. 2001. 7 July 2001. .

Kathleen Scogna

Blood alcohol test see Drug tests

Function Normal blood coagulation is a complex process that involves 20 to 30 components, called blood coagulation factors, and a series of complex chemical reactions. When a blood vessel is injured, platelets in the area of the damage clump together and stick to the edges of the cut to begin the coagulation process. Platelets are fragments of cells containing clotting factors. These clotting factors combine with a protein called prothrombin in a reaction that converts prothrombin to thrombin. Thrombin then converts fibrinogen (a protein present in plasma) into long, sticky threads of another protein called fibrin. The fibrin forms a mesh-like net over the opening and traps red blood cells as they try to leak out of the cut. As the clot hardens, it forms a protective seal over the cut. The platelets also release messengers into the blood that perform additional functions including: constriction of the damaged blood vessels to reduce bleeding, attracting more platelets to the injury site to enlarge the clot, and activating other clotting factors, such as fibrinogen.

Role in human health The ability of the blood to form a self-sealing clot when a blood vessel is injured is crucial. Without coagulation, a cut or puncture wound, no matter how minor, would continue to bleed and quickly lead to death. A deficiency in any of the protein coagulation factors can result in hemorrhages following injury. In some coagulation disorders, such as hemophilia, the deficiency is due to an inherited defect. In others, the deficiency is due to an acquired condition, such as vitamin K deficiency.

Common diseases and disorders

Blood coagulation Definition Blood coagulation is the process that causes blood to clot and helps prevent excessive blood loss when a vein or artery is pierced or broken.

Description Blood coagulation is the body’s natural way of preventing its blood supply from being lost through a cut, puncture, or other trauma to blood vessels. All of the components necessary for coagulation are found in the blood. The coagulation process involves a series of proteins, protein cofactors, and enzymes that interact on membrane surfaces. It is normally activated by damaged tissue.

Hemophilia is an inherited coagulation disorder characterized by the blood’s inability to clot. Both types of the disorder, hemophilia A and hemophilia B, are caused by an inherited sex-linked recessive trait, with the defective gene located on the X chromosome. This means only males are affected with the disorder but females can carry the abnormal gene and pass it on to their children. About 80% of hemophiliacs have type A, which is the result of a deficiency of clotting factor VIII. Symptoms can vary and include bruising, spontaneous bleeding, bleeding into joints, hemorrhaging in the gastrointestinal and urinary tracts, and most notably, prolonged bleeding even from the most minor of cuts. Prevention of injury is paramount for people with the disorder. When bleeding occurs, the standard treatment is infusion of blood plasma with concentrations of

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Delves, P. J. and I. M. Roitt. “The Immune System: First of Two Parts.” New England Journal of Medicine 343 (6 July 2000): 37-49.

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KEY TERMS Coagulation—The process of becoming gel-like or solid. Enzymes—Numerous complex proteins produced by cells in the body and catalyze specific biochemical reactions at body temperatures. Hemorrhaging—Heavy or uncontrollable bleeding. Protein cofactor—A substance that acts in conjunction with protein to bring about certain effects. X chromosome—A sex chromosome that usually occurs in pairs in females and single in male cells.

clotting factor VIII. This clotting factor has been cloned through genetic engineering, eliminating the possibility that the blood may contain viruses such as hepatitis and human immunodeficiency virus (HIV). Hemophilia A occurs in about one out of 10,000 males. Hemophilia B (also called Christmas disease) is a result of a deficiency of clotting factor IX. Symptoms are generally the same as for type A. Treatment is usually infusion of blood plasma with clotting factor IX. The condition occurs in one out of about 70,000 males. The most common coagulation disorder is thrombosis, which is a blood clot that blocks otherwise normal blood vessels. This is most disastrous when the clot blocks a blood vessel leading to the heart (causing a heart attack), brain (causing a stroke), a limb, or other organ. Thrombocytopenia is a blood disease characterized by an abnormally low number of platelets in the bloodstream. The normal amount of platelets is usually between 150,000 and 450,000 cells per microliter of blood. When this number drops below 150,000, the patient is said to be thrombocytopenic. This blood disorder is one of the most common causes of hemorrhaging.

not dissolve clots that have already formed, although the drug may prevent an existing clot from worsening. Because these drugs affect the blood’s ability to clot, they can increase the risk of severe bleeding and heavy blood loss. Anticoagulant drugs must be used exactly as directed and a physician should be consulted regularly while taking the medicine. Medications called fibrinolytic agents are sometimes used to dissolve clots and include streptokinase, urokinase, and tissue plasminogen activator. These are most commonly used for thrombosis. Resources BOOKS

Colman, Robert W., (Ed.), et al. Hemostasis and Thrombosis: Basic Principles and Clinical Practice. New York: Lippincott, Williams & Wilkins, 2000. Recent Progress in Blood Coagulation and Fibrinolysis. Belle Mead, NJ: Excerpta Medica, 2000. PERIODICALS

D’epiro, Nancy Walsh. “Clotting and Bleeding: A New Understanding.” Patient Care (June 15, 1998): 87. Hirsh, J., et al. “Vitamin K in Anticoagulation Therapy.” The Lancet (February 24, 2001): 637. Hirsh, Jack. “Perioperative Anticoagulation: Minimizing the Risks, Maximizing the Benefits.” Consultant (January 1998): 42-44. “Homemade Anticoagulation Monitor.” The Lancet (September 19, 1998): 962. “Ultrasound Clot Buster.” Popular Mechanics (November 2000): 28. ORGANIZATIONS

National Heart, Lung and Blood Institute. PO Box 30105, Bethesda, MD 20824. (301) 592-8573. .

Ken R. Wells

Blood coagulation disorders see Bleeding disorders Blood count see Complete blood count Blood crossmatching see Type and screen

Treatment and management Individuals at high risk for developing clots or those who have had them previously can prevent further clots by taking anticoagulant drugs, such as sodium warfarin and heparin. Anticoagulant drugs help prevent the formation of harmful clots in the blood vessels by reducing the blood’s ability to clump together. Although these drugs are sometimes called blood thinners, they do not actually thin the blood. Furthermore, this type of medicine will 310

Blood culture Definition A blood culture is a lab test designed to detect the presence of bacteria, yeast, or fungi in the bloodstream.

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Purpose Physicians normally order this test for patients with symptoms of bacteremia. Symptoms can include fever, chills, mental confusion, anxiety, rapid heartbeat, hyperventilation, blood clotting problems, and shock. These symptoms are especially significant if the patient already has another illness or infection, is hospitalized, or has trouble fighting infections because of a weak immune system. Because bacteremia can be a serious clinical condition that, untreated, can lead to death, a blood culture should be performed as soon as an infection is suspected. Early detection will give the patient the best chance for effective treatment and survival. Blood cultures are sometimes used to determine the causes of infections in other parts of the body because these infections often spread to the blood. For example, bacterial pneumonia (an infection of the lung) and infectious endocarditis (an infection of the inner layer of the heart, including the heart valves) are known to leak bacteria into the bloodstream. Other sources might be boils, urinary tract infections, and oral bacteria spread during mouth trauma (such as injury or dental treatment).

Precautions Patients who have bleeding disorders or are taking blood thinners might have trouble with bleeding following a venipuncture. Before having a blood sample drawn, such patients should tell the phlebotomist about their condition.

Description There are many variables involved in performing a blood culture. Before ordering a blood culture, the physician must make the following decisions based on a knowledge of infections and the patient’s clinical condition and medical history. • type of blood culture that will best target the suspected microorganism • number of blood cultures to request • how often the blood cultures should be performed

Some factors influencing these decisions are the patient’s symptoms or previous culture results, and whether or not the patient has had recent antibiotic therapy. Types, numbers, and timing of blood cultures Several groups of microorganisms can cause blood infections. These groups include bacteria (both aerobes and anaerobes), yeast, fungi, viruses, and mycobacteria. Routine blood culture medium will normally grow both aerobic and anaerobic bacteria, yeast, and most fungi. Viruses, mycobacteria, and certain other fungi require special media or special collection techniques and a longer incubation period. For example, Histoplasma is a fungus that requires a six-week incubation period. A single set of blood cultures, which consists of two bottles of growth medium (one for aerobes and one for anaerobes) is not recommended. Two to three sets are usually adequate. After a blood infection has been diagnosed, confirmed by culture, and treated, an additional blood culture might be performed to ensure that the infection is gone. Timing can be an important factor in performing blood cultures. Most blood infections are intermittent bacteremias, which means the microorganisms enter the blood at various times. For such infections, blood drawn randomly might miss the microorganisms. Since the microorganisms enter the blood 30–90 minutes before the person’s fever spikes, collecting the culture just after the fever spike offers the best probability of finding the microorganism. The second and third cultures can be collected at the same time, but from different areas of the body. The physician might want to have the collections spaced at 30-minute or one-hour intervals. In continuous bacteremias, such as infective endocarditis, microorganisms are always in the blood, so the timing of culture collection is less important. Blood cultures should always be collected before antibiotic treatment begins, if possible. However, some studies of the effectiveness of automated computer-assisted blood cultures in detecting microorganisms in the blood of newborns show that the newer technology with improved media is faster in detecting positive cultures even when antibiotic therapy had already been started. Laboratory analysis Bacteria are the most common microorganisms found in blood infections, so routine blood cultures target bacterial growth, although they also support the growth of many other microorganisms. Laboratory analysis of a bacterial blood culture differs slightly from that of a fungal culture, and significantly from that of a viral culture.

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A routine blood culture involves injecting a sample of the patient’s blood into two bottles of sterile nutrient broth (one for aerobes and one for anaerobes), incubating the bottles at 35°C, and monitoring the bottles for growth over a period of five days. For positive cultures, it also involves identifying any organism that grows and performing antibiotic sensitivity tests to determine which antibiotics will be effective in treating the infection.

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by the instrument. Many data points are collected daily for each bottle, and input into a computer for analysis. Sophisticated mathematical calculations can determine when microorganisms have grown. When growth is detected, an alarm is triggered to alert the technologist. This, combined with more frequent blood tests, make it possible to detect microbial growth earlier. In addition, all CMBC system instruments have the detection system, incubator, and agitator in one unit.

Cultures on agar plates. (Photograph by T. McCarthy, Custom Medical Stock Photo. Reproduced by permission.)

For a routine blood culture, 20 ml of blood is drawn from the patient (see Preparation), put directly into a paired set of blood culture bottles (aerobic and anaerobic), and delivered to the lab immediately for incubation. For a blood culture to be successful, the laboratory must complete several processes: • Provide an environment suitable for microbial growth. • Detect growth when it occurs. • Identify any microorganisms that grow. • Test any isolated microorganisms against certain antibiotics to determine which antibiotic will be effective. The broth in the blood culture bottle is the first step in providing an environment suitable for microbial growth. It contains all the required nutrients. A commonly used medium for blood culture is tryptic soy broth supplemented with amino acids and carbohydrates. The aerobic bottles have ideal conditions for growing aerobes, while the anaerobic bottles have ideal conditions for growing both strict anaerobes and facultative anaerobes. The second step is providing an ideal temperature for growth by placing the bottles in an incubator at body temperature (35°C). To detect growth when it occurs, the laboratories can monitor the bottles by a daily manual (visual) method. Visual signs of growth include cloudiness or a color change in the broth, gas bubbles, or clumps of bacteria. Many laboratories use one of the newer continuous-monitoring blood culture (CMBC) systems. CMBC systems are considered important technical advances in blood cultures. The instruments automatically monitor the bottles containing the patient’s blood for evidence of microorganisms, usually every 10 minutes. A common approach is to measure the production of carbon dioxide in the culture medium which causes a color change that is sensed 312

To identify any microorganisms that grow, the laboratory does a Gram stain and a subculture. If there is no evidence of growth after five days, the laboratory usually performs a Gram stain and subculture before discarding a bottle and reporting a negative result. For the subculture, a drop of blood is placed on a culture plate and spread over the surface of the plate. The plate is then placed in an incubator at 35°C. If a bacterium is isolated, the laboratory identifies it using biochemical tests and the Gram stain. The bacterium is also tested against many different antibiotics to see which antibiotics can effectively treat the infection. This process is called sensitivity (or susceptibility) testing. All test results are reported to the physician as soon as possible. An early report, known as a preliminary report, is usually available after one day. This report indicates whether any bacteria have been found yet and, if so, the results of the Gram stain. The next preliminary report might include a description of the bacteria growing on the subculture. The laboratory notifies the physician immediately when an organism is found and as soon as sensitivity tests are complete. Sensitivity tests could be complete before the bacterium is completely identified. The final report, which might not be available for five to seven days, includes a complete identification and a list of the antibiotics to which the bacterium is sensitive.

Preparation To prevent contamination from the patient’s skin, the blood sample must be drawn using strict sterile technique. Before drawing the blood, the phlebotomist should disinfect the skin by swabbing it first with 70% alcohol, then with iodine in a circular motion, starting at the puncture site and moving outward. The iodine should be allowed to dry completely before the blood culture is drawn. During this time, the caps of the blood culture bottles should be removed and the rubber stoppers should be cleansed with 70% alcohol.

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After drawing the blood sample, the phlebotomist should use alcohol to remove the iodine from the skin to prevent hypersensitivity. Then, to reduce bruising, pressure should be applied to the puncture site until the bleeding stops. If the patient is taking blood thinners or has a blood disorder that causes bleeding, special care should be taken to ensure that the bleeding has stopped completely before pressure is withdrawn.

Complications After having blood drawn, the patient might feel dizzy or faint, and might have discomfort or bruising at the puncture site. Warm packs can relieve discomfort.

Results A negative (normal) blood culture indicates that there are no microorganisms growing in the patient’s bloodstream. However, a single negative set of blood cultures does not completely rule out a blood infection. Three sets of negative cultures are needed to rule out bacteremia. False negatives can occur for the following reasons: • Antibiotic therapy was started before the blood was drawn. • Time of blood collection was inappropriate.

KEY TERMS Aerobe—An organism that grows in the presence of oxygen. If an aerobe cannot grow without oxygen, it is called a strict of obligate aerobe. Anaerobe—An organism that grows in the absence of oxygen. If an anaerobe cannot grow when oxygen is present, it is called a strict or obligate anaerobe. An anaerobe that can also grow in the presence of oxygen is called a facultative anaerobe. Bacteremia—Bacteria in the blood. Continuous bacteremia—A kind of bacteremia in which bacteria are always in the blood. Intermittent bacteremia—A kind of bacteremia in which the bacteria enter the blood at various time intervals. Phlebotomist—A person who draws blood from a vein. Venipuncture—The puncture of a vein to withdraw a blood sample.

usually found in only one set of bottles after several days of incubation. Contaminated cultures frequently contain more than one microorganism.

• Environment was not right for growth. • Fastidious bacteria did not grow. A positive blood culture indicates that microorganisms are growing in the patient’s bloodstream. Finding the same microorganism in more than one set of bottles helps to rule out the possibility of contamination from poor collection or handling techniques. The physician’s skill in interpreting the results is essential in distinguishing a blood culture that is positive because of a true infection from one that is positive because of contamination. In a true bacteremia, the patient’s clinical condition is consistent with a blood infection caused by the microorganism that was isolated. The microorganism usually grows soon after the bottles are incubated, is usually found in more than one set of bottles, and is often the cause of an infection somewhere else in the patient’s body. When a culture is positive because of contamination, the patient’s clinical condition usually is not consistent with an infection from the microorganism that was isolated. The microorganism is often one that is commonly found on the skin and that rarely causes infection. It is

Health care team roles Several health care professionals work together to ensure a successful blood culture. The physician uses his training and expertise to decide when a blood culture should be ordered. A phlebotomist, or sometimes a nurse, collects the blood, and the clinical laboratory scientist, CLS(NCA)/medical technologist, MT(ASCP) monitors the cultures and performs appropriate tests when the cultures are positive. Resources BOOKS

Komaroff, Anthony L. Harvard Medical School Family Health Guide. Harvard Medical School, 1999. Warren, John R. “Sepsis.” In The Biologic and Clinical Basis of Infectious Diseases, edited by Standford T. Shulman, et al. Philadelphia: W. B. Saunders Company, 1997, 475-489. PERIODICALS

Garcia-Prats, Joseph A., et. al. “Rapid Detection of Microorganisms in Blood Cultures of Newborn Infants

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Utilizing an Automated Blood Culture System.” Pediatrics 105 (March 2000): 523. Reimer, L.G., M.L. Wilson, and M.P. Weinstein. “Update on Detection of Bacteremia and Fungemia.” Clinical Microbiology Review (July, 1997): 444-465. ORGANIZATIONS

American Society of Microbiology. 1752 N Street NW, Washington DC 20036. 202-737-3600. . OTHER

“Guidelines for Blood Culture Collection.” University of Pennsylvania Health System. University of Pennsylvania, 2001. . Lindquist, John. “Oxygen Relationships and the Use of Thioglycollate Medium.” Differential Media February 2001. Dept of Bacteriology, UW-Madison, November 2000. .

Beverly G. Miller MT (ASCP)

Blood gas analysis Definition Blood gas analysis, also called arterial blood gas (ABG) analysis, is a procedure to measure the partial pressure of oxygen (O2) and carbon dioxide (CO2) gases and the pH (hydrogen ion concentration) in arterial blood.

Purpose Blood gas analysis is used to diagnose and evaluate respiratory diseases and conditions that influence how effectively the lungs deliver oxygen to and eliminate carbon dioxide from the blood. The acid-base component of the test is used to diagnose and evaluate metabolic conditions that cause abnormal blood pH. Because high concentrations of inhaled oxygen can be toxic and can damage lungs and eyes, repeated blood gas analysis is especially useful for monitoring patients on oxygen, for example, premature infants with lung disease, so that the lowest possible inhaled oxygen concentration can be used to maintain the blood oxygen pressure at a level that supports the patient. In intubated patients under artificial ventilation, monitoring the levels of arterial carbon dioxide and oxygen allow assessment of respiratory adequacy so that the rate or depth of ventilation, the ventilator dead space, or airway pressure can be changed to preserve the patient’s optimal physiologic balance. 314

The measurement of arterial blood pH and carbon dioxide pressure with subsequent calculation of the concentration of bicarbonate (HCO3-), especially in combination with analysis of serum electrolytes, aids in the diagnosis of many diseases. For example, diabetes mellitus is often associated with a condition known as diabetic acidosis. Insulin deficiency often results in the excessive production of ketoacids and lactic acid that lower extracellular fluid and blood pH. Unabated acidbase disorders are life threatening. Acidosis is associated with severe consequences, including shock and cardiac arrest, and alkalosis with mental confusion and coma.

Precautions The syringe used to collect the sample for a blood gas analysis must contain a small amount of heparin to prevent clotting of the blood. It is very important that air be excluded from the syringe both before and after the sample is collected. The syringe must be filled completely and never exposed to air. For transportation, the syringe should be capped with a blind hub, placed on ice, and immediately sent to the laboratory for analysis to guarantee the accuracy of the results. A blood gas analysis requires a sample of arterial blood in order to evaluate gas exchange by the lungs. Arterial puncture is associated with a greater risk of bleeding than venipuncture. The test may be contraindicated in persons with a bleeding disorder such as hemophilia or low platelet count. During the arterial puncture, the patient may feel a brief throbbing or cramping at the puncture site. In cases where the primary concern is ascertaining that the blood is adequately oxygenated, a pulse oximeter may be used in lieu of arterial blood gas analysis. Medical personnel must follow standard precautions for prevention of exposure to bloodborne pathogens when performing arterial blood collection.

Description The sample of choice for blood gas analysis is arterial blood. This is usually collected from the radial artery in the wrist, but in cases where no radial pulse is obtained, the femoral or brachial artery may be used. The sample may also be collected from an arterial line after flushing the line to remove excess anticoagulant and fluid. In neonates and in adults when arterial puncture is contraindicated or unsuccessful, a capillary blood sample may be used. The sample is inserted into an analytical instrument that uses electrodes to measure the concentration of hydrogen ions (H+), which is reported as pH, and the partial pressures of oxygen [PO2] and carbon dioxide PO2 gases. The pH-measuring electrode consists of a special

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glass membrane that is selectively permeable to hydrogen ions. An electical potential develops across the inner and outer surfaces of this membrane that is related to the log of hydrogen ion activity in the sample. A Severinghaus electrode is used to measure PCO2. The measuring principle is the same as for hydrogen ions, except that the electrode tip is covered with a gas permeable membrane, so that the pH change is proportional to carbon dioxide diffusing from the sample to the electrode surface. The PO2 is measured using a polarographic (Clark) electrode. Oxygen diffuses from the sample to the cathode, where it is reduced to peroxide ions. The electrons come from a silver anode that is oxidized, generating current in proportion to oxygen concentration at the cathode. Electrode signals are dependent upon temperature as well as concentration, and all measurements are performed at 37°C. Since the in vivo pH and levels of oxygen and carbon dioxide are temperature dependent, results may need to be adjusted for the patient’s actual temperature. Portable blood gas analyzers are available that can be used at the bedside. Blood gas analyzers calculate blood bicarbonate concentration using the formula: pH = 6.1 + Log bicarbonate/.0306 x PCO2. They also calculate oxygen content, total carbon dioxide, base excess, and percent oxygen saturation of hemoglobin. These values are used by physicians to assess the extent of hypoxia and acid-base imbalance.

Preparation Patients do not need to restrict food or drink before the test. For patients receiving oxygen therapy, the oxygen concentration must remain constant for 20 minutes before sample collection; if the test is specifically ordered to be without oxygen, the gas must be turned off for 20 minutes before the blood sample is taken to guarantee accurate test results. The patient should breathe normally during sample collection. Infants and children may require physical and psychological preparation appropriate to the child’s age. A parent or other trusted adult may be enlisted to restrain the child during sample collection.

A blood gas analyzer from Corning Corporation. (Photograph by Hank Morgan, Photo Researchers, Inc. Reproduced by permission.)

Complications Complications posed by the arterial puncture are minimal when the procedure is performed correctly, but may include bleeding or delayed bleeding or bruising at the puncture site, or, rarely, impaired circulation around the puncture site.

Results Normal values

Aftercare After the blood sample has been taken, the health care practitioner or patient applies pressure to the puncture site for about 10 minutes or until bleeding has stopped, after which a dressing is applied. The patient should rest quietly while applying pressure to the puncture site and be observed for signs of bleeding or impaired circulation at the puncture site.

The following results are for arterial blood at sea level (at altitudes of 3,000 feet and above, the values for oxygen are lower). • Partial pressure of oxygen (PO2 75–100 millimeters of mercury (mm Hg). Note that PO2 values normally decline with age. • Partial pressure of carbon dioxide PCO2 35–45 mm Hg.

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thus, the total CO2 is normally about 5% higher than the bicarbonate value.

KEY TERMS Acid—A chemical compound that reacts with a base to form a salt, that can give off hydrogen ions in water solution, or that contains an atom that can accept a pair of electrons from a base. Acidosis—A blood condition in which the pH is < 7.35 and the bicarbonate concentration is below normal. Alkalosis—A blood condition in which the pH is > 7.45 and the bicarbonate concentration is above normal. Base—A chemical compound that reacts with an acid to form a salt, that takes up or accepts protons, or that contains an atom with a free pair of electrons to be donated to an acid. Buffer—A chemical substance that resists changes in pH in response to changes in acid and base concentration; a buffer system consists of a weak acid or weak base in combination with its salt. Hemoglobin—The red–colored, iron-containing protein in red blood cells that carries oxygen to the tissues. Heparin—A biochemical that may be isolated from various animal tissues that has anticoagulant properties. Ketoacidosis—An excessive level of acid accompanied by an increase in the level of ketones in blood that occurs as a complication of diabetes mellitus; ketones are substances normally processed by the liver from fats. Oxygen saturation of hemoglobin—The percentage of hemoglobin that is bound to oxygen. pH—An exponential measurement scale for expressing the concentration of acid in solution pH = -log [H+].

• pH: 7.35–7.45. • Oxygen content (O2CT): 15–23 volume%. • Oxygen saturation (SaO2): 94%–100%. • Concentration of bicarbonate(HCO3–): 22–26 millimols per liter (mEq/liter). Total CO2 is often reported with blood gas analysis results and is defined as the sum of carbonic acid and bicarbonate concentrations. Normally, the ratio of bicarbonate to carbonic acid at physiological pH is about 20:1, 316

The A-a gradient (alveolar-arterial PO2 difference) is calculated from the partial pressures of oxygen and carbon dioxide as returned from the blood gas analysis, and the partial pressure of oxygen in the air and a factor called the respiratory quotient that are specific to the site of the test. A normal value for A–a gradient may be estimated as one-fourth the patient’s age plus 2.5. Abnormal results Values that differ from the normal values may indicate the presence of respiratory, metabolic, or renal diseases. For most clinical decisions, the bicarbonate value, PCO2, and pH are used to evaluate acid-base status. The pH value defines the magnitude of the disturbance and the bicarbonate and PCO2 determine the cause. The bicarbonate level is under the control of the kidneys, which may increase or decrease bicarbonate blood levels in response to pH changes. Bicarbonate is also the principal blood buffer anion, and it functions as the conjugate base to increase pH. PCO2 is the respiratory component because it is regulated by the lungs. It is determined by the concentration of dissolved carbon dioxide (anhydrous carbonic acid) and is the principal acid component of the blood. Abnormal results are classified on the basis of pH and whether the abnormal pH is caused by the metabolic or respiratory component. pH 7.45 indicates alkalosis. Metabolic or non-respiratory acidosis is characterized by pH 7.45 and the PCO2: is low. If the kidneys are functioning normally and given sufficient time, the HCO3- will be decreased in compensation. Respiratory alkalosis may be caused by hyperventilation psychologically induced (anxiety), by drugs that stimulate the respiratory center, excessive ventilation therapy, and mild hypoxia. A decrease in PO2 is a sensitive measure of respiratory function and hypoxia. In addition to ventilation defects that also result in increased PCO2, PO2 will be low in persons with poor ratios of ventilation to perfusion; mild emphysema and other gas diffusion defects; pulmonary arterial-venous shunts; and those breathing air with a low oxygen content. Elevated PO2 is caused by excessive administration of oxygen which can lead to optic nerve damage and acidosis by displacing hydrogen ions from hemoglobin. It is important to note that in cases of carbon monoxide poisoning the PO2: will be normal, but lifethreatening hypoxia may be present. Blood gas analyzers calculate the oxygen saturation of hemoglobin from PO2, temperature, and pH. In cases of CO poisoning, the calculation will be falsely elevated. Accurate assessment of hypoxia in CO poisoning requires direct measurements of carboxyhemoglobin and oxygen saturation of hemoglobin by oximetry or colorimetry methods.

Health care team roles A physician, nurse, respiratory care technician, or laboratory technician collects the blood sample by arteri-

al puncture and sees to the timely and appropriate transport to the laboratory for analysis. A member of the health care team should observe the patient for 10–15 minutes to ensure that bleeding from the puncture site has stopped. Blood gas measurements are performed by a registered respiratory therapist, RRT; certified respiratory technician, CRTT; clinical laboratory scientist CLS (NCA) or medical technologist MT (ASCP); clinical laboratory technician CLT (NCA) or medical laboratory technician MLT (ASCP). A physician interprets the blood gas analysis results with a thorough understanding of the acid-base chemistry and physiology of blood and in view of the clinical situation, and applies the results to the diagnosis, treatment, and management of the patient. Resources BOOKS

Burtis, C.A., and E.R. Ashwood, eds. Fundamentals of Clinical Chemistry. 5th ed. Philadelphia: Saunders, 2001. Marshall, William J. Clinical Chemistry 4th ed. Edinburgh, London, New York, Philadelphia, St. Louis, and Toronto: Mosby, 2000. OTHER

Argyle, B. Mad Scientist Software, Blood Gases Computer Program Manual. 1996 Mad Scientist Software, Alpine UT. . Clinical Web Server 2.University of Kansas Medical Center. . HealthCentral website. 1998 A.D.A.M. Software, Inc. .

Patricia L. Bounds, Ph.D.

Blood gases Definition Blood gases are defined as the mixture of gases, including oxygen (O2), carbon dioxide (CO2), and nitrogen (N2), dissolved in the fluid fraction of blood.

Description Oxygen from the air is transported from the lungs to all tissues of the body, where it is needed for metabolism; and carbon dioxide, a by-product of metabolism, is taken from the tissues to the lungs to be eliminated.

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severe pneumonia and pulmonary fibrosis; thoracic conditions such as multiple broken ribs and kyphoscoliosis. Respiratory acidosis is also caused by neuromuscular disease, and by depression of the respiratory center in the brain due to drugs, head trauma, or cranial tumor. The blood gas analysis results may deviate only slightly from normal values, and pH may even fall within the normal range (compensated respiratory acidosis) in cases of chronic compared to acute acidosis.

Blood gases

Respiration The overall process of delivering oxygen to the tissues and carrying carbon dioxide away is called respiration. When the blood reaches the tissues, oxygen diffuses into the cells, and carbon dioxide diffuses from the cells into the blood. In the lungs, the air enters a branching complex of multiple air sacs, called alveoli, where tiny capillaries separate the air from the red blood cells by only a very thin membrane, about 0.3 µm thick. During respiration the inspired air is filtered and moistened by the nose and tracheal linings and is completely saturated with water vapor by the time it enters the alveolar sac. In the alveolus, oxygen diffuses into the blood, and carbon dioxide diffuses out of the blood to mix with the alveolar air. Diffusion is a very rapid process, and the gases do not have time to totally equilibrate across the alveolar membrane. A small pressure difference for each gas develops. About 2% of the blood flow through the lungs bypasses the pulmonary capillaries and does not become oxygenated; thus, the partial pressure of oxygen is somewhat higher in the alveolus than in the blood. This pressure difference, calculated for the lung as a whole, is called the arterial-alveolar (A–a) gradient. Composition of gases in air Dry air is made up of 20.98% oxygen, 0.04% carbon dioxide, 78.06% nitrogen, and 0.92% other gases (mostly argon). In blood-gas analysis, the content of the gases oxygen and carbon dioxide are reported in terms of their partial pressures, with normal values for oxygen (PO2) of 75 mm to 100 mm of mercury (mm Hg) and for carbon dioxide (PCO2) of 35 to 45 mm Hg. The partial pressure of water vapor in the lung, where the air is completely water-saturated, at body temperature (98.6°F, or 37°C) is 47 milliliters of mercury (mm Hg).

Function As blood circulates through the body, oxygen diffuses from the area of higher partial pressure. The blood moves toward the area of lower partial pressure, the cells, and carbon dioxide diffuses from the cells into the blood. In the lung, oxygen diffuses into the blood, where it is taken up by hemoglobin, and carbon dioxide diffuses out of the blood, to be exhaled. Oxygen Oxygen in the blood is carried by hemoglobin. The hemoglobin content of normal blood is about 15 to 16 grams per 100 ml, and each gram of hemoglobin binds 318

about 1.34 ml of oxygen gas. Thus, arterial blood contains about 20 ml of oxygen per 100 ml when fully saturated. The volume of oxygen in the blood, the O2 content, is dependent on the hemoglobin concentration and does not provide as good a measure of lung function as the partial pressure of oxygen (PO2) in arterial blood. The amount of oxygen in the blood relative to the carrying capacity of the hemoglobin is called the oxygen saturation. The oxygen saturation of hemoglobin is directly proportional to the PO2; the relationship is not linear but is described by a sigmoidal (S-shape) curve. Oxygen saturation is affected by the acid-base status of the blood: at a given PO2, the degree of oxygen saturation may be lowered by increasing the acidity of the blood. Oxygen saturation is expressed as a percentage; hemoglobin in arterial blood is about 97% saturated, while the more acidic venous blood is about 75% saturated. Carbon dioxide Carbon dioxide is formed in the cells during aerobic metabolism and diffuses into the capillaries, where only a small amount remains dissolved. It enters the red blood cells, where carbonic anhydrase quickly catalyzes its conversion to carbonic acid, which dissociates to hydrogen ion and bicarbonate. About two-thirds of the bicarbonate diffuses out into the plasma and is replaced by chloride in the red cell. The hydrogen ion binds to hemoglobin, and is transported to the lungs. Arterial blood normally contains an amount of bicarbonate that is the equivalent of about 50 ml of carbon dioxide gas per 100 ml of blood. About 5 ml of additional carbon dioxide enters the blood in the capillaries and is converted to bicarbonate and hydrogen ion, making the blood more acidic and causing the pH to drop from 7.4 to 7.36. On reaching the lungs, the bicarbonate and hydrogen ion are converted back to carbon dioxide, which diffuses into the alveoli for exhalation. Over a period of 24 hours at rest, about 200 ml of carbon dioxide, the equivalent of 12,500 milliequivalents of acid, is produced by metabolism and eliminated via the lungs. The carbonicacid concentration can change in seconds in response to hypo- or hyperventilation, while changes in the bicarbonate concentration take much longer—hours or days— because elimination by the kidney is relatively slow. Carbon monoxide Small amounts of carbon monoxide (CO) are produced during metabolism. Carbon monoxide binds tightly to hemoglobin to form a CO-hemoglobin complex called carboxyhemoglobin in which the binding of oxygen molecules is prevented. Thus, carbon monoxide reduces the oxygen saturation of hemoglobin at any

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Nitrogen and other gases The nitrogen and other gases inhaled are, under normal circumstances, inert and play no role in human health. A painful and potentially fatal condition, called decompression sickness or the bends, can be caused by formation of nitrogen bubbles in the blood and tissues by moving too quickly from areas of higher atmospheric pressures to lower pressures, such as when deep-sea divers return too quickly to the surface of the water.

Role in human health Acid-base balance in the blood Carbon dioxide in the blood is transported as bicarbonate, since carbon dioxide combines with water to form carbonic acid: CO2 + H2O = H2CO3 which is in equilibrium with hydrogen ions and bicarbonate: H2CO3 = H+ + HCO3The concentration of hydrogen ions (H+) determines the pH, a measure of the acidity, of the blood. The carbonic acid-bicarbonate equilibrium is an example of a buffer system and is involved in the maintenance of the acid-base balance in the body. The pH of the blood is related to the ratio of bicarbonate to carbonic acid, which is normally about 20:1. The carbonic acid-bicarbonate buffering system is extended by the body’s ability to convert carbonic acid to carbon dioxide (catalyzed by the enzyme carbonic anhydrase) and the removal of CO2 in respired air. In addition, the body has the ability to eliminate hydrogen or bicarbonate ions via the kidneys to maintain pH. Since most body systems function best at a pH near 7.4, the pH of the body must be maintained within a narrow range. When the blood pH is higher or lower than the normal level of 7.35 to 7.45, enzymes may function less effectively or not at all, nerve and muscle activity weakens, and finally all metabolic activity is undermined. Proteins also function as buffers; hemoglobin in particular is an important buffering agent in the blood. Oxygen-bound hemoglobin is a stronger acid than hemoglobin without oxygen, and tends to release hydrogen ions; when hemoglobin is exposed to the lower oxygen concentrations in the capillaries, oxygen is released, the

Blood gases

given PO2. City dwellers and smokers are exposed to a much higher level of carbon monoxide in the air: in heavy smokers, as much as 10% of hemoglobin may be carboxyhemoglobin.

Normal arterial blood gas values Arterial pH PaCO2 PaO2 O2 sat CO2 content Base excess

Term infant

Child

Adult

7.26–7.41 34–54 mm Hg 60 mm Hg 40%–95% 20–28 mEq/L –7 to –1 mEq/L

7.35–7.45 35–45 mm Hg 75–100 mm Hg 95%–98% 18–27 mEq/L –4 to +2 mEq/L

7.35–7.45 35–45 mm Hg 75–100 mm Hg 95%–98% 23–29 mEq/L –2 to +2 m Eq/L

SOURCE:

Rothstein, J.M., S.H. Roy, and S.L. Wolf. The Rehabilitation Specialist’s Handbook. 2nd ed. Philadelphia: F.A. Davis Co., 1998

hemoglobin becomes a weaker acid, and hydrogen ions are taken up. The relationship between pH and the ability of hemoglobin to bind oxygen, which is reflected in saturation levels of hemoglobin in arterial versus venous blood, is known as the Bohr effect. Buffer base and base excess The buffer base is the sum of all anionic buffer components in the blood, including bicarbonate, sulfates, and phosphates. The base excess refers to how much a patient’s buffer base is higher than normal, and is expressed in terms of the amount of acid in milliequivalents per liter (mEq/L) that would have to be added to the patient’s blood to bring it to a normal pH of 7.4. Many physicians rely only on the difference between the patient’s bicarbonate and an average value for bicarbonate of 24 mEq/L as an indication of the need for bicarbonate replacement. However, the base excess is more meaningful, since other buffers are taken into account and is accurate also in anemic patients, where the buffering capacity of hemoglobin is diminished. Base excess can be negative in value for acidotic patients; that is, acid would have to be taken away to bring the pH to normal. The clinical determination of how much bicarbonate to administer in the treatment of severe acidosis is usually based on the base excess of the blood. The base excess of blood, however, is not a true indication of the base excess of the extracellular fluid (ECF) of the whole body. Only blood contains hemoglobin, and other extracellular fluids have different protein contents and buffering capacities. Furthermore, fluid distribution in the body varies with the state of hydration, and ECF as a percentage of body weight varies with age and fat content. In general, however, the recommendation for bicarbonate therapy is 0.1 to 0.2 mEq  body weight  base excess.

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KEY TERMS Acid—A chemical compound that reacts with a base to form a salt, that can give off hydrogen ions in water solution, or that contains an atom that can accept a pair of electrons from a base. Acidosis—A blood condition in which the pH is 7.45 and is above normal. Alveoli—Air sacs of the lungs located at the termini of the bronchial passageways. Base—A chemical compound that reacts with an acid to form a salt, that takes up or accepts protons, or that contains an atom with a free pair of electrons to be donated to an acid. Buffer—A chemical substance that resists changes in pH in response to changes in acid and base concentration; a buffer system consists of a weak acid or weak base in combination with its salt. Carbonic anhydrase—An enzyme that catalyzes the reversible reaction of carbon dioxide with water to form carbonic acid in red blood cells. Hemoglobin—The red-colored, iron-containing protein in red blood cells that carries oxygen to the tissues. Ketoacidosis—An excessive level of acid accompanied by an increase in the level of ketones in blood that occurs as a complication of diabetes mellitus; ketones are substances normally processed by the liver from fats. Metabolism—The physical and chemical processes carried out by an organism to produce, maintain, and destroy material substances and to make energy available. pH—An exponential measurement scale for expressing the concentration of acid in solution pH = -log [H+].

Common diseases and disorders Disorders involving the levels of blood gases are primarily diagnosed on the basis of disturbances in the acidbase balance as acidosis or alkalosis. Acid-base disorders may be respiratory or nonrespiratory (metabolic) in origin, or of mixed origin. Acidosis with elevated PCO2 is classified as respiratory acidosis. Causes include: • airway obstruction due to chronic conditions such as bronchitis or emphysema, or acute causes such as bronchospasm or aspiration of foreign material • neuromuscular diseases such as poliomyelitis, motorneuron disease, or tetanus, or due to neurotoxins such as botulin or curare • pulmonary diseases including pneumonia and pulmonary fibrosis, and extrapulmonary thoracic disorders such multiple broken ribs or kyphoscoliosis • respiratory-center depression due to cerebral trauma or tumor, or secondary to anesthesia or application of sedatives Alkalosis with depressed PO2 is classified as respiratory alkalosis. Causes include: • hypoxia due to high altitude, anemia, or pulmonary disease • hyperventilation, whether voluntary or secondary to trauma, infection, cerebral tumor, or ingestion of a respiratory stimulant

Control of respiration The levels of blood gases act to control the rate of respiration. The aortic and carotid bodies, special chemical receptors near the aorta and carotid arteries, respond to changes in the levels of acid, carbon dioxide, or oxygen, stimulating the brain respiratory centers in the brain stem to regulate the speed and depth of breathing. When blood acid is increased, such as during diabetic 320

ketoacidosis, or when there is a rise in CO2 during the increased metabolism of exercise, respiration is stimulated. The respiratory centers in the brain also respond directly to increases in PCO2 and stimulate respiration. The resulting deep, rapid breathing acts to mix alveolar air with CO2-poor air to decrease the carbon dioxide in the blood as it passes by the alveolus, and the reduction in CO2 returns the blood toward normal. Lack of oxygen can also weakly stimulate respiration. Oxygen levels usually play little role in the regulation of respiration in healthy individuals at normal altitudes, but at very low PO2 (i.e., . National Institute of Occupational Safety and Health. <www.cdc.gov/niosh/carbon2.html>. U.S. Environmental Protection Agency. <www.epa.gov/iaq/pubs/coftsht.html>.

L. Fleming Fallon, Jr., MD, DrPH

Carbunculosis see Boils Carcinoembryonic antigen test see Tumor marker tests Cardiac blood pool scan see Multiplegated acquisition (MUGA) scan

Cardiac catheterization Definition Cardiac catheterization (also called heart catheterization) is a diagnostic and occasionally therapeutic procedure that allows a comprehensive examination of the heart and surrounding blood vessels. It enables the physician to take angiograms, record blood flow, calculate cardiac output and vascular resistance, perform an endomyocardial biopsy, and evaluate the heart’s electrical activity. Cardiac catheterization is performed by inserting one or more catheters (thin flexible tubes) through a peripheral blood vessel in the arm (antecubital artery or vein) or leg (femoral artery or vein) under x-ray guidance.

Purpose Cardiac catheterization is most commonly performed to examine the coronary arteries, because heart attacks, angina, sudden death, and heart failure most often originate from disease in these arteries. Coronary artery disease is the first-ranked cause of death for both men and women in the United States. Cardiac catheterization with coronary angiography is recommended in patients with angina (especially unstable angina); suspected coronary artery disease; suspected silent ischemia and a family history of heart attack; ischemic cardiac myopathy; congestive heart failure; congenital heart disease; and pericardial disease. Catheterization is

Doctors at work during a cardiac catheterization procedure. With the patient under a local anesthetic, the catheter is inserted into an artery in the thigh, then guided to the coronary arteries. A dye is then released, revealing blockages. (Photograph by Simon Fraser, Photo Researchers, Inc. Reproduced by permission.)

also recommended for patients with suspected valvular disease, including aortic stenosis or regurgitation and mitral stenosis or regurgitation. In addition, the procedure may be performed after acute myocardial infarction; before major noncardiac surgery in patients at high risk for cardiac problems; before cardiac surgery in patients at risk for coronary artery disease; and before such interventional technologies and procedures as stents and percutaneous transluminal coronary angioplasty (PTCA). Cardiac catheterization may reveal the presence of other conditions, including enlargement of the left ventricle; ventricular aneurysms (abnormal dilation of a blood vessel); narrowing of the aortic valve; insufficiency of the aortic or mitral valve; and septal defects that allow an abnormal flow of blood from one side of the heart to the other.

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Symptoms and diagnoses that may be associated with the above conditions and may lead to cardiac catheterization include: • chest pain characterized by prolonged heavy pressure or a squeezing pain • abnormal results from a treadmill stress test • myocardial infarction (heart attack)

condition. As of 2000, however, the American Heart Association (AHA) and the American College of Cardiology (ACC) issued a joint statement denying approval of the use of separate cardiac catheterization laboratories that are not part of a hospital, on the grounds that a small number of patients having the procedure on an outpatient basis will have unexpected reactions or complications.

• congenital heart defects

Precautions

• valvular disease

Contraindications

Left- and right-side catheterization Cardiac catheterization can be performed on either side of the heart to evaluate different functions. Testing the right side of the heart allows the physician to evaluate tricuspid and pulmonary valve function, in addition to measuring blood pressures and collecting blood samples from the right atrium, right ventricle, and pulmonary artery. Catheterization of the left side of the heart is performed to test the blood flow in the coronary arteries as well as the level of function of the mitral and aortic valves and left ventricle. The physician can assess the adequacy of blood supply through the coronary arteries, blood pressures, and blood flow throughout the chambers of the heart, collect blood samples, and take x rays of the heart’s ventricles or arteries. Coronary angiography Coronary angiography, which is also known as coronary arteriography, is an imaging technique that involves injecting a dye into the vascular system to outline the heart and coronary vessels. Angiography allows the visualization of any blockages, narrowing, or abnormalities in the coronary arteries. If these signs are visible, the cardiologist may assess the patient’s readiness for coronary bypass surgery, or a less invasive approach such as dilation of a narrowed blood vessel by surgery or the use of a balloon (angioplasty). Because some interventions may be performed during cardiac catheterization, the procedure is considered therapeutic as well as diagnostic. Outpatient catheterization Cardiac catheterization is usually performed in a specially designed cardiac catheterization suite in a hospital, so that any procedural complications may be handled rapidly and effectively. Cardiac catheterization may also be performed on patients presenting to the emergency department with chest pain or chest injuries. The procedure may be performed on an outpatient basis, depending on the patient’s pre- and post-catheterization 408

Cardiac catheterization is categorized as an invasive procedure that involves the heart, its valves, and coronary arteries, in addition to a large artery in the arm or leg. Cardiac catheterization is contraindicated for patients with the following conditions: • A bleeding disorder, or anticoagulation treatment with Coumadin (sodium warfarin). These may affect bleeding and clotting during the catheterization procedure. • Renal insufficiency or poor kidney functioning (especially in diabetic patients), which may worsen following angiography. • Severe uncontrolled hypertension. • Severe peripheral vascular disease that limits access to the arteries. • Untreated active infections, severe anemia, electrolyte imbalances, or coexisting illnesses that may affect recovery or survival. • Endocarditis (an inflammatory infection of the heart’s lining that often affects the valves). Radiation hazards Cardiac catheterization involves radiation exposure for staff members as well as the patient. The patient’s dose of radiation is minimized by using lead shielding in the form of blankets or pads over certain body parts and by choosing the appropriate dose during fluoroscopy. Staff members’ exposure to radiation is monitored by the wearing of radiation badges that detect exposure and lead aprons that shield the body. The radiographic/fluoroscopic system may be equipped with movable lead shields that do not interfere with access to the patient and are placed between staff members and the source of radiation during the procedure.

Description More than 1.5 million cardiac catheterizations are performed every year in the United States, primarily to diagnose or monitor heart disease.

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The heart consists of four chambers separated by valves. The right side of the heart, which consists of the right atrium (upper chamber; sometimes called the right auricle) and the right ventricle (lower chamber), pumps blood to the lungs. The left side of the heart, which consists of the left atrium (or auricle) and the left ventricle, simultaneously pumps blood to the rest of the body. The right and left coronary arteries, which are the first vessels to branch off from the aorta, supply blood to the heart. The left anterior descending coronary artery supplies the front of the heart; the left circumflex coronary artery wraps around and supplies the left side and the back of the heart; and the right coronary artery supplies the back of the heart. There is, however, a considerable amount of variation in the anatomy of the coronary arteries.

Subclavian v. Pulmonary a. Superior vena cava

Right atrium

Right ventricle

Basilic v.

Catheterization procedure The patient lies on a table on his or her back during the catheterization procedure, connected to monitoring equipment, including an electrocardiography device. The insertion site is numbed with a local anesthetic, and access to the vein or artery is obtained using a needle. A sheath, a rubber tube that facilitates insertion of catheters and infusion of drugs, is placed in the puncture site. Under fluoroscopic guidance, a guidewire, which is a thin wire that guides the catheter insertion, is threaded through a brachial or femoral artery and up to the heart. The catheter, a flexible or preshaped tube approximately 32–43 inches (80–110 cm) long, is then inserted over the wire and threaded to the heart. The patient may experience pressure as the catheter is threaded into the heart. The contrast agent or dye used for imaging is then injected so that the physician can view the heart and surrounding vessels. The patient may experience a hot flushed feeling or slight nausea following injection of the contrast medium. Depending on the type of catheterization (left- or right-heart) and the area being imaged, different catheters with various shapes and ends are used.

Cardiac catherization procedure. (Delmar Publishers, Inc. Reproduced by permission.)

commonly used sealing device is called Perclose, which allows the doctor to sew up the hole in the groin. Two other devices called AngioSeal and VasoSeal use collagen seals to close the holes in the femoral artery.

Preparation

The radiographic/fluoroscopic system has an x-ray subsystem and video system with viewing monitors that allow the physician to view the procedure in real time using fluoroscopy as well as taking still x rays for documentation purposes. Most newer systems use a digital angiography system that allows images to be recorded, manipulated, and stored digitally on a computer.

Before undergoing cardiac catheterization, the patient may have had other noninvasive diagnostic tests, including an electrocardiogram (ECG), echocardiography, computed tomography (CT), magnetic resonance imaging (MRI), laboratory studies (e.g., blood work), and/or nuclear medicine cardiac imaging. The results of these noninvasive tests may have indicated a need for cardiac catheterization to confirm a suspected cardiac condition, further define the severity of a previously diagnosed condition, or establish the need for an interventional procedure (e.g., cardiac surgery).

The procedure usually lasts about two or three hours. If further intervention is necessary, an angioplasty, stent implantation, or other procedure can be performed. At the end of the catherization, the catheter and sheath are removed, and the puncture site is closed using a sealing device or manual compression to stop the bleeding. One

Patients should give the physician or nurse a complete list of their regular medications, including aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs), because they can affect blood clotting. Diabetics who are taking either metformin or insulin to control their diabetes should inform the physician, as these drugs may

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Cardiac anatomy

Cardiac catheterization

at the point of insertion but usually fades within two weeks. The incision site may bleed during the first 24 hours following surgery. The patient may apply pressure to the site with a clean tissue or cloth for 10–15 minutes to stop the bleeding.

Cardiac monitoring pressures and volumes Pressure

Normal values

Aortic artery pressure (routine blood pressure) Central venous pressure End-diastolic left ventricular pressure Pulmonary wedge pressure Pulmonary artery pressure Systolic left ventricle pressure

90–140/60–90 mm Hg

Volumes Cardiac index (CI)

Cardiac output (CO) Ejection fraction (EF) End-diastolic volume (EDV) End-systolic volume (ESV) Stroke volume (SV)

The patient should be instructed to call the doctor at once if tenderness, fever, shaking, or chills develop, which may indicate an infection. Other symptoms requiring medical attention include severe pain or discoloration in the leg, which may indicate that a blood vessel was damaged.

2–14 cm H2 4–12 mm Hg Left atrial: 6–15 mm Hg 15–28/5–16 mm Hg 90–140 mm Hg 2.8–4.2 L/min/m2 for a patient with 1.5m2 of body surface area 3–6 L/min 0.67±0.07 50–90ml/m2 25 ml/m2 45±12 ml/m2

SOURCE: Pagana, K.D. and T.J. Pagana. Mosby’s Diagnostic and Laboratory Test Reference. 3rd ed. St. Louis: Mosby, 1997.

need to have their dosages changed before the procedure. Patients should also notify staff members of any allergies to shellfish containing iodine, iodine itself, or the dyes commonly used as contrast agents before cardiac catheterization. Because cardiac catheterization is considered surgery, the patient will be instructed to fast for at least six hours prior to the procedure. A mild sedative may be administered about an hour before the procedure to help the patient relax. If the catheter is to be inserted through the groin, the area around the patient’s groin will be shaved and cleansed with an antiseptic solution.

Aftercare While cardiac catheterization may be performed on an outpatient basis, the patient requires close monitoring following the procedure; he or she may remain in the hospital for up to 24 hours. The patient will be instructed to rest in bed for at least eight hours immediately after the test. If the catheter was inserted into a vein or artery in the leg or groin area, the leg will be kept extended for four to six hours. If a vein or artery in the arm was used to insert the catheter, the arm will need to remain extended for a minimum of three hours. Most doctors advise patients to avoid heavy lifting or vigorous exercise for several days after cardiac catheterization. Those whose occupation involves a high level of physical activity should ask the doctor when they can safely return to work. In most cases, a hard ridge will form over the incision site that diminishes as the site heals. A bluish discoloration under the skin often occurs 410

Complications As with all invasive procedures, cardiac catheterization involves some risks. The most serious complications include stroke, myocardial infarction, and death resulting from clotting or rupture in one of the coronary or cerebral vessels. Other complications include cardiac arrhythmias, pericardial tamponade, vessel injury, and renal failure. The most common complications resulting from cardiac catheterization are vascular-related, including external bleeding at the arterial puncture site, hematomas, and pseudoaneurysms. The patient may be given anticoagulant medications to lower the risk of developing an arterial blood clot (thrombosis) or of blood clots forming and traveling through the body (embolization). The risk of complications from cardiac catheterization is higher in patients over the age of 60; those who have severe heart failure; or those with advanced valvular disease. Allergic reactions related to the contrast agent (dye) and anesthetics may occur in some patients during cardiac catheterization. Allergic reactions may range from minor hives and swelling to severe shock. Patients with allergies to seafood or penicillin are at a higher risk of allergic reaction; giving antihistamines prior to the procedure may reduce the occurrence of allergic reactions to contrast agents.

Results Normal findings from a cardiac catheterization will indicate no abnormalities in the size or configuration of the heart chamber, the motion or thickness of its walls, the direction of blood flow, or motion of the valves. Smooth and regular outlines on the x ray indicate normal structure of the coronary arteries. The measurement of intracardiac pressures, or the pressure in the heart’s chambers and vessels, is an essential part of the catheterization procedure. Pressure readings that are higher than normal are significant for a

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Aneurysm—An abnormal dilatation of a blood vessel, usually an artery. It may be caused by a congenital defect or weakness in the vessel’s wall.

Ischemia—A localized deficiency in the blood supply, usually caused either by vasoconstriction or by obstacles to the arterial blood flow.

Angiography—A procedure that allows x-ray examination of the heart and coronary arteries following injection of a radiopaque substance (often referred to as a dye or contrast agent).

Magnetic resonance imaging (MRI)—A diagnostic imaging procedure that uses a magnetic field to produce anatomical images. It may be performed prior to cardiac catheterization.

Angioplasty—A procedure in which a balloon catheter is used to mechanically dilate the affected area of a diseased artery and enlarge the constricted or narrowed segment. It is an alternative to vascular surgery.

Mitral valve—The bicuspid valve that lies between the left atrium and left ventricle of the heart. “Bicuspid” means that the valve has two flaps.

Aortic valve—The valve between the heart’s left ventricle and ascending aorta that prevents regurgitation of blood back into the left ventricle. Arrhythmia—A variation in the normal rhythm of the heartbeat. Catheter—A flexible or preshaped curved tube, usually made of plastic, used to evacuate fluids from or inject fluids into the body. In cardiac catheterization, a long, fine catheter is inserted through a blood vessel directly into the chambers of the heart.

Percutaneous transluminal coronary angioplasty (PTCA)—A cardiac intervention in which an artery blocked by plaque is dilated, using a balloon catheter to flatten the plaque and open the vessel. It is also called balloon angioplasty. Pericardial tamponade—The collection of blood in the sac surrounding the heart that causes compression. Tamponade is a possible complication of cardiac catheterization Pseudoaneurysm—A dilation of a blood vessel that resembles an aneurysm. Pseudoaneurysms may occur as a complication of cardiac catheterization.

Computed tomography (CT)—A diagnostic imaging procedure that uses x rays to produce cross-sectional images of the anatomy. It may be performed prior to cardiac catheterization.

Pulmonary valve—The heart valve that separates the right ventricle and the opening into the pulmonary artery.

Coronary bypass surgery—A surgical procedure that places a shunt to allow blood to travel from the aorta to a branch of the coronary artery at a point below an obstruction.

Septum—The muscular wall that separates the two sides of the heart. An opening in the septum that allows blood to flow from one side to the other is called a septal defect.

Echocardiography—An ultrasound examination of the heart that may be performed prior to cardiac catheterization.

Shunt—A passageway (or an artificially created passageway) that diverts blood flow from one main route to another.

Fluoroscopy—A diagnostic imaging procedure that uses x-rays and contrast agents to visualize anatomy and motion in real time.

Stent—A small tubelike device made of stainless steel or other material, used to hold open a blocked artery.

Hematoma—An accumulation of clotted blood that may occur in the tissue around the catheter insertion site following cardiac catheterization.

Tricuspid valve—The right atrioventricular valve of the heart. It has three flaps, whereas the mitral valve has only two.

patient’s overall diagnosis. Pressure readings that are lower, other than those resulting from shock, are usually not significant. The ejection fraction is also determined by performing a cardiac catheterization. The ejection fraction is a

comparison of the quantity of blood ejected from the heart’s left ventricle during its contraction phase with the quantity of blood remaining at the end of the left ventricle’s relaxation phase. The cardiologist will look for a normal ejection fraction reading of 60–70%.

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KEY TERMS

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Abnormal results are obtained by viewing the still and live motion x rays during cardiac catheterization for evidence of coronary artery disease, poor heart function, disease of the heart valves, and septal defects. The most prominent sign of coronary artery disease is narrowing or blockage (stenosis) in the coronary arteries, with narrowing greater than 50% considered significant. A clear indication for intervention by angioplasty or surgery is a finding of significant narrowing of the left main coronary artery and/or blockage or severe narrowing in the high left anterior descending coronary artery. A finding of impaired wall motion is an additional indicator of coronary artery disease, an aneurysm, an enlarged heart, or a congenital heart problem. Using an ejection fraction test that measures wall motion, cardiologists regard an ejection fraction reading under 35% as increasing the risk of complications while also decreasing the possibility of a successful long- or short-term outcome from surgery. Detecting the difference in pressure above and below the heart valve can verify the presence of valvular disease. The greater the narrowing, the higher the difference in pressure. To confirm the presence of septal defects, measurements are taken of the oxygen content on both the left and right sides of the heart. The right heart pumps unoxygenated blood to the lungs, and the left heart pumps blood containing oxygen from the lungs to the rest of the body. Elevated oxygen levels on the right side indicate the presence of a left-to-right atrial or ventricular shunt. Low oxygen levels on the left side indicate the presence of a right-to-left shunt.

Resources BOOKS

Bennett, J. Claude, and Fred Plum, eds. “Cardiac Catheterization and Angiography.” In Cecil Textbook of Medicine, 20th ed., Vol. 1. Philadelphia: W. B. Saunders Company, 1996. “Diagnostic Cardiovascular Procedures: Invasive Procedures.” The Merck Manual of Diagnosis and Therapy, 17th edition, ed. Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 1999. Segen, Joseph C., and Joseph Stauffer. “Cardiac Catheterization.” In The Patient’s Guide To Medical Tests: Everything You Need To Know About The Tests Your Doctor Prescribes. New York: Facts On File, Inc., 1998. PERIODICALS

Norris, Teresa G. “Principles of Cardiac Catheterization.” Radiologic Technology 72, no. 2 (November-December 2000): 109-136. Segal, A. Z., et al. “Stroke as a Complication of Cardiac Catheterization: Risk Factors and Clinical Features.” Neurology 56 (April 2001): 975-977. ORGANIZATIONS

American College of Cardiology. Heart House, 9111 Old Georgetown Road, Bethesda, MD 20814-1699. (800) 253-4636. . American Heart Association National Center. 7272 Greenville Avenue, Dallas, TX 75231. (800) AHA-USA1. . OTHER

Cardiology Channel. “Cardiac Catheterization.” .

Jennifer E. Sisk, M.A.

Health care team roles A cardiac catheterization team consists of a physician (e.g., interventional cardiologist), a nurse, a circulating nurse, and a radiologic technologist. Nurses assist the physician and monitor the patient during the procedure. Because clinical laboratory equipment may be used during the procedure to monitor certain parameters (e.g., blood coagulation time), nursing or other staff should be familiar with the operation of laboratory devices used in the cardiac catheterization suite. The radiologic technologist assists the physician with the operation of the xray and fluoroscopy equipment during the procedure and oversees any image processing, printing, and/or storage needs. The radiologic technologist may work with a medical physicist to monitor radiation safety protocols for the patient and staff. 412

Cardiac cycle Definition The cardiac cycle is the sequence of events that occur when the heart beats. The cycle has two main phases: diastole, when the heart ventricles are relaxed, and systole, when the ventricles contract. One cardiac cycle is defined as the contraction of the two atria followed by contraction of the two ventricles.

Description The heart is a muscular organ that works as a pumping system. It takes in blood with reduced levels of oxy-

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The heart is divided into four hollow chambers, two on the left and two on the right. The right chambers are the right atrium and the right ventricle. They receive blood from the veins. The left chambers are the left atrium and the left ventricle. They receive blood from the pulmonary circulation, and the left ventricle forces blood into the systemic circulation. In a cardiac cycle, blood enters the right atrium of the heart from the superior and inferior vena cavae, and flows across the tricuspid valve into the right ventricle. From the right ventricle the blood flows into the pulmonary artery, which is separated from the ventricle by the pulmonary valve. After oxygenation in the lungs, blood returns to the heart via four pulmonary veins that enter the left atrium. From the left atrium, blood flows across the mitral valve and into the left ventricle. From the left ventricle blood is ejected across the aortic valve into the aorta. Together, the mitral and triscupsid valves are known as the atrioventricular valves and the aortic and pulmonary valves as the semilunar valves. From a mechanical point of view, the cardiac cycle is due to blood movement occurring as a result of pressure differences within the chambers of the heart. In order for blood to flow through a blood vessel or across and heart valve, there must be a force acting on the blood. This force is provided by the difference in blood pressure (a pressure gradient) across these structures by the contractions of the heart. Each heart beat, or cardiac cycle, is divided into two phases of contraction and relaxation, stimulated by electrical impulses from the sinoatrial node (SA node), a patch of tissue in the heart that sets the rate of contractions. It contracts itself and then sends nerve impulse to the atria. The time during which ventricular contraction occurs is called systole. The time between ventricular contractions, during which ventricular filling occurs, is called diastole (also known as the relaxation phase). In early diastole, the ventricles relax, the semilunar valves close, the atrioventricular valves open and the ventricles fill with blood. In mid diastole, the atria and ventricles are relaxed, the semilunar valves are closed, the atrioventricular valves are open, and the ventricles keep filling with blood. In late diastole, the SA node sends an electrical impulse to the atria, which causes the atria to contract and the ventricles to fill with more blood. The electrical signal that causes contraction moves from the atria toward the ventricles. Before it

does, though, it reaches the atrioventricular node (AV node). The AV node delays the signal so that the ventricle can contract all at once rather than a little bit at a time. Prior to systole, the electrical signal passes from the AV node down the AV bundle, also known as the bundle of His, to the Purkinje fibers. The fibers allow the fast spread of the electrical signal to all parts of the ventricles, and the electrical signal causes the ventricles to contract. Systole begins with the closure of the atrioventricular valves. During systole, the ventricles contract, the semilunar valves open, and blood is pumped from the ventricles to the aorta. Blood pressure is highest during systole, and lowest during diastole. It has two components, the systolic and diastolic pressure. Normal systolic pressure for an adult is 120 mm Hg, and normal diastolic pressure is 80 mm Hg. These values are commonly recorded as 120/80. The normal heart beats at a rate of about 72 beats per minute (with a range of 60-100 beats per minute), but can vary with normal daily activity. The cardiac cycle produces well-known sounds that can be clearly heard with a stethoscope. The first heart sound is associated with closure of the atrioventricular valves and signals the start of ventricular systole. The second heart sound is associated with the closure of the semilunar valves and indicates the start of ventricular diastole. A third heart sound is due to the rapid phase of ventricular filling, and a fourth heart sound is due to atrial systole. The two last sounds are usually not loud enough to hear, so neither of them is heard under normal exam procedures.

Role in human health The role of the cardiac cycle is essential to maintain life, as the heart distributes the oxygen-carrying blood required for the functioning of the body.

Common diseases and disorders Although diseases of the valves are common, and other cardiac disorders can also disrupt normal blood flow, they do not cause an abnormal cardiac cycle per se. Since the normal sequence of events occurs, even though it’s impaired, it is considered a normal cardiac cycle (but not a normal heart beat). Most of the common abnormalities in the cardiac cycle are caused by disturbances in electrical conduction of the heart. Disturbances in the electrical cycle are known as arrhythmias. However, two types of disturbances, sinus tachycardia and sinus bradycardia, do not affect the sequence of events, because they speed up (tachycardia)

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gen from the veins (deoxygenated blood), and delivers it to the lungs for oxygenation. When it receives the oxygenated blood back from the lungs, it pumps the blood back into the arteries to be distributed throughout the body.

Cardiac cycle

R

P Wave

T Wave

Right coronary artery Left coronary artery

Q S QRS Complex

The heartbeat is controlled by electric impulses. To the right is a schematic representation of these impulses. (Delmar Publishers, Inc. Reproduced by permission.)

or slow down (bradycardia) the beating of the heart. The other arrthymias have one of two origins. They can be caused by a lack of normal electrical conduction. For example, a lack of electrical signaling from the sinoatrial node can lead to the placement of an exogenous pacemaker (something that causes the heart to beat other than the sinoatrial node). The other cause of arrhythmias is abnormally strong ectopic (in the wrong place) electrical activity. For example, premature atrial contractions can be caused by excessive electrical activity somewhere in the atrium other than the sinoatrial node. Some arrhythmias may be a combination of the two. Cardiac cycle disturbances can be complex, but can be dissected by an electrocardiogram (EKG or ECG). They can be caused by a wide variety of problems, including, but not limited to, coronary heart disease, damage to the heart muscle secondary to a heart attack, genetic heart defects, valvular disease of the heart, and medications. Following is a list of common arrhythmias. Atrial arrhythmias: • paroxysmal atrial tachycardia • multifocal atrial tachycardia 414

• atrial fibrillation • atrial flutter Ventricular arrhythmias: • premature ventricular contractions (PVCs) • ventricular tachycardia • ventricular fibrillation Arrhythmias arising because of abnormalities in the AV node, Purkinje fibers, or bundle of His: • nodal rhythm • first degree block • second degree block • third degree block • bundle branch block Resources BOOKS

Guyton, A. C., G. Guyton, and F. Hall. Textbook of Medical Physiology, Ninth ed. Philadelphia: W.B. Saunders Co., 1995. G A L E E N C Y C L O P E D I A O F N U R S I N G A N D A L L I E D H E A LT H

Aorta—The largest artery of the body that originates from the left ventricle of the heart, arches over the heart to the left, and descends just in front of the spinal column. The aorta divides into three arteries: the brachiocephalic artery (that supplies blood to the brain and head), the left carotid artery, and the left subclavian artery. Aortic valve—The heart valve that divides the left ventricle and the aorta. Blood from the left ventricle is ejected across the aortic valve into the aorta for further distribution. It opens during contraction of the left ventricle and closes afterwards to prevent the backward flow of blood from the aorta. Arterial blood pressure—The ejection of blood into the aorta by the left ventricle results in the characteristic aortic pressure pulse. The maximum of the aortic pressure pulse is called the systolic pressure and the lowest pressure in the aorta is called the diastolic pressure. Arterial pulse pressure—The arterial pulse pressure is the difference between the systolic and diastolic arterial pressures. Artery—Blood vessel that carries blood away from the heart for distribution throughout the body. Atrioventricular node (AV node)—Nodal tissue located on the right side of the partition that divides the atria, near the bottom of the right atrium. It delays impulses from the SA node, thus allowing the atria to empty themselves. Atrioventricular valves—Heart valves located between the atria and the ventricles. They are the mitral valve and the tricuspid valve. Diastole—The time in between ventricular contractions during which ventricular filling occurs. Also called the relaxation phase. Diastolic pulse pressure—The pressure exerted on the walls of the arteries during diastole. A normal value ranges around 90 mmHg. Heart—In humans, the heart is divided into four chambers: the right atrium and ventricle and the left atrium and ventricle. Blood flows from the veins into the right atrium, then to the right ventricle and into the lungs for oxygenation, from where it is returned to the left atrium, then to the left ventricle for distribution to the body via arteries. Mitral valve—The heart valve that divides the left atrium and the left ventricles. It opens during con-

traction of the left atrium to allow blood flow into the left ventricle and closes to prevent the backward flow of blood to the left atrium. Oxygenation—The process of adding oxygen to something. Oxygen is added to the blood in the lungs. Oxygen contained in the inhaled air is delivered to the blood, where the oxygen binds to a protein called hemoglobin (which functions as an oxygen-carrier). Pulmonary artery—Short blood vessel that carries deoxygenated blood from the heart to the lungs. Pulmonary vein—One of four blood vessels that carry oxygenated blood from the lungs to the heart. Pulmonary valve—The heart valve that divides the right ventricle from the pulmonary artery. Semilunar valves—Heart valves shaped like a halfmoon that located between the aorta and the left ventricle and between the pulmonary artery and the right ventricle. They are the aortic valve and the pulmonary valve. Sinoatrial node (SA node)—Also called the pacemaker of the heart. It consists of nodal tissue located in the upper wall of the right atrium. It controls the rate of contraction of the heart by generating nerve impulses that travel throughout the heart wall causing both atria to contract. Systole—The time during which ventricular contraction occurs. Systolic pulse pressure—The pressure exerted on the walls of the arteries during the contraction of the heart. A normal value ranges around 150 mmHg. Tricuspid valve—The heart valve, named for its three cusps, that divides the right atrium from the right ventricle. Blood flows from the right atrium, across the tricuspid valve, and into the right ventricle. When closed, it prevents the blood from flowing back into the right atrium. Vein—Blood vessel that returns blood to the heart from the body. All the veins from the body converge into two major veins that lead to the right atrium of the heart. These veins are the superior vena cava and the inferior vena cava. The pulmonary vein carries the blood from the right ventricle of the heart into the lungs.

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KEY TERMS

Cardiac marker tests

Tortora, Gerard, and Sandra Grabowski. “The Cardiovascular System: The Heart.” In Principles of Anatomy and Physiology, 8th ed. New York: Harper Collins, 1996. ORGANIZATIONS

American Heart Association National Center. 7272 Greenville Avenue, Dallas, Texas 75231. (800) AHA-USA1. . OTHER

Anderson, R. The Cardiac Cycle. Windows/Macintosh CDrom, 1996. Cardiovascular Physiology Web Resource. The Cardiac Cycle. .

Monique Laberge, PhD

Cardiac exercise stress testing see Stress test Cardiac mapping see Electrophysiology study of the heart

Cardiac marker tests Definition Cardiac marker tests identify blood analytes associated with myocardial infarction (MI), commonly known as a heart attack.

Purpose Cardiac markers help physicians to assess acute coronary syndromes and to identify and manage highrisk patients. Creatine kinase-MB (CK-MB), myoglobin, homocysteine, C-reactive protein (CRP), troponin T (cTnT), and troponin I (cTnI) are all used for assessment of the suspected acute myocardial infarction. CK-MB, cTnT, and cTnI may also be used to identify and manage high-risk patients.

Precautions C-reactive protein results may be affected by the use of oral contraceptives, NSAIDs, steroids, salicyltes, intrauterine devices (IUDs), and overnight sample refrigeration. Homocysteine levels may be affected by smoking, diabetes, and coffee. 416

Description Creatine kinase (CK) Creatine kinase is an enzyme responsible for transferring a phosphate group from ATP to creatine. It is composed of M and/or B subunits that form CK-MM, CKMB, and CK-BB isoenzymes. Total CK (the activity of the MM, MB, and BB isoenzymes) is not myocardial-specific. However, the MB isoenzyme (also called CK-2) comprises about 40% of the CK activity in cardiac muscle and 2% or less of the activity in most muscle groups and other tissues. In the proper clinical setting, MB is both a sensitive and specific marker for myocardial infarction. MB usually becomes abnormal three to four hours after an MI, peaks in 10 to 24 hours, and returns to normal within 72 hours. However, an elevated serum MB may occur in people with severe skeletal muscle damage (such as in muscular dystrophy or a crush injury) and renal failure. In such cases, the CK index (MB divided by total CK) is very helpful. If the index is under 4%, a nonmyocardial cause of a high MB should be suspected. C-MB is considered the benchmark for cardiac markers of myocardial injury. Measurement of CK-MB may be performed via electrophoresis or immunoassays; the latter demonstrates better analytical sensitivity and better precision. CK-MB isoforms can be used to determine whether thrombolytic therapy (such as treatment with tissue plasminogen activator to dissolve a blood clot in the coronary artery) has succeeded. MB isoforms are different molecular forms of MB found in the circulation. When MB is released into the blood, the terminal lysine of the M subunit is removed by an enzyme in the plasma. This results in a molecule with faster electrophoretic mobility, called CK-21. This is the prevalent form of MB in the blood. The slower form, designated CK-22, is the unmodified cardiac form of MB. After successful thrombolytic therapy, the unmodified form of MB is rapidly flushed into the blood, causing it to become the dominant isoform. Myoblobin Myoglobin is a protein found in both skeletal and myocardial muscle. It is released rapidly after tissue injury and may be elevated as early as one hour after myocardial injury, though it may also be elevated due to skeletal muscle trauma. However, if myoglobin values do not rise within three to four hours after a person shows acute symptoms, it is highly unlikely that he or she had an MI. There are several measurement methods available, including fluorometric, nephelometric, and turbidmetric assays; plus immunochromatography-based tests designed for qualitative, point-of-care testing.

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Troponin C, I, and T are proteins that form the thin filaments of muscle fibers and regulate the movement of contractile proteins in muscle tissue. Skeletal and cardiac forms are structurally distinct, and antibodies can be produced that react only with the cardiac forms of troponin I and troponin T. Cardiac troponin T (cTnT) and cardiac troponin I (cTnI) are the newest additions to the list of cardiac markers. Troponins are specific to heart muscle. They have enabled the development of assays that can detect heart muscle injury with great sensitivity and specificity. While these markers have been used mainly to aid in the diagnosis of chest-pain patients with nondiagnostic electrocardiograms, they are also used as prognostic indicators of a MI. According to the American Heart Association, “Several studies have identified a measurable relationship between cardiac troponin levels and long-term outcome after an episode of chest discomfort. They suggest that these tests may be particularly useful to evaluate levels of risk. In other words, it’s possible that the results of a troponin test could be used to identify people at either low risk or high risk for later, serious heart problems.” Several commercially available quantitative immunoassays are available for for the measurement of cTnI and cTnT. There is also a qualitative cTnI test, targeted at bedside testing. C-reactive protein (CRP) CRP is a protein found in serum or plasma at elevated levels during a inflammatory processes. The protein can be measured via a variety of methods, including EIA or ELISA, for the quantitative or semiquantitative determination of C-reactive protein in human serum, particle agglutination tests that provide semiquantitative results, and laser and rate nephelometery tests that measure antigen-antibody complexes by light dispersion. CRP binds to the C polysaccharide of the capsule of Streptococcus pneumoniae. It is a sensitive marker of acute and chronic inflammation and infection, and in such cases is increased several hundred-fold. Several recent studies have demonstrated that CRP levels are useful in predicting the risk for a thrombotic event. These studies suggest that a high-sensitivity assay for CRP be used that is capable of measuring the very low level normally found in serum (0.1 to 2.5 mg/L). Heart patients who have persistent CRP levels between 4 and 10 mg/L, with clinical evidence of low-grade inflammation, should be considered to be at increased risk for thrombosis. People can be stratified into four groups of increased risk based upon the quartile in which their CRP levels fall.

Homocysteine Homocysteine is an amino acid. According to the American Heart Association, studies have shown that too much homocysteine in the blood is related to a higher risk of coronary heart disease, stroke, and peripheral vascular disease; and that it may also have an effect on atherosclerosis. High levels of homocysteine are the result of inheritance or dietary excess and have been implicated in vascular-wall injury. One immunoassay is available for it. It is believed that laboratory testing for plasma homocysteine levels can improve the assessment of risk, particularly in patients with a personal or family history of cardiovascular disease, but in whom the well-established risk factors (smoking, high blood cholesterol, high blood pressure, physical inactivity, obesity, and diabetes) do not exist. Homocysteine levels are obtained via high-performance chromatography with electrochemical detection.

Preparation These assays require a sample of blood, which is typically obtained via a standard venipuncture procedure. Homocysteine tests require the patient to fast. Homocysteine is stable only in separated refrigerated or frozen plasma for 48 hours.

Aftercare Discomfort or bruising may occur at the puncture site, or the person may feel dizzy or faint. Applying pressure to the puncture site until the bleeding stops reduces bruising. Warm packs to the puncture site relieve discomfort.

Complications There are no complications associated with these tests.

Results Normal results vary, based on the laboratory and method used. Unless otherwise specified, the following information is from the American College of Cardiology and the American Heart Association. • Total CK: Reference value is 38 to 174 units/L for men and 96 to 140 units/L for women. The values begin to rise within four to six hours and peak at 24 hours. Values return to normal within three to four days. • CK-MB: Reference value is 10 to 13 units/L. The values begin to rise within three to four hours and peak at 10 to 24 hours. Values return to normal within two to four days.

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Troponin T and troponin I

Cardiac monitor

Resources

KEY TERMS

BOOKS

Cardiac marker—A substance in the blood that rises following a myocardial infarction. Diagnostic window—A cardiac marker’s timeline for rising, peaking, and returning to normal after a heart attack. Myocardial infarction (MI)—Commonly known as a heart attack, a myocardial infarction is an episode in which some of the heart’s blood supply is severely cut off or restricted, causing the heart muscle to suffer and die from lack of oxygen. Myoglobin—A protein that holds oxygen in heart and skeletal muscle. It rises after damage to either of these muscle types.

• Troponin T: Reference value is less than 0.1 ng/mL. The values begin to rise within two to four hours and peak at 10 to 24 hours. Values return to normal within five to 14 days. • Troponin I: Reference value is less than 1.5 ng/mL. The values begin to rise within two to four hours and peak at 10 to 24 hours. Values return to normal within five to 10 days. • CK-MB isoforms: Reference value is a ratio of 1.5 or greater. The values begin to rise within two to four hours and peak at six to 12 hours. Values return to normal within 12 to 24 hours. • Myoglobin: Reference value is less than 110 ng/mL. The values begin to rise within one to two hours and peak at four to eight hours. Values return to normal within 12 to 24 hours. • Homocysteine: The normal fasting level for plasma is five to 15 micromol/L. Moderate, intermediate, and severe hyperhomocysteinemia refer to concentrations between 16 and 30, between 31 and 100, and less than 100 micromol/L, respectively. • C-reactive protein: According to the U.S. Food and Drug Administration, in healthy people, reference values are below 5 mg/dL; in various diseases, this threshold is often exceeded within four to eight hours after an acute inflammatory event, with CRP values reaching approximately 20 to 500 mg/dL.

PERIODICALS

Brown, C. S., and B. D. Bertolet. “Cardiac Troponin. See Ya Later, CK!” Chest (January 1997): 2-4. Chesebro, M. J. “Using Serum Markers in the Early Diagnosis of Myocardial Infarction.” American Family Physician (June 1997): 2667-2674. Christenson, R. H., et al. “Cardiac Markers in the Assessment of Acute Coronary Syndromes.” Proceedings from the First Maryland Chest Pain Center Research Conference (date not available). Keffer, J. “Myocardial Markers of Injury. Evolution and Insights.” American Journal of Clinical Pathology (March 1996): 305-320. Mercer, D. W. “Role of Cardiac Markers in Evaluation of Suspected Heart Attack. Selecting the Most Clinically Useful Indicators.” Postgraduate Medicine (November 1997): 113-117, 121-122. Hamm, C. W., et al. “Emergency Room Triage of Patients with Acute Chest Pain by Means of Rapid Testing for Cardiac Troponin T or Troponin I.” The New England Journal of Medicine (December 4, 1997): 67-78. “In Vitro Diagnostic C-Reactive Protein Immunological Test System.” U.S. Food and Drug Administration: Center for Devices and Radiological Health. July 20, 1998. Wong, S. S. “Strategic Utilization of Cardiac Markers for the Diagnosis of Acute Myocardial Infarction.” Annals of Clinical and Laboratory Science (July 1996): 301-312. OTHER

“ACC/AHA Guidelines for the Management of Patients with Acute Myocardial Infarction,” American College of Cardiology and the American Heart Association, 1999. American Heart Association. . ARUP Laboratories. .

Victoria E. DeMoranville

Cardiac monitor Definition

Health care team roles Cardiac marker tests are usually performed by clinical laboratory scientists, medical technologists, or clinical laboratory technicians. 418

Wu, A., editor. Cardiac Markers. Washington, DC: American Association of Clinical Chemistry (AACC) Press, 1998.

The cardiac monitor is a device that shows the heart’s electrical activity as a wave pattern on a monitor. It is a bedside monitor.

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Purpose The cardiac monitor continuously shows the cardiac rhythm and sends the electrocardiogram (EKG) tracing to a main monitor in the nursing station. Most commonly used in emergency rooms and critical care areas, cardiac monitoring allows for continual observation of several patients. Aside from monitoring cardiac patients, continuous monitoring is useful for observation of postoperative patients, patients with severe electrolyte imbalances, and other unstable patients. Continuous cardiac monitoring allows for prompt identification and initiation of treatment for cardiac arrhythmias and other conditions.

Precautions The American Heart Association warns of potential interference between some pacemakers and cardiac monitors. Minute ventilation rate-adaptive pacemakers can occasionally interact with certain cardiac monitoring and diagnostic equipment, causing the pacemakers to pace at their maximum-programmed rate. Minute ventilation is sensed in rate-adaptive pacemakers by technology known as bioelectric impedance measurement (BIM). Many medical devices in addition to pacemakers use this technology. When one of these devices is used on a patient with an active, minute ventilation rate-adaptive pacemaker, the pacemaker can erroneously interpret the mixture of BIM signals created in the patient, resulting in an elevated pacing rate. Cardiac monitors, echocardiograph equipment, apnea monitors, respiration monitors, and external defibrillators are common devices that may use BIM technology.

Description The monitor provides a visual display of the patient’s heart rhythm, which is particularly useful information during heart attacks, when patients can develop lethal cardiac arrhythmias. The monitor sounds an alarm if the patient’s heart rate goes above or below a predetermined number. An automatic blood pressure cuff and a pulse oximeter, which measures the oxygen saturation in the blood, are also included with some monitors. Equipment required for continuous cardiac monitoring includes: • cardiac monitor • monitor cable • leadwires • electrodes • dry washcloth or gauze pad • alcohol sponges

Cardiac monitors display vital information for patients in the intensive care unit. (Photograph by Hank Morgan. Science Source/Photo Researchers. Reproduced by permission.)

Preparation All electrical equipment and outlets are grounded to avoid electrical shock and artifact (electrical activity caused by interference). The nurse should plug in the monitor, turn on power, and connect the cable if not already attached. He or she should connect the lead wires to the proper position and ensure that color-coded wires match the color-coded cable. If the device is not color coded, the right arm (RA) wire should be attached to the RA outlet, the left arm (LA) wire attached to the LA outlet, and so forth. The nurse should open the electrode package, and attach an electrode to each lead wire. The hands should be washed and the procedure should be explained to the patient. Privacy should be ensured for the patient, and the patient should be clean and dry to prevent electrical shock. Next, the chest should be exposed and the sites selected for electrode placement. Using the rough patch on the electrode, a dry washcloth, or gauze pad, each site should be rubbed briskly until it reddens, but care should be taken not to damage or break the skin. Dead skin cells are removed in this manner, thereby promoting better electrical conduction. Patients who are extremely hairy may need to be shaved prior to application of the electrodes. An alcohol pad is used to clean the sites in patients with oily skin. Areas should dry completely to promote good adhesion. Alcohol should not become trapped beneath the electrode, as this can lead to skin breakdown. In addition to oily skin, diaphoretic skin can cause interference in the recording. To minimize this interference, the electrode site should be rubbed with a dry 4x4 gauze pad before application. The backing of the electrode should be removed, and the gel inspected. If the electrode

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Results

KEY TERMS Amyloidosis—A metabolic disorder, characterized by starch-like formation in tissue structures. Artifact—Extra electrical activity typically caused by interference. Cardiomyopathies—Diseases of the heart muscle. Usually refers to a disease of obscure etiology. Electrodes—Adhesive pads which are placed on the skin and attached to the leads. Lead—Color coded wires that connect the electrode to the monitor cable. QRST complex—The combined waves of an electrocardiogram for monitoring the heart.

A normal cardiac tracing shows a regular rate and rhythm with no deviations in the QRST complex (the combined waves of an electrocardiogram). Abnormal results may include bradycardia, or tachycardia, accompanied by the alarm. Q waves (the short initial downward stroke of the QRST complex) are abnormal, and may or may not signal an infarction. Some causes of noninfarction Q waves are: • ventricular hypertrophy • ventricular preexcitation (Wolf-Parkinson-White syndrome) • cardiomyopathies • pulmonary embolism • incomplete left bundle branch block

has dried out, which can happen if the electrode package is opened before immediate use, it should be discarded and another used. The nurse should apply one electrode to each site, press one side of the electrode against the skin, and pull gently. Then, the opposite side of the electrode should be pressed against the skin. The nurse should press two fingers on the electrode in a circular pattern to affix the gel and stabilize the electrode, then repeat for each electrode. To avoid potential artifact, do not place the electrodes on bony prominences or hairy areas.

Causes of changes in ST Segment (part of the EKG between the QRS complex and the T wave) and T Wave (deflection in an EKG that represents electrical activity of the ventricular repolarization) include: • aberrant conduction • amyloidosis • bundle branch block • cardiomyopathy • cocaine vasospasm • electrolyte disturbances • intracranial hemorrhage

Aftercare

• myocardial metastases

After placing all electrodes, the nurse should observe the monitor and evaluate the quality of the tracing, making size and tracing position adjustments as needed. He or she should confirm that the monitor is detecting each heartbeat by taking an apical pulse and comparing the pulse to the digital display. The upper and lower alarm limits should be set according to institutional policy, and the alarm activated. A rhythm strip should be recorded for the medical record, and labeled with patient name, room number, date, time, and interpretation of the strip.

• paced rhythm • pancreatitis or acute abdomen • pericarditis • physical training • Printzmetal’s angina • pulmonary embolism • tachycardia • ventricular aneurysm • ventricular hypertrophy

Complications

• ventricular rhythms

There is a potential for skin breakdown at the electrode placement site. The patient may be allergic to the adhesive used, or the electrode may have been left on the skin too long. The electrodes should be removed and new electrodes applied, using hypoallergenic electrodes if necessary. 420

• myocarditis

• Wolff-Parkinson-White syndrome Alarm signals are abnormal and must be investigated. A false high alarm rate may be caused by skeletal muscle activity or by the monitor incorrectly interpreting large T waves as a QRS complex, which would double the true heart rate. The electrodes should be repositioned

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Health care team roles Cardiac monitoring is usually ordered by a physician. A nurse practitioner or physician assistant can place the electrodes on the patients body. A nurse provides ongoing care during the monitoring, assesses patient to determine hemodynamic effects of rhythms, and intervenes for dysrhythmias as appropriate. The nurse also instructs the patient and family about the cardiac monitor’s use. Resources BOOKS

Cahill, Matthew. Providing Cardiovascular Care Nursing Photobook. Springhouse, PA: Springhouse Corporation, 1996. Marriott, Henry J. L. Pearls and Pitfalls in Electrocardiography: Pithy, Practical Pointers 2nd ed. Baltimore: Williams and Wilkins, 1998. Milford, Cheryl, and Purvis, Gladys. “Cardiovascular Care” In Nursing Procedures 3rd ed. Springhouse, PA: Springhouse Corporation, 2000. Woods, Susan, and Sivarajan, Erika. Cardiac Nursing 4th ed. Philadelphia: Lippincott, 2000. PERIODICALS

Perry, A., et al. “Measuring the Costs and Benefits of Heart Disease Monitoring.” Heart 83 (June 2000): 651-656. ORGANIZATIONS

American Association of Critical-Care Nurses. 101 Columbia, Aliso Viejo, CA 92656-4109. (800) 899-2226. . The American College of Cardiology. Heart House, 9111 Old Georgetown Road, Bethesda, MD 20814-1699. (800) 253-4636. . American Heart Association. 7272 Greenville Ave., Dallas TX 75231-4596. (800) 242-1793. . Applied Biometrics. P.O. Box 3170, Burnsville, MN 55337. (952) 890-1123. OTHER

Advanced Cardiac Monitoring: Ventricular Ectopy vs. Aberrancy. Videotape. RamEx, Inc.

Maggie Boleyn, RN, BSN

Cardiac rehabilitation Definition Cardiac rehabilitation is a multi-disciplinary treatment and secondary prevention program for patients with various cardiac disorders, including recovery from heart attack and bypass surgery, which includes exercise, education, counseling, and lifestyle changes to help the patient return to previous levels of health and functioning and prevent recurrence of cardiac problems.

Purpose The purpose of cardiac rehabilitation is to provide comprehensive, multifaceted treatment, education, and secondary prevention for cardiac patients and individuals with heart disease risk factors, in order to aid recovery and prevent recurrence of heart problems. Cardiac rehabilitation programs can improve quality of life, help patients return to their previous level of functioning in work and daily life, increase fitness, facilitate hearthealthy behavior changes and management of risk factors, and reduce costs by decreasing frequency and expense of hospital stays.

Precautions Exercise, or certain kinds of exercise, may be contraindicated in the presence of some medical conditions. Conditions included are acute heart failure, angina at rest, second or third degree heart block, excessively low or high blood pressure, orthopedic problems, continued ischemia, aortic stenosis or mitral valve disease, or other health conditions in addition to the cardiac disorder. Exercise might also need to be discontinued if certain problems or symptoms such as the following occur: failure of monitoring equipment, lightheadedness, confusion, nausea, angina that occurs while exercising, excessive rise in blood pressure, or unusual heart rate. In addition, certain precautions may be taken before any cardiac patient begins an exercise program or session. Some of these include recording heart rate, blood pressure, and cardiac rhythm at each supervised session, and educating the patient in how to prepare for the exercises (proper breathing, dressing appropriately, avoiding smoking, etc.). Any preexisting medical conditions should also be taken into consideration when planning exercise treatments.

Description Cardiac rehabilitation is a comprehensive, multidisciplinary approach to treatment and secondary preven-

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as needed to ensure that the electrode is not over a major muscle mass and that QRS complex is larger than the T wave. A false low alarm rate may be due to patient movement, or poor contact between electrodes and skin. Electrodes should be reapplied as needed. Artifact is a common abnormal finding, and may be caused by improperly placed electrodes, patient movement, static electricity, seizures, anxiety, or chills. The position of electrodes should be checked and static-causing bed linen changed. The cables should not have exposed connectors.

Cardiac rehabilitation

Association, is a level higher than CPR, and allows the practitioner to perform intubation and use a defibrillator. Cardiac rehabilitation can be broken into three phases. Phase I, inpatient treatment in a hospital, can begin as early as 24 hours after a cardiovascular event. Phase II, outpatient treatment, can take place at the hospital, in a community center, in a medical center, or at the patient’s home or place of employment. Phase III, referred to as the secondary prevention or maintenance phase, is performed more independently by the patient, with the goal of maintaining benefits and preventing further cardiac problems. An individual patient may participate in cardiac rehabilitation for a few weeks, six months, or longer. Many programs are conducted in groups, but the exercise prescription and other facets of treatment are individually designed to meet the specific medical needs and preferences of each patient.

This 40-year-old male works out on a treadmill, monitored by his physician, following heart surgery. (Custom Medical Stock Photo. Reproduced by permission.)

tion for patients with various forms of cardiac disorders, such as post myocardial infarction (heart attack), bypass surgery, chronic stable angina pectoris, and heart transplant. It involves a cardiac rehabilitation team, which can be comprised of primary care and specialty physicians, nurses, physical therapists, exercise physiologists, occupational therapists, mental health professionals and dieticians. The physician may choose to participate in various roles, or refer patients to physical therapists and other practitioners or hospital departments. A specially qualified physical therapist or RN may provide or direct cardiac rehabilitation services. At least one member of the physical therapy department or other team of practitioners in charge should be ACLS (Advanced Cardiac Life Support) certified, and a cardiopulmonary specialist should be included. The ACLS certification, which can be obtained during a one-day training course provided by the American Heart 422

The main components of a cardiac rehabilitation program are exercise, education, counseling, and behavior modification. Physical therapists may play a large part in the exercise component, as well as some aspects of patient education. Some of the goals of exercise are to restore or improve fitness, increase exercise tolerance and functional capacity, regain levels of functioning equivalent to those prior to the disease or surgery, and improve confidence and mood. Exercise and education by a physical therapist or other qualified practitioner can also help the patient manage and improve other risk factors and associated conditions such as diabetes, obesity, high blood lipids (fats), and stress. Inactivity itself is now recognized as a coronary risk factor, and thus exercise is an essential part of treatment for many reasons. A physical therapist may also be especially appropriate for work with cardiac patients who also have musculoskeletal problems. For example, bypass recipients may have problems with mobility of the shoulder or other joints. The other components of the rehabilitation program may include education about the heart condition and its risk factors, counseling for psychological aspects of heart disease, stress management, vocational or occupational counseling, and guidance in adopting healthier behaviors. Some of the lifestyle or behavioral changes encouraged include smoking cessation and a lower fat diet, and management of other controllable coronary disease risk factors such as smoking, high blood pressure, high cholesterol, obesity, stress, and a sedentary lifestyle. Many economic and medical benefits have been associated with cardiac rehabilitation, including decreased disability and improved functional capacity, less likelihood of mortality and recurrent morbidity, and decreased medical costs. Another benefit is that the use of electrocardiograph and other forms of objective and sub-

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Preparation A cardiac rehabilitation program is usually prescribed and overseen by a physician, and generally begins in the hospital, under the direction of appropriate hospital departments, and after exercise testing and other preparatory procedures have been administered. An EKG will likely be given before the rehabilitation program begins, and then be used as an ongoing monitoring method by the physical therapist or other rehabilitation team members.

Aftercare The patient may continue with a maintenance or secondary prevention program, and should maintain the healthy habits they have gained, including regular exercise to maintain improved fitness and associated physical and psychological benefits.

Complications Patients are closely monitored for any exercise-related health complications, and the rehabilitation team is equipped to detect and manage possible emergencies. Cardiac rehabilitation is a safe treatment option, and serious problems are rare.

Results Participation in a cardiac rehabilitation program can help the heart patient return to physical and emotional/social well-being and be able to function in their lives and work as near as possible to their pre-illness level of functioning. In fact, their overall quality of life and health may be improved. Patients also learn new ways of taking care of their health so that recurrence of illness or symptoms and re-hospitalization are minimized, and deterioration of existing conditions is less likely.

KEY TERMS Electrocardiogram (EKG/ECG)—A test that records electrical activity of the heart. It may be used to detect a heart attack, because injured cardiac muscle causes abnormal conduction of electrical impulses. Ischemia—Shortage of blood supply to a body tissue or organ (to the heart in the case of cardiac ischemia), which can cause tissue death. Cardiac ischemia can lead to heart attack or abnormal cardiac rhythms. Myocardial infarction (MI)—The medical term for a heart attack. When cardiac ischemia, narrowing of a coronary artery or arteries, decreases blood supply to the heart muscle (myocardium), it can cause muscle tissue death (infarction). Secondary prevention—The prevention of a recurrence of illness, such as another heart attack.

Health care team roles After a prescription is made by the primary care physician or cardiac specialist, various health care professionals are involved in the program, including a physical therapist or exercise physiologist, nurses, an occupational therapist, dietician, and mental health professional. A nurse specializing in cardiac rehabilitation, exercise physiologist or physical therapist, or physical therapy department may manage the patient’s rehabilitation program, in consultation with a physician. Resources ORGANIZATIONS

Agency for Health Care Policy and Research (AHCPR). “Cardiac Rehabilitation: Exercise Training and Education, Counseling, and Behavioral Interventions” and “Recovering from Heart Problems Through Cardiac Rehabilitation” (patient guide). These can be obtained by writing or calling: Cardiac Rehabilitation. AHCPR Publications Clearinghouse. P.O. Box 8547. Silver Spring, MD 20907. (800) 358-9295. American Association of Cardiovascular and Pulmonary Rehabilitation (AACVPR). 7600 Terrace Avenue, Suite 203. Middleton, WI 53562. (608) 831-6989. . American College of Sports Medicine (ACSM). 401 W. Michigan St. Indianapolis, IN 46202-3233. (317) 6379200.

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jective assessment in ongoing supervised rehabilitation can lead to detection of problems and adjustments in the patient’s treatment. Reasons for cost effectiveness of this form of treatment include reduction in disability and health care costs, fewer re-hospitalizations, and improved productivity. Despite these benefits, only about 11-38% of qualified candidates generally participate. Although many insurance companies cover all or part of a cardiac rehabilitation program, coverage is not available to all patients, and may be limited in terms of length of treatment or conditions covered.

Cardiopulmonary resuscitation (CPR)

American Physical Therapy Association (APTA). 1111 North Fairfax Street. Alexandria, VA 22314. (703) 684-2782. . OTHER

Johns Hopkins Bayview Medical Center. . Mayo Clinic. .

Diane Fanucchi, B.A., C.M.T.

Cardiogenic shock see Shock

Cardiopulmonary resuscitation (CPR) Definition Cardiopulmonary resuscitation (CPR) is a procedure to support and maintain breathing and circulation on a person who has stopped breathing (respiratory arrest) and/or whose heart has stopped (cardiac arrest).

Purpose CPR is performed to restore and maintain breathing and circulation and to provide oxygen and blood flow to the heart, brain, and other vital organs. It should be performed if a person is unconscious and not breathing. Respiratory and cardiac arrest can be caused by allergic reactions, an ineffective heartbeat, a heart attack, asphyxiation, breathing passages that are blocked, choking, drowning, drug reactions or overdoses, electric shock, exposure to cold, severe shock, or trauma. CPR can be performed on infants, children, and adults by trained bystanders or healthcare professionals. It should always be performed by the person on the scene who is most experienced in CPR.

Precautions CPR should never be performed on a healthy person, since it can cause serious injury to a beating heart.

Description CPR is part of the emergency cardiac care system designed to save lives. Many deaths can be prevented by prompt recognition of the medical situation and notification of the emergency medical system (EMS). This should be followed by early CPR, defibrillation (which delivers a brief electric shock to the heart in an attempt to 424

get the heart to beat normally), and advanced cardiac life support measures. CPR must be performed within four to six minutes of the time that breathing stopped in order to prevent brain damage or death. It is a two-part procedure that involves rescue breathing and external chest compressions. To provide oxygen to the person’s lungs, the rescuer administers mouth-to-mouth breaths, then helps circulate the blood through the heart to vital organs by external chest compressions. Mouth-to-mouth breathing and external chest compression should be performed together, but if the rescuer isn’t strong enough to do both, the external chest compressions should be done alone. Some bystanders are reluctant to initiate CPR because of the possible transmission of infectious disease during mouthto-mouth breathing or their inexperience with CPR. External chest compressions alone have been found to have similar results when compared to mouth-to-mouth breathing and external chest compressions combined. External chest compressions, as well as CPR that is performed inexpertly, are more effective than no resuscitation attempt. When performed by a bystander, CPR is designed to support and maintain breathing and circulation until emergency medical personnel arrive and take over. When performed by healthcare personnel, it is used in conjunction with other basic and advanced life support measures. According to the American Heart Association, early CPR and defibrillation combined with early advanced emergency care can increase survival rates for people with a type of abnormal heart beat called ventricular fibrillation by as much as 40%. CPR by bystanders may prolong life during deadly ventricular fibrillation, giving emergency medical service personnel time to arrive. It must be appreciated, however, that most CPR attempts are not ultimately successful in restoring the victim to a good quality of life. Often, there is brain damage even if the heart starts beating again. CPR is therefore not generally recommended for the chronically or terminally ill or frail elderly. For these people, it is traumatic and not a peaceful end of life. CPR has been practiced for more than 40 years. Each year, it helps save thousands of lives in the United States. More than five million Americans receive training in CPR through the American Heart Association and the American Red Cross courses annually. In addition to courses taught by instructors, the American Heart Association also has an interactive video called Learning System, which is available at more than 500 healthcare institutions. Both organizations teach CPR the same way, but use different terms. They recommend that family members or other people who live with patients at risk of

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Figure A

Figure D

Figure B

Figure E

Figure C

Figure F CPR in basic life support. Figure A: The victim should be flat on his back and his mouth should be checked for debris. Figure B: If the victim is unconscious, open airway, lift neck, and tilt head back. Figure C: If victim is not breathing, begin artificial breathing with four quick full breaths. Figure D: Check for carotid pulse. Figure E: If pulse is absent, begin artificial circulation by depressing sternum. Figure F: Mouth-to-mouth resuscitation of an infant. (Illustration by Electronic Illustrators Group.)

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respiratory or cardiac arrest be trained in CPR. A handheld device called CPR Prompt is available to walk people trained in CPR through the procedure, using American Heart Association guidelines. In 2000, focus groups from the American Heart Association and the American Red Cross joined forces with international councils in order to create a consistent, single description of resuscitation guidelines. These guidelines have been released and many changes in CPR have been instituted. These changes replace the recommendations from their publications in 1992. Performing CPR The basic procedure for CPR is the same for adults, infants, and children, with a few modifications for infants and children to account for their smaller size. PERFORMING CPR ON AN ADULT. In most cases, the first step is to call the emergency medical system for help by telephoning 911. There are exceptions to calling for help first. The new concept of “phone fast” is being recommended for trauma victims, water submersion victims, and medication/drug overdoses. CPR should be started immediately on these types of victims because the rate of survival increases with early rescue efforts. To start CPR, use the following steps:

• The rescuer opens the person’s airway by placing the head face up, with the forehead tilted back and the chin lifted. The rescuer checks again for breathing (three to five seconds), then begins rescue breathing (mouth-tomouth artificial respiration). He pinches the person’s nostrils shut while holding the chin in the other hand. The rescuer places his mouth against the person’s mouth with the lips making a tight seal, then gently exhales for about one to one and a half seconds. The rescuer breaks away for an instant and then repeats. The person’s head is repositioned after each mouth-tomouth breath. • After two breaths, the rescuer checks for indications of blood circulation (regular respiratory inhalations, vomiting, or any attempt to move). If the rescuer is a health care professional, the person’s pulse is checked by moving the hand that was under the person’s chin to the artery in the neck (carotid artery). If the person shows no signs of circulating blood, the rescuer continues rescue breathing until help arrives or the person begins breathing spontaneously. If the person is breathing, the rescuer turns the person onto his or her side. • If there is no heartbeat, the rescuer performs chest compressions. The rescuer kneels next to the person, placing the heel of one hand in the spot on the lower chest where the two halves of the rib cage come together. The 426

rescuer puts his other hand on top of the one on the chest and interlocks the fingers. He straightens his arms, leans forward to position the shoulders directly above the hands on the person’s chest, and presses down, using only the palms, so that the person’s breastbone sinks in about 11⁄2-2 in (4-5 cm). The rescuer releases without removing the hands, then repeats about 15 times in 10-15 seconds. • The rescuer tilts the person’s head and returns to rescue breathing for one or two quick breaths. Then he alternates breathing and heart presses for one minute, and checks for any signs of blood circulation. If the rescuer finds signs of a heartbeat and breathing, CPR is stopped. If the person is breathing but has no pulse the heart presses are continued; if the person has a pulse but is not breathing, rescue breathing is continued. The number of heart presses has recently increased to 15 heart presses to two breaths for single or double rescuer CPR. The recommended number of heart presses is at least 100 a minute. The rationale for this increase relates to establishing adequate heart and brain circulation. • For children over the age of eight, the rescuer performs CPR the same as on an adult. PERFORMING CPR ON AN INFANT OR CHILD UNDER THE AGE OF EIGHT. The procedures outlined above are

followed with these differences: • The rescuer administers CPR for one minute, then calls for help. • The rescuer makes a seal around the infant/child’s mouth (and nose with infants) to give gentle breaths. The rescuer delivers 20 rescue breaths per minute, taking 11⁄2-2 seconds for each breath. • Chest compressions are given with only one hand for a child and with two or three fingers for an infant. The breastbone is depressed only 1-11⁄2 in (2.5-3.75 cm) for a child and 1⁄2-1 in (1-2.5 cm) for an infant, the rescuer gives at least 100 chest compressions per minute. New developments in CPR The use of the automated external defibrillator (AED) has saved many lives and is now considered part of the CPR chain of survival. The AED is a machine that is attached to the unresponsive victim, analyzes the heart rhythm and has the ability to shock the victim with electricity. The AED has two pads that have to be placed on the victim’s right upper chest wall and the left lower chest wall. Most cardiac arrest victims have a heart rhythm called ventricular fibrillation and the only way to correct this deadly heartbeat is with electricity. Some airports, airplanes, and shopping malls have automated external

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Cardiopulmonary resuscitation (CPR)

defibrillators onsite with user-friendly instructions, and survival rates in these places have increased significantly.

Preparation If a person suddenly becomes unconscious, the rescuer should call out for help from other bystanders, and then determine if the person is responsive by shaking him or her gently on the shoulder and asking, loudly, if they are OK. Upon receiving no answer, the rescuer should call the emergency medical system with the exception of the “phone fast” victims. The rescuer should check to see whether the person is breathing by kneeling near the person’s shoulders, looking at the person’s chest, and placing his cheek next to the person’s mouth. The rescuer should look for signs of breathing in the chest and abdomen, and listen and feel for signs of breathing through the person’s lips. If no signs of breathing are present after three to five seconds, CPR should be started.

Aftercare Emergency medical care is always necessary after successful CPR. Once the person’s breathing and heartbeat have been restored, the rescuer should make him or her comfortable and stay there until emergency medical personnel arrive. The rescuer can continue to reassure the person that help is coming and talk positively until the professionals arrive and take over.

Complications CPR can cause injury to the person’s ribs, liver, lungs, and heart. But these risks must be accepted if CPR is necessary to save the person’s life. As health care professionals, many complications will be apparent in the acute care setting. Medical and nursing management of these complications will be addressed by prioritizing the most traumatic or deadly first.

Health care team roles CPR and basic life support are important skills to have for anyone in the health care field. Recognition of the need to initiate CPR and the activation of proper resuscitation can save many lives. The international, universal pneumonic used to prompt health care professionals with the basics of CPR quickly is ABCD. This pneumonic stands for: • Airway: Is the person’s airway open? • Breathing: Is the person breathing?

Emergency team treating heart attack patient. (Custom Medical Stock Photo. Reproduced by permission.)

• Circulation: Does the person have a pulse (health care professional)? Does the person have any signs of blood circulation (layperson)? • Defibrillation: Where is the defibrillator (AED)? Legally, health care professionals coming to a person’s aid in an emergency situation are covered under the federal Good Samaritan Law. Protection under this law requires that the situation be an emergency, that no monetary compensation for the treatment provided, and that the care provided has to be done “in good faith.” In most states, health care professionals have no mandatory obligation to help in an emergency situation, but this law is in place to protect those who do from liability. Patient education All health care professionals should emphasize the importance of laypeople in their communities being trained in CPR. Classes are offered through the American Heart Association and the American Red Cross. Many

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Cardiovascular system

KEY TERMS Automated external defibrillator (AED)—A device that analyzes a person’s heartbeat and can automatically deliver an electric shock if needed. Cardiopulmonary—Relating to the heart and the lungs. Defibrillation—A procedure to stop the type of irregular heart beat called ventricular fibrillation, usually by using electric shock. Resuscitation—Bringing a person back to life after an apparent death. Ventricular fibrillation—An irregular heartbeat where the heart beats very fast but ineffectively. Ventricular fibrillation is fatal if not quickly corrected.

hospitals and local health departments have classes available for the public. Training CPR training is recommended every two years, and most health care institutions require their workers to obtain certification in Basic Cardiac Life Support (BCLS), which covers CPR. Studies have been done on the differences between video aided/practice training and lecture training. Video and practice training has been found to be the most effective. Resources BOOKS

DeBakey, Michael E, and Antonio M.Gotto, Jr. “The Healthy Heart and How it Works.” In The New Living Heart, Holbrook, MA: Adams Media Corporation, 1997, pp. 267-82. PERIODICALS

American Heart Association. “Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Part 3: Adult Basic Life Support.” Circulation 102 (August 22, 2000): 22-59. Brown, Sylvia, M. “Good Samaritan Laws: Protection and Limits.” RN 62 (November, 1999) 65-67. Hallstrom, Alfred, et. al. “Cardiopulmonary Resuscitation by Chest Compression Alone or with Mouth-to-Mouth Ventilation.” New England Journal of Medicine 342 (May 25, 2000): 1546-1553. Hull, Bob. “Response in a Heartbeat.” American School & University 73 (October, 2000): 40-41.

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Definition The cardiovascular system includes the heart and the blood vessels and is responsible for the transport of blood throughout the body.

Description The main components of the cardiovascular system are the heart, arteries, arterioles, capillaries, venules, and veins. Adults have approximately 60,000 miles (96,000 km) of blood vessels. By moving blood throughout this network of vessels, the cardiovascular system supplies all cells of the body with oxygen and nutrients and removes carbon dioxide and other waste products. The heart The heart is the focal point of the cardiovascular system. It supplies the driving force for the movement of blood. The heart functions as a pump, actively forcing blood out of its chambers and passively relaxing to allow the next quantity of blood to enter. On refilling, the blood does not get actively sucked into the heart, but moves into the chambers due to the underlying pressure of the cardiovascular system as a whole. The heart is cone-shaped, pointing down and to the left, and is located left of center of the chest between the lungs. The organ is made of three types of tissue: the myocardium (middle layer), the epicardium (outer layer), and the endocardium (thin inner layer). A fluid-filled sac called the pericardium surrounds the heart, helping to reduce friction during contraction. When the myocardium applies force on the blood by contracting, the cells of the tissue become short and thick. The contraction phase of the myocardium is called systole. This is followed by relaxation of the cells, where they become thinner and longer. The relaxation phase is called diastole. The heart functions as a double pump, with both the right and left heart having a structure to receive blood and a structure to pump the blood. The blood-receiving structures are called the atria and the blood-pumping structures are called the ventricles. During a heartbeat, the two atria contract together, moving the blood from the atria to the ventricles. Then, while the two atria relax and refill, the two ventricles contract, moving the blood out of the heart. This system means that blood leaves the heart in pulsed waves. The right atrium and ventricle pump blood from the heart to the lungs using a subset of the blood vessels called the pulmonary circulation system. The blood trav-

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Valves within the heart ensure that the blood travels in the right direction. On the right side of the heart, the tricupsid valve allows blood to travel only from the right atrium to the right ventricle. The mitral valve performs the same function on the left side of the heart. As the blood leaves the right ventricle to go to the lungs, the pulmonary valve controls the direction of the blood flow, while the aortic valve functions between the right ventricle and the aorta, the largest artery. During diastole, when the ventricles relax, the mitral and tricupsid valves open, allowing blood to flow into the ventricles. At the same time, the aortic and pulmonary valves are closed to prevent reentry of the blood that had been pumped from the heart. During systole, when the ventricles contract, the mitral and tricupsid valves close to prevent backflow, and the aortic and pulmonary valves open to allow the blood to leave the heart. There are no valves at the atrial inputs, part of what ensures consistent blood inflow into the ventricles. The heart works on an electrical conduction system, as the cells contract in response to electrical signals. All cells of the heart can contract spontaneously, with the beginning of the heartbeat dependent on the cells with the most rapid innate rate. These cells are located in the sinoatrial (SA) node of the heart, sometimes called the heart’s natural pacemaker. The electrical signal moves from the SA node to the atrium, in a cluster of conducting cells called the atrio-ventricular (AV) node. The slowing of the signal at this point allows the atria to contract slightly before the ventricles, giving the ventricles more time to fill before they contract. The signal passes on to the electrical network of the ventricles, called the His-Purkinje system, which causes the ventricles to contract. The electrical workings of the heart can be visualized using an electrocardiography unit. Overall, heart rate is controlled by signals from the autonomous nervous system to the SA node. The autonomic nervous system automatically controls the heart rate as well as many other functions of the body including breathing, blood pressure, and excretion. The system is extremely flexible and can double the heart rate in as fast as three to five seconds.

The arteries and arterioles Blood leaving the heart from either the left or right ventricle enter a network of vessels called the arteries. Arteries are highly elastic vessels, having flexible fibers in their structure and a relatively thick layer of smooth muscle. Larger arteries have three layers—the inner (intima), the middle (media), and the outer (adventitia). Blood flows through the central opening, known as the lumen, which is lined with endothelial cells. The layers of the blood vessels interact to exert major control over blood pressure and where the blood flows. The adventitia contains the nervous control and blood vessels for the arteries, the media contains smooth muscles, and the endothelial layer of the intima is important for sensing environmental changes. The aorta, the largest artery, branches directly off the left ventricle, and is especially elastic because of the addition of cardiac muscle cells in the area where it branches off the heart. The elastic qualities of arteries are important so that they can expand to receive the blood volume under high pressure, and contract to continue forcing the blood into the rest of the circulatory system. The elasticity of the arteries is a significant component of the blood pressure during diastole, when the ventricles of the heart relax. From the left ventricle the coronary arteries, which supply blood to the heart itself, emerge from the aorta. Then the aorta makes a large U-turn in the chest, eventually becoming the abdominal artery. Major branches to the head (carotid arteries), arms (axillary arteries), and legs (femoral arteries) come off this one vessel. The flow of blood in the arteries is pulsile, increasing and decreasing with each heartbeat, about 70 times per minute. The flow of blood in the branch arteries accounts for the pulse that can be felt in the wrists and neck. The other major artery, the pulmonary artery, carries blood from the right ventricle to the lungs. Although the systemic arteries carry oxygenated blood, the arteries of the pulmonary system carry deoxygenated blood to the lungs. A vessel is called an artery because it carries blood away from the heart, not because the blood it carries contains oxygen. As arteries move away from the heart, they branch into smaller vessels called arterioles. Arterioles are structurally similar to arteries and play an important role in directing blood to the parts of the body needing it most, such as muscles under stress. The veins and the venules The major veins of the body are collectively called the venae cavae. The superior vena cava takes in blood

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els to the lungs where it gives off waste carbon dioxide and receives oxygen, then returns to the left side of the heart to be pumped to the rest of the tissues and organs of the body. The blood vessels that carry blood to the body are called the systemic circulation system. In a healthy heart, blood does not pass directly between the left and right sides of the heart. The two atria are separated by a wall known as the atrial septum, and the wall separating the two ventricles is known as the ventricular septum.

Cardiovascular system The heart and major veins and arteries of the cardiovascular system. (Courtesy of Gale Group.)

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The pulmonary vein brings blood oxygenated in the lungs back to the left atrium, so it can be pumped to cells throughout the body. As with arteries, veins are not so named because the vessel carries deoxygenated blood, but by their role in bringing blood back to the heart. Veins have the same three structural layers as arteries but the layers contain less elastic tissue and muscle components, making the walls thinner and six to ten times more expandable. The blood pressure in veins is lower than in the arteries, so to keep the blood flowing to the heart there are one-way valves that prevent backflow. Additionally, the action of the muscles in the legs help to return the blood to the heart, a mechanism called the venous pump. As veins move farther from the heart they branch into smaller structures known as venules. The venules end in very thin blood vessels known as the capillaries. The capillaries The arteries and the veins are connected by the vessel web of the capillaries. The lumen of these vessels is very small, to the extent that blood cells must line up single file to pass through the thinnest of them. Capillary walls are also very thin, allowing the passage of gases and nutrients between the blood cells and the cells of the body. The exact role of the capillaries varies depending on the part of the body in which they are located. The capillaries of the pulmonary circulation are found in the air sacs of the lungs, called alveoli, and it is there that the exchange of oxygen into the blood and carbon dioxide out of the blood occurs. In the kidneys, the capillaries in the organ’s tubules are the point where waste products are taken out of the blood to be excreted in the urine. The capillaries of the intestine are the location where nutrients from digested food are absorbed into the bloodstream. Capillaries serving the muscles bring in oxygen and nutrients and take away carbon dioxide and waste products.

Function For reference, at any particular point in time, about 9% of the body’s blood is located in the pulmonary circulation and about 7% is in the heart’s circulation. The

remaining 84% is located in the systemic circulation, with 64% in the veins, 13% in the arteries, and 7% in the arterioles and capillaries. The greater percentage in the veins is due to the less elastic nature of the vessels and the tendency of the blood to pool there. As the pulmonary circulation has a relatively smaller network of vessels when compared to the systemic circulation, the right side of the heart doesn’t have to work as hard as the left side to move the blood. Accordingly, the left side of the heart is larger and more muscular. The passive-filling nature of the heart keeps the unequal balance in blood volume between the pulmonary and systemic circulation. Without active filling, the physical differences between the systemic and pulmonary capillaries such as relative size of the vessel bed and relative elasticity determine the blood distribution. If the heart was a different kind of pump, cardiac characteristics, such as rate or stroke volume (amount of blood pumped by one contraction of the left ventricle) would govern the relative volumes. One way to visualize the function of the cardiovascular system is to follow the movement of one blood cell throughout the body. The path can begin at the left ventricle, where an oxygenated blood cell is pumped out by contraction of the myocardium, through the aortic valve into the aorta. The cell follows the curve into the abdominal artery and into the axillary artery into the arm. The artery subdivides into smaller and smaller branches, small enough to be called arterioles. Blood is needed at a muscle in the arm, so the arterioles are open to keep a large quantity of blood flowing in that direction. The blood cell continues through smaller vessels until it is in a capillary bed next to a muscle cell. There the cell gives up its oxygen cargo, takes up carbon dioxide waste produced by the muscle, and begins the journey back to the heart. Travelling through the capillaries to the venules and then into the axillary vein, the cell goes into the superior vena cava and into the right atrium. The right atrium contracts, and the cell moves through the tricupsid valve into the right ventricle. On the next systole, the cell rushes out of the right ventricle, through the pulmonary valve into the pulmonary artery to the lungs. The branches of vessels grow smaller and smaller, until the cell is in the capillaries of the alveoli where it releases the carbon dioxide to the lung space to be exhaled, and picks up another load of oxygen. Travelling back to the heart through the veins of the pulmonary circulation system, the cell enters the left atrium through the pulmonary vein. When the atrium contracts, the cell goes through the mitral valve into the left ventricle, having made one cycle through the cardiovascular system. In this way, the cardiovascular system sup-

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from the arms through the axillary veins, from the head through the jugular veins, and from the heart through the coronary veins. The inferior vena cava collects the blood from the legs from the femoral veins and from the abdomen from the hepatic, portal, and renal veins, among others. Both the superior and inferior venae cavae empty into the right atrium.

Cardiovascular system

plies all the cells of the body with oxygen and nutrients and carries away carbon dioxide and other wastes.

Role in human health It is difficult to overestimate the role the cardiovascular system plays in human health, with literally every cell of every tissue dependent on its function for survival. The cardiovascular system is the way the body transports things to and from the body’s cells. Oxygen, nutrients, and hormones are carried from the point these substances are made or brought into the body to the cells for their use. Cellular wastes are transported from the cells to the lungs, kidneys, or liver to be broken down or removed from the body. The circulatory system is also one of the transport systems (along with the lymph) for the immune cells responsible for protecting the body from disease. Changes in the functioning of the circulatory system have far reaching effects. A defect of the circulatory system, heart disease, is the number one cause of death in humans. Some of the common names and medical terms for the symptoms of a malfunctioning cardiovascular system include • chest pain (angina pectoris)

High blood pressure The most common cardiovascular disease is high blood pressure (hypertension), affecting one in four Americans (one in three black Americans). Blood pressure is measured in millimeters of mercury, based on how high the pressure in the arteries can raise a column of mercury above baseline using a blood pressure cuff. With a generally accepted normal of systolic to diastolic of 120/80, the disease is categorized into three stages. The systolic measurement, the diastolic measurement, or both can be elevated with hypertension. Stage 1 disease is present with systolic measurements of 5.12–5.47 in (130–139 mm) Hg, stage 2 with 6.29–7.04 in (160–179 mm) Hg, and stage 3 with 7.08 in (180 mm) Hg or higher. For diastolic measurements, stage 1 occurs from 3.54–3.89 in (90 to 99 mm) Hg, stage 2 with 3.93–4.29 in (100 to 109 mm) Hg, and stage 3 with measurements above 4.33 in (110 mm) Hg. Treatment decisions for hypertension take into account not only the measured blood pressure, but also the presence of other cardiovascular disease, hereditary risk factors, evidence of damage to internal organs, and lifestyle (stress, diet, exercise). Primary hypertension is associated with a persistent increase in resistance of blood flow in the arterioles, the smaller branches off the arteries. The precise cause is unknown.

• shortness of breath (dyspnea) • general tiredness (fatigue) • swelling (edema)

Heart disease

• loss of consciousness (syncope) • light-headedness (presyncope) • palpitations (arrhythmia or extrasystoles) • limb pain or tiredness (claudication) • abnormal skin color (pallor, cyanosis, erythemia, necrosis) • sores on skin (ulceration) • collapse (shock) • sudden changes in vision, strength, coordination, speech, or sensation

Common diseases and disorders Diagnosing cardiovascular disease can be complicated because often more than one cardiovascular problem exists at the same time in the same person. Symptoms of one problem can mask symptoms of another. Sometimes the multiple problems have a common cause or one cardiovascular problem can be causing another. This can make diagnosis and treatment a difficult task. 432

Some specific diseases of the heart include cardiomyopathy, congenital heart disease, heart valve defects, myocardial infarcation (heart attack), problems of the pericardium, and arrhythmias. If any of these diseases cause the heart to lose its ability to pump blood effectively, the patient is said to have heart failure. Because poor pumping ability often results in an accumulation of fluid in the tissues and lungs, it is often called congestive heart failure. Cardiomyopathy is a disease of the heart muscle with multiple causes and is the number one reason people undergo heart transplants. Categorized by the type of muscle damage, there are three general types of cardiomyopathy: dilated, hypertrophic, and restrictive. Dilated cardiomyopathy refers to the enlargement of the heart that is a response to the overall myocardial weakness. Many problems can cause dilated cardiomyopathy, including viral infections, excessive alcohol intake, and myocarditis (inflammation of the heart). Hypertrophic cardiomyopathy is an abnormal overgrowth of the heart muscle. An inherited disease, the overgrown muscle blocks the movement of blood both

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Congenital heart disease is caused by defects of the heart present at birth. Defects can be relatively mild and asymptomatic to severe and life-threatening. Some more common problems are abnormally formed blood vessels that block blood flow, malformed heart valves, incorrect connections between arteries, veins, and the heart, or defects in the atrial or ventricular septa. The most common congenital heart defect is a combination of four problems called the teralogy of Fallot. With this problem the ventricular septum is incomplete, there is an obstruction to blood flow beneath the pulmonary artery, the aorta is shifted rightward, and the right ventricular wall is thickened. Any of the hearts valves can obstruct blood flow if they are too stiff (stenosis) or don’t close properly and allow blood to leak (regurgitation). Valve problems can cause congestive heart failure or heart enlargement, which can lead to angina or heart arrhythmias. Causes of valve disease include congenital defects, calcium deposits, and infections, such as endocarditis (a bacterial infection of the endocardium, the lining of the heart). Severe valve problems can be treated by removal of the diseased valve and replacement with an artificial valve. A myocardial infarction (heart attack) is death of heart tissue due to the sudden lack of blood flow from the coronary arteries. Doctors believe the most common cause of the blockage is a blood clot that formed at a rupture of an atherosclerotic plaque that has broken loose. The results of the heart attack are dependent on the amount of heart tissue that is damaged. With less than 10% of the heart affected, there is a reduction in the ability of the heart to pump blood, but a normal lifestyle can often be maintained. At 25%, enlargement of the heart and heart failure is a common result. If 40% or more of the heart is damaged, shock or death usually occurs. Pericarditis is inflammation of the pericardium, usually caused by a viral infection. Although this disease can cause sharp, piercing chest pain, it is usually self-limiting and ordinarily does not lead to further problems. Pericardial effusion is a collection of fluid around the heart in the pericardial sac. If the fluid amount is great enough, it can reduce the heart’s ability to expand and receive blood, reducing its efficiency. This condition is known as cardiac tamponade. A final condition of the pericardium is pericardial constriction, an abnormal inflexibility of the

pericardial membrane. Some types of pericarditis often result in this problem. If the inflexible membrane causes heart failure, it can be removed surgically. Arrhythmias are abnormal heartbeats. Very broadly, arrhythmias can be classified into four different types: conduction system abnormalities, abnormally slow, abnormally fast, and irregular. Conduction system abnormalities are seen using electrocardiography units and do not directly cause an outwardly altered heartbeat. An example is some heart blocks, where the electrical signal adopts alternative paths in the heart to avoid nonconductive tissue. Slow heartbeat (brachycardia) is the most common cause for the implantation of a pacemaker and can be caused by problems with the autonomic nervous system, the SA node, or the conduction system. Abnormally fast heartbeats (tachychardia) can be atrial flutter, the presence of an extra, abnormal pathway for electrical conduction in the heart, or ventricular tachychardia (V tach). Some common irregular heartbeats include extra beats (extrasystoles) and atrial fibrillation, where the atria stop having effective contractions and beat chaotically at several hundred times per minute. Arterial disease Some diseases of the arteries include atherosclerosis, arterial thrombosis, aneurysm, and arteritis. The most common cause of heart attacks, coronary artery disease is the blockage of one or more of the vessels that supply blood to the heart. The arteries can be obstructed by a blood clot (thrombosis), atherosclerosis, or a coronary spasm. These problems can be treated with drugs that dissolve the clot or surgical procedures that remove or circumvent the blockages, such as coronary angioplasty or bypass surgery. Atherosclerosis is caused by the degradation of the lining of the arteries (endothelium) and the resultant plaque, a build-up of platelets, cholesterol, and other substances such as calcium that forms at the site. Atherosclerosis occurs to some extent in everyone and can occur in any of the body’s arteries. Depending on the location, the disease can lead to other cardiovascular problems such as heart attack, leg pain, stroke, and aneurysm. Arterial thrombosis is another way that arteries can be blocked, but in this case an abnormal blood clot, called an embolus, is responsible. This condition presents with very similar symptoms to atheroscloerosis. If it occurs in a coronary artery, it can cause heart attacks. An aneurysm is an abnormally widened area of an artery. A common site for this problem is in the abdominal aorta and it is usually caused by atherosclerosis. Aneurysms can be surgically treated if detected before rupture. A final disease of the arteries is arteritis, an

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into and out of the heart. The most common cause triggering hypertrophic cardiomyopathy is hypertension. Restrictive cardiomyopathy is due to a stiffening of the heart muscle that prevents it from fully relaxing during diastole. This problem is a symptom of other diseases such as hemochromatosis (a defect in iron use by the body) or amyloidosis (overproduction of antibodies by the bone marrow that cannot be broken down).

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KEY TERMS Adventitia—The outer layer of the arteries containing nerves and blood vessels. Diastole—Phase of the heartbeat where the ventricles relax and fill with blood. Endocardium—The thin, innermost layer of the heart which is infected with endocarditis. Epicardium—The outermost layer of the heart. Intima—The innermost layer of the arteries containing a layer of endothelial cells that are damaged with atherosclerosis.

These conditions are generally treated with bloodthinning drugs. If the clot does travel and get lodged in the lungs the condition is called a pulmonary embolism. This is a serious problem that often requires hospitalization. If blood-thinning drugs do not resolve the problem, surgical removal of the clot can be necessary. Varicose veins refer to a condition where the veins become abnormally dilated and most commonly appear as soft bluish bulges in the legs. Caused by elevated pressure in the veins and the resulting damage to the valves within the vessels, varicose veins, unless severe, are a cosmetic problem. They can be treated with surgery, injections (sclerotherapy), or lasers.

Media—The middle layer of arteries containing the smooth muscle.

Resources

Myocardium—The middle, working layer of the heart containing the heart muscle cells.

Braunwald, Eugene et al. Heart Disease: A Textbook of Cardiovascular Medicine. Philadelphia, PA: W.B. Saunders Company, 2001. Gersh, Bernard J., ed. Mayo Clinic Heart Book. New York: William Morrow and Company, Inc., 2000.

Pulsile—Movement in waves, a characteristic of the blood when leaving the heart and in the circulation. Regurgitation—A defect of the heart valves that interferes with its ability to close completely, allowing blood to leak in the direction opposite of circulation. Septum—A physical divider between chambers, found between the atria and the ventricles. Stenosis—A stiffening of the heart valves, which narrows its opening and can interfere with function. Systole—Phase of the heartbeat where the ventricles contract and force blood from the heart.

inflammation of the arteries. This problem is usually a part of another general disease, such as Takayasu’s disease, temporal arteritis, Buerger’s disease, and polyarteritis nodosa.

PERIODICALS

Crumlish, Christine et al. “When Time is Muscle.” American Journal of Nursing 100 (January 2000): 26. Thomas, Donna Jean G. and Harrah, Barbara F. “A New Look at Heart Failure.” Home Healthcare Nurse 18 (March 2000). ORGANIZATIONS

American Heart Association. 7272 Greenville Avenue, Dallas, Texas 75231. (800) AHA-USA1. . OTHER

Anderson, Robert M. The Gross Physiology of the Cardiovascular System. 2000. (April 19, 2001). Heart Information Network. April 4, 2001. (April 19, 2001).

Michelle L. Johnson, M.S., J.D.

Caries see Dental caries

Venous disease Some diseases of the veins include venous thrombosis, thrombophlebitis, pulmonary embolism, and varicose veins. Blockages in the veins are not usually caused by atherosclerosis, but by blood clots or venous thrombi. Venous thrombosis and the resulting inflammation, thrombophlebitis, can occur in superficial veins, usually a relatively minor problem, or in deep veins, a more serious condition where the threat of the clot breaking off and traveling to the heart or lungs is present. 434

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Carpal tunnel syndrome Definition Carpal tunnel syndrome is a common disorder caused by compression at the wrist of the median nerve supplying the hand, causing numbness and tingling.

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The carpal tunnel is an area in the wrist where the bones and ligaments create a small passageway for the median nerve. The median nerve is responsible for both sensation and movement in the hand, in particular the thumb and first three fingers. When the median nerve is compressed, an individual’s hand will feel as if it has “gone to sleep.” Persistent pressure causes pain that may manifest as a burning or tingling sensation in the fingers (acroparesthesia). Reduced motor ability in the hand and wrist may gradually develop as well. Women between the ages of 30 and 60 have the highest rates of carpal tunnel syndrome; they are two to five times as likely as men to develop the disorder. It is the most frequently occurring nerve compression found in the upper part of the body, and is a very significant cause of missed work days. Research has shown that the prevalence of carpal tunnel syndrome in the general population ranges from 2.1 to 4%. At least 200,000 carpal tunnel release surgical interventions are performed every year in the United States, and is the most frequently performed surgery on the hand. The costs associated with the procedure are at least $1 billion each year. The cost to employers is also substantial because of the significant loss of work time associated with the condition.

Causes and symptoms Compression of the median nerve in the wrist can occur during a number of different conditions, particularly those conditions which lead to changes in fluid accumulation throughout the body. Because the area of the wrist through which the median nerve passes is very narrow, any swelling in the area will lead to pressure on the median nerve. This pressure will ultimately interfere with the nerve’s ability to function normally. Pregnancy, obesity, arthritis, certain thyroid conditions, diabetes, and certain pituitary abnormalities all predispose individuals to carpal tunnel syndrome. Other conditions which increase the risk for carpal tunnel syndrome include the presence of organic lesions, tumors, congenital malformations, and various injuries to the arm and wrist (including fractures, sprains, and dislocations). A type of carpal tunnel syndrome that is transmitted by hereditary means has also been found. Furthermore, activities which cause an individual to repeatedly bend the wrist inward toward the forearm can predispose to carpal tunnel syndrome. Certain jobs that require repeated strong wrist motions carry a relatively high risk of precipitating carpal tunnel syndrome. Injuries of this type are referred to as “repetitive motion” injuries, and are more frequent among people

working at computer keyboards or cash registers, factory workers, and some musicians. Symptoms of carpal tunnel syndrome include numbness, burning, tingling, and a prickly pin-like sensation over the palmar surface of the hand, and into the thumb, forefinger, middle finger, and half of the ring finger. Some individuals notice a shooting pain going from the wrist up the arm, or down into the hand and fingers. This pain can radiate into the shoulder, neck, and chest regions, in some cases. Although pain is generally increased during repetitive movement, it is typically greatest during the night. With continued median nerve compression, an individual may begin to experience muscle weakness, making it difficult to open jars and hold objects with the affected hand. Eventually, the muscles of the hand served by the median nerve may begin to grow noticeably smaller (atrophy), especially the fleshy part of the thumb. Untreated, carpal tunnel syndrome may eventually result in permanent weakness, loss of sensation, and even paralysis of the thumb and fingers of the affected hand. Noticeable differences in strength and sensory perception can develop between the affected hand and the unaffected hand.

Diagnosis The diagnosis of carpal tunnel syndrome is made in part by checking to see whether pain or paresthesia (Phalen’s sign) can be brought on by holding his or her hand in position with wrist bent for about a minute. Xrays are often taken to rule out the possibility of a tumor causing pressure on the median nerve. A health practitioner examining a patient suspected of having carpal tunnel syndrome will perform a variety of simple tests to measure muscle strength and sensation in the affected hand and arm. The practitioner will likely test for Tinel’s sign (tingling or shock-like pain) by tapping the surface of the wrist over the median nerve to try to produce symptoms. A similar test known as the carpal compression test, where the thumb is placed over the patient’s carpal tunnel for 30 seconds, may also be performed. Further testing might include electromyographic or nerve conduction velocity testing to determine the exact severity of nerve damage. These tests involve stimulating the median nerve with electricity and measuring the resulting speed and strength of the muscle response, as well as recording speed of nerve transmission across the carpal tunnel. A variety of conditions need to be ruled out to confirm the diagnosis of carpal tunnel syndrome. These include osteoarthritis, blood vessel compression or occlusion, other nerve compression conditions, and tendinitis.

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Description

Carpal tunnel syndrome

Treatment Carpal tunnel syndrome is initially treated with splints, which support the wrist and prevent it from flexing inward into the position that exacerbates median nerve compression. Nurses and physical therapists often instruct the patient on how to use these splints or braces. Some people get significant relief by wearing such splints at night while sleeping, whereas others will need to wear the splints all day, especially if they are performing jobs which stress the wrist. If possible, the patient should avoid the repetitive action that may have precipitated the condition initially. Elevation of the affected arm may help some patients. Nurses often provide information on how to minimize strain on the carpal tunnel during daily activities. Physical therapists and nurses can provide information on various exercises, which may help with the symptoms associated with carpal tunnel syndrome. There is some evidence that vitamin B6 can help symptoms in some patients who have less serious symptoms, although this treatment is currently considered controversial and should be considered an alternative form of medicine. Acetaminophen, ibuprofen, or other nonsteroidal anti-inflammatory drugs may be prescribed to decrease pain and swelling. The clinician or pharmacist can provide advice on how to most effectively use these drugs to minimize carpal tunnel symptoms. When carpal tunnel syndrome is more advanced, injection of steroids into the wrist to decrease inflammation may be necessary. This must be carefully performed to avoid damaging the median nerve. Some patients may benefit from receiving low doses of oral corticosteroids. The most severe cases of carpal tunnel syndrome may require surgery to decrease the compression of the median nerve and restore its normal function. Such a repair involves cutting the ligament that crosses the wrist, thus allowing the median nerve more room and decreasing compression. This surgery is done almost exclusively on an outpatient basis and is often performed under local anesthesia. Careful injection of numbing medicines (local anesthesia) or nerve blocks (the injection of anesthetics directly into the nerve) create sufficient numbness to allow the surgery to be performed painlessly, without the risks associated with general anesthesia. Nurses provide information on what the patient should do postoperatively. Recovery from this type of surgery is usually quick and without complications. The return of muscle strength in the affected limb occurs gradually in most patients. However, when the muscle has severely atrophied in advanced cases, complete restoration of previous muscle strength is not likely. A less-invasive surgical technique using an endo436

scope has been developed for this procedure and is being used to a small extent.

Health care team roles The x-ray technologist will perform the radiography that will help the practitioner determine whether a tumor or injury has occurred in the lower arm of the patient. An x ray of the neck and upper back region of the patient can help rule out any degenerative condition of the spine that could produce some of these symptoms. Likewise, an imaging technologist performing magnetic resonance imaging (MRI) could help the practitioner find abnormalities in the lower arm and hand all the way up to the upper back and neck regions of the spine. Nurses can be involved at many points of the diagnostic and therapeutic process. They may assist in the initial physical diagnostic procedures performed by a physician. Patient education Physical therapists can design exercises that improve posture and strengthen certain muscle groups in order to alleviate or prevent carpal tunnel strain. These therapists often design rehabilitation programs for patients who have undergone carpal tunnel release surgery. These programs have the goal of restoring muscle strength to the weakened muscles of the lower arm and hand. Nurses may provide instruction about maintaining good posture and performing exercises that reduce strain on the carpal tunnel in patients that are at the beginning stages of carpal tunnel syndrome. They may also instruct the patient on how to wear a splint or a brace and assist the practitioner in the process of steroid injection into the carpal tunnel. Nurses assist in the carpal tunnel release surgery and in the ensuing recovery process. They also play an important role in the postoperative period by providing instructions about arm elevation and other issues, such as the use of splints. Occupational therapists can play a significant role in the prevention of carpal tunnel syndrome by providing information on good posture techniques and ergonomics while working.

Prognosis There is a wide range of outcomes in patients with carpal tunnel syndrome. A few patients have spontaneous remission of symptoms. However, most patients need to undergo some form of therapy. Continued pressure on the median nerve puts an individual at risk for permanent disability in the affected hand. Most people are able to control the symptoms of carpal tunnel syndrome using conservative methods, such as splinting and anti-inflammatory agents. Steroid injections often produce only tem-

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Prevention

KEY TERMS Carpal tunnel—A passageway in the wrist, created by the bones and ligaments of the wrist, through which the median nerve passes. Corticosteroids—Any one of several hormonal substances obtained from the adrenal gland cortex and which are classified according to biological activity. Endoscope—A device made of a tube and an optical system for observing the inside of the body.

Prevention is generally aimed at becoming aware of the repetitive motions which put the wrist into a bent position. People who must work long hours at a computer keyboard, for example, may need to take advantage of recent advances in ergonomics, which position the keyboard and computer components in ways that increase efficiency and decrease stress. An interruption in the repetitive movement once an hour throughout the day may help prevent and reduce symptoms. Early use of a splint may also be helpful for people whose jobs increase the risk of carpal tunnel syndrome. Splints may also improve sleeping posture and prevent or reduce carpal tunnel symptoms.

Electromyography—A type of test in which a nerve’s function is tested by stimulating a nerve with electricity, and then measuring the speed and strength of the corresponding muscle’s response.

Resources

Tendinitis—Inflammation of a tendon.

Median nerve—A nerve which runs through the wrist and into the hand. It provides sensation and some movement to the hand, the thumb, the index finger, the middle finger, and half of the ring finger. Osteoarthritis—A chronic disease that involves the joints and which is characterized by damaged cartilage, bone overgrowth, spur formation, and reduced function.

BOOKS

Asbury, Arthur K. “Carpal Tunnel Syndrome.” In Harrison’s Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998. “Carpal Tunnel Syndrome.” In Current Medical Diagnosis & Treatment 2001 edited by Lawrence M. Tierney, et al. New York: Lange, 2001. Mercier, Lonnie R. “Carpal Tunnel Syndrome.” In Ferri’s Clinical Advisor, edited by Fred F. Ferri, et al. St. Louis: Mosby, 2001. The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers and Robert Berkow, et al. Whitehouse Station: Merck, 1999. Wirth, Fremont P. “Carpal Tunnel Syndrome.” In Dambro: Griffith’s 5-Minute Clinical Consult Philadelphia: Lippincott Williams & Wilkins, 1999.

ORGANIZATIONS

Association for Repetitive Motion Syndromes, P.O. Box 471973, Aurora, CO 80047-1973. 1-303-369-0803. . National Institutes of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bldg. 31, Rm. 4C05, Bethesda, MD 20892-2350. 1-877-226-4267. .

Mark Alan Mitchell

PERIODICALS

Atroshi Isam, et al. “Prevalence for Clinically Proved Carpal Tunnel Syndrome is 4 Percent.” Lakartidningen 97 no.14 (April 5, 2000):1668-70. Franzblau, Alfred, Werner, Robert A. “What is Carpal Tunnel Syndrome?” Journal of the American Medical Association 282 no.2 (July 14, 1999):186-87. Mackinnon, Susan E. et al.”Clinical Diagnosis of Carpal Tunnel Syndrome.” Journal of the American Medical Association 284 no 15 (October 18, 2000):1924-29.

Cast care Definition A cast is a rigid dressing used to immobilize a fractured bone or soft tissue injury. It is made of strips impregnated with plaster or fiberglass material. The injured area is first covered with a layer of padding made of cotton or synthetic materials to protect the skin from

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porary improvement in symptoms. Most of these individuals have a recurrence of symptoms. Many women develop carpal tunnel syndrome in the third trimester of pregnancy, but symptoms usually disappear after the baby is born. Symptoms often reappear in later pregnancies in these women. Because symptoms generally resolve at the end of the pregnancy, surgery is not recommended in these women. In patients who do require surgery, about 95% will have complete cessation of symptoms.

Cast care

irritation. The plaster or fiberglass strips are then dipped in water and applied over the padding to form the cast.

minutes, but the force of the patient’s full body weight may cause the cast to crack in the first 24 hours after application.

Purpose In general, casts are applied to injured limbs to support and protect the bones and soft tissue. The cast helps to reduce the pain, swelling, and muscle spasms following the injury. If the bone is broken, the cast holds the fractured bone ends in correct alignment during the healing process. A cast, because of its rigid properties, will also provide protection from further injury. Body casts are used to prevent movement of the vertebrae of the back and may be used after a traumatic injury to the spine or a surgical repair of the vertebrae.

Precautions For health professionals Wet casts must be handled carefully, using only the palms of the hands, because a wet cast can be dented or compressed if handled too much after application. Dents or compression of the cast can cause pressure or irritation to the skin beneath the dressing, which may develop sores or ulcers. Patients in a hip cast or body cast should be repositioned every two hours during the first 24 hours to allow even drying of the cast and every two hours when awake thereafter to avoid developing pressure sores on the skin. For patients The use of crutches may be recommended for patients with a leg cast or a sling for patients with an arm cast for use during the first 24-48 hours. Patients should be instructed to rest and keep the affected limb elevated on a pillow as much as possible during the first 24 hours.

Casts are usually applied by physicians or orthpedic technicians, with the assistance of other health professionals. If the bone is broken, the physician will first place the fractured bone into alignment. Stockinette cut to size is applied to the limb and then cast padding (cotton batting) is wrapped around the extremity. The physician dips the casting material in water, squeezes out excess water, and then applies it wet over the cast padding to form the cast. After applying the cast, the physician will roll the stockinette over the edges of the cast to provide smooth edges at the top, bottom and any openings on the cast. The patient’s toes and fingertips are not covered by the cast. The cast is then usually placed on pillows elevated above the patient’s heart level for 15–20 minutes to dry.

Preparation A health professional will assist the patient in removing any clothing that will be difficult to pull over the cast later. The patient is positioned with the affected extremity resting on a pillow. The skin around the affected area is gently cleansed and thoroughly dried. The patient may be given medication for pain as directed by the physician. After the cast has been applied, extra pillows are placed under the cast to elevate it. The patient should be kept warm and comfortable while the cast is drying. It is helpful to explain to the patient that the cast will feel warm at first but then cool and damp as the material dries.

Aftercare Aftercare includes measuring the patient for crutches or a sling as appropriate. In addition, patients should be given aftercare instructions as follows:

Description Materials Of the two types of materials used for the hard supportive layer of cats, fiberglass has the advantages of being lighter, longer-wearing, and better able to “breathe” than plaster. Fiberglass is less trouble for the patient, because plaster casts are more likely to lose their shape if they become wet than fiberglass casts. It is also easier for x rays to penetrate fiberglass than plaster casts. Plaster, on the other hand, is less expensive and is easier to mold or shape to the body. A plaster cast will harden in 15–30 minutes but takes 24–48 hours to dry completely. A fiberglass cast will dry faster, in 15–30 438

Application

• The cast should be kept dry. Water weakens plaster casts and may cause skin irritation beneath the cast. The patient should use two layers of plastic to keep the cast dry while bathing or showering. • To decrease swelling and pain in the first 24–48 hours, the patient should place crushed ice in a plastic bag, covered with a pillow case or towel, on the cast over the injury every 15 minutes per hour while awake. • Dirt, sand, or powder should be kept away from the inside of the cast. Cast boots can be purchased to cover the foot area of a leg cast.

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• The patient should not break off or trim the edges of the cast without consulting the physician. • The cast should be inspected regularly. If it develops cracks or soft spots, the physician should be notified. • The patient should never attempt to remove the cast. The physician will remove the cast at the appropriate time with a special saw that cuts through the casting material but will not damage skin.

Complications Compartment syndrome A serious complication that can occur after cast application is known as compartment syndrome. This is a rare phenomenon that occurs when a cast is too tight. As the affected limb swells, the cast acts as a closed compartment, tightly compressing the nerves and blood vessels. Compartment syndrome can cause permanent nerve damage or loss of limb due to decreased circulation and oxygen to the tissue. Patients should be instructed to call the physician at once if any of the following signs or symptoms appear: • increased pain combined with the feeling that the cast is too tight • numbness and tingling in the hand or foot

KEY TERMS Compartment syndrome—A potentially serious complication of cast application, caused by pressure of the cast on the nerves and blood vessels in the injured limb.

the physician may replace the initial cast with a shorter one or a splinted cast that can be removed for bathing. When the cast is removed, the patient’s skin will appear dry and the muscles of the limb may be slightly wasted. Skin care with moisturizers and special exercises to regain muscle strength or to relieve joint stiffness may be ordered by the physician.

Health care team roles Cast application is usually performed by a physician but may be performed by a specially trained orthopaedic technician under the direction of the physician. The licensed nurse will assess the inpatient patient in a medical setting with a newly casted limb for the first 24-48 hours after cast application. In the outpatient setting, the licensed nurse will observe the patient for the first hour after cast application and instruct the patient and patients family about cast care, signs and symptoms of complications and the importance of follow-up visits with the physician for routine reassessment and cast removal.

• burning and stinging sensations

Resources

• excessive swelling in the part of the limb below the cast

BOOKS

• inability to actively move the toes or fingers Compromised healing Another complication of cast application is that the injury may not heal properly. In some cases the bone endings are set incorrectly, producing a deformity; or do not unite at all. Either may require surgical correction. Delayed union of the bone endings may occur in elderly or malnourished patients; their casts may need to remain in place for a longer period of time.

Results Cast application is an effective treatment for a fractured bone, serious soft tissue injury or surgical joint repair. Casts generally remain in place until bone healing occurs (four to six weeks). The physician will order x rays to monitor bone healing. X rays can be done through the cast. As bone healing occurs and the limb strengthens,

“Care of the Child with a Cast, Splint, or Brace.” Lippincott Manual of Nursing Practice. Philadelphia: Lippincott, Williams and Wilkins, 2001. OTHER

Brown, Jennifer, M.D. and Krause, Richard M.D.Cast Care From AAEM Emergency Medicine and Family Health Guide. EMedicine Online, April 2001. . Care of Casts and Splints. American Academy of Orthopaedic Surgeons. About Orthopaedics Online, 2000. . “Cast Care.” McKinley Health Center Online, June 1999. . Cast Protocol. Department of Nursing. UNC Online, March 1998. .

Mary Elizabeth Martelli, R.N., B.S.

CAT scan see CT scans

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• Padding should not be pulled out of the cast. In addition, the patient should not stick coat hangers, knitting needles, or similar items inside the cast in order to scratch itchy skin.

Cataracts

Cataracts Definition The lens of the eye is normally transparent. A cataract is a condition in which the lens of the eye becomes cloudy or opaque. This cloudiness can impair vision and may lead to eventual blindness.

Description The human eye has several parts. The outer layer of the eyeball consists of a transparent dome-shaped cornea and an opaque, white sclera. The cornea and sclera help protect the eye. The next layer includes the iris, pupil, and ciliary body. The iris is the colored part of the eye and the pupil is the small, dark, round hole in the center of the iris. The pupil is primarily responsible for allowing light into the eye. The ciliary body contains muscles that help the eye focus. The lens, which lies behind the pupil and iris, is covered by a cellophane-like capsule. It is normally transparent, elliptical in shape, and somewhat elastic. Due to this elasticity, the lens can focus on both near and far objects. The lens is attached to the ciliary body by fibers (zonules of Zinn). Muscles in the ciliary body act on the zonules, which then change the shape of the lens. This process is called accommodation—the lens focuses images to help make vision clear. As people age, the lens hardens and changes shape less easily. As a result, accommodation becomes more difficult, making it harder to see things up close. This normal aging condition, called presbyopia, generally occurs around age 40 and continues until about age 65. Individuals with this condition generally need reading glasses. The lens is made up of approximately 35% protein and 65% water. As people age, degenerative changes in the lens’s proteins occur. Changes in the proteins, water content, enzymes, and other chemicals are some of the reasons for the formation of a cataract. The major areas of the lens are the nucleus, the cortex, and the capsule. The nucleus is in the center of the lens, the cortex surrounds the nucleus, and the capsule is the outer layer. Opacities can occur in any area of the lens, and cataracts can be classified according to their location (nuclear, cortical, or posterior subcapular cataracts). The density and location of the cataract determines the amount of vision affected. If the cataract forms in the area of the lens directly behind the pupil, vision may be significantly impaired. A cataract that occurs on the outer edges or side of the lens causes less visual impairment. 440

Cataracts in the elderly are so common that they are thought to be a normal part of aging. Cataracts affect about 50% of individuals between the ages of 52-64, while at least 70% of those 70 and older are affected. Cataracts associated with aging (senile or age-related cataracts) are usually bilateral (occur in both eyes) with asymmetric progression (different rates of progression). Initially, cataracts may not affect vision. If the cataract remains small or at the periphery of the lens, the visual changes may be minor. Cataracts are much less common in younger people. Congenital cataracts are rare in newborns. When they do occur, they may be due to genetic defects or an infection or disease in the mother during pregnancy. Traumatic cataracts may develop after a foreign body or trauma injures the lens or the eye. Systemic illnesses, such as diabetes, also may result in cataracts. Cataracts can occur secondary to other eye diseases—for example, uveitis or glaucoma. Such cataracts are called complicated cataracts. Toxic cataracts result from chemical toxicity, such as steroid use. Cataracts also can result from exposure to the sun’s ultraviolet (UV) rays.

Causes and symptoms Recent studies have investigated the effect of nutrition on cataract formation. The results have been mixed, with some studies finding that there is a connection between nutrition and cataract formation and other studies finding none. Much interest has been focused on the use of antioxidant supplements as a protection against cataracts. Antioxidants, such as vitamins A, C, E, and beta-carotene, help the body neutralize oxygen-free radicals. Smoking and alcohol intake, however, have been implicated in cataract formation, as have the use of oral corticosteriods and antihypertensive agents. Some studies have determined that a diet high in fat increases the likelihood of cataract formation, while an increase in foods rich in antioxidants reduces the incidence. More research is needed to determine the precise role played by diet, smoking, alcohol consumption, and antioxidants in the formation of cataracts. Some unrelated physical conditions, such as diabetes mellitus, also may contribute to cataracts. Eye injuries and sun exposure also are causative factors. There are several common symptoms of cataracts: • gradual, painless onset of blurry, filmy, or fuzzy vision • poor central vision • frequent changes in eyeglass prescriptions • changes in color vision

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• increased glare from lights, especially oncoming headlights when driving at night • “second sight” improvement in near vision (no longer needing reading glasses) • poor vision in sunlight • presence of a milky whiteness in the pupil as the cataract progresses

Diagnosis Ophthalmologists and optometrists detect and monitor cataract growth and prescribe prescription lenses for visual deficits. Ophthalmologist perform cataract extraction. Cataract diagnosis begins with a complete eye exam. The ophthalmic assistant, technician, or nurse gathers information to determine the progression of the vision loss. It is unusual for cataracts to cause rapid vision loss, but sometimes patients believe the vision problem is acute because vision in the better eye has only recently been compromised. Patient history includes a review of refractive history, previous ocular disease, ambylopia, eye surgery, and trauma. Ophthalmic personnel also question patients about difficulties driving, reading, and performing daily activities, and record any medication the patient currently uses. The ocular exam determines the severity of the cataract and assesses other factors that might contribute to the potential for good vision after surgery. The exam includes measurement of visual acuity under both low and high illumination, biomicroscopy with pupillary dilation, stereoscopic fundus examination with pupillary dilation, assessment of ocular motility and binocularity, visual fields, evaluation of pupillary responses, refraction, and measurement of intraocular pressure (IOP).

Treatment No treatment may be necessary for cataracts that cause no symptoms or that cause only minor visual changes. It is important for an ophthalmologist or optometrist to continue to monitor and assess the cataract during regular office visits. Increased strength in prescription eyeglasses or contact lenses may be diagnostic and beneficial. Cataract surgery—the only option for patients whose cataracts interfere with vision to the extent that their daily activities are affected—is the most frequently performed surgery in the United States. It generally improves vision in more than 90% of patients. Most cataracts are removed before the lens is completely opaque or mature. This is done to minimize the impact of

A dense cataract on the lens of an eye. (Photograph by Margaret Cubberly, Phototake NYC. Reproduced by

the cataract on the patient’s daily life and also to decrease the risk of other eye complications. Sometimes cataracts need to be removed so the surgeon can examine the back of the eye more carefully. This is important in patients with diseases that may affect the eye. If cataracts are present in both eyes, surgery is performed on one eye at a time. The first eye heals before the second cataract is removed, sometimes as soon as the following week. A final eyeglass prescription is usually given about four to six weeks after surgery. Patients will still need reading glasses. The overall health of the patient must be considered in making the decision to have undergo cataract surgery. However, age alone need not preclude effective surgical treatment of cataracts, and people in their 90s can have successful return of vision after cataract surgery. Surgery to remove cataracts is generally an outpatient procedure. A local anesthetic is used, and some newer techniques take only minutes to complete. Removal of the cloudy lens can be accomplished with one of the three types of cataract surgery available: • Extracapsular cataract extraction. In this type of cataract extraction, the lens and the front portion of the capsule are removed. The back part of the capsule remains in place. • Extracapsular cataract extraction by phacoemulsification. This type of extracapsular extraction requires only a very small incision, resulting in faster healing. Ultrasonic vibration is applied to the lens to break it up into very small pieces, and the ophthalmologist then aspirates the pieces out of the eye with suction. As of 2001, this is the most commonly performed type of cataract surgery. • Intracapsular cataract extraction. The lens and the entire capsule are removed. This method carries an increased risk for detachment of the retina and swelling after surgery, and, as a result, it is rarely used.

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KEY TERMS Glaucoma—Disease of the eye characterized by increased pressure of the fluid inside the eye. Untreated, glaucoma can lead to blindness. Ultraviolet radiation (UV)—Invisible light rays that may be responsible for sunburns, skin cancers, and cataract formation. Uveitis—Inflammation of the uvea. The uvea is a continuous layer of tissue which consists of the iris, the ciliary body, and the choroid. The uvea lies between the retina and sclera.

A replacement lens is inserted at the time of the surgery. A plastic artificial lens called an intraocular lens (IOL) is placed in the remaining posterior lens capsule of the eye. When the intracapsular extraction method is used, an IOL may be clipped onto the iris. Contact lenses and cataract glasses (aphakic lenses) are prescribed if an IOL cannot be inserted due to complications. A folding IOL is used with the phacoemulsification procedure to allow it to pass through the small incision. Antibiotic drops to prevent infection and steroids to reduce inflammation are prescribed after surgery. An eye shield or glasses protect the eye from injury while it heals. During the night, an eye shield is worn. The patient returns to the doctor the day after surgery for assessment, with several follow-up visits over the next two months to monitor the healing process. Return visits at three and six months are optional.

Prognosis The cataract extraction success rate is very high with a good prognosis. A visual acuity of 20/40 or better is expected as a result of cataract extraction. If an extracapsular cataract extraction was performed, a secondary cataract may develop in the remaining back portion of the capsule. This can occur one to two years after surgery. YAG capsulotomy is most often used for this type of cataract. YAG stands for yttrium aluminum garnet, the name of the laser used for this procedure. This is a painless outpatient procedure and requires no incision. The laser beam makes a small opening in the remaining back part of the capsule, allowing light through. Complications occur in a very small percentage (35%) of surgical cataract extractions. Possible complications include infections, corneal edema (swelling), diplopia, bleeding, retinal detachment, iris prolapse or vitreous in the wound, intraocular lens dislocation, and 442

the onset of glaucoma. Some problems may occur one to two days, or even several weeks, after surgery. Follow-up examinations should check the patient for haziness or redness in the eye, decrease in vision, nausea, and pain.

Health care team roles Skilled ophthalmic technicians and assistants record the patient history and perform many of the preliminary tests. Depending on skill level, these ophthalmic assistants may perform measurement of visual acuity under both low and high illumination, biomicroscopy with pupillary dilation, assessment of ocular motility and binocularity, visual fields, evaluation of pupillary responses to rule out afferent pupillary defects, refraction, and measurement of intraocular pressure (IOP). Before the surgery, nurses and assistants also prepare the operating room (OR). Many ophthalmologists now have their own ambulatory surgery centers (ASCs) where skilled technicians and ophthalmic nurses play a critical role in preparing the OR and patients for the surgery. Ophthalmic nurses also assist the ophthalmologist during surgery and discuss outcomes with patients postoperatively. Patient education When a cataract is found, the patient should be informed, even if surgery is not immediately indicated. The optometrist or ophthalmologist should discuss the different treatment options, as well as the risks and benefits of surgery with the patient.

Prevention The eyes should be protected from UV radiation by wearing glasses with a special coating. Dark lenses alone are not sufficient, but the lenses must be coated to filter out UV light (specifically, UV-A and UV-B). Antioxidants also may help prevent cataracts by reducing free radicals that can damage lens proteins. A healthy diet rich in sources of antioxidants, including citrus fruits, sweet potatoes, carrots, green leafy vegetables, and/or vitamin supplements, may be beneficial. When taking certain medications, such as steroids, more frequent eye exams may be necessary. Patients should also be told not to smoke. Resources BOOKS

“Cataract.” In Medical-Surgical Nursing: Concepts and Clinical Practice, edited by Wilma J. Phipps, et al. 5th ed. St. Louis, MO: Mosby-Year Book, 1995, pp. 20882090.

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“Nutrients and Cataract Risk in Older Individuals.” Nutrition Research Newsletter 19 (July 2000): 15. ORGANIZATIONS

American Academy of Ophthalmology (National Eyecare Project). P.O. Box 429098, San Francisco, CA 941429098. Phone: (800) 222-EYES. . American Optometric Association. 243 North Lindbergh Blvd., St. Louis, MO 63141. (314) 991-4100. . The Lighthouse. 111 East 59th Street, New York, NY 10022. (800) 334-5497. . Prevent Blindness America. 500 East Remington Road, Schaumburg, IL 60173. (800) 331-2020. . OTHER

• To obtain a sterile urine specimen for diagnostic evaluation; to empty bladder content when the patient is unable to void (urinate) due to urinary retention, bladder distention, and obstruction, or to measure residual urine after urination. • To instill medication for a localized therapeutic effect and to instill contrast material (dye) into the bladder through the urethral catheter for cystourethralgraphy (x ray of the bladder and urethra). • To empty the bladder for increased space in the pelvic cavity to protect the bladder during labor and delivery and during pelvic and abdominal surgery. • To strictly monitor the urinary output and fluid balance of critically ill patients. Indwelling catheterization is:

Aker, Alan B., and David C. Brown. “How to Commit Efficiency.” Ophthalmology Management Online. . “Cataracts: No Nasal Spray Connection.” Ophthalmology Management Online. . McCune, Donna M. “Are You Sharing Post-Op Care Correctly?” Ophthalmology Management Online. . “Optometric Clinical Practice Guideline: Care of the Adult Patient with Cataract.” American Optometric Association Online. .

Mary Bekker

Catecholamines tests see Adrenomedullary hormone tests

Catheterization, female Definition Urinary catheterization is the insertion of a catheter through the urethra into the urinary bladder for withdrawal of urine. Straight catheters are used for intermittent withdrawals; indwelling (Foley) catheters are inserted and retained in the bladder for continuous drainage of urine into a closed system.

Purpose Intermittent catheterization is used for the following reasons:

• Indicated as palliative care for terminally ill or severely impaired incontinent patients, for whom bed and clothing changes are uncomfortable, and as a way to manage skin ulceration caused or exacerbated by incontinence. • Used to maintain a continuous out flow of urine for patients undergoing surgical procedures that cause a delay in bladder sensation, and for persons with chronic neurological disorders that cause paralysis or loss of sensation in the perineal area. • Indicated for urologic surgery, bladder outlet obstruction, and for patients with an initial episode of acute urinary retention to allow the bladder to regain its tone.

Precautions Because the urinary tract is normally a sterile system, catheterization presents the risk of causing a urinary tract infection (UTI). The catheterization procedure must be sterile and the catheter must be free from bacteria. Urinary catheterization aids or replaces the body’s normal ability to urinate. Intermittent use of the procedure can stimulate normal bladder function, however frequent and continuous catheterization can lead to total dependency. Catheterization is invasive and has the potential of injuring the urethra and bladder, inviting urinary tract infections. Therefore aseptic techniques should be use in all catheter management activities. The normal flow of urine from the kidneys through the ureters, bladder, urethra prevents the movement of bacteria up through the urinary system. The antibacterial properties of the bladder wall, urethra lining, and low urine pH also serve as protective barriers to urinary tract infections. Urinary tract infections occur when bacteria invade the protective barriers of one or more urinary structures.

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Catheterization, female

itate catheter insertion. But since there are no lubricating glands in the female urethra (as found in the male urethra), the risk of trauma from a simple catheter insertion is more likely; therefore, ample supply of an anesthetic or antibacterial lubricant should be used.

Preparation Health care practitioners performing the catheterization should have a good understanding of the anatomy and physiology of the urinary system, trained in antiseptic techniques and in catheter insertion and catheter care. A Foley catheter is left in place for continuous drainage of the bladder. (Custom Medical Stock Photo. Reproduced by permission.)

Infection control Every attempt should be made to keep the urinary drainage system closed. Breaks in the system invite infections. Health care workers and patients should wash their hands before and after manipulation of the patient’s catheter or collection system to control UTI. Cross-contamination is the most frequent cause of nosocomial (hospital acquired) catheter related infections. Good hand washing practices are the best prevention measure. The extended portion of the catheter should be washed with a mild soap and warm water to keep it free of accumulated debris. Frequent intermittent catheterization and long term use of indwelling catheterization predisposes the patient to UTI. Care should be taken to avoid trauma to the urinary meatus or urothelium (urinary lining) with catheters that are too large or inserted with insufficient use of lubricant. Patients with an indwelling catheter must be reassessed periodically to determine if alternative treatment will be more effective in treating the problem.

Determine the primary purpose for the catheterization and give the patient and/or caregiver a detail explanation. Patients requiring self-catheterization should be instructed and trained in the technique by a qualified health professional. Sterile disposable catheterization sets are available in clinical settings and for home use. These sets contain most of the items needed for the procedure, such as antiseptic agent, perineal drapes, gloves, lubricant, specimen container, label, and tape. Anesthetic or antibacterial lubricant, catheter, and drainage system may need to be added. It is always wise to review the content of the pre-packaged catheterization set while assembling the materials. Catheter choices TYPES. Silastic catheters have been recommended for short-term catheterization after surgery because they are known to decrease incidence of urethritis. However, due to lower cost and acceptable outcomes, latex is the catheter of choice for long-term catheterization. Silastic catheters should be used for patients who are allergic to latex products.

There are also additional types of catheters: • PTFE-coated latex Foley catheters • hydrogel-coated latex Foley catheters

Description

• pure silicone Foley catheters

The female urethral orifice is a vertical, slit-like or irregularly ovoid (egg shaped) opening, 4 or 5 mm in diameter, located between the clitoris and the vagina. The urinary meatus (opening) is concealed between the labia minora, which are the small folds of tissue that need to be separated in order to visualize the opening and insert the catheter. With proper positioning, good lighting and gloved hands, these anatomical landmarks can be identified. If necessary, provide perineal care to ensure a clean procedural environment. Catheterization of the female patient is traditionally performed without the use of local anesthetic gel to facil444

• silicone-coated latex Foley catheter SIZE. The diameter of the catheter is measured in millimeters. Authorities recommend the “narrowest and softest tube” that will serve the purpose. Rarely is a catheter larger than size 18 F required, and sizes 14 or 16 F are used more often. Catheters greater than size 16 F have been associated with patient discomfort and urine bypassing. A size 12 catheter has been successfully used in children and female patients with urinary restriction. LENGTH. Female adult patients should be given the choice of a short, female length or a standard length catheter for urethral catheterization.

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DRAINAGE SYSTEM. Review the design, capacity, and emptying mechanism of the variety of urine drainage bags with the patient. Select the system that is most adaptable to the patient’s lifestyle and her ability to manage the device independently. For women with normal bladder sensation, a catheter valve for intermittent drainage may be an acceptable option.

Procedure The standard technique for catheter insertion is: • Explain the procedure to the patient, position the patient and ensure privacy and good lighting. • Wash hands, remove outer tray wrapper and put on sterile gloves before opening the sterile inner packet. Prepare a sterile field and place a specimen collection vessel between the patient’s legs. • Cleanse the labia according to established guidelines and identify the urethral meatus. If an anesthetic lubricating gel is used, instill approximately 0.16 fl oz (5 ml) of 2% lignocaine hydrochloride gel into the urethra or apply the gel to the meatus to achieve surface anesthesia within three to five minutes. • Hold the catheter in the dominant hand and gently insert it into the urethral meatus; pass it slowly through the urethra and into the bladder. If the catheter is accidentally inserted into the vagina or the tip is contaminated, discard it and take new sterile catheter before proceeding. • Once the urine starts to flow, collect the specimen and pass the catheter an additional 2 inches (5 cm) to ensure that the balloon is in the bladder before slowly inflating the balloon with 10 ml sterile water.

Aftercare Patients using intermittent catheterization to manage incontinence may require a period of adjustment as they try to establish a catheterization schedule that is adequate for their normal fluid intake. Antibiotics should not be prescribed as a preventative measure for patients at risk for urinary tract infections. Prophylactic use of antibacterial agents may lead to the development of drug-resistant bacteria. Patients

who practice intermittent self-catheterization can reduce their risks for UTI by using antiseptic techniques for insertion and catheter care. Attach the indwelling catheter tem, slightly curve the tubing, and urethral traction. In women the secured to the anteromedial thigh adhesive.

to the drainage sysanchor it to prevent catheter should be with non-allergenic

Complications Complications that are liable to occur include: • Trauma and/or introduction of bacteria into the urinary system, leading to infection and, rarely, septicemia. • Trauma to the urethra and/or bladder from incorrect insertion or removal of the catheter with the balloon inflated. Repeated trauma may cause scaring and/or stricture, or narrowing of the urethra. • Bypassing of urine around the catheter. Inserting a smaller catheter size can minimize this problem. Sexual activity and menopause can also compromise the sterility of the urinary tract. Irritation of the urethra during intercourse promotes the migration of perineal bacteria into the urethra and bladder, causing UTIs. Postmenopausal women may experience more UTIs than younger women. The presence of residual urine in the bladder secondary to incomplete voiding provides an ideal environment for bacterial growth.

Results Urinary catheterization should be avoided whenever possible. Clean intermittent catheterization, when practical, is preferable to long-term catheterization. Catheters should not be changed routinely. When each patient is monitored for indication of obstruction, infection, or complications before the catheter is changed, some patients require catheter changes weekly, and others may need a change in several weeks. Fewer catheter changes will reduce trauma to the urethra and reduce incidence of UTI.

Health care team roles Observation Before commencing with the catheterization, the nurse should observe the patient’s general condition, palpate the pubic area to note gross distension. The patient should be monitored for indications of infections and encourage adequate fluid intake.

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BALLOON SIZE. Select a catheter with a balloonfilling volume of 0.33 fl oz (10 ml) for routine drainage. Sterile water must always be used to inflate the balloon as other fluids may contain particles, which could block the inflation channel. Some indwelling catheters are manufactured pre-filled with 0.33 fl oz (10 ml) of sterile water, ready for balloon inflation after catheter insertion.

Catheterization, male

PERIODICALS

KEY TERMS Catheterization—A procedure of inserting a catheter through the urethra into the bladder to remove urine. Catheter—A tube for evacuating or injecting fluid. Contaminate—To make an item unsterile or unclean by direct contact. Foley catheter—A double channel retention catheter. One channel provides for the inflow and outflow of bladder fluid, the second (smaller) channel is used to fill a balloon that holds the catheter in the bladder. Intermittent catheterization—Periodic catheterization to facilitate urine flow. The catheter is removed when the bladder is sufficiently empty. Perineal area—The genital area between the vulva and anus in a woman. Urinary incontinence—The inability to retain urine or control one’s urine flow. Urinary retention—The inability to void (urinate) to discharge urine. Urethritis—Inflammation of the urinary bladder.

Colley, Wendy. RGN, DNCret. FETC. “Know How.” Nursing Times (July 2, 1997). Cravens, David D., Steven Zweig. “Urinary Catheter Management.” American Family Physicians 61, no. 2 (January 15, 2000): 369. Sanyay Saint, Joann G. Elmore, Sean D. Sullivan, Scott S. Emerson, Thomas D. Koepsell, “The efficacy of silver alloy-coated urinary catheters in preventing urinary tract infection: a meta-analysis.” American Journal of Medicine 105, no. 3 (September 1998): 236.

Aliene S. Linwood, B.S.N., RN, D.P.A., FACHE

Catheterization, male Definition Urinary catheterization is the procedure of inserting a catheter through the urethra into the bladder to remove urine. Intermittent catheterization is performed for periodic relief of bladder distension; indwelling (Foley) catheters are inserted and retained in the bladder for continuous drainage of urine into a closed system.

Purpose The nurse should seek medical advice if the catheter cannot be inserted easily, or if the patient complains of undue pain or bleeding other than that associated with minor trauma. Patient education The patient and/or caregiver should be taught to use aseptic technique for catheter care. Nursing interventions and patient education can make a difference in the incidence of urinary tract infections in the hospital and nursing homes and home care units. The sexuality of the patient with an indwelling catheter for continuous urinary drainage is seldom considered. If a patient is sexually active, the practitioner must explain that intercourse can take place with the catheter in place. The patient or her partner can be taught to remove the catheter before, and replace it with a new one following intercourse. Resources BOOKS

Nettina, Sandra M. Lippincott Manual of Nursing Practice. 7th edition. Philadelphia: Lippincott, 2001, pp.692-697. 446

Intermittent catheterization is recommended to obtain a sterile urine specimen, to relieve urinary retention, for urologic surgery or surgery on contiguous structures, for critically ill patients requiring accurate measurement of intake and output, and for temporary obstruction of the bladder opening due to injury. Indwelling catheterization is recommended for continuous drainage of urine when the bladder outlet obstruction can not be corrected by medical or surgical intervention; in cases of intractable skin ulceration caused or exacerbated by exposure to urine; and as palliative care for terminally ill or severely impaired incontinent patients.

Precautions The urinary tract is normally a sterile system. The normal flow of urine from the kidneys through the ureters, bladder, and urethra prevents the migration of bacteria up through the urinary system. Antibacterial properties of the bladder wall, urethra, low pH of urine, and the prostatic fluid in men also inhibit bacteria growth. Urinary tract infections (UTI) usually result from bacterial invasion of the protective barriers of one or

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Frequent intermittent catheterization and long-term use of indwelling catheters predisposes the patient to UTI. Care should be taken to avoid trauma to the urinary meatus and urothelium (urinary lining) with catheters that are too large or inserted with an insufficient amount of lubricant. Further medical advice should be sought if the catheter cannot be inserted easily, or the patient complains of undue pain or bleeding other than that associated with minor trauma. Every attempt should be made to keep the urinary drainage system closed. Breaks in the system invite infections. Health care workers and patients should wash their hands before and after manipulation of the patient’s catheter or collection system to control UTI. Cross-contamination is the most frequent cause of nosocomial (hospital acquired) catheter related infections. Good hand washing practices are the best prevention measure. Patients with indwelling catheters should be re-evaluated periodically to determine if an alternative treatment method will be more effective.

Description Intermittent catheterization is preferable to chronic indwelling catheterization in certain patients with bladder dysfunction. It has become the standard care for patients with spinal cord injuries. Elderly patients, following surgical repair of hip fractures, regain the ability to control urination more quickly on a program of intermittent catheterization every six to eight hours compared to the use of indwelling catheters. Intermittent catheterization may be performed four or five times a day by the health care practitioner or caregiver. Patients who are interested in self-catheterization should be instructed and trained by a qualified health professional. This is also true for patients who require indwelling catheterization, as the procedure for insertion is similar to that for intermittent catheterization, with added responsibility of inflating the balloon.

Preparation Health care practitioner performing the catheterization should have a good understanding of the male urinary system anatomy and physiology and should be trained in aseptic technique, catheter insertion technique, and catheter care.

Sterile disposable catheterization sets are available in clinical settings and for home use. These sets contain most of the items needed for the procedure, such as antiseptic agents, perineal drapes, gloves, lubricant, specimen container, label, and adhesive strips. Local anesthetic gel, antibacterial lubricant, catheter, and drainage system may need to be added. It is wise to check the content of the pre-packaged catheterization set when assembling materials and supplies. Catheter choices Silastic catheters have a decreased incidence of urethritis and are recommended for short-term and intermittent catheterization. Latex is the catheter of choice for long-term catheterization. Silastic catheters are recommended for patients who are allergic to latex products. There are additional types of Foley catheters: • PTFE-coated latex • hydrogel-coated latex • silicone-coated latex • pure silicone Select the smallest and softest catheter available. Catheters larger than 18 F are seldom used. Catheters size 14 or 16 F are used more frequently. A size 12 F catheter has been used successfully in catheterizing men with acute urinary retention. When indwelling catheters are required, select a catheter that can be inflated with 5 to 10 ml of sterile water. Review the design, capacity, and emptying mechanism of a variety of urine drainage systems available. Select the system that is most adaptable to the patient’s lifestyle and ability to manage the device independently. For patients with normal bladder sensation, a catheter valve for intermittent drainage may be an acceptable option. Procedural precautions Before starting the catheterization, observe the patient’s general condition and palpate the suprapubic area to detect gross distension. The genital area should be washed with a mild soap and warm water and patted dry. Phimosis is constriction of the prepuce (foreskin) so that it cannot be drawn back over the glans penis. This may make it difficult to identify the external urethral meatus. Care should be taken when catheterizing men with phimosis to avoid trauma from forced retraction of the prepuce or by incorrect positioning of the catheter. The male urethra is longer than the female urethra and has two curves in it as it passes through the penis to the bladder, which makes catheter insertion more diffi-

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more urinary structures. As a result, urinary catheterization should be avoided whenever possible. Precautions must be taken to keep the procedure sterile and the catheter free from bacteria. The extended portion of the catheter should be washed with a mild soap and warm water to keep it free of accumulated debris.

Catheterization, male

cult. One curve can be straightened out by lifting the penis; the other curve is fixed. The penis should be held upright, at right angle to the patient’s body when the catheter is inserted. The male urinary meatus is located at the end of the penis and is exposed by retracting the prepuce in uncircumcised patients. Men with a retracted penis can be even more difficult to catheterize. Gentle finger pressure on both sides of the penis will often cause the penis to emerge and extend from the body to facilitate the catheterization. To perform the procedure:

accumulated debris. Patients with indwelling catheters should be re-evaluated periodically to determine if an alternative treatment method will be more effective. Catheters should not be changed routinely. Each patient should be monitored for indication of obstruction or complications before changing the catheter. Some patients require catheter changes weekly, and others may need a change in several weeks. In summary, the following guidelines are recommended for male catheterization:

• Position the patient in a horizontal recumbent position.

• Catheterize the patient only when it is absolutely necessary.

• Place the opened catheterization tray on the bedside stand in comfortable reaching distance.

• Secure the catheter properly.

• Retract the foreskin. Using an aseptic technique, clean the prepuce and insert anesthetic gel to anesthetize the glans penis and dilate the prepuce exposing the meatus. Anesthetic gel can then be introduced into the urethra and catheterization can commence.

• Avoid catheter irrigation unless it is needed to prevent or relieve bladder obstruction.

• Use two or three aseptic swabs to clean the meatus with circular motion, beginning with the center of the opening and rotating outwards. • Lubricate about 8 inches (20 cm) of the catheter. • Hold the penis in the dominant hand and pull it upward and slightly backward to straighten the urethra. • Gently insert the catheter with a smooth continuous motion until urine begins to flow. Do not force. • Once the urine starts to flow, collect the specimen. Advance the catheter an additional 5 cm before inflating the balloon with 5 to 10 ml of sterile solution to hold the catheter in place. • Connect the indwelling catheter to the drainage system. Put a slight curve in the catheter and anchor it to the upper outer thigh with hypoallergenic adhesive to prevent urethral traction.

Aftercare Patients using intermittent catheterization as treatment of incontinence or retention will have a period of adjustment as they try to establish a catheterization schedule adequate for their normal fluid intake. The urinary drainage system should be kept closed. Breaks in the drainage unit may result in an infection. Avoiding cross-contamination is important in controlling catheterrelated UTIs. Practitioners and caretakers should always wash their hands before and after handling a patient’s catheter or urine collection unit. The extended portion of the catheter should be washed with a mild soap and warm water to remove 448

• Maintain a closed sterile urine collection system and unobstructed urine flow.

• Always use the smallest effective catheter. • Do not change the catheter as an elective treatment option. • Isolated minor episodes of UTI should not be treated with antibiotics. Antibiotic prophylaxis promotes emergence of drug-resistant bacteria. • Provide continuing education in catheter care for practitioners and caretakers.

Complications A few complications that may rise during the procedure are: • urinary tract infections and catheter obstruction • trauma and/or the introduction of bacteria into the urinary system, leading to infection and, rarely, septicemia • trauma to the bladder, urethra, and meatus caused by incorrect insertion of the catheter or forceful removal with the bladder inflated by confused patients • scaring, stricture and/or narrowing of the urethra due to repeated trauma • urine bypass around the catheter (A smaller catheter size may minimize leakage.) • leakage around the catheter due to forceful bladder spasms that overwhelm the catheter’s drainage capacity

Results Urinary catheterization aids or replaces the body’s normal ability to urinate. Intermittent use of the procedure can stimulate normal bladder function. However frequent and continuous catheterization can lead to total

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Bacteriuria—Bacteria in the urine (asymptomatic or symptomatic). Foley catheter—A double channel retention catheter. One channel provides for the inflow and outflow of fluid; the second and smaller channel is used to fill a balloon that holds the catheter in the bladder.

The nurse usually teaches the patient and/or caregiver to use aseptic technique for catheter care. Nursing interventions and patient education can make a difference in the incidence of urinary tract infections in the hospital, nursing homes, and home care units.

Phimosis—Tightness of the foreskin, which cannot be drawn back from the glans penis.

The sexuality of the patient with an indwelling catheter for continuous urinary drainage is seldom considered. If a patient is sexually active, the patient or her partner can be taught to remove the catheter before intercourse, and replace it with a new one following intercourse.

Prepuce—A fold of cutaneous tissue over the glans penis.

Resources

Urinary catheterization—The insertion of a catheter through the urethra into a patient’s bladder. Urinary incontinence—The inability to retain urine or control one’s urine flow. Urinary retention—The inability to void (urinate) to discharge urine.

dependency. Practically every patient with chronic catheterization and frequent intermittent catheterization will develop bacteriuria. Some physicians do not recommend antibiotic therapy for asymptomatic bacteriuria. When symptomatic infections are treated in patients with indwelling catheters, the catheter is removed and a fresh urine specimen is obtained for culture to determine the source of the infection and direct the medical therapy.

BOOKS

Nettina, Sandra M. Lippincott Manual of Nursing Practice. 7th edition. Philadelphia: Lippincott, 2001, pp.692-697. PERIODICALS

Cravens, David D. and Steven Zweig. “Urinary Catheter Management.” American Family Physician 16, no. 12 (January 15, 2000): 369. Marchiondo, Kathleen. “A New Look at Urinary Tract Infection.” American Journal of Nursing 98, no. 3 (March 1998):p34-39. Pomfret, Ian. “Women at Work.” Nursing Times 95, no. 6 (February 10, 1999): 59-60.

Aliene S. Linwood, BSN, RN, D.P.A., FACHE

Cavities see Dental caries CBC see Complete blood count CD4 count see AIDS tests

Health care team roles The physician orders the catheter and a registered nurse performs the procedure and provides patient education. Catheterization is a rather simple procedure, but female nurses are sometimes reluctant to perform urethral catheterization on male patients despite established patient care guidelines and advice on the male catheterization procedure. However, both intermittent and indwelling male catheterization is required to achieve optimum quality of life; therefore nurses should make the best possible practice and techniques available. Before commencing with the catheterization, the health care professional observes the patient’s general condition, palpates the pubic area to note gross distension, monitors the patient for indications of infections, and encourages adequate fluid intake.

Cell division Definition The process by which a cell distributes its genetic material (DNA) and cytoplasm to daughter cells.

Description In higher organisms including humans, there are two types of cell division, mitosis and meiosis. Strictly speaking, mitosis and meiosis refer to division of the DNA and associated materials in the nucleus of the cell. In mitosis, the cells produced by division have exactly the same genetic information as the original cell, while in meiosis the cells produced by division have only half the genetic

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KEY TERMS

Cell division

information as the original cell. Both processes are accompanied by cytokinesis, the division of the cytoplasm. Mitosis Mitosis produces two daughter cells, each of which has the same genetic information as the parent cell. The entire process includes a series of precise steps to insure that the genetic material is accurately duplicated and distributed. The life of a cell is generally made up of two parts, interphase and mitosis. During interphase, DNA synthesis occurs. Since the process uses the original DNA as a template, the copy is exact (or nearly exact if mutations occur). After a pause, the cell then enters mitosis. Although the lifespan of a cell varies in length depending on the cell type, mitosis itself usually takes about one to two hours and involves four stages: prophase, metaphase, anaphase, and telophase. PROPHASE. During prophase, the chromosomes, which contain the DNA, condense in length and become visible under a microscope. Humans have 23 chromosome pairs, for a total of 46 chromosomes. Since DNA duplication has already occurred, each of the 46 chromosomes at this stage is present in two copies referred to as sister chromatids. The two sister chromatids of a pair are attached to each other at a point called the centromere. As the chromosomes condense, the membrane surrounding the nucleus disappears, and fibers appear, which come together to form a spindle within the cell. The spindle has two opposite poles and a mid-section, the equatorial plate. METAPHASE. At the beginning of metaphase, the chromosomes line up individually on the equatorial plate. Fibers emanating from the poles of the spindle attach to the centromeres of the sister chromatids. One member of each pair of sister chromatids is attached to a spindle fiber that radiates from one pole, and the other is attached to a fiber that radiates from the opposite pole. ANAPHASE. After all chromosomes (92 sister chromatids in 46 pairs) have aligned on the equatorial plane of the spindle, the centromere of each chromosome splits, and the fibers begin to contract. One sister chromatid of each pair is pulled to one pole of the spindle and the other is pulled to the opposite pole. TELOPHASE. Separate membranes form around the chromosome sets at each pole to form two nuclei. The chromosomes elongate and the spindle disappears. Cytokinesis then occurs, resulting in two daughter cells each with 46 chromosomes and roughly half the cytoplasm of the parent cell.

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Function and role in human health Mitosis is the process by which a single human zygote (fertilized egg cell) becomes a complex organism consisting of over 100 trillion cells. During the lifetime of an individual, mitosis continues. In some tissues such as epithelium (skin, mucous membranes), mitosis actively occurs to replace cells and repair damage. Other cell types such as nerve cells do not readily undergo mitosis after a certain point in development. Thus the capacity for mitosis is programmed into each cell type and is cellspecific. In addition, there are many molecules within the body that can influence cell division. Scientists are just beginning to learn about some of these and their possible roles in human health. For example, cancer occurs when the normal pattern of cell division within a tissue or organ is disrupted, and the cells begin to repeatedly undergo mitosis. Changes within the cell as well as external influences can play a part in disrupting the normal control of mitosis. Meiosis Meiosis is a special type of cell division that, in higher organisms, occurs only in cells of the ovaries or testes. Within these organs, cells destined to become eggs and sperm undergo meiosis in order to halve the amount of DNA that will be packaged into an egg or sperm. As with all the other cells in the body, these precursor cells are diploid; that is, they have the full complement of 46 chromosomes (23 pairs). Whereas mitosis creates two diploid cells from one existing diploid cell, meiosis results in eggs and sperm that have only one member of each pair of chromosome. Thus these cells, collectively known as germ cells, have only 23 chromosomes and are said to be haploid. At fertilization, the union of one egg and one sperm produces a diploid zygote (fertilized egg) with 46 chromosomes, half from the mother and half from the father. This zygote then begins the many mitotic divisions that will take it from a single cell to a complex, fully differentiated organism. The steps in meiosis are similar in many ways to those in mitosis, but there are several important differences. One obvious distinction is that, unlike mitosis which includes only one division of the nucleus and cytoplasm, meiosis is actually composed of two divisions, meiosis I and meiosis II. As in a mitotic division, DNA duplication occurs during interphase before meiosis so that the cells begin meiosis I with double the diploid amount of DNA (92 sister chromatids). MEIOSIS I PROPHASE. Prophase of meiosis I (prophase I) includes several significant features. As the chromosomes condense, chromosome pairing occurs. This is an important phenomenon that occurs only during

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PHASES OF MITOSIS

Interphase

Prophase

Anaphase

Metaphase

Telophase

Phases of mitosis. (Gale Research.)

meiosis. Higher organisms receive half of their genetic material from their mother and half from their father; that is, one set of chromosomes is maternal in origin and the other set is paternal. During interphase of a cell cycle, as well as during mitotic divisions, these various chromosomes from the maternal and paternal sets do not associate in pairs. Pairing only occurs in prophase of meiosis I. This pairing brings the same chromosome from the mother and father together in close association. This pairing is essential for the important step that happens next. A process of crossing over occurs between the maternal and paternal member of each chromosome pair. These crossover points, which can be seen through the microscope, are the places where maternal and paternal chromosomes have exchanged sections of genetic material in a process known as recombination. This essential step occurs during meiosis and serves to recombine the genetic material an individual received from their mother and father. That individual can then pass on new combinations of the genes from their parents to their offspring. This greatly increases the possible combinations of genetic traits and helps create diversity in the offspring. At the end of prophase, recombination is complete and the chromosome pairs, still attached at their cross-over points, move to the equatorial plate of the spindle that is beginning to form. In females the process of meiosis begins while the individual herself is still an embryo. The eggs within that early embryo complete prophase I up to a certain point

and then go into an arrested state. Eggs only begin to be released from that arrest many years later after a woman has reached puberty. Each month as one egg is ovulated (released from the ovary), meiosis resumes. MEIOSIS I METAPHASE. During metaphase I, the 23 chromosome pairs line up on the equatorial plate of the spindle with one member of each pair attached by a spindle fiber to one pole and the other member attached to the other pole. At this point the two members of a pair (each of which is itself composed of a pair of sister chromatids) are being held together only at the anchor points created by the cross-overs. When all chromosome pairs are properly aligned on the equatorial plate of the spindle, the anchors release and anaphase I begins. MEIOSIS I ANAPHASE. During this stage, the two members of a chromosome pair travel to opposite spindle poles. Unlike anaphase of mitosis, the centromeres do not separate. Thus, each chromosome at a pole is composed of a pair of sister chromatids attached at their centromeres. An important point to understand is that the pairs of chromosomes do not line up on the spindle with all of the individual’s mother’s chromosomes pointing toward one pole and the father’s pointing to the other. The alignment is random, so the function of meiosis I is similar to the shuffling of a deck of cards before dealing a hand. The half set of 23 chromosomes that collects at one spindle pole during anaphase will have chromosomes, and thus genetic information, from both the individual’s mother and father. This is another way in which

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KEY TERMS Amniocentesis—A procedure performed around the fourth month of pregnancy in which a needle is inserted through a woman’s abdomen into her uterus to draw out a small sample of the amniotic fluid from around the baby. Fetal cells in the fluid can be used to check the chromosome make-up of the baby. Chorionic villus sampling (CVS)—A procedure used for prenatal diagnosis at eight to 10 weeks gestation. Under ultrasound guidance a needle is inserted either through the mother’s vagina or abdominal wall and a sample of cells is collected from around the early embryo. These cells can be used to study the chromosomes of the fetus. Chromosomes—Structures in the nucleus of a cell that contain a thread of DNA containing the genetic information (genes). Humans have 46 chromosomes in 23 pairs. Cytoplasm—The portion of the cell that surrounds the nucleus. DNA—Deoxyribonucleic acid, the molecule that encodes the genes. Genetic counselor—An individual, usually with an advanced degree and board certification, who specializes in assessing genetic risk and informing patients about these risks and the options for dealing with them. Geneticist—A individual with an advanced degree (MS, MD, PhD) in genetics. Human geneticists and medical geneticists specialize in genetic issues pertaining to humans. Many geneticists are certified by specialty boards. Nucleus—The membrane-bound body within a cell that contains the chromosomes.

meiosis increases diversity in the offspring. When the Austrian monk Gregor Mendel put forth his principles of heredity in 1865, the process of meiosis had not been discovered. However, scientists later came to realize that the inheritance pattern Mendel described for specific traits such as color and shape in the garden pea, were due to the events of the first meiotic division. MEIOSIS I TELOPHASE. At the poles, a separate nuclear membrane forms around each haploid chromosome set and cytokinesis occurs, resulting into two daughter cells. In females, cytokinesis produces one large cell with the bulk of the cytoplasm, and one very small

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cell, the first polar body. The larger cell proceeds to meiosis II. In males, cytoplasmic division is equal and both cells enter meiosis II. Because meiosis I has reduced the diploid number of 46 chromosomes to 23, meiosis I is often referred to as the reduction division. MEIOSIS II INTERPHASE. Unlike in mitosis, there is no further DNA duplication and interphase is brief. MEIOSIS II PROPHASE. The nuclear membrane breaks down and a new spindle begins to form. MEIOSIS II METAPHASE. The haploid set of 23 chromosomes, each consisting of a pair of sister chromatids, moves to the equatorial plate of the spindle. Fibers from the two poles attach at each centromere pair and exert tension to align the chromosomes. MEIOSIS II ANAPHASE. The centromeres separate, and the sister chromatids are pulled to opposite poles. In this regard meiosis II is very similar to mitosis. In females, anaphase II is triggered by the sperm entering the recently ovulated egg. MEIOSIS II TELOPHASE. The chromosomes begin to de-condense, a nuclear membrane forms around each set, and cytokinesis occurs. In sperm, cytokinesis is again equal and the result is the production of four haploid spermatids, which will go through a process of maturation to become sperm. In males, there is no arrest of meiosis and the entire meiotic process takes about 60 days. In females, meiosis II produces a small second polar body containing one set of chromosomes and a small amount of cytoplasm. The majority of the cytoplasm together with the other set of chromosomes comprises the ovum (mature egg). Since a sperm has already penetrated the envelope of the egg, all that remains is for the haploid chromosome sets from the egg and sperm to merge to produce the diploid zygote.

Common diseases and disorders In humans, errors in chromosome division occur frequently during meiosis. Although these errors can take place either during the formation of the egg or the sperm, most errors occur during meiosis in the female for reasons that are not yet clearly understood. If mistakes occur during meiosis, eggs and sperm can be formed with either too many or too few chromosome. Fertilization then results in a fertilized egg than has less than or more than 46 chromosomes, a situation with major health consequences. For example, roughly 20% of all clinically recognized pregnancies result in miscarriage. Half of these are due to an extra or missing chromosome(s) in the developing embryo. Among live births, one in 150 infants has some type of chromosome abnormality. One of the more common is Down syndrome. Most cases of

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Resources BOOKS

Carlson, Bruce M. Human Embryology and Developmental Biology. 2nd ed. St. Louis: Mosby, 1999. Endow, Sharyn A., and David M. Glover, eds. Dynamics of Cell Division. New York: Oxford University Press, 1998. Jorde, Lynn B., et al. Medical Genetics. 2nd ed. New York: Mosby, 1999. Tortora, Gerard, and Sandra Reynolds Grabowski. Principles of Anatomy and Physiology. 9th ed. New York: HarperCollins, 2000. OTHER

The Biology Project. . Mitosis Animation. .

Sallie Boineau Freeman, PhD

Cell membranes Definition A cell membrane (also known as a plasma membrane) is a thin semifluid structure that separates the contents of a cell or organelle from its surroundings.

Description The environment inside of a cell is drastically different from that of its surroundings. Outside the cell, watersoluble ions and molecules create a harsh and toxic environment. From this, the cell must selectively absorb nutrients that are essential to its growth and function. It

must also excrete toxic byproducts of its metabolism. The cell membrane subsequently has two major functions: • It acts as a barrier, enclosing and protecting the components of a cell. • It acts as a gate, controlling the flow of molecules in and out of the cell. Higher-level cells known as eukaryotes contain specialized components, called organelles, that play dedicated roles in its growth and development. Each organelle is surrounded by a separate membrane whose function is similar to that of plasma membranes, but with a slightly different composition that enables the organelle to perform specific tasks. Structure Plasma and organelle membranes are composed primarily of lipids (fatty acids, sterols, or other water-insoluble molecules) and proteins (chains of amino acids). They differ in their proportion of lipids to proteins. For example, cell membranes of structures predominantly involved in energy production (e.g., the mitochondria) have a higher percentage of proteins, while membranes acting as insulators (e.g., the Schwann cell, which insulates some nerve fibers) have a higher proportion of lipids. LIPIDS. A membrane is actually two layers of lipids that form a shell around the cell. This lipid bilayer is composed primarily of phosopholipids (lipids containing one or more phosphate groups), each with a hydrophilic (water-soluble) “head” and a hydrophobic (water-insoluble) “tail.” The bilayer is the most stable configuration for phospholipids in a water environment, with the waterrepelling tails sequestered in the middle of two layers of water-soluble heads. Thus the membrane forms a stable yet flexible configuration with a certain amount of fluidity: individual phospholipids can move rapidly across the surface of the membrane, and part to allow molecules soluble in organic media (e.g., other lipids, dissolved gases, etc.) to enter the cell. PROTEINS. One type of protein can be loosely associated with the outside of the membrane; these are called extrinsic (or peripheral) proteins. Other proteins are tightly embedded in the membrane, and may extend from one side of the membrane to the other; these intrinsic or integral proteins are difficult to remove without destroying the membrane itself.

There are two general types of membrane proteins: transporters and receptors. Although some lipid-soluble molecules can permeate the cell membrane, many of the nutrients that a cell needs to function are too large to readily enter the cell. Transporters allow the cell to be

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Down syndrome are due to an error in meiosis that results in an extra chromosome (extra chromosome 21) being present in the fertilized egg. This condition is called trisomy 21. The individual who develops from this egg will have the clinical features of Down syndrome including mental retardation. Trisomy 21, as well as other similar chromosome errors, occurs more often in the pregnancies of women as they get older. For example, older women have a higher risk for miscarriages associated with chromosome errors. They also have a higher risk of giving birth to an infant with trisomy 21 Down syndrome or a similar chromosome abnormality. For this reason, women in their mid-30s or older are usually referred to a geneticist or genetic counselor to learn about prenatal testing options such as amniocentesis and chorionic villus sampling (CVS).

Cell membranes

KEY TERMS Active transport—Movement of a substance against its concentration gradient, from a low concentration to a high concentration. Eukaryote—An organism whose cells contain a true nucleus bound by a membrane. Extrinsic proteins—Proteins that are loosely associated with the outside of a plasma membrane; also known as peripheral proteins. Hydrophilic—Having an affinity for water or for absorbing water. Hydrophobic—Lacking an affinity for or resistant to water. Intrinsic proteins—Proteins that are tightly embedded in a plasma membrane, and might extend from one side of the membrane to the other. Ions—Atoms with positive or negative electric charge. Lipid—A molecule of composed fatty acids, sterols, or other water-insoluble molecules. Metabolism—The physical and chemical processes occurring within a cell that are necessary for life. Organelle—A specialized compartment of a cell that performs specific functions, such as a mitochondrion, lysosome, or ribosome. Passive transport—Movement of a substance across a membrane without the expenditure of metabolic energy. Permeation—Movement of a substance through a permeable membrane from a region of high concentration to a region of low concentration. Receptor—An extracellular structure capable of binding specific substances. Transporter—A transmembrane protein that transports different substances across the membrane.

selective in which molecules it allows into its cytoplasm. Examples of transporters are channels, which facilitate free movement of molecules across the membranes, and pumps, which require a certain amount of energy in order to transport molecules. Transport proteins also exist in organelle membranes; transport channels have been shown to exist in the organelles of yeast cells and are essential to cell viability. 454

A cell must be able to communicate with its surroundings if it is going to adapt to changing conditions. Receptors are transmembrane proteins that detect signals from the extracellular environment and translate those signals into a cellular response. An example of a signal is the compound epinephrine (also known as adrenaline). Receptors specific to epinephrine detect its presence in the environment and bind to the molecule. This binding induces a cascade of events in the cell, resulting in increased production of glucose used as energy.

Function The cell is constantly bombarded by ions and molecules of different type and size. While lipid-soluble molecules can pass readily through the membrane, water-soluble and larger particles require another mode of entry. The plasma membrane consequently has numerous means of importing or exporting substances: • Permeation occurs when a substance moves through the membrane from a region of high concentration to a region of low concentration, a process called diffusion. Only lipid-soluble molecules and some small particles (e.g., biologically important gases such as oxygen and nitrogen) can readily permeate the cell membrane. • Passive transport or facilitated diffusion occurs when water-soluble molecules and ions move through the membrane with the help of transporters (also called permeases). • Active transport occurs when a substance is moved against its concentration gradient, from a low concentration to a high concentration. This process requires a higher amount of energy expended by the cell.

Role in human health Thousands of bacteria, protozoa, and fungi cause human disease. These microbial cells also have membranes that are essential to their vitality. This vulnerability is a target of the human immune system and some types of drugs that fight microbial diseases. For example, the polymyxin class of antibiotics disrupts the cell membranes of bacteria such as Pseudomonas aeruginosa (causes respiratory tract, burn wound, ear, and eye infections). Compromising the cell membranes of such microorganisms effectively kills them.

Common diseases and disorders Some human diseases the result of faulty membrane transport systems. An example would be type II (adult onset) diabetes mellitus. Excess glucose in the bloodstream, caused by eating a meal rich in carbohydrates,

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Cystic fibrosis. a genetic disease, causes an abnormality in the mucus normally found in the lungs, resulting in increased bacterial infections and difficulty breathing. This is caused by a defective chloride and fluid transport that decreases the water content of the mucus and causes it to be excessively thick. Other disorders of membrane transport include Giddleman’s syndrome and Liddle’s syndrome, which can cause either hypo- or hypertension. Membrane disorders are also important causes of water and electrolyte disturbances, disorders of neural transmission, and many other syndromes. Hazardous substances such as tetrodoxin (produced by the puffer fish), dendrotoxin (venom of the black mamba snake), and cobrotoxin (another snake venom) affect the function of different ion channels in neurons, blocking signals from the nervous system to muscles. The result may be paralysis and in some cases, death. Resources BOOKS

Kadner, Robert J. “Cell Membrane: Structure and Function.” In Encyclopedia of Microbiology, edited by Joshua Lederberg. San Diego, CA: Academic Press, 2000, pp.710–21. Murray, P .R., K. S. Rosenthal, G. S. Kobayashi, and M. A. Pfaller. “Antibacterial Agents.” In Medical Microbiology. St. Louis, MO: Mosby, Inc., 1998, pp.160–67. Nelson, D. L., and M. M. Cox. “Biological Membranes and Transport.” In Lehninger Principles of Biochemistry. New York, NY: Worth Publishers, 2000, pp. 389–431. Nicklin, J., K. Graeme-Cook, T. Paget, and R. Killington. “Bacterial Structure and Function.” In Instant Notes in Microbiology. Oxford, UK: BIOS Scientific Publishers, Inc., 1999, pp.70–85. PERIODICALS

Schatz, G. “Protein Transport: The Door to Organelles.” Nature (October 1998): 439–40.

ORGANIZATIONS

American Society for Microbiology. 1752 N Street N.W., Washington, DC 20036. (202) 737-3600. .

Stephanie Islane Dionne

Central catheter maintenance Definition Central venous therapy involves placing a catheter into one of the patient’s central veins, with the tip situated in the superior vena cava. Central catheter maintenance includes those actions performed by a nurse or other health care professional to keep the catheter functioning properly and to minimize any negative effects on the patient.

Purpose There are a number of reasons for a patient to require a central catheter. Sometimes a person’s peripheral venous access is inadequate for the type or duration of intravenous therapy planned. In other cases, a central line allows central venous pressure to be measured and monitored.

Precautions Several factors should be considered when deciding which type of central catheter is appropriate for a patient. The duration of therapy and the types of medications ordered, the setting in which the client will receive intravenous therapy, and the client’s activity level and lifestyle will all help to determine the catheter the patient has inserted.

Description There are several types of central catheters, which are divided into two categories: nontunnelled and tunnelled. They are made from a variety of materials: Teflon, polyurethane, silicone, polyvinyl chloride, and a silicone/elastomer blend called silastic. Each type has advantages and disadvantages, and each type requires specific maintenance. Nontunnelled catheters are used primarily for shortterm intravenous therapy, and when quick venous access is required to administer life-saving drugs or fluids. They may be inserted at the client’s bedside by the physician. One type of nontunnelled catheter is the peripherally

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is usually taken up by myocytes (muscle cells) and adipocytes (fat cells). The glucose transporter GluT4 is normally present in the cell membrane in small amounts. The presence of insulin (a hormone secreted by the pancreas in response to high glucose levels) causes more GluT4 transporters to be exposed, increasing uptake of glucose into the cell. In type II diabetes there is resistance to the metabolic effects of insulin, either at the cell membrane or in post-receptor signaling systems. This means that little glucose can be taken up by myocytes and adipocytes, and high blood glucose levels are the result.

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inserted central catheter (PICC). Specially trained nurses can insert the PICC, which is suitable for the administration of any intravenous therapy in any setting. Nontunnelled central catheters are easily inserted, costeffective, and easily removed. On the other hand, they can easily be dislodged by the patient’s movements, require sterile dressing changes, and must be flushed by heparin when not used continually. Tunnelled central venous catheters include the Broviac, Hickman, and Groshong. These are made from either polyurethane or silicone and can be distinguished from each other by the inside gauge of lumen and the type of catheter tips. Each of these catheters has their advantages and disadvantages. • Broviac: This is a smaller-bore catheter that is anchored to the chest wall so a patient’s movement is not restricted. Its small lumen makes it suitable for children and the elderly. Its disadvantages are that it requires surgical insertion, tears and kinks easily, must be removed by a physician, and is difficult to repair. Because it has a smaller gauge, it is not suitable for many patients. It also requires routine flushing with saline and heparin to maintain its patency. • Hickman: This catheter is also anchored to the chest wall, and it may have multiple lumens allowing multiple uses. However, it also requires surgical insertion, is difficult to repair, and the ports must be capped and clean at all times. Routine flushing is required for the Hickman with saline and heparin. • Groshong: The Groshong has some of the same advantages as the Broviac and Hickman. In addition, because of its valve at the tip, the need for daily Heparin flushes is eliminated. Instead the line can be flushed weekly with 0.9% saline solution. The Groshong is also easy to repair, and generally requires less time and cost for maintenance than the Broviac or Hickman. It too has disadvantages, however. The Groshong tears and kinks easily and must be surgically inserted and removed by a physician. In addition to flushing, all central catheters require routine sterile dressing changes. The frequency of with which the dressing must be changed depends upon whether the patient is hospitalized or in the home environment. Another type of central catheter is an implanted port, which consists of a portal body, a septum, a reservoir, and a catheter. The port is inserted surgically into a subcutaneous pocket in the patient’s trunk, and the catheter is then threaded into the central vascular system. The septum consists of a self-sealing silicone, which is accessed by the nurse using a special noncoring needle. One of its primary advantages is that is does not require frequent flushing when not in use, and since it is implanted 456

KEY TERMS Central catheter—A catheter placed into a central vein for the purpose of administering drugs, fluids, nutrients, and blood products. It may also be used to withdraw blood for laboratory testing. Noncoring needle—Also known as a Huber needle, this special type of needle has a hole on its side rather than at the tip, and may be either straight or angled. Its special shape slices rather than punctures in the septum, reducing the chance of leakage through the opening. Patency—Degree of openness; once inserted, catheters can become clogged unless they are flushed with heparin and/or saline to keep them clear. Urokinase—A kidney enzyme found in urine used to dissolve blood clots.

beneath the skin, it aids in maintaining the patient’s body image.

Preparation The patient should be told why a central catheter is being placed, what care it may require afterwards, and, if possible, should consent to the procedure before it is performed. Tunnelled catheters are usually placed surgically by the physician. Prior to the procedure, a sedative is often ordered to relax the patient.

Aftercare After the catheter is placed, the placement must be confirmed by x ray prior to use.

Complications The two primary complications with central catheters are infection and occlusion. Infections can be decreased with strict sterile technique when changing dressings, and monitoring the patient closely for any signs of infection, including fever, redness or soreness at the site of insertion, and drainage from the insertion site. Occlusions are the most common noninfectious complication seen with central venous access devices. Thrombotic, or blood clot, occlusions can be prevented with regular flushing using the proper technique. A positive-pressure technique prevents blood reflux after the

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Mechanical occlusions can also occur if the catheter develops a kink, or if the suture holding the catheter in place is too tight. In addition, if the catheter was positioned with the tip touching the vessel wall, a partial occlusion could result that would allow infusion, but not the aspiration of blood. These types of occlusions may require the replacement of the catheter.

Results Ideally the central catheter will stay in place for as long as it is needed without complications developing. After it is no longer needed, the catheter is removed.

Health care team roles With the exception of PICC lines, most central catheters are inserted by a physician. These lines are normally maintained and cared for by nurses. Resources BOOKS

Ignatavicius, Donna D., et al. Medical-Surgical Nursing across the Health Care Continuum. Philadelphia: W.B. Saunders Company, 1999. PERIODICALS

cells other than nerve cells. The nerve cell consists of a nucleus in a cell body, dendrites, and axons. The CNS is heavily guarded with protective features, however, this does not make it immune to disease and disorder. The CNS is cushioned with cerebrospinal fluid (CFS), protected by three layers of meninges, and protected from the body by the blood-brain barrier. The blood-brain barrier prevents harmful substances and disease-causing organisms from contaminating the bloodstream entering the CNS. The skull (cranium) encloses the brain. Three main areas of the brain, the cerebrum, cerebellum, and brainstem, contain myelinated nerve fibers and white matter, in contrast to the cortex of the brain, the layer of gray matter. The cerebrum, the largest part of the brain containing the left and right hemispheres, controls conscious activities like motor functions. The cerebellum, located above the brainstem, communicates with other regions of the brain and spinal cord to control balance and coordination. The brainstem, the lowest part of the brain extending to the spinal cord, controls unconscious activities necessary for survival like breathing and blood pressure. The spinal cord is protected by the vertebral column from the cervical area to the sacrum. The spinal cord nerves relay sensory information to the brain and motor information to the body.

Function

Andris, Deborah A., and Elizabeth A. Krzywda. “Central Venous Catheter Occlusion: Successful Management Strategies.” MedSurg Nursing 8 (August 1999): 229. “Comparing Central Venous Catheters.” Nursing 31 (February 2001): 17.

Deanna M. Swartout-Corbeil, R.N.

Central nervous system Definition The central nervous system (CNS) consists of the brain and spinal cord.

Description Comprised of the brain and spinal cord, the CNS is central to the body as opposed to peripheral. It is responsible for unconscious and conscious body functions as well as intellectual functions that allow humans to think. The neuron is the basic nerve cell of the nervous system, however, the nervous system contains many types of

The central nervous system (CNS) is a processing center that integrates sensory and motor activities via the brain and spinal cord. Nerves are like an electrical wire with an insulating sheath, called myelin, that facilitates the smooth, high-speed transmission of messages. Information in the nervous system is carried by brief electrical impulses that are conducted away from the body of the nerve cell along the axons. When impulses reach the tips of axons, information is transmitted to the next nerve cell in line, or to a muscle or organ. At the point of contact, or synapse, the information is carried across the gap between cells by neurotransmitters. The CNS has two-way communication. Nerve fibers either relay messages to the brain to communicate sensory stimuli, or they relay messages away from the brain to the body’s tissues and organs. It is through the spinal cord that messages are sent back and forth to the brain. Spinal nerves in the spinal cord connect the message relay system to rest of the body

Role in human health Many health care providers, neurologists, neurosurgeons, physiatrists, neuropsychologists, nurses, occupational therapists, speech language pathologists, physical

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flushing. Some thrombotic occlusions may require flushing with an agent like urokinase.

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Subarachnoid space

Arachnoid

Pia mater Cerebrum

Choroid plexuses of lateral and third ventricles

Dura mater Aqueduct of Sylvius

Intraventricular foramen Cerebellum

Cisterna magna Pons

Spinal cord

Major features of the brain and spinal cord, which comprise the central nervous system (CNS). (Delmar Publishers, Inc. Reproduced by permission.)

therapists, and vocational rehabilitation counselors play a role on the health care team and share in the responsibility of the neurologic patient. A combination of methods for assessing patients with neurologic diseases and disorders enables health care professionals to make informed treatment recommendations. These include neurologic and physical examination, laboratory tests such as lumbar puncture, brain-imaging scans such as MRI, neuropsychological testing, and nuclear medicine tests. Treating neurologic diseases and disorders requires active patient participation along with education and support from health care professionals. While patient education may be time-consuming, it is extremely important to the process of maintaining health and preventing disease.

Common diseases and disorders There are hundreds of disabling neurological diseases and disorders that affect every age, race, and eth458

nicity. A few examples include developmental disorders (cerebral palsy), degenerative diseases (Parkinson’s and Alzheimer’s disease), metabolic diseases (Tay-Sachs disease), cerebrovascular diseases (stroke), autoimmune diseases (multiple sclerosis), and tumors (glioblastoma). Alzheimer’s disease Alzheimer’s disease (AD), a progressive, neurodegenerative disease, is the most common cause of dementia in later life. The course of the disease varies from person to person. Although the cause of AD is not yet known, researchers have found a familial tendency for AD. They have also implicated several possibilities including genetics, environmental factors, and biochemical changes in the brain caused by low levels of certain neurotransmitters. AD usually begins after age 65, however, it may have an early onset as early as age 40.

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• sudden difficulty seeing in one or both eyes • sudden trouble walking • sudden dizziness, loss of balance or coordination • sudden severe headache • paralysis, pain

• changes in behavior and personality

Risk factors for stroke are either changeable or not. For example, a person cannot change their age or family history, but they can change behaviors, like smoking, that put them at risk for a stroke. Risk factors for stroke include:

• disorientation, wandering, sleep disturbance

• high blood pressure

• agitation, anxiety, depression

• heart disease

There is no specific test to confirm a diagnosis of AD. A combination of tools including brain imaging technologies, patient and family history, physical and neurological examination, and neuropsychological testing are utilized to definitively diagnose AD. There is no cure for AD and no clinically proven way to slow the progression of the disease. For some patients, medication may alleviate some of the symptoms. Treatments are intended to make the patient more comfortable.

• diabetes

• memory loss, confusion, loss of concentration • difficulty recognizing family and friends • poor judgment, indifference

Stroke Stroke, also called cerebral vascular accident (CVA), occurs when the blood flow to part of the brain is disrupted. There are primarily two categories of stroke, ischemic and hemorrhagic. The most frequent cause of stroke is a blockage (ischemic) of a blood vessel in the brain. The blockage can have several causes but all with the same result, brain cell damage or death. Brain cells cannot survive without a blood supply of oxygen and nutrients. Blockage of blood flow in the brain can be caused by a clot in a blood vessel (thrombosis) of the brain, the movement of a clot from another part of the body (embolism) to the brain, or a severe narrowing of an artery in the brain (stenosis). In a hemorrhagic stroke, a blood vessel in the brain bursts, bleeding into the brain (intracerebral hemorrhage) or into the spaces surrounding the brain. SYMPTOMS. The signs and symptoms of stroke

depend on the areas of the brain affected and the functions they control. The right cerebral hemisphere controls the left side of the body and the left cerebral hemisphere controls the right side of the body. The symptoms of stroke may be: • sudden numbness or weakness, especially on one side of the body • sudden confusion, difficulty speaking, or understanding speech

• smoking • heavy alcohol consumption • drug abuse • high blood cholesterol levels • family history of stroke or TIA • age over 55 According to the National Center for Health Statistics, stroke is the third leading cause of death in the United States. In order to improve this statistic, patients need prompt interventions. The public education campaign, “Know Stroke: Know the Signs. Act in Time,” promoted by the National Institute of Neurological Disorders and Stroke (NINDS) teaches people how to recognize the signs and symptoms of stroke and the importance of prompt medical treatment to improve recovery. Tissue plasminogen activator (t-PA), the first Food and Drug Administration (FDA) approved acute ischemic stroke treatment, needs to be given within a three-hour window of the onset of symptoms to dissolve the clot. Stroke is diagnosed by a neurological examination, blood tests, brain imaging scans, Doppler ultrasound, or arteriography. Multiple sclerosis Multiple sclerosis (MS) is a common neurological disease that occurs mainly in young adults. The course of the disease varies from person to person and is categorized by type. Relapsing-remitting MS (RRMS) has a course of acute attacks with full or partial recovery during remissions. Secondary progressive MS (SPMS) is initially relapsing-remitting and then becomes progressive. Primary progressive MS (PPMS) has a progressive course from the beginning of the disease with no remissions. Progressive-relapsing MS (PRMS) has a progres-

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SYMPTOMS. The severity and progression of symptoms vary from person to person. Some of the early symptoms of AD, such as forgetfulness or loss of concentration, can easily be overlooked because they resemble signs of aging or could result from fatigue, depression, or the use of certain medications. Symptoms of AD include:

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technologies such as MRI, CSF analysis, evoked potentials (EVP), medical history, and clinical examination.

KEY TERMS Antigen—A substance that stimulates the immune system to produce antibodies. Autoimmune—The immune system sees self as a foreign antigen and attacks a part of the body.

SYMPTOMS. The symptoms of MS are unpredictable, can vary greatly from person to person, and come and go. The neurological symptoms of MS are the result of demyelination. Symptoms include:

• blurred, double vision, and blind spots

Cerebrospinal fluid—Fluid surrounding and cushioning the brain and spinal cord.

• numbness, tingling, and paresthesias (pins and needles)

Cognitive—Information processing functions carried out by the brain that include comprehension, memory, attention, planning, problem-solving, etc.

• difficulties with memory loss, concentration, and attention

• fatigue, dizziness, and vertigo

Dura mater—The outermost layer of meninges.

• difficulty with coordination, balance, and gait

Exacerbation—The appearance of new symptoms or the aggravation of old symptoms.

• muscle and nerve pain, muscle weakness, and tremors

Gene—Basic units of heredity in every cell that tell the cell how to put together different proteins.

There are many conventional and alternative treatment therapies to alleviate the symptoms of MS, but there is no cure. However, four medications have been shown to slow down disease progression. The FDA approved Interferon beta 1b (Betaseron) in 1993, Interferon beta 1a (Avonex) in 1996, and glatiramer acetate (Copaxone) in 1996 for the treatment of RRMS. They were clinically shown to decrease the frequency and severity or attacks by approximately 30%. Mitoxantrone (Novantrone), a chemotherapy agent that suppresses immune function, was FDA approved in 2000 for the treatment of worsening RRMS and SPMS.

Interferon—A naturally occuring immune system protein. Lumbar puncture—A diagnostic procedure that uses a hollow needle to penetrate the spinal canal between the vertebrae to remove cerebrospinal fluid for analysis. Meninges—Three layers of protective connective tissue covering the brain and spinal consisting of the pia mater, arachnoid, and dura mater. Myelin—A protective coating made of fat and protein that insulates the nerve and enhances efficient nerve fiber conduction. Neurotransmitter—A chemical that transmits a nerve impulse at the synapse.

sive course from the beginning with acute relapses, with or without full recovery. MS is believed to be an autoimmune disease, where the immune system targets the myelin in the central nervous system. MS is the most common demyelinating disease. During an attack (exacerbation), inflammation occurs in the white matter of the central nervous system. This process is followed by destruction of myelin causing areas called plaques. Not only is the myelin damaged, but the attack may also damage or sever the nerve fibers underneath the myelin. The nerve cannot conduct or send a signal properly without the myelin sheath. MS can be difficult to diagnose because there are other diseases with similar symptoms, and there is no specific test to confirm the diagnosis. A process of elimination may be done along with a combination of imaging

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• bladder and bowel problems

Research Research in neuroscience and the development of new research techniques and technologies offer hope to the millions of patients and families affected by neurological diseases and disorders. Research into new treatments doesn’t solve the problem, therefore, scientists are researching areas such as neurogenetics to discover how to prevent certain disorders. New treatment options and the possibility of cures can bring a sense of optimism to patients. However, the research process takes years before a treatment is available to the public. Only controlled clinical trials with human participants can determine if a treatment is safe and effective for patients. Resources BOOKS

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision: DSM-IV-TR. Washington, DC: American Psychiatric Association, 2000. Burks, J. S., and K. P. Johnson. Multiple Sclerosis: Diagnosis, Medical Management and Rehabilitation. New York: Demos, 2000.

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doxical effect in attention deficit hyperactivity disorder (ADHD).

PERIODICALS

The anerexiants, benzphetamine (Didrex), diethylpropion (Tenuate), phendimetrazine (Bontril, Plegine), phentermine (Fastin, Ionamine), and sibutramine (Meridia) are CNS stimulants used for appetite reduction in severe obesity. Although these drugs are structurally similar to amphetamine, they cause less sensation of stimulation, and are less suited for use in conditions characterized by lack of adrenergic stimulation.

“Recommendations for the Establishment of Stroke Centers: A Consensus Statement from the Brain Attack Coalition.” Journal of American Medical Association (June 21, 2000): 3102-3109. Stroke Council of the American Heart Association. “Primary Prevention of Ischemic Stroke.” Circulation (Jan. 2, 2001): 163-182. ORGANIZATIONS

Alzheimer’s Association. 919 N. Michigan Ave., Ste. 1100, Chicago IL 60611-1676. (800) 272-3900. . Alzheimer’s Disease Education and Referral Center. PO Box 8250. Silver Spring, MD 20907-8250. (800) 438-4380. . American Academy of Neurology. 1080 Montreal Ave., St. Paul, MN 55116. (651) 695-1940. American Neurological Association. 5841 Cedar Lake Rd., Ste. 204, Minneapolis, MN 55416. . American Stroke Association. . Multiple Sclerosis Association of America. 706 Haddonfield Rd. Cherry Hill, NJ 08002. (800) 532-7667. . National Institute of Neurological Disorders and Stroke. National Institutes of Health. Bethesda, MD 20892. . National Multiple Sclerosis Society. 733 Third Ave., 6th Flr., New York NY 10017-3288. (800) 344-4867. .

Deborah Eileen Parker, R.N.

Central nervous system stimulants Definition Central nervous system (CNS) stimulants are medicines that speed up physical and mental processes.

Purpose Central nervous system stimulants are used to treat conditions characterized by lack of adrenergic stimulation, including narcolepsy and neonatal apnea. Additionally, methylphenidate (Ritalin) and dextroamphetamine sulfate (Dexedrine) are used for their para-

Phenylpropanolamine and ephedrine have been used both as diet aids and as vasoconstrictors.

Description The majority of CNS stimulants are chemically similar to the neurohormone norepinethrine, and simulate the traditional “fight or flight” syndrome associated with sympathetic nervous system arousal. Caffeine is more closely related to the xanthines, such as theophylline. A small number of additional members of the CNS stimulant class do not fall into specific chemical groups.

Precautions Amphetamines have a high potential for abuse. They should be used in weight reduction programs only when alternative therapies have been ineffective. Administration for prolonged periods may lead to drug dependence. These drugs are classified as schedule II under federal drug control regulations. The amphetamines and their cogeners are contraindicated in advanced arteriosclerosis, symptomatic cardiovascular disease, and moderate to severe hypertension and hyperthyroidism. They should not be used to treat patients with hypersensitivity or idiosyncrasy to the sympathomimetic amines, or with glaucoma, a history of agitated states, a history of drug abuse, or during the 14 days following administration of monoamine oxidase (MAO) inhibitors. Methylphenidate may lower the seizure threshold. Benzphetamine is category X during pregnancy. Diethylpropion is category B. Other anorexiants have not been rated; however their use during pregnancy does not appear to be advisable. Safety for use of anorexiants has not been evaluated. Amphetamines are all category C during pregnancy. Breast feeding while receiving amphetamines is not recommended because the infant may experience withdrawal symptoms. There have been reports that when used in children, methylphenidate and amphetamines may retard growth.

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Caplan, L.R. Caplan’s Stroke: A Clinical Approach. Boston: Butterworth-Heinenmann, 2000.

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KEY TERMS Agranulocytosis—An acute febrile condition marked by severe depression of the granulocyteproducing bone marrow, and by prostration, chills, swollen neck, and sore throat sometimes with local ulceration. Anorexiant—A drug that suppresses appetite. Anxiety—Worry or tension in response to real or imagined stress, danger, or dreaded situations. Physical reactions, such as fast pulse, sweating, trembling, fatigue, and weakness may accompany anxiety. Attention-deficit hyperactivity disorder (ADHD)—A condition in which a person (usually a child) has an unusually high activity level and a short attention span. People with the disorder may act impulsively and may have learning and behavioral problems. Central nervous system—The brain and spinal cord. Depression—A mental condition in which people feel extremely sad and lose interest in life. People with depression may also have sleep problems and loss of appetite, and may have trouble in concentrating and carrying out everyday activities. Leucopenia—A condition in which the number of leukocytes circulating in the blood is abnormally low and which is most commonly due to a decreased production of new cells in conjunction with various infectious diseases, as a reaction to various drugs or other chemicals. Pregnancy category—A system of classifying drugs according to their established risks for use during pregnancy. Category A: Controlled human studies have demonstrated no fetal risk. Category B: Animal studies indicate no fetal risk, but no human studies, or adverse effects in animals, but not in well-controlled human studies. Category C: No adequate human or animal studies, or adverse fetal effects in animal studies, but no available human data. Category D: Evidence of fetal risk, but benefits outweigh risks. Category X: Evidence of fetal risk. Risks outweigh any benefits. Withdrawal symptoms—A group of physical or mental symptoms that may occur when a person suddenly stops using a drug on which he or she has become dependent.

Although these reports have been questioned, it may be suggested that the drugs not be administered outside of school hours (because most children have behavior problems in school), in order to permit full stature to be attained. The most common adverse effects of CNS stimulants are associated with their primary action. Typical responses include overstimulation, dizziness, restlessness, and similar reactions. Rarely, hematologic reactions, including leukopenia, agranulocytosis, and bone marrow depression have been reported. Lowering of the seizure threshold has been noted with most drugs in this class. Withdrawal syndrome Abrupt discontinuation following prolonged high dosage results in extreme fatigue, mental depression, and changes on the sleep EEG. This response is most evident with amphetamines, but may be observed with all CNS stimulants taken over a prolonged period of time. Resources PERIODICALS

“Are Our Children Overmedicated?” Parade, (October 12, 1997): 4. “Attention Deficit Hyperactivity Disorder: Not Just for Kids.” Mayo Clinic Health Letter, 13 (September 1995): 6. “Attention Deficit Hyperactivity Disorder: There is No Easy Answer on whether to Medicate or Not.” British Medical Journal, 315 (October 11, 1997): 894. “The Run on Ritalin: Attention Deficit Disorder and Stimulant Treatment in the 1990s.” The Hastings Center Report, 26 (March-April 1996): 12. ORGANIZATIONS

Children and Adults with Attention Deficit Disorders (CH.A.D.D.). 499 N.W. 70th Avenue, Suite 109, Plantation, FL 33317. (305) 587-3700. OTHER

Attention deficit hyperactivity disorder. Pamphlet. National Institute of Mental Health, 1994. Facts about childhood hyperactivity. Pamphlet. National Institute of Child Health and Human Development, 1990.

Nancy Ross-Flanigan

Cerebral palsy Definition Cerebral palsy (CP) is the term used for a group of nonprogressive disorders of movement and posture

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Description Voluntary movement (walking, grasping, chewing, etc.) is primarily accomplished using muscles that are attached to bones, known as the skeletal muscles. Control of the skeletal muscles originates in the cerebral cortex, the largest portion of the brain. Palsy means paralysis, but may also be used to describe uncontrolled muscle movement. Therefore, cerebral palsy encompasses any disorder of abnormal movement and paralysis caused by abnormal function of the cerebral cortex. However, CP does not include conditions due to progressive disease or degeneration of the brain. For this reason, CP is also referred to as static (nonprogressive) encephalopathy (disease of the brain). Also excluded from the definition of CP are any disorders of muscle control that arise in the muscles themselves or in the peripheral nervous system (nerves outside the brain and spinal cord). CP is not a specific diagnosis but is more accurately considered a description of a broad but defined group of neurological and physical problems. The symptoms of CP and their severity are quite variable. Persons with CP may have only minor difficulty with fine motor skills, such as grasping and manipulating items with their hands. A severe form of CP could involve significant muscle problems in all four limbs, mental retardation, seizures, and difficulties with vision, speech, and hearing. Muscles that receive defective messages from the brain may be constantly contracted and tight (spastic), and the person with CP may exhibit involuntary writhing movements (athetosis) or have difficulty with voluntary movement (dyskinesia). There can also be a lack of balance and coordination with unsteady movements (ataxia). A combination of any of these problems may also occur. Spastic CP and mixed CP constitute the majority of cases. Effects on the muscles can range from mild weakness or partial paralysis (paresis), to complete loss of voluntary control of a muscle or group of muscles (plegia). CP is also designated by the number of limbs affected. For instance, affected muscles in one limb is called monoplegia, affected muscles in both arms or both legs is called diplegia, affected muscles in both limbs on one side of the body is called hemiplegia, and affected

muscles in all four limbs is called quadriplegia. Muscles of the trunk, neck, and head may be affected as well. Approximately 500,000 children and adults in the United States have CP, and it is newly diagnosed in about 6,000 infants and young children each year. The incidence of CP has changed little since the 1960s and 1970s. Ironically, advances in medicine have decreased the incidence from some causes—Rh disease for example, but have increased its incidence from other causes—notably, prematurity and multiple pregnancies. (Medical advances have made it possible for more babies born prematurely or in multiple but underweight births to survive, thus allowing more time for CP to be recognized when it does occur.) No particular ethnic groups seem to be at higher risk for CP. However, people of disadvantaged background are at higher risk due to poorer access to adequate prenatal care and advanced medical services.

Causes and symptoms CP can be caused by a number of different mechanisms at various times—from several weeks after conception, through birth, and into early childhood. For many years it was accepted that most cases of CP were due to brain injuries received during a traumatic birth, known as birth asphyxia. However, extensive research in 1980s showed that only 5–10% of CP could be attributed to birth trauma. Other possible causes include abnormal development of the brain, prenatal factors that directly or indirectly damage neurons in the developing brain, premature birth, and brain injuries that occur in the first few years of life. Because CP has many causes, a discussion of the genetics of CP is complicated. A number of hereditary or genetic syndromes have signs and symptoms similar to CP, but usually also have problems not typical of CP. Put another way, some hereditary conditions mimic CP. Isolated CP, meaning CP that is not a part of some other syndrome or disorder, is usually not inherited. It might be possible to group the causes of CP into those that are genetic and those that are nongenetic, but most would fall somewhere in between. Grouping causes into those that occur during pregnancy (prenatal), those that happen around the time of birth (perinatal), and those that occur after birth (postnatal), is preferable. CP related to premature birth and multiple pregnancies (twins, triplets, etc.) is somewhat different and considered separately. Prenatal causes Although much has been learned about human embryology in the latter part of the twentieth century, a

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caused by abnormal development of, or damage to, motor control centers of the brain or, in some cases, hypoxemia (insufficient oxygen in the blood) during the birth process. CP is caused by events before, during, or after birth. The abnormalities of muscle control that define CP are often accompanied by other neurological and physical abnormalities.

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great deal remains unknown. Studying prenatal human development is difficult because the embryo and fetus develop in a closed environment, namely the mother’s uterus. However, the relatively recent development of a number of prenatal tests provides a window on the process. Add to that more accurate and complete evaluations of newborns, especially those with problems, and a clearer picture of what can go wrong before birth is now possible. The complicated process of brain development before birth is susceptible to many chance errors that can result in abnormalities of varying degrees. Some of these errors will result in structural anomalies of the brain, while others may cause undetectable, but significant, abnormalities among connections (sometimes referred to as wiring) in the cerebral cortex. An abnormality in structure or wiring is sometimes hereditary, but is most often due to chance, or a cause unknown at this time. Whether and how much genetics played a role in a particular brain abnormality depends to some degree on the type of anomaly and the form of CP it causes. Just as a stroke can cause neurologic damage in an adult, so too can this type of event occur in the fetus. A burst blood vessel in the brain followed by uncontrolled bleeding (coagulopathy), known as intracerebral hemorrhage, could cause a fetal stroke. Alternatively, a cerebral blood vessel could be obstructed by a clot (embolism). Infants who later develop CP, along with their mothers, are more likely than other mother-infant pairs to test positive for factors that put them at increased risk for bleeding episodes or blood clots. Some coagulation disorders are strictly hereditary, but most have a more complicated basis. A teratogen is any substance to which a pregnant woman is exposed that has the potential to harm an embryo or fetus. Links between a drug or other chemical exposure during pregnancy and a risk for CP are difficult to prove. However, any substance used by the pregnant woman that might affect fetal brain development, directly or indirectly, could increase the risk for CP. Furthermore, any substance used by the mother that increases the risk for premature delivery and low birth weight—such as alcohol, tobacco, or cocaine, among others—might indirectly increase the risk for CP. The fetus receives all nutrients and oxygen from blood that circulates through the placenta. Therefore, anything that interferes with normal placental function might adversely affect development of the fetus, including the brain, or might increase the risk for premature delivery. Structural abnormalities of the placenta, premature detachment of the placenta from the uterine wall 464

(abruption), and placental infections (chorioamnionitis), are thought to pose some risk for CP. Certain conditions in the mother during pregnancy might pose a risk to fetal development leading to CP. Women with autoimmune antithyroid or antiphospholipid (APA) antibodies are at slightly increased risk for CP in their children. A potentially important clue points toward high levels of cytokines in the maternal and fetal circulation as a possible risk for CP. Cytokines are proteins associated with inflammation, such as from infection or autoimmune disorders, and they may be toxic to neurons in the fetal brain. More research is needed to determine the exact relationship, if any, between high levels of cytokines during pregnancy and CP. A woman with high cytokine levels has some risk of developing the same complications in more than one pregnancy, slightly increasing the risk for more than one child with CP. Serious physical trauma to the mother during pregnancy could result in direct trauma to the fetus as well. Injuries to the mother can compromise the availability of nutrients and oxygen to the developing fetal brain. Perinatal causes Birth asphyxia significant enough to result in CP is now uncommon in developed countries. Tight nuchal cord (umbilical cord around the baby’s neck) and prolapsed cord (the cord presents through the birth canal before the baby and becomes kinked or buckled) are possible causes of birth asphyxia, as are bleeding and other complications associated with placental abruption and placenta previa (placenta lying over the cervix exit). Infection in a mother is sometimes not passed to her fetus through the placenta but, rather, transmitted to the baby during delivery. Many of these infections are sexually transmitted diseases, such as gonorrhea, syphilis, and even AIDS. Any such infection that results in serious illness in the newborn has the potential to produce some neurological damage. Postnatal causes The remaining 15% of CP is due to neurologic injury sustained after birth. CP with a postnatal cause is sometimes referred to as acquired CP, but this is only accurate for those cases caused by infection or trauma. Incompatibility between the Rh blood types of mother and child (mother Rh negative, baby Rh positive) can result in severe anemia in the baby (erythroblastosis fetalis). This occurs because the mother’s blood develops antibodies to the infant’s blood and attempts to destroy what it perceives as the “foreign” blood. This may lead to other complications, including severe jaundice, which

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A physical therapist works with a child with cerebral palsy. (Lois Silver/Custom Medical Stock Photo. Reproduced by permission.)

can cause CP. Rh disease in the newborn is now rare in developed countries due to routine screening of maternal blood type and treatment of pregnancies at risk. The routine, effective treatment of jaundice due to other causes has also made it an infrequent cause of CP in developed countries. Rh blood type incompatibility poses a risk for recurrence of Rh disease with each pregnancy if treatment is not provided. Serious infections that affect the brain directly, such as meningitis and encephalitis, may cause irreversible damage to the brain, leading to CP. A seizure disorder early in life may cause CP, or may be the product of a hidden problem that causes CP in addition to seizures. Unexplained (idiopathic) seizures are hereditary in only a small percentage of cases. Although rare in infants born healthy at or near term, intracerebral hemorrhage and brain embolism, like fetal stroke, are sometimes genetic. Physical trauma resulting in brain injury to an infant or child, such as physical abuse, accidents causing impact to the head, or near drowning/suffocation, might cause CP. Likewise, ingestion of a toxic substance such as lead, mercury, poisons, or certain chemicals could cause neurological damage. Accidental overdose of cer-

tain medications might also cause similar damage to the central nervous system. Prematurity and multiple pregnancy Advances since the 1980s in the medical care of premature infants have dramatically increased the rate of survival of these fragile newborns. However, as gestational age at delivery and birth weight of a baby decrease, the risk for CP dramatically increases. A term pregnancy is delivered between 37 and 41 weeks of gestation. The risk for CP in a preterm infant (32–37 weeks) is increased about five-fold over the risk for an infant born at term. Survivors of extremely preterm births (less than 28 weeks) face as much as a 50-fold increase in risk. About 50% of all cases of CP being diagnosed are in children who were born prematurely. Two factors are involved in the risk for CP associated with prematurity. First, premature babies are at higher risk for various CP-associated medical complications, such as intracerebral hemorrhage, infection, and difficulty in breathing, to name a few. Second, the onset of premature labor may be induced, in part, by complications that have already caused neurologic damage in the fetus.

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A combination of both factors almost certainly plays a role in some cases of CP. The tendency toward premature delivery tends to run in families, but the genetic mechanisms are far from clearly understood. An increase in multiple pregnancies, especially in the United States, is attributed to the increased use of fertility drugs. As the number of fetuses in a pregnancy increases, the risks for abnormal development and premature delivery also increase. Children from twin pregnancies have four times the risk of developing CP as children from single pregnancies. This is because more twin pregnancies are delivered prematurely or, in some cases, overcrowding occurs in the uterus causing pressure on one infant from contact with the other. The risk for CP in a child of triplets is up to 18 times greater. Furthermore, evidence suggests that a baby from a pregnancy in which its twin died before birth is at increased risk for CP. By definition, the defect in cerebral function causing CP is nonprogressive. However, the symptoms of CP often change over time. Most of the symptoms of CP relate in some way to the aberrant control of muscles. To review, CP is categorized first by the type of movement or postural disturbance(s) that are present, then by a description of which limbs are affected, and finally by the severity of motor impairment. For example, spastic diplegia refers to continuously tight muscles that have no voluntary control in both legs, while athetoid quadraparesis describes uncontrolled writhing movements and muscle weakness in all four limbs. These three-part descriptions are helpful in providing a general picture, but cannot give a complete description of any one person with CP. In addition, the various presentations of CP do not occur with equal frequency. For example, spastic diplegia is seen in more individuals than is athetoid quadraparesis. CP can also be loosely categorized as mild, moderate, or severe, but these are very subjective terms with no firm boundaries between them. A muscle that is tensed and contracted is hypertonic, while excessively loose muscles are hypotonic. Spastic, hypertonic muscles can cause serious orthopedic problems, including scoliosis (spine curvature), hip dislocation, or contractures. A contracture is shortening of a muscle, usually affecting muscles involved in flexion or extension of a joint, and are aided sometimes by a weak opposing force from a neighboring muscle. Contractures may become permanent or they may resolve without some sort of intervention. Fixed contractures may cause postural abnormalities in the affected limbs. Clenched fists and contracted feet (equinus or equinovarus) are common in people with CP. Spasticity in the thighs causes them to turn in and cross at the knees, resulting in an unusual method of walking known as a scissors gait. Any 466

of the joints in the limbs may be stiff (immobilized) due to spasticity of the attached muscles. Athetosis and dyskinesia often occur with spasticity, but do not often occur alone. The same is true of ataxia. It is important to remember that the terms mild CP or severe CP refer not only to the number of symptoms present, but also to the level of involvement of any particular class of symptoms. Mechanisms that can cause CP are not always restricted to motor-control areas of the brain. Other neurologically based symptoms may include: • mental retardation or learning disabilities • behavioral disorders • seizure disorders • visual impairment • hearing loss • speech impairment (dysarthria) • abnormal sensation and perception These problems may have a greater impact on a child’s life than the primary physical impairments of CP, although not all children with CP are affected by other problems. Many infants and children with CP have growth impairment. About one-third of individuals with CP have moderate-to-severe mental retardation, one-third have mild mental retardation, and one-third have normal intelligence.

Diagnosis The signs of CP are not usually noticeable at birth. Children normally progress through a predictable set of developmental milestones through the first 18 months of life. Children with CP, however, tend to develop these skills more slowly because of their motor impairments, and delays in reaching milestones are usually the first symptoms of CP. Babies with more severe involvement with of CP are usually diagnosed earlier than others. Selected developmental milestones, and the ages for normally acquiring them, are given below. If a child does not acquire the skill by the age shown in parentheses, there is some cause for concern: • sits well unsupported (6–10 months) • babbles (6–8 months) • crawls (9–12 months) • finger feeds, holds bottle (9–12 months) • walks alone (12–18 months) • uses one or two words other than “dada” or “mama” (12–15 months)

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• turns pages in books; removes shoes and socks (24–30 months) Children do not consistently favor one hand over the other before 12–18 months of age, and doing so may be a sign that the child has difficulty using the other hand. This same preference for one side of the body may show up as asymmetric crawling or, later on, favoring one leg while climbing stairs. It must be remembered that children normally progress at somewhat different rates, and slow beginning accomplishment is often followed by normal development. Other causes for developmental delay, both benign and serious should be ruled out before considering CP as an explanation. CP is nonprogressive, so continued loss of previously acquired milestones indicates that CP is not the cause of the problem. No single test is diagnostic for CP, but certain factors increase suspicion. The Apgar score measures a baby’s condition immediately after birth. Babies that have low Apgar scores are at increased risk for CP. Presence of abnormal muscle tone or movements may indicate CP, as may the persistence of infantile reflexes. Imaging of the brain using ultrasound, x rays, MRI, and/or CT scans, may reveal structural anomalies. Some brain lesions associated with CP include scarring, cysts, expansion of the cerebral ventricles (hydrocephalus), periventricular leukomalacia (an abnormality of the area surrounding the ventricles), areas of dead tissue (necrosis), and evidence of an intracerebral hemorrhage or blood clot. Blood and urine biochemical tests, as well as genetic tests, may be used to rule out other possible causes, including muscle and peripheral nerve diseases, mitochondrial and metabolic diseases, and other inherited disorders. Evaluations by a pediatric developmental specialist and a geneticist may be of benefit.

Treatment Therapy Spasticity, muscle weakness, lack of coordination, ataxia, and scoliosis are all significant impairments that affect the posture and mobility of a person with CP. Physical and occupational therapists work with affected persons and their families to maximize ability to move affected limbs, develop normal motor patterns, and maintain posture. So-called assistive technology, items such as wheelchairs, walkers, shoe inserts, crutches, and braces, are often required. A speech therapist and hightechnology aids, such as computer-controlled communication devices, may make a tremendous difference in the life of those who have speech impairments with CP.

Medications Before fixed contractures develop, muscle-relaxant drugs such, as diazepam (Valium), dantrolene (Dantrium), and baclofen (Lioresal) may be prescribed. Botulinum toxin (Botox), a newer and highly effective treatment, is injected directly into the affected muscles. Alcohol or phenol injections into the nerves controlling specific muscles are another option. Multiple medications are available to control seizures, and athetosis can be treated using medications such as trihexyphenidine (Artane) and benztropine (Cogentin). Surgery Fixed contractures are usually treated with either serial casting or surgery. The most commonly used surgical procedures are tenotomy (tendon transfer) and dorsal rhizotomy. In tenotomy, tendons of an affected muscle are cut and either repositioned or reattached in a different position, and the limb is then immobilized in a cast in a more normal position while the tendons regrow. A neurosurgeon performing dorsal rhizotomy carefully cuts selected nerve roots in the spinal cord to prevent them from stimulating the spastic muscles. Neurosurgical techniques in the brain, such as implanting tiny electrodes directly into the cerebellum or cutting a portion of the hypothalamus, have very specific applications and have had mixed results. Education Parents of a child newly diagnosed with CP are not likely to have the necessary expertise to coordinate the full range of care their child will need. Although knowledgeable and caring medical professionals are indispensable for developing a care plan, a potentially more important source of information and advice is other parents who have dealt with the same set of difficulties. Support groups for parents of children with CP can be significant sources of both practical advice and emotional support. Many cities have support groups that can be located through the United Cerebral Palsy Association, and most large medical centers have special multidisciplinary clinics for children with developmental disorders.

Prognosis Cerebral palsy can affect every stage of maturation—from childhood through adolescence to adulthood. At each stage, those with CP, along with their caregivers, must strive to achieve and maintain the fullest range of experiences and education consistent with their abilities. The advice and intervention of various professionals remains crucial for many people with CP. Although CP

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• walks up and down steps (24–36 months)

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KEY TERMS Asphyxia—Lack of oxygen. In the case of CP, lack of oxygen to the brain. Ataxia—Impaired balance and coordination. Athetosis—A condition marked by slow, writhing, involuntary muscle movements. Coagulopathy—A disorder in which blood does not coagulate normally; it can coagulate (clot) either abnormally slowly or abnormally quickly. Contracture—A shortening of a muscle causing a joint to become stiff or immovable. Cytokine—A protein associated with inflammation that, at high levels, may be toxic to nerve cells in the developing brain. Diplegia—Paralysis of corresponding parts on both sides of the body. Dorsal rhizotomy—A surgical procedure that cuts nerve roots to reduce spasticity in affected muscles. Dyskinesia—Difficulty with voluntary movement of a muscle. Hemiplegia—Paralysis of the limbs on one side of a body. Hypotonia—Reduced tone, referring to a muscle that is loose or flaccid. Quadriparesis—Partial or incomplete paralysis of all four limbs. Quadriplegia—Paralysis of all four limbs. Serial casting—A series of casts designed to gradually move a limb into a more functional position. Spastic—A condition in which the muscles are rigid, posture may be abnormal, and fine motor control is impaired. Static encephalopathy—A disease of the brain that does not get better or worse. Tenotomy—A surgical procedure that cuts the tendon of a contracted muscle to allow lengthening.

The cause of most cases of CP remains unknown, but it has become clear that birth difficulties are not to blame in most cases. Rather, developmental problems before birth, usually unknown and generally undiagnosable, are responsible for most cases. The rate of survival for preterm infants has leveled off, and methods to improve the long-term health of at-risk babies are being sought. Current research is also focusing on the possible benefits of recognizing and treating coagulopathies and inflammatory disorders in the prenatal and perinatal periods. The use of magnesium sulfate in pregnant women with preeclampsia or threatened preterm delivery may reduce the risk of CP in very preterm infants. The risk of CP can be decreased through good maternal nutrition, avoidance of drugs and alcohol during pregnancy, and prevention or prompt treatment of infections.

Health care team roles The number of health care professionals who provide care for persons with CP is extensive. Pediatricians or family physicians may make the initial diagnosis. However, in the growing environment of primary care, the pediatric nurse practitioner may be the first to describe symptoms or developmental delays associated with CP. Care and treatment is then provided by many health professionals, including general or orthopedic surgeons and neurosurgeons. Radiologists assist in diagnosis and monitoring; speech and language specialists and physical and occupational therapists provide rehabilitative therapy. Psychologists, pastoral counselors, and social workers may provide emotional support to patients and their families, while social workers will help families access resources for care and equipment. Manufacturers of prostheses and assistive devices may also provide services. For most persons with CP, assistive care is a life-long need. In an outpatient environment, nurses play a continuing role as educators for such needs as medication administration and side-effect recognition, in-home adaptations for physical therapy necessary between visits to physical therapists, and as a conduit for connecting parents with support groups. Should the child require surgery, the nurse has a perioperative role in caring for the patient.

Prevention itself is not considered a terminal disorder, it can affect a person’s lifespan by increasing the risk for certain medical problems. People with mild cerebral palsy may have near-normal life spans, but the lifespan of those with more severe forms may be shortened. However, more than 90% of infants with CP survive into adulthood. 468

Several maternal-to-fetal cross infections are known to increase the risk for CP, including rubella (German measles, now rare in the United States), cytomegalovirus (CMV), and toxoplasmosis. Each of these infections is considered a risk to the fetus only if the mother contracts it for the first time during that pregnancy. Even in those cases, though, most babies will be born normal. Most

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Cerebral palsy cannot be cured, but many of the disabilities it causes may be managed through planning and timely care. Treatment for a child with CP depends upon the severity, nature, and location of the primary muscular symptoms, as well as any associated problems that might be present. Optimal care of a child with mild CP may involve regular interaction with only a physical therapist and occupational therapist, whereas care for a more severely affected child may include visits to multiple medical specialists throughout life. With proper treatment and an effective care plan coverage, most people with CP can lead productive, happy lives. Adequate prenatal monitoring by competent health care professionals is needed to prevent CP. Risk factors should be identified and appropriate tests conducted. Pregnant women who discontinue the use of substances that are potentially harmful to their fetuses significantly reduce the risk of CP in their children. Resources BOOKS

Adams, Raymond D., Maurice Victor, and Allan H. Ropper. Adam’s & Victor’s Principles of Neurology. 6th ed. New York, McGraw Hill, 1997. Brazis, Paul. Localization in Clinical Neurology. Philadelphia: Lippincott Williams & Wilkins Publishers, 2001. Carter, Alden R., and Carol Carter. Stretching Ourselves: Kids With Cerebral Palsy. Morton Grove: Albert Whitman & Co., 2000. Haslem, Robert H. A. “Cerebral Palsy.” In Nelson Textbook of Pediatrics. 16th ed. Eds. Richard E. Behrman, et al. Philadelphia: Saunders, 2000, 1843–1845. Perlot, Velickovic, and B. G. R. Neville. Cerebral Palsy. New York: Elsevier Science, 2001. Stamer, Marcia H. Posture and Movement of the Child With Cerebral Palsy. San Antonio: Communication Skill Builders, 2000. Stanley, Fiona, and Eve Blair. Cerebral Palsies: Epidemiology and Causal Pathways. Cambridge: MacKeith Press, 2000. PERIODICALS

Byrne J. M., J. F. Connolly, S. E. MacLean, T. L. Beattie, J. M. Dooley, and K. E. Gordon. “Brain Activity and Cognitive Status in Pediatric Patients: Development of a Clinical Assessment Protocol.” Journal of Child Neurology 16, no. 5 (2001): 325–332. Greenfield A. L., F. Miller, and G. W. Gross. “Diagnosis and Management of Orthopedic Problems in Children with

Cerebral Palsy.” Seminars in Musculoskeletal Radiology 3, no. 4 (1999): 317–334. Hargreaves, D. G., D. J. Warwick, and M. A. Tonkin. “Changes in Hand Function Following Wrist Arthrodesis in Cerebal Palsy.” Journal of Hand Surgery [Britain] 25, no. 2 (2000): 193–194. Moster, D., R. T. Lie, L. M. Irgens, T. Bjerkedal, and T. Markestad. “The Association Of Apgar Score with Subsequent Death and Cerebral Palsy: A PopulationBased Study In Term Infants.” Journal of Pediatrics 138, no. 6 (2001): 798–803. Paneth, N. “Cerebral Palsy In Term Infants—Birth or Before Birth?” Journal of Pediatrics 138, no. 6 (2001): 791–792. Philp, I., and M. Law. “Web Sites Related to Cerebral Palsy.” Physical Occupational Therapy in Pediatrics 20, no. 4 (2001): 79–88. ORGANIZATIONS

American Academy of Family Physicians. 11400 Tomahawk Creek Pkwy., Leawood, KS 66211-2672. (913) 906-6000. . American Academy of Neurology. 1080 Montreal Ave., St. Paul, MN 55116. (651) 695-1940. . American Academy of Pediatrics. 141 Northwest Point Bvd. Elk Grove Village, IL 60007-1098. (847) 434-4000. . American Academy of Physical Medicine and Rehabilitation. One IBM Plaza, Ste. 2500, Chicago, IL 60611-3604. (312) 464-9700. . American College of Foot and Ankle Surgeons, 515 Busse Hwy., Park Ridge, IL 60068-3150. (888) 843-3338. . American College of Physicians, 190 N. Independence Mall West, Philadelphia, PA 19106-1572. (800) 523-1546 x2600 or (215) 351-2600. . American College of Surgeons. 633 North St. Clair St., Chicago, IL 60611-32311. (312) 202-5000. . American Medical Association. 515 N. State St., Chicago, IL 60610. (312) 464-5000. . National Association of Pediatric Nurse Associates and Practitioners. 1101 Kings Highway, N., Ste. 206, Cherry Hill, NJ 08034-1912. (856) 667-1773 or (877) 662-7627. . United States Cerebral Palsy Athletic Association. SCPAA National Center, 25 W. Independence Way, Kingston, RI 02881. (401) 792-7130. . OTHER

American Cerebral Palsy Information Center. . Cerebral Palsy and Deaf Organization. .

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women are immune to all three infections by the time they reach childbearing age, but a woman’s immune status can be determined using the so-called TORCH (for TOxoplasmosis, Rubella, Cytomegalovirus, and Herpes) test before or during pregnancy.

Cerebrospinal fluid (CSF) analysis

Internet Resources for Special Children. . National Institute of Neurological Disorders and Stroke. . National Library of Medicine. . Nemours Foundation. . UCP National. . University of Virginia Medical Center. .

L. Fleming Fallon, Jr., M.D, Dr.P.H.

Cerebrospinal fluid (CSF) analysis Definition Cerebrospinal fluid (CSF) analysis is a set of laboratory tests that examine a sample of the fluid surrounding the brain and spinal cord. This fluid is an ultrafiltrate of plasma. It is clear and colorless. It contains glucose, electrolytes, amino acids, and other small molecules found in plasma, but has very little protein and few cells. CSF protects the central nervous system from injury, cushions it from the surrounding bone structure, provides it with nutrients, and removes waste products by returning them to the blood. CSF is withdrawn from the subarachnoid space through a needle by a procedure called a lumbar puncture or spinal tap. CSF analysis includes tests in clinical chemistry, hematology, immunology, and microbiology. Usually three or four tubes are collected. The first tube is used for chemical and/or serological analysis and the last two tubes are used for hematology and microbiology tests. This reduces the chances of a falsely elevated white cell count caused by a traumatic tap (bleeding into the subarachnoid space at the puncture site), and contamination of the bacterial culture by skin flora.

Purpose

• metastatic tumors (e.g., leukemia) and central nervous system tumors that shed cells into the CSF • syphilis, a sexually transmitted bacterial disease • bleeding (hemorrhaging) in the brain and spinal cord • multiple sclerosis, a degenerative nerve disease that results in the loss of the myelin coating of the nerve fibers of the brain and spinal cord • guillain-BarrÇ, a demyelinating disease involving peripheral sensory and motor nerves Routine examination of CSF includes visual observation of color and clarity and tests for glucose, protein, lactate, lactate dehydrogenase, red blood cell count, white blood cell count with differential, syphilis serology (testing for antibodies indicative of syphilis), Gram stain, and bacterial culture. Further tests may need to be performed depending upon the results of initial tests and the presumptive diagnosis. For example, an abnormally high total protein seen in a patient suspected of having a demyelinating disease such as multiple sclerosis dictates CSF protein electrophoresis and measurement of immunoglobulin levels and myelin basic protein. GROSS EXAMINATION. Color and clarity are important diagnostic characteristics of CSF. Straw, pink, yellow, or amber pigments (xanthochromia) are abnormal and indicate the presence of bilirubin, hemoglobin, red blood cells, or increased protein. Turbidity (suspended particles) indicates an increased number of cells. Gross examination is an important aid to differentiating a subarachnoid hemorrhage from a traumatic tap. The latter is often associated with sequential clearing of CSF as it is collected; streaks of blood in an otherwise clear fluid; or a sample that clots. GLUCOSE. CSF glucose is normally approximately two-thirds of the fasting plasma glucose. A glucose level below 40 mg/dL is significant and occurs in bacterial and fungal meningitis and in malignancy. PROTEIN. Total protein levels in CSF are normally very low, and albumin makes up approximately twothirds of the total. High levels are seen in many conditions including bacterial and fungal meningitis, multiple sclerosis, tumors, subarachnoid hemorrhage, and traumatic tap. LACTATE. The CSF lactate is used mainly to help differentiate bacterial and fungal meningitis, which cause increased lactate, from viral meningitis, which does not.

The purpose of a CSF analysis is to diagnose medical disorders that affect the central nervous system. Some of these conditions are:

LACTATE DEHYDROGENASE. This enzyme is elevated in bacterial and fungal meningitis, malignancy, and subarachnoid hemorrhage.

• meningitis and encephalitis, which may be viral, bacterial, fungal, or parasitic infections

WHITE BLOOD CELL (WBC) COUNT. The number of white blood cells in CSF is very low, usually necessitat-

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L3 Subarachnoid space L4

Site for insertion of needle

Collection of cerebrospinal fluid (CSF) by lumbar puncture. (Delmar Publishers, Inc. Reproduced by permission.)

ing a manual WBC count. An increase in WBCs may occur in many conditions including infection (viral, bacterial, fungal, and parasitic), allergy, leukemia, multiple sclerosis, hemorrhage, traumatic tap, encephalitis, and Guillain-Barré syndrome. The WBC differential helps to distinguish many of these causes. For example, viral infection is usually associated with an increase in lymphocytes, while bacterial and fungal infections are associated with an increase in polymorphonuclear leukocytes (neutrophils). The differential may also reveal eosinophils associated with allergy and ventricular shunts; macrophages with ingested bacteria (indicating meningitis), RBCs (indicating hemorrhage), or lipids (indicating possible cerebral infarction); blasts (immature cells) that indicate leukemia; and malignant cells characteristic of the tissue of origin. About 50% of metastatic cancers that infiltrate the central nervous system and about 10% of central nervous system tumors will shed cells into the CSF. RED BLOOD CELL (RBC) COUNT. While not normally found in CSF, RBCs will appear whenever bleeding has occurred. Red cells in CSF signal subarachnoid hemorrhage, stroke, or traumatic tap. Since white cells may enter the CSF in response to local infection, inflammation, or bleeding, the RBC count is used to correct the

WBC count so that it reflects conditions other than hemorrhage or a traumatic tap. This is accomplished by counting RBCs and WBCs in both blood and CSF. The ratio of RBCs in CSF to blood is multipled by the blood WBC count. This value is subtracted from the CSF WBC count to eliminate WBCs derived from hemorrhage or traumatic tap. GRAM STAIN. The Gram stain is performed on a sediment of the CSF and is positive in at least 60% of cases of bacterial meningitis. Culture is performed for both aerobic and anaerobic bacteria. In addition, other stains (e.g., the acid-fast stain for Mycobacterium tuberculosis, fungal culture, and rapid identification tests (tests for bacterial and fungal antigens) may be performed routinely. SYPHILIS SEROLOGY. This involves testing for antibodies that indicate neurosyphilis. The fluorescent treponemal antibody-absorption (FTA-ABS) test is often used and is positive in persons with active and treated syphilis. The test is used in conjunction with the VDRL test for nontreponemal antibodies, which is positive in most persons with active syphilis, but negative in treated cases.

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four hours, then every 30 minutes for another four hours. The puncture site should be observed for signs of weeping or swelling for 24 hours. The neurological status of the patient should also be evaluated for such symptoms as numbness and/or tingling in the lower extremities.

Normal cerebrospinal fluid values in adults Measurement

Value

Volume Clarity Pressure Total cell count Glucose Protein

90–150 ml; child 60–100 ml Crystal clear, colorless 50–180 mm H2O 0–5 white blood cells/µl 40–70 mg/dl 15–45 mg/dl (lumbar) 15–25 mg/dl (cisternal) 5–15 mg/dl (ventricular) 7.30–7.40 25–30 mEq/L

pH CO2 content

Complications

SOURCE: Fischbach, F.T. A Manual of Laboratory Diagnostic Tests. 4th ed. Philadelphia: J.B. Lippincott, 1992.

Precautions In some circumstances, a lumbar puncture to withdraw a small amount of CSF for analysis may lead to serious complications. Lumbar punctures should be performed only with extreme caution, and only if the benefits are thought to outweigh the risks. In people who have bleeding disorders, lumbar puncture can cause hemorrhage that can compress the spinal cord. If there is increased spinal column pressure, as may occur with a brain tumor and other conditions, removal of CSF can cause the brain to herniate, compressing the brain stem and other vital structures and leading to irreversible brain damage or death. Meningitis may be caused by bacteria introduced during the puncture. For this reason, aseptic technique must be followed strictly, and a lumbar puncture should never be performed at the site of a localized skin lesion. Specimens should be handled with caution to avoid contamination with skin flora. They should be refrigerated if analysis cannot be performed immediately.

The most common side effect after the removal of CSF is a headache. This occurs in 10–30% of adult patients and in up to 40% of children. It is caused by a decreased CSF pressure related to a small leak of CSF through the puncture site. These headaches usually are a dull pain, although some people report a throbbing sensation. A stiff neck and nausea may accompany the headache. Lumbar puncture headaches typically begin within two days after the procedure and persist from a few days to several weeks or months.

Results • Gross appearance: Normal CSF is clear and colorless. • CSF opening pressure: 50-175 mm H2O. • Specific gravity: 1.006-1.009. • Glucose: 40-80 mg/dL. • Total protein: 15-45 mg/dL. • LD: 1/10 of serum level. • Lactate: less than 35 mg/dL. • Leukocytes (white blood cells): 0-5/microL (adults and children); up to 30/microL (newborns). • Differential: 60-80% lymphocytes; up to 30% monocytes and macrophages; other cells 2% or less. Monocytes and macrophages are somewhat higher in neonates. • Gram stain: negative.

Description

• Culture: sterile.

Lumbar puncture is performed by inserting the needle between the fourth and fifth lumbar vertabrae (L4–L5). This location is used because the spinal cord stops near L2, and a needle introduced below this level will miss the cord. In rare instances, such as a spinal fluid blockage in the middle of the back, a physician may perform a spinal tap in the cervical spine.

Aftercare After the procedure, the site of the puncture is covered with a sterile bandage. The patient should remain lying for four to six hours after the lumbar puncture. Vital signs should be monitored every 15 minutes for 472

• Syphilis serology: negative. • Red blood cell count: Normally, there are no red blood cells in the CSF unless the needle passes though a blood vessel on route to the CSF.

Health care team roles Spinal tap is performed by a physician, and laboratory tests are ordered by a physician. Nurses should check the patient’s vital signs before the procedure, and monitor the patient for complications. Laboratory tests are performed by a clinical laboratory scientist, CLS(NCA)/ medical technologist, MT(ASCP)

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Encephalitis—An inflammation or infection of the brain and spinal cord caused by a virus or as a complication of another infection. Guillain-Barré syndrome—A demyelinating disease involving nerves that affect the extremities and causing weakness and motor and sensory dysfunction. Meningitis—An infection of the membranes that cover the brain and spinal cord. Multiple sclerosis—A disease that destroys the covering (myelin sheath) of nerve fibers of the brain and spinal cord. Spinal canal—The cavity or hollow space within the spine that contains the spinal cord and the cerebrospinal fluid. Vertebrae—The bones of the spinal column. There are 33 along the spine, with five (called L1–L5) making up the lower lumbar region.

Definition Cerebrovascular accident (CVA) is the medical term for what is commonly termed a stroke. It refers to the injury to the brain that occurs when flow of blood to brain tissue is interrupted by a clogged or ruptured artery, causing brain tissue to die because of lack of nutrients and oxygen.

Description The severity associated with cerebrovascular accident can best be demonstrated by the following facts: • CVA is the leading cause of adult disability in the world. • Worldwide, one-quarter of all strokes are fatal. • Stroke is the third leading cause of death in the United States and the leading cause of disability. • It is estimated that four of every five families in the United States will be affected by stroke in their lifetime,

or clinical laboratory technician, CLT(NCA) or medical laboratory technician, MLT(ASCP).

• More than half a million people in the United States experience a new or recurrent stroke each year.

Resources

• Stroke kills about 150,000 Americans each year, or almost one out of three stroke victims.

BOOKS

Chernecky, Cynthia C., and Barbara J. Berger. Laboratory Tests and Diagnostic Procedures. 3rd ed. Philadelphia: W. B. Saunders Company, 2001. Conn, Howard F., ed., et al. Conn’s Current Therapy 1997: Latest Approved Methods of Treatment for the Practicing Physician. Philadelphia: W.B. Saunders Co., 1997. Fauci, Anthony S., ed., et al. “Approach to the Patient with Neurologic Disease.” In Harrison’s Principles of Internal Medicine. 14th ed. McGraw-Hill, 1998. Kee, Joyce LeFever. Handbook of Laboratory and Diagnostic Tests. 4th ed. Upper Saddle River, NJ: Prentice Hall, 2001. Tierney Jr., Lawrence M., ed., et al. “General Problems in Infectious Diseases.” In Current Medical Diagnosis and Treatment 1997. 36th ed. Stamford, CT: Appleton and Lange, 1997. ORGANIZATIONS

American Academy of Neurology. 1080 Montreal Ave., St. Paul, MN 55116-2325. (800) 879-1960. .

Victoria E. DeMoranville

• Three million Americans are currently permanently disabled from stroke. • In the United States, stroke costs about $43 billion per year in direct costs and loss of productivity. • Two-thirds of strokes occur in people over the age of 65. • Strokes affect men more often than women, although women are more likely to die from a stroke. • Strokes affect African Americans more often than Caucasians, and are more likely to be fatal among African Americans. • The incidence of strokes among people ages 30 to 60 is less than 1%. This figure triples by the age of 80. • The rate of occurrence for strokes in the United States fell by 15.52% between 1988 and 1998. But the number of deaths from stroke actually rose by 5%.

Causes and symptoms Arterial blood carries oxygen and nutrients to the cells of the body. When arteries are unable to carry out this function due to rupture, constriction, or obstruction,

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KEY TERMS

Cerebrovascular accident

the cells nourished by these arteries die. There are two forms of stroke, ischemic, which is caused by a blocked blood vessel that supplies blood to the brain, and hemorrhagic, which is bleeding into or around the brain. The most common type of stroke is ischemic, which refers to the loss of oxygen and nutrients for brain cells that occurs because the blood supply to a portion of the brain has been cut off. Ischemic strokes account for approximately 80% of all strokes, and can be further broken down into two subtypes: thrombotic, also called cerebral thrombosis, and embolic, also termed cerebral embolism. Thrombotic strokes are by far the more prevalent of ischemic strokes, and can be seen in nearly all aging populations worldwide. As people grow older, atherosclerosis, or hardening of the arteries, occurs. This results in a buildup of a waxy, cholesterol-laden substance in the arteries, which eventually narrows the interior space, or lumen, of the artery. This arterial narrowing occurs in all parts of the body, including the brain. As the process continues, the occlusion, or shutting off, of the artery eventually becomes complete so that no blood supply can pass through. Usually the occurrence of the symptoms of a thrombotic stroke are much more gradual and less dramatic than other strokes due to the slow, ongoing process that produces it. Transient ischemic attacks (TIAs) are one form of thrombotic stroke, and usually the least serious. TIAs represent the occlusion of a very small artery, or arteriole. This blockage affects only a small portion of brain tissue and does not leave noticeable permanent ill effects. These transient ischemic attacks last only a matter of minutes, but are a forewarning that part of the brain is not receiving its necessary supply of blood, and, consequently, an insufficient amount of oxygen and nutrients. Embolic strokes are usually a more spectacular, emergency event. They take place when the heart’s rhythm is changed for a number of reasons, and blood clot formation takes place. Such a blood clot can move through the circulatory system until it blocks a blood vessel and stops the blood supply to cells in a specific portion of the body. If the blood clot occludes an artery that nourishes heart muscle, it causes myocardial infarction, or heart attack. If it blocks off a vessel that feeds brain tissue, it is termed an embolic stroke. Normally, these blockages occur in the brain itself, as when arteries directly feeding portions of brain tissue are blocked by a clot. But occasionally, the obstruction is found in the arteries of the neck, especially the carotid artery. Approximately 20% of cerebrovascular accidents are termed hemorrhagic strokes, and are generally classified as subarachnoid hemorrhage or intracerebral hemor474

rhage, depending upon the location of the hemorrhage. Hemorrhagic strokes occur when an artery to the brain has a weakness and balloons outward, producing an aneurysm. Such an aneurysm often ruptures due to this inflation and thinning of the arterial wall, causing a hemorrhage in the affected portion of the brain. Both ischemic and hemorrhagic strokes display similar symptoms. However, which symptoms appear depends upon which portion of the brain is cut off from its supply of oxygen and nourishment. The brain is divided into left and right hemispheres, which control bodily movement on opposing sides of the body. For example, the left hemisphere of the brain is responsible for both motor control of the right side of the body, and its sensory discrimination, just as the right hemisphere is responsible for body movements and feeling on the left side. Deeper brain tissue in the left hemisphere of the brain directs muscle tone and coordination for both the right arm and leg. As the communication and speech centers for the brain are also located in the left hemisphere of the brain, interruption of blood supply to that area can also affect the person’s ability to speak. Besides age, high blood pressure (hypertension) is one of the foremost causes of thrombotic stroke. Heart disease, obesity, diabetes, smoking, oral contraceptives in women, polycythemia (an increased number of red blood cells), and sleep apnea are also risk factors for thrombotic stroke, as is a diet high in cholesterol-producing, or fatty, foods. The risk factors for hemorrhagic stroke include high blood pressure that can, over a period of time, cause the ballooning out of arteries known as aneurysm, and also causes the hereditary malformation that produces defective and weakened veins and arteries. Substance abuse is another major cause of hemorrhagic stroke. Cocaine, stimulants such as amphetamine drugs, and chronic alcoholism can cause a weakening of blood vessels that can result in hemorrhagic stroke. The symptoms of stroke depend upon the part of the brain that is affected, and how large a portion of brain tissue has been damaged by the CVA. Unconsciousness and even seizures can be initial components of a stroke. Other effects materialize over a time period ranging from minutes to hours, and even, in some rare instances, over several days. Headache, mental confusion, vertigo, vision problems, difficulty speaking and communicating, including slurring of words (aphasia), and weakness or paralysis of one side of the body (hemiplegia) are all symptoms of stroke that are frequently observed. Stroke victims often have facial drooping, or slackness of the facial muscles, on the affected side, as well as difficulty swallowing. The severity of these symptoms will depend

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Diagnosis Normally, initial diagnosis will be made based upon observation by health care professionals, and usually a complete neurological examination. Once stroke is suspected, a computed tomography (CT) scan or magnetic resonance imaging (MRI) scan is performed to distinguish a stroke caused by blood clot from one caused by hemorrhage, a critical distinction that guides therapy. Blood and urine tests are done routinely to look for possible abnormalities associated with ischemic activity within the body. Electrocardiogram (EKG), angiography, and lumbar puncture are all used to rule out any other possible causes of the symptoms.

Treatment Emergency treatment Strokes are always considered a medical emergency, and every minute is important in initiating treatment. With the possible exception of TIAs, all other types of stroke are a life-threatening event. A severe CVA that results in coma or unconsciousness will require medical monitoring and support, including oxygen and possibly intubation to ensure an adequate airway and to facilitate the patient’s breathing. Providing fluids that the person may not be able to take by mouth due to swallowing difficulties may also be necessary. Emergency treatment of stroke caused by a blood clot is directed at dissolving the clot. This thrombolytic therapy is currently performed most often with tissue plasminogen activator, or t-PA. As t-PA must be administered within three hours of the stroke event, people that awaken with stroke symptoms are usually considered beyond the time limit for t-PA therapy. A five-year clinical trial completed in 1995, and reported by the New England Journal of Medicine, showed that stroke patients treated with t-PA within three hours of the stroke were one-third more likely to be left with no permanent residual difficulty. T-PA therapy carries a 6.4% risk of inducing a cerebral hemorrhage, and is not appropriate for patients with bleeding disorders, very high blood pressure, known aneurysms, any evidence of intracranial hemorrhage, or incidence of stroke, head trauma, or intracranial surgery within the past three months. Patients with clot-related (thrombotic or embolic) stroke who are ineligible for tPA treatment may be treated with heparin or other blood thinners, or, in some cases, with aspirin or other anti-clotting agents.

Emergency treatment of hemorrhagic stroke is aimed at controlling intracranial pressure. Intravenous urea, or mannitol, plus hyperventilation are the most common treatment. Corticosteroids may also be used. Patients with bleeding disorders such as those due to anticoagulant treatment should have these disorders reversed, if possible. Sometimes surgical removal of a clot obstructing an artery is necessary. Hemorrhagic stroke can cause a buildup of pressure on the brain that must be relieved as quickly as possible to prevent further brain damage. In extreme cases, this may require an incision through the skull to relieve the pressure. Surgery for hemorrhage due to aneurysm may be performed if the aneurysm is close enough to the cranial surface to allow access. Ruptured vessels are closed off to prevent bleeding. For aneurysms that are difficult to reach surgically, endovascular treatment may be used. In this procedure, a catheter is guided from a larger artery up into the brain to reach the aneurysm. Small coils of wire are discharged into the aneurysm. Longer term or rehabilitative treatment Rehabilitation refers to a comprehensive program designed to regain function as much as possible and to compensate for permanent losses. It is based on the patient’s individual deficits and strengths. Strokes on the left side of the brain primarily affect the right half of the body, and vice versa. In addition, in left-brain-dominant people, who constitute a significant majority of the population, left brain strokes usually lead to speech and language deficits. Right brain strokes may affect spatial perception, and patients with right brain strokes may also deny their illness, neglect the affected side of their body, and behave impulsively. Much of the needed care in the days and weeks following a stroke will be to prevent further damage than what has already occurred. The severely ill stroke patient will require frequent repositioning to prevent complications such as pneumonia and venous or pulmonary embolism. Deep venous thrombosis, in which a clot forms within a limb immobilized by paralysis, is one of the most common medical complications following stroke. Clots that break free often become lodged in an artery feeding the lungs. This type of pulmonary embolism often causes death in the weeks following a stroke. Resuming activity within a day or two after the stroke is an important preventive measure, along with use of elastic stockings on the lower limbs. Drugs that prevent clotting may be given, including intravenous heparin and oral warfarin.

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upon the amount of brain tissue that has been damaged and its location in the brain.

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supportive braces for arms or hands, or using footboards or wearing sneakers when in bed to prevent foot drop. Occupational therapy improves self-care skills such as feeding, bathing, and dressing, and helps develop effective compensatory strategies and devices for activities of daily living. A speech-language pathologist focuses on communication and swallowing skills. When dysphasia is a problem, a nutritionist can advise alternative meals that provide adequate nutrition.

CAT scan of a brain showing a stroke resulting in hemorrhage (white area). (Custom Medical Stock Photo. Reproduced by permission.)

Weakness and loss of coordination of the swallowing muscles may impair swallowing (dysphasia), and allow food to enter the lower airway. This may lead to aspiration pneumonia, another common cause of death shortly after a stroke. Because of the difficulty swallowing, the person who has suffered a stroke may need a temporary or permanent feeding tube inserted into the stomach to ensure adequate nutrition. Such tubes can be either nasogastric, a thin tube that is inserted through the nose, into the esophagus, and then into the stomach, or a gastric one, which is a wider-lumen tube surgically implanted into the stomach. Less extreme dysphasia may be treated with retraining exercises and temporary use of pureed foods. Other possible medical complications can include urinary tract infections, pressure ulcers, and falls. Urinary catheters are often inserted into the bladder to prevent the skin damage that can be caused by incontinence, but the presence of a catheter may also contribute to infections and loss of bladder tone. Bladder training, which consists of regular interval exercises to regain bladder tone, should begin as soon as possible. Frequent repositioning and good skin care will prevent the development of pressure ulcers, or decubitus ulcers. Paralysis requires prevention of contractures (the tightening up of paralyzed limbs). Contractures and spasticity may be treated with a combination of stretching and splinting and, besides exercise, may include the use of 476

Rehabilitation may be complicated by cognitive losses, including diminished ability to understand and follow directions. Poor results are more likely in patients with significant or prolonged cognitive changes, sensory losses, language deficits, or incontinence. Depression occurs in an estimated 30–60% of all stroke patients, which is not surprising as they are typically dealing with a tremendous loss of abilities and independence. As such depression will impact upon the person’s rehabilitation and recovery, it needs to be addressed, and may require the services of a psychiatrist and psychiatric nurse or mental health assistant. Antidepressants and psychotherapy may be used in combination.

Prognosis The National Institute of Neurological Disorders and Stroke reports that 25% of people who suffer a stroke recover completely, while 20% die within three months after the stroke. Stroke is fatal for nearly twice as many people of African-American heritage as it is for European-Americans. Of the remaining 55% of people who have strokes, 5% will require long-term (nursing home) care. For the rest, rehabilitative and restorative services will be necessary in order for them to regain as much of their former capabilities as possible. Brain tissue that dies in a stroke cannot regenerate, and stroke survivors may be left with significant deficits. It has been estimated that the most common irreversible damage from stroke is that done to intellectual functions. But as is increasingly shown, emergency treatment and comprehensive rehabilitation can significantly improve both survival and recovery. In some cases, many functions that are lost due to stroke may be performed by other brain regions after a training period, or compensatory actions may be developed to replace lost abilities.

Health care team roles Rehabilitation is provided by a team of medical professionals, including the services of a neurologist, a physician who specializes in rehabilitation medicine, nurses to both provide care and assist the physician in

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Several different physicians may be involved, at one time or another, in the care of the stroke patient: • A primary care physician (PCP) provides basic medical care to patients. • A physical medicine and rehabilitation specialist assists patients to recover from or overcome disability or impairment. Often physical therapists work under their supervision. • A neurologist specializes in disease conditions of the nervous system, and may be consulted to evaluate the extent of actual damage from a stroke. • In the case of cerebral hemorrhage, a neurosurgeon, a specialist in both neurology and the surgical correction of nervous system damage, may be called upon to do surgery. • Psychiatrists are licensed medical doctors that are often called upon to evaluate cognitive ability and to treat depression. • Registered nurses (RNs) or licensed practical nurses (LPNs) are the health care provider that deal most often with the person who has had a CVA. Their duties include taking vital signs and monitoring the patient for complications of the stroke. They also educate the patient and family about the nature of strokes, the importance of preventing contractures and maintaining good range of motion, and about adequate nutrition and fluid intake. • Physical therapists work with disabled stroke patients to maintain and restore range of motion and strength in affected limbs, and to maximize mobility in walking, wheelchair use, and transferring (for instance, from wheelchair to toilet or from standing to sitting). The physical therapist advises on mobility aids such as wheelchairs, braces, and canes. • A social worker may help coordinate services and ease the transition out of the hospital back into the home, or into an extended care facility, if necessary. Social workers may help counsel the patient and family during the difficult rehabilitation period. • Nutritionists educate stroke patients about eating nutritious foods and following through on a therapeutic diet as ordered by the physician.

• Occupational therapists help stroke patients to relearn muscular control and coordination in order to carry out normal activities of daily living such as bathing, dressing, and preparing meals. • Speech-language therapists assist stroke patients who have damage to the speech center in the brain. • Clinical laboratory scientists draw blood samples or test urine or sputum specimens that are ordered by the physician. • Radiologic technologists take x rays, CT scans, and MRIs to visualize and monitor the brain or other affected organs after a stroke. All health care team members are aware that the person who has suffered a stroke and the family members who may care for the person at home will need to learn entirely new sets of skills and adaptations. Both the patient and family often experience stress, anxiety, and depression. They may need to learn about physical and mental symptoms that are common in stroke patients, and the family may even need to learn how to deliver necessary care. Support groups can provide an important source of information, advice, and comfort for stroke patients and for caregivers. For the stroke patient, joining a support group can be one of the most important steps in the rehabilitation process.

Prevention An important facet of rehabilitation is preventing the recurrence of stroke. Control of blood pressure is the single most important factor in the prevention of strokes. People should regularly have their blood pressure checked, and if it is found to be consistently elevated (diastolic, or lower blood pressure beat above 90 to 100, systolic or top beat above 140 to 150), a physician should be consulted. Diet, including the reduction of sodium (salt) intake, exercise, and weight loss, if necessary, are all non-drug treatments for lowering blood pressure. Other natural remedies include the consumption of artichoke, which lowers the fat content of the blood, garlic, now believed to lower cholesterol and blood pressure as well as reduce blood’s clotting ability, and ginkgo, which improves circulation and strengthens arteries and veins. The use of folic acid, lecithin, and vitamins B6, B12, C, and E is recommended as supportive measures in reducing blood pressure. Multiple studies have found that aspirin acts as a blood-thinning, or clot-reducing, medication when taken

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coordinating the necessary services the stroke patient needs, a physical therapist, an occupational therapist, a speech-language pathologist, a nutritionist, and a social worker. Rehabilitation services may be provided in an acute care hospital, rehabilitation hospital, long-termcare facility, outpatient clinic, or at home.

Cerebrovascular accident

KEY TERMS Aneurysm—A pouch-like bulging of a blood vessel. Angiography—The procedure that enables blood vessels to be seen on film after the vessels have been filled with a substance that shows up opaque on x rays. Arrhythmia—An abnormality of the rhythm or rate of the heartbeat. Arteriole—The tiny extensions that arteries eventually break down into as they circulate blood. Artery—Pliable, three-layered vessels that carry the blood away from the heart. Atherosclerosis—Disease of the arterial wall in which the inner layer thickens, causing narrowing of the channel and thus impairing blood flow. Computerized tomography (CT) scan—The diagnostic technique in which the combined use of a computer and x rays passed through the body at different angles produces clear, cross-sectional images of the tissue being examined. Ischemic—Insufficient blood supply to a specific organ or tissue. Lumbar puncture—A procedure in which a hollow needle is inserted into the lower part of the spinal

in small doses. One aspirin tablet per day provides this anti-coagulant prevention. If necessary, a physician may also order medication to lower blood pressure. These medications include the following categories of drugs: • Beta blockers are used to reduce the force and speed of the heart-beat.

canal to withdraw cerebrospinal fluid (the clear liquid which surrounds the brain and spinal cord), or to inject drugs or other substances. Magnetic resonance imaging (MRI)—The diagnostic technique that provides high quality cross-sectional images of organs or structures within the body without x rays or other radiation. Myocardial infarction—Heart attack; sudden death of part of the heart muscle characterized in most cases by severe, unremitting chest pain. Polycythemia—Increased number of red cells in the blood. Sleep apnea—A condition in which a person experiences episodes of cessation of breathing lasting 10 seconds or longer during sleep. Thrombotic—Pertaining to a blood clot formed within an intact blood vessel as opposed to a clot formed to seal the wall of a blood vessel after an injury. Transient ischemic attack (TIA)—Occlusion of smaller blood vessels to the brain that can produce stroke-like symptoms for anywhere from a few minutes to 24 hours, but leaves no permanent damage.

Sammons, James H., John T. Baker, Frank D. Campion, Heidi Hough, James Ferris, and Brenda A. Clark. The American Medical Association Guide to Prescription and Over-theCounter Drugs. New York, NY: Random House, 1988. ORGANIZATIONS

American Heart Association. .

• Vasodilators are used to dilate the blood vessels.

American Stroke Association. .

• Diuretics reduce the total volume of circulating blood and thus the heart’s work by removing fluid from the body.

National Institute of Neurological Disorders and Stroke, U.S. Department of Health and Human Services, National Institutes of Health. .

• Lipid-lowering drugs increase the loss of cholesterol from the body or prevent the conversion of fatty acids to cholesterol. This lowers fat levels in the bloodstream. Resources

Certified nurse midwife (CNM) see Nurse midwifery Ceruloplamin test see Plasma protein tests

BOOKS

Caplan, L. R., M. L. Dyken, and J. D. Easton. American Heart Association Family Guide to Stroke Treatment, Recovery, and Prevention. New York, NY: Times Books, 1996. 478

Joan Schonbeck

Character disorders see Personality disorders Charts see Medical charts

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Definition Chemotherapy is the treatment of cancer with anticancer drugs.

Purpose The purpose of chemotherapy is to kill cancer cells. Not only is it often used to treat patients with cancer that has metastasized (spread) from the site in the body where it originated, today chemotherapy can be used to prevent metastasis as well. Chemotherapy destroys cancer cells throughout the body, killing cells that have broken off from the main tumor and traveled through the blood or lymph systems to other parts of the body. Chemotherapy can cure some types of cancer. In some cases, it is used to slow the growth of cancer cells or to keep the cancer from spreading to other parts of the body. When a cancer has been removed by surgery, chemotherapy may be used to keep the cancer from recurring; this is known as adjuvant therapy. Chemotherapy also can ease the symptoms of cancer, helping some patients to have a better quality of life.

Precautions There are many different types of chemotherapy drugs. Oncologists (specialists in cancer) determine which drugs are best suited for each patient. This decision is based on the type of cancer, the patient’s age, health, and preferences, as well as other drugs the patient is taking. Some patients may not tolerate certain chemotherapy drugs if they have other illnesses such as heart disease, kidney disease, or diabetes. Chemotherapy, whether administered in the hospital, clinic, or at home, is prepared by the pharmacist. The pharmacy and pharmacy assistants provide and reinforce patient education about common as well as infrequent side effects of chemotherapy. When administered in the hospital, clinic, physician’s office, or other treatment setting, it is usually administered by a specially trained nurse, mid-level practitioner (physician assistant of nurse practitioner), or physician.

Description More than 50 chemotherapy drugs are currently available to treat cancer, and many more are being tested for their ability to destroy cancer cells. Most chemotherapy drugs interfere with the ability of cells to grow or multiply. Although these drugs affect all cells in the

body, most useful treatments are more effective against rapidly growing cancer cells. Since chemotherapy affects rapidly growing cells, it often affects cells that normally grow rapidly such as cells in the bone marrow, stomach intestines, and hair follicles. This is why some of the most common side effects of chemotherapy are bone marrow suppression, nausea, vomiting, and hair loss. Types of chemotherapy drugs Chemotherapy drugs are classified based on their mechanisms of action (how they work). The main types of chemotherapy drugs are: • Alkylating drugs kill cancer cells by directly attacking DNA, the genetic material of the genes. Cyclophosphamide is an example of an alkylating drug. • Antimetabolites interfere with the production of DNA thereby preventing cells from growing and multiplying. An example of an antimetabolite is 5-fluorouracil (5-FU). • Antitumor antibiotics are made from natural substances such as fungi in the soil. They interfere with important cell functions, including production of DNA and cell proteins. Doxorubicin and bleomycin belong to this group of chemotherapy drugs. • Plant alkaloids prevent cells from dividing normally. Vinblastine and vincristine are plant alkaloids obtained from the periwinkle plant. • Steroid hormones slow the growth of some cancers that depend on hormones. For example, tamoxifen is used to treat breast cancers that depend on the hormone estrogen for growth. Combination chemotherapy The oncologist decides which chemotherapy drug or combination of drugs will work best for each patient. The use of two or more drugs together often works better than a single drug alone. This is called combination chemotherapy. Scientific studies and clinical research trials of different drug combinations help determine which combinations are most effective for each type of cancer. How chemotherapy is administered Chemotherapy is administered in different ways, depending on the drugs to be given and the type of cancer. The prescribed dose depends on several factors, one of which is the patient’s body weight. Chemotherapy may be administered by one or more of the following methods: • orally

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Chemotherapy

Chemotherapy

cutaneously (under the skin). Injection of chemotherapy directly into the cancer is called intralesional injection. Chemotherapy may also be given by a catheter or port permanently inserted into a central vein or body cavity. A port is a small reservoir or container that is placed in a vein or under the skin in the area where the drug will be administered. These methods eliminate the need for repeated injections and may allow patients to spend less time in the hospital while receiving chemotherapy. A common location for a permanent catheter is the external jugular vein in the neck. Intraperitoneal (IP) chemotherapy is administered into the abdominal cavity through a catheter or port. Chemotherapy administered by catheter or port into the spinal fluid surrounding the brain or spine is called intrathecal (IT) administration. Catheters and ports may also be placed in the chest cavity, bladder, or pelvis, depending on the location of the cancer to be treated. Topical chemotherapy is given as a cream or ointment applied directly to the cancer. It may be used to treat certain types of skin cancer. Treatment location and schedule Patients may take chemotherapy at home, in the physician’s office, or as an inpatient or outpatient at the hospital. Many patients stay in the hospital when first beginning chemotherapy, so they can be observed and monitored for any side effects.

Patient undergoing high dose stem cell chemotherapy. (Custom Medical Stock Photo. Reproduced by permission.)

• intramuscular (IM) or subcutaneous injection • through a catheter or port • topically Oral chemotherapy, given by mouth, may be in the form of a pill, capsule, or liquid. This is the easiest method of administration and can usually be done at home. Intravenous (IV) chemotherapy is injected into a vein. A small needle is inserted into a vein on the hand or lower arm. The needle is usually attached to a small tube called a catheter, which delivers the drug to the needle from an IV bag or bottle. Intramuscular (IM) chemotherapy is injected into a muscle. Chemotherapy given by intramuscular injection is absorbed into the blood more slowly than IV chemotherapy. Because of this, the effects of IM chemotherapy may last longer than chemotherapy given intravenously. Chemotherapy may also be injected sub480

The frequency and duration of chemotherapy given depends on the type of cancer, the patient response to the drugs, patients’ overall health and ability to tolerate the drugs, and on the types of drugs used. Chemotherapy administration may take only a few minutes or may last as long as several hours. Chemotherapy may be given daily, weekly, or monthly. A rest period may follow a course of treatment before the next course begins. In combination chemotherapy, more than one drug may be given at the same time, or they may be given alternately, one following the other.

Preparation A number of medical tests are performed before chemotherapy is started. The oncologist will determine the extent to which the cancer has spread from the results of x rays and other imaging tests and from biopsies. Radiologic technologists and technicians perform imaging studies. Analysis of the biopsy will be performed by a pathologist, assisted by laboratory technicians. Blood tests, drawn by laboratory technicians or nurses, provide important information about the function of the blood cells and levels of chemicals in the blood. A complete blood count (CBC) is commonly performed

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Sometimes, patients taking chemotherapy drugs known to cause nausea are given antiemetics before chemotherapy is administered to lessen feelings of nausea. Two anti-nausea medications that may be used are Kytril and Zofran. Patients may also be advised to prepare for chemotherapy and reduce nausea by eating and drinking normally until about two hours before a chemotherapy session. They should eat high carbohydrate, low-fat foods and avoid spicy foods.

Aftercare Patient education about how to control side effects after chemotherapy includes: • Encouraging patients to adhere to instructions given by their health care team. • Reinforcing correct use of all prescribed medications. • Advising patients to eat small amounts of bland foods and drink lots of fluids. • Instructing patients to get plenty of rest. Some patients find that breathing fresh air or mild exercise, such as walking, helps to relieve the stress and side effects associated with chemotherapy.

Complications Chemotherapy drugs are toxic to normal cells as well as cancer cells. Doses that will destroy cancer cells will likely cause damage to some normal cells. Physicians adjust (titrate) doses to do the least amount of harm possible to normal cells. Some patients feel few or no side effects, and others may experience more serious side effects. In some cases, a dose adjustment is all that is needed to reduce or stop a side effect. Some chemotherapy drugs have more side effects than others. The most common side effects include: • nausea and vomiting

Chemotherapy

before and on a regular basis during treatment. The CBC shows the numbers of white blood cells, red blood cells, and platelets in the blood. Because chemotherapy affects the bone marrow, where blood cells are made, levels of these cells often drop during chemotherapy. The white blood cells and platelets are most likely to be affected by chemotherapy. A drop in the white blood cell count means that the immune system may not function properly and the patient may become prone to infection. Low levels of platelets may cause a patient to bleed from minimal trauma or even spontaneously with no trauma. A low red blood cell count can lead to anemia (deficiency of red blood cells) and fatigue.

• loss of appetite • hair loss (alopecia) • anemia and fatigue • infection • easy bleeding or bruising • sores in the mouth and throat • neuropathy and other damage to the nervous system • kidney damage Nausea and vomiting are common, but can usually be controlled by taking antinausea drugs, drinking enough fluids, and avoiding spicy foods. Loss of appetite may be due to nausea or the stress of undergoing cancer treatment. Also, although some chemotherapy drugs cause alopecia, it is almost always temporary and reversible. Low blood cell counts caused by the effect of chemotherapy on the bone marrow can lead to anemia, infections, and easy bleeding and bruising. Patients with anemia have too few red blood cells to deliver oxygen and nutrients to the body’s tissues. Anemic patients feel tired and weak. If red blood cell levels fall too low, a blood transfusion may be given. Patients receiving chemotherapy are more likely to get infections because white blood cells are reduced. It is important to take measures to avoid infections. When the white blood cell count drops too low, the physician may prescribe medications called colony-stimulating factors that help white blood cells grow. Neupogen and Leukine are two colony stimulants used as treatments to help fight infection. Platelets are blood particles that make the blood clot. When patients do not have enough platelets, they may bleed or bruise easily, even from small injuries. Patients with low blood platelets should be advised to take precautions to avoid injuries. Medicines such as aspirin and other pain relievers can impair platelet function and slow the clotting process. Chemotherapy can cause irritation and dryness in the mouth and throat. Painful sores may form that can bleed and become infected. Patients should be advised about actions they might take to prevent or reduce mouth irritation. Precautions to avoid this side effect include dental care before chemotherapy begins, brushing the teeth and gums regularly with a soft brush, and avoiding mouthwashes that contain salt or alcohol.

Results The primary goal of chemotherapy is to cure cancer. Some cancers, such as Hodgkin’s disease and acute lym-

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Health care team roles

KEY TERMS Adjuvant therapy—Treatment given after surgery or radiation therapy to prevent the cancer from coming back. Alkaloid—A type of chemical commonly found in plants and often having medicinal properties. Alykylating drug—A drug that kills cells by directly damaging DNA. Antiemetic—A medicine that helps control nausea; also called an anti-nausea drug. Antimetabolite—A drug that interferes with a cell’s growth or ability to multiply. Platelets—Blood cells that function in blood clotting.

Patients with cancer are usually cared for by a multidisciplinary team of health professionals. The patient’s family physician or primary care physician collaborates with other specialists, such as surgeons and oncologists. Radiologic technicians perform imaging studies, and nurses and laboratory technicians may obtain samples of blood, urine, and other laboratory tests. Before and after chemotherapy, nurses explain the goals and effects of drug treatment and help to prepare patients and families. Depending on the treatment plan, cancer patients may also benefit from rehabilitation therapy with physical therapists, nutritional counseling from dieticians, and counseling from social workers or other mental health professionals. Resources BOOKS

phocytic leukemia, may be cured by chemotherapy. Used as adjuvant therapy, in combination with surgery, it may prevent a cancer from spreading to other parts of the body. Some widespread, fast-growing cancers are more difficult to treat. In these cases, chemotherapy may slow the growth of the cancer cells. Physicians determine the extent to which chemotherapy is effective by closely monitoring the results of medical tests. Physical examination, blood tests, and imaging studies are used to monitor and assess the effects of treatment on the cancer. The outcomes of chemotherapy include: • Complete remission or complete response. The cancer completely disappears. The course of chemotherapy is completed, and the patient is tested regularly for a recurrence. • Partial remission or partial response. The cancer shrinks in size but does not disappear. The same course of chemotherapy may be continued, or a different combination of drugs may be tried.

Dollinger, Malin, Ernest H. Rosenbaum, and Greg Cable. Everyone’s Guide to Cancer Therapy. Kansas City, MO: Andrews McMeel Publishing, 1998. ORGANIZATIONS

American Cancer Society. 1599 Clifton Road, N.E., Atlanta, GA 30329. (800) ACS-2345. Cancer Information Service of the National Cancer Institute. (800) 4-CANCER. OTHER

“Chemotherapy and You: A Guide to Self-Help During Treatment.” National Cancer Institute. National Institutes of Health. . “Introduction to Chemotherapy.” OncoLink, University of Pennsylvania Cancer Center. 1998. .

Barbara Wexler, M.P.H.

Chemotherapy drugs see Anticancer drugs Chest computed tomography scan see Chest CT scan

• Stabilization. The cancer does not grow or shrink. Other therapy options may be explored. A tumor may remain stabilized for many years. • Progression. The cancer continues to grow. Other therapy options may be explored. • A new type of malignancy may develop, and this secondary cancer may require additional chemotherapy or other treatment. 482

Chest CT scan Definition Computed tomography (CT) of the chest is performed to diagnose a variety of symptoms, including vas-

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cular, cardiac, airway disease as well as cancers that can occur in the thoracic region of the body.

Purpose The purpose of the CT scan is to noninvasively and quickly visualize internal organs which may be damaged by disease or trauma.

Precautions Pregnant women usually defer these types of scans due to the amount of radiation received during the examination; however due to an emergent situation, (e.g., trauma or pulmonary embolism) it may be necessary to scan a gravid woman. Proper shielding is always recommended in these situations. Radiation dose should always be limited to the amount necessary to adequately penetrate the selected body part. Lead shielding will also provide some protection to patients, although most radiation to other organs outside of the chest is from scattering within the body, which cannot be reduced by shielding. The greatest radiation protection is a welltrained technologist who understands the type of exam and who can asses the body habitus of the patient to determine the correct amount of radiation needed for the patient. Patients with a mild allergy to iodine may be premedicated to prevent sequlae of the administration of contrast. If a patient has a severe allergy, then a scan without IV contrast may be undertaken or a different imaging modality may be used to answer the clinical question. Diabetic patients who are taking Glucophage or Glucovance should stop taking the medication at the time of or before the scan and 48 hours after. The medications should only be reinstated after normal renal status has been established through lab values. Stopping and restarting of medications should only be done after consultation with the attending nephrologist.

Description A brief list of these conditions, which can be imaged by CT, includes infection, trauma, aortic dissections, staging for cancer, and assessment of interstitial lung disease. The entire chest is imaged, unless a specialized limited exam is ordered to focus on a smaller area. The technique for CT examination of the chest is similar to other anatomic regions of the body. The patient lies on a special table, which moves a patient through an opened gantry, which contains a rotating combination of a x-ray tube and a complex array of sensitive detectors. A radiologic technologist gives the patient instructions to lie still and hold the breath while the images are being acquired. This limits the number of artifacts caused by voluntary

A chest computed tomography (CT) scan shows the collapse of the right lobe of a patient’s lung. (Photo Researchers,Inc. Reproduced by permission.)

and involuntary motion. X rays are passed through a patient. As they pass through a patient, the energy of the beam is attenuated, or decreased by the density of the tissue they pass through. The denser the tissue, the fewer number of x rays that pass through the body. Sensitive detectors, which continually rotate around the patient, translate the beam into numbers, which then are translated into shades of gray and viewed as a final image for the radiologist to interpret. The patient may be scanned with or without IV contrast depending on which type of pathology is to be demonstrated. If a tumor or vascular pathology is suspected, intravenous contrast is usually given. Certain exams do not require IV contrast to get high quality images. These exams include low-dose lung cancer screening, lung nodule work ups, and high-resolution chest exams for conditions such as asbestosis. If a lung nodule is the indication for the exam, a non-contrast study may be performed first, to confirm if there is calcium in the nodule. If calcium is present in the pattern, then no further examination is required because that is an indicator of a benign lesion. Occasionally, oral contrast will be used to demonstrate a hiatal hernia or a barium paste will be ingested to demonstrate esophageal lesions or stricture. As scanners become faster, patients do not have to hold the breath for as long a period. With current multislice technology, a standard chest CT can be completed in less than ten seconds. This is a great benefit to patients who are short of breath, due to any number of lung conditions, including emphysema and chronic obstructive pulmonary disease (COPD). As computer speed and detector sensitivity increases, examination time will continue to decrease with lower cost and radiation exposure.

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KEY TERMS Computed tomography—The technique of imaging a patient with ionizing radiation to diagnose disease process. Non-ionic intravenous contrast—A injectable xray dye that mixes with the blood to enhance structures aiding their ability to be judged as health or diseased.

Preparation If IV contrast is to be used the patient should remain NPO (not given anything by mouth) for at least four hours. Occasionally to view possible esophageal pathology, patients will ingest oral contrast to help delineate possible mediastinal lymph nodes or gastric tumors. Patients should also remove any metal jewelry or clothing accessories to prevent artifacts from decreasing the diagnostic quality of the images. Certain lab values may be necessary before the scan is undertaken. These would include the BUN (blood uria nitrogen) and creatinine levels to asses the patients renal status. A high creatinine could contraindicate the use of IV contrast as the kidneys are the main organs which excrete the contrast. If a patient is on renal dialysis, then the values are usually higher, and the scan is prior to that day’s dialysis treatment.

Aftercare If the patient received IV contrast, a small bandage will be placed over the injection site, and it should be treated with the same care one would receive after donating blood. Patients should also drink plenty of clear fluids to help flush the iodinated contrast out of their kidneys to prevent any kidney damage.

vision of the injection of the IV contrast as an infiltration could result in a painful collection of contrast around the IV site. If the patient has a known allergy to iodine, then premedication will be necessary to prevent any sort of histamine reaction. The reaction can be mild, such as hives, to life-threatening if the patient were to have a larygospasm. With newer and safer non-ionic contrast, reactions have become less frequent, however this does not mean that technologists should be any less vigilant for signs of a mild reaction to the contrast media. There is also a small risk of renal failure in certain high-risk patients.

Results The results are given in a written report that is sent to multiple locations including the patients referring physician, the file room of the radiology department and to the patients permanent medical record if they were an inpatient at the time of their study. A verbal report will occasionally be used as well to help speed up the communication of results to the appropriate physicians. If there are previous examinations, the radiologist will consider if there has been a change ad judeged by the appearance of any pathology on the images.

Health care team roles The main team member involved in the CT of the chest is the radiologic technologist who has been trained to perform CT exams. If the physician ordering the procedure can confirm the lab values before the patient arrives, and if they are an inpatient, assuring that the patient’s IV line is patent and safe for use will streamline the examination.

If the patient is in renal failure then it will be necessary to dialyze the patient soon after the procedure. These arrangements should be made before hand with the knowledge and consent of the consulting nephrologist.

Resources

If the patient received any oral contrast it will pass through the GI tract with the next day or two. As the contrast used for CT is much thinner than the standard barium used for GI flouroscopy studies there should be no problems with constipation.

Horton, K. M., and E. K. Fishman “Spiral CT of the Esophagus and Stomach.” In Spiral CT: Principles, Techniques and Applications. E. K. Fishman and R. B. Jeffery, eds. New York, NY: Lippincott-Raven Press 1998; pp.221–230

Complications

American College of Radiology. Manual on Contrast Media. 4th Edition.

J. Paul Dow, Jr.

Several complications are possible, though are relatively unlikely as long as care is taken during the procedure. These precautions would include the careful super484

BOOKS

Chest drainage therapy see Chest physical therapy

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Definition Chest physical therapy (CPT) is the term for a group of treatments designed to improve respiratory efficiency, promote expansion of the lungs, strengthen respiratory muscles, and eliminate secretions from the respiratory system.

• are bleeding from the lungs or are coughing up blood • are experiencing intense pain • have increased pressure in the skull • have head or neck injuries • have collapsed lungs or a damaged chest wall • recently experienced a heart attack • have a pulmonary embolism or lung abscess

Purpose The purpose of chest physical therapy, also called chest physiotherapy, is to help patients breathe more freely and to get more oxygen into the body. Chest physical therapy includes postural drainage, chest percussion, chest vibration, turning, breathing exercises, coughing, and incentive spirometry. CPT is usually done in conjunction with other treatments to rid the airways of secretions. These other treatments include suctioning, nebulizer treatments, and the administration of expectorant drugs. Chest physical therapy can be used with newborns, infants, children, and adults. People who benefit from chest physical therapy exhibit a wide range of problems that make it difficult to clear secretions from their lungs. Patients who may receive chest physical therapy include those with cystic fibrosis, neuromuscular diseases (such as Guillain-Barré syndrome), progressive muscle weakness (such as myasthenia gravis), or tetanus. People with lung diseases such as pneumonia, bronchitis, and some forms of chronic obstructive pulmonary disease (COPD), including chronic bronchitis, also benefit from chest physical therapy. CPT should not be used in the treatment of patients diagnosed with asthma. People without specific lung problems but who are likely to aspirate their mucous secretions because of diseases such as cerebral palsy or muscular dystrophy also receive chest physical therapy, as do those who are bedridden or confined to a wheelchair. In addition, CPT may be part of treatment after surgery for patients who develop difficulty taking deep breaths.

Precautions While the doctor ultimately determines which type of therapy can be performed, health care professionals know that not all forms of chest physical therapy are appropriate for all patients. Postural drainage and percussion should not be administered to patients who: • have just eaten or are vomiting • have acute asthma or tuberculosis

• have an active hemorrhage • have injuries to the spine • have open wounds or burns • have had recent surgery

Description Chest physical therapy can be performed in a variety of settings including critical care units, hospitals, nursing homes, outpatient clinics, and in the patient’s home. Depending on the circumstances, chest physical therapy may be performed by anyone ranging from a respiratory care therapist to a trained member of the patient’s family. Patients can be taught to perform some therapies. Lengths of therapies and their costs vary. Some therapies may be part of ongoing treatment for a chronic condition. Special equipment may be needed for some procedures, such as percussion, and may be covered by the patient’s health plan. Chest physical therapy encompasses a variety of procedures; which ones are applied depends on the patient’s needs. Hospitalized patients are reevaluated frequently to establish which procedures are most effective and best tolerated. Patients receiving long term chest physical therapy are reevaluated about every three months. Turning Turning from side to side permits lung expansion. Patients who cannot turn themselves are turned by a caregiver. The head of the bed is also elevated to promote drainage if the patient can tolerate this position. Critically ill patients and those dependent on mechanical respiration are turned once every one to two hours around the clock. Coughing Coughing helps break up secretions in the lungs so that the mucus can be suctioned out or expectorated. However, for patients with conditions like COPD, it can be painful to cough normally. An important part of chest

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• have brittle bones or broken ribs

Chest physical therapy

Chest physical therapy

Incentive spirometry The incentive spirometer helps the patient improve lung function. This self-administered therapy involves inhaling into a tube attached to a device. The specific technique and goal depends on the type of spirometer. The patient receives directions from the doctor, nurse, or respiratory therapist. With a breath flow-oriented device, the patient inhales through a tube to raise a ball inside the plastic spirometer chamber. The drop in pressure causes the ball to rise, and the goal is to keep the ball in the air for as long as possible.

A patient with cystic fibrosis receives chest physical therapy after using nebulizer therapy to loosen the mucus in her lungs. (Photograph by Simon Fraser. Science Source/Photo Researchers. Reproduced by permission.)

physical therapy is teaching patients to clear their airways by gentler methods, such as with a controlled cough or by “huffing.” Before either technique, patients are advised to sit upright and drink a glass of water. For the controlled cough, patients purse their lips and take a deep breath. They hold their breath for several seconds and then make two brief, gentle coughs. Huffing also starts with pursing the lips and taking a deep breath. After holding the breath for several seconds, patients exhale by using the stomach muscles to push the air out. The vocal chords remain open so that the cough has almost a whispery sound. Coughing and huffing are repeated several times a day as needed. Deep breathing exercises Deep breathing helps expand the lungs and forces better distribution of the air into all areas. The patient may initially need to lie down to do these exercises, but eventually it is done while sitting upright, then while walking. Patients may find it helpful to monitor their breathing by placing a hand on their abdomen to provide a sense of their regular breathing pattern. The patient then starts by taking a deep breath through the nose, then purses the lips as if to whistle. The patient then exhales the air slowly through pursed lips. The exhalation should take twice as long as the inhalation. A patient may start by inhaling for two seconds and then exhaling for four. After taking several deep breaths, the patient breathes at a normal rhythm and begins another cycle of deep breathing. The patient builds up to taking deeper breaths, following a schedule given by the health care team. Generally, COPD patients practice deep breathing exercises for 20 minutes each day. 486

For a volume-oriented device, the patient sets a pointer on the chamber at the desired breath volume level. The patient inhales into the tube and attempts to raise a piston inside the chamber so that the volume marker reaches that level. Hybrid volume accumulators combine a flow-oriented device with a volume-oriented device. A piston inside a cylinder responds to negative pressure from the patient’s inhalation. Some devices have a component designed for exhalation. If the model does not include an exhaling function, the patient breathes out air naturally. At the end of the session, the patient takes a deep breath and then coughs. The length of therapy and the number of exercises done depend on the patient’s condition and is determined by a respiratory therapist or other health professional. Postural drainage Postural drainage uses gravity to assist in draining secretions from the lungs and into the central airway where they can either be coughed up or suctioned out. This therapy generally lasts a maximum of 30 minutes. If various positions are tried to induce a cough, the patient may remain in one position for from five to 15 minutes. The health care team guides the patient in determining the amount of time needed. Each position reaches a specific area of the lungs. Chest drainage positions include: • the patient seated with head back • the patient seated with head bent forward • the patient lying face up with feet higher than the head • the patient lying face down with feet higher than the head • the patient lying first on one side, then the other, with feet higher than the head Critical care patients and those depending on mechanical ventilation receive postural drainage therapy

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Percussion Percussion, also called cupping or clapping, involves rhythmically striking the chest wall with cupped hands. Mechanical devices can also be used. Percussion results in breaking up thick secretions in the lungs so that they can be more easily removed. Percussion is performed on each lung segment for one to two minutes at a time.

• oxygen deficiency if the head is kept lowered for drainage • increased intracranial pressure • temporary low blood pressure • bleeding in the lungs • pain or injury to the ribs, muscles, or spine • vomiting • inhaling secretions into the lungs • heart irregularities

Results Vibration Vibration therapy is done for one minute after percussion therapy or may be used instead of percussion therapy for patients who may be too sore or frail to tolerate percussion. The purpose is also to help break up lung secretions. Vibration can be performed either mechanically or manually. When done manually, the person performing the vibration places his or her hands against the patient’s chest and creates vibrations by quickly contracting and relaxing arm and shoulder muscles while the patient exhales. The procedure is repeated several times each day for about five exhalations.

The health care team should tell patients that CPT is often an ongoing treatment, with some or all therapies done daily. A positive response to treatment can be assessed by: • increased volume of sputum secretions • ease in breathing • changes in breath sounds • improved vital signs • improved chest x ray • increased oxygen in the blood as measured by arterial blood gas values

Preparation Preparation for chest physical therapy starts with an evaluation of the patient’s condition to determine which chest physical therapy techniques would be most beneficial. Since most therapies are done at home, patient education is extremely important. The doctor, nurse, physical therapist, or respiratory therapist instructs the patient or caregiver in chest physical therapy techniques. The therapy should be explained and demonstrated by the health professional. Then the patient or caregiver should try the therapy. This will demonstrate whether the patient understands the therapy or if more instruction is needed.

Aftercare Patients should be advised to practice oral hygiene procedures to lessen the bad taste and odor of the secretions that they spit out.

Complications Risks and complications associated with chest physical therapy depend on the health of the patient. Although chest physical therapy usually poses few problems, the health care team should be aware that in some patients it may cause:

Health care team roles The doctor typically orders chest physical therapy for a patient. A nurse or respiratory therapist provides therapy when a patient is hospitalized. For people seen on an outpatient basis, the emphasis is generally on patient education. Patient education Effective patient education is vital because chest physical therapy is often performed at home. A doctor, nurse, or respiratory therapist explains and demonstrates techniques such as breathing, percussion, and incentive spirometry. The patient or caregiver performs the therapy under the health professional’s observation to be sure it can be done correctly independently. Nurses and respiratory therapists also participate in public awareness education, such as anti-smoking campaigns. Training Chest physical therapy is part of training for physicians and nurses specializing in cardiopulmonary treatment, and for respiratory therapists (also known as respi-

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four to six times daily. Patients at home are given schedules set by their doctor or respiratory therapist. Percussion and vibration may be performed in conjunction with postural drainage.

Chest tube maintenance

ratory care practitioners). Therapists must have at least an associate degree, which is earned after completion of a two-year program. There are also four-year bachelor degree programs for this profession. Graduates with both types of degrees are certified after passing the examination given by the National Board for Respiratory Care. Resources BOOKS

Frownfeller, Donna, et al. Principles & Practices of Cardiopulmonary Physical Therapy, 3rd Edition. St. Louis: Harcourt Health Sciences, 1996. Haas, Francois, and Sheila Sperber Haas. The Chronic Bronchitis and Emphysema Handbook. New York: John Wiley & Sons, 2000. Hough, Alexandra. Physiotherapy in Respiratory Care. London: Chapman & Hall, 1996. ORGANIZATIONS

American Association for Respiratory Care. 11030 Ables Lane, Dallas, TX 75229. . American College of Chest Physicians. 3300 Dundee Road, Northbrook, IL 60062-2348. (847) 498-1400. . American Lung Association. 1740 Broadway, New York, NY 10019. (212) 315-8700. . American Physical Therapy Association. www.apta.org. Cystic Fibrosis Foundation. 6931 Arlington Road, Bethesda, MD 20814. (800) FIGHT-CF. . National Board for Respiratory Care. 830 Nieman Road, Lenexa, KS 66214. (913) 599-4200. . National Heart, Lung, and Blood Institute. National Institutes of Health. Building 31, 4A21, 9000 Rockville Pike, Bethesda, MD 02005. .

Liz Swain

Chest radiography see Chest x ray

Chest tube maintenance

Purpose Under normal circumstances, intrapleural pressure is below atmospheric pressure. When this pressure changes because of excess air and/or fluid, the lung may collapse. If this occurs, a chest tube is inserted into the intrapleural space. This lets excess fluids drain, restores normal pressure, reinflates the lung, and allows adequate gas exchange. Persons experiencing a pleural effusion (accumulation of fluid in the spaces of the pleura), hemothorax (accumulation of blood in the pleural cavity), pneumothorax (collapsed lung), and empyema (accumulation of pus in the pleural cavity) may all require the insertion of a chest tube.

Precautions The patient requiring a chest tube is acutely ill because any change in the intrapleural pressure compromises the patient’s ability to breathe. An oxygen source, suction, and emergency equipment must be nearby when this procedure is performed.

Description Depending on the patient’s condition, the chest tube insertion may occur at the bedside, in the emergency room, or in the operating room. In any case, the insertion of a chest tube is a sterile procedure. Most hospitals have chest tube insertion trays containing all of the necessary supplies. First, the health care provider administers a local anesthetic. The patient is positioned according to the type of lung collapse being treated. After making a small incision, the physician inserts the chest tube. To avoid accidental puncture of the lung or pleura, the patient should be reminded not to cough or move during the procedure. Once the chest tube is in and sutured in place, the tube will be attached to a drainage system. Vaseline gauze may be placed at the chest tube insertion site to make certain an adequate seal has been achieved. Sterile 4  4 gauze pads will be placed over the Vaseline gauze, then securely taped. It is wise to tape the far end of the chest tube to the patient’s chest to prevent dislodgement.

Definition A chest tube is a drain placed into the pleural space to restore intrapleural pressure and reinflate the lung after it has collapsed. It also acts to prevent fluid and air from returning to the chest. Chest tube maintenance includes the actions performed by the nurse or other health care professional to keep the tube functioning properly. 488

Preparation The patient may be anxious about the procedure. Providing privacy and emotional support, along with explaining the procedure may help calm the patient. The nurse should perform a baseline assessment and take vital signs. An informed consent should be signed if the patient is able to do so. The physician may order pre-

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Aftercare After the chest tube has been inserted, it is the nurse’s responsibility to maintain a patent (clear) and intact pleural drainage system. The chest tube will be connected to about 6 ft (1.8 m) of rubbery tubing that leads to a collection device several feet below the chest. The patient should be Instructed to avoid lying on the tubing, and the nurse must make certain no kinks occur. All tubing connections should be taped to prevent air leaks. The chest drainage system has a separate water seal that acts as a one-way valve. The nurse adds a specified amount of sterile saline to this water seal chamber and makes sure the end of the tubing stays in the fluid. When air is pushed out of the pleural space and through the tubing, it bubbles into the saline and cannot return to the chest. If necessary, suction may be added to the drainage system. The depth of the saline determines the maximal allowable suctioning for the system. The nurse should note and document the amount and color of the chest tube drainage, and the level of drainage should be marked at the end of each shift. The patient’s respiratory status should be assessed frequently. It is normal to note decreased breath sounds on the side of the chest tube. The patient should be encouraged to perform coughing and deep-breathing exercises.

Complications Several complications can occur when managing a patient with a chest tube. If the tube accidentally becomes dislodged, the open insertion site should be quickly covered with Vaseline gauze and the physician notified. If the tubing becomes disconnected from the drainage system, the chest tube should be clamped. (Padded clamps should be kept at the bedside at all times.) Both of these situations, if untreated, could allow air to enter the lung. Sometimes clots can form within the tube and prevent free drainage. If this happens, the tube should be milked gently, squeezing it to move the clot, but not handling it so firmly that the tubing becomes occluded. If the drainage system unit is damaged or cracked, allowing atmospheric pressure into the system, the uncontaminated end of the connective tubing should be placed into sterile saline or water to a depth of 0.79 in (2 cm) until a new system can be obtained. Finally, a patient with a chest tube is at increased risk for infection. This risk can be reduced by cleaning the chest tube site and changing the dressing regularly.

KEY TERMS Atmospheric pressure—The force exerted by air at any point on the earth’s surface. Mean atmospheric pressure at sea level is approximately 1,000 millibars (100 kilopascals), give or take 5%. Empyema—A collection of pus in the pleural space. Hemothorax—Blood in the pleural cavity, usually caused by a chest injury. Intrapleural—Situated within the pleura or pleural cavity Pleura—Thin membrane that covers each half of the thorax, surrounding and protecting the lung on that side. Pleural cavity—The space within each pleura, which contains the lungs. Pleural effusion—Fluid in the pleural cavity, caused by, among other things, congestive heart failure, cancer, tuberculosis, and lung infections. Pneumothorax—Air in the pleural cavity, which causes the lung to collapse. Causes include lung disease, penetrating trauma, and certain medical procedures, including ventilation and cardiopulmonary resuscitation. Valsalva maneuver—Holding the breath while bearing down. This maneuver may be used to interrupt a mild heart arrhythmia or to prevent air from entering the pleural cavity when a chest tube is removed.

Results The chest tube can be removed when one of the following has happened: • The lung has fully expanded. • No air leak has developed during a 24–48 hour period. • Less than 5.07 oz (150 ml) of fluid has drained in a 24hour period. Normally, the physician removes the chest tube while the patient performs a Valsalva maneuver. Vaseline gauze is immediately applied over the insertion point. This prevents any air from entering the pleural space.

Health care team roles The physician is responsible for inserting the chest tube and is usually responsible for its removal. (Some nurse prac-

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medications, which should be administered by the nurse as prescribed.

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tice acts allow nurses to remove chest tubes.) The nurse assists with the insertion procedure, assesses the patient’s respiratory status afterwards, and maintains a patent chest tube. Resources BOOKS

Ignatavicius, Donna D., et al. Medical-Surgical Nursing Across the Health Care Continuum. Philadelphia: W.B. Saunders Company, 1999. PERIODICALS

Blank-Reid, Cynthia A., and Paul C. Reid. “Taking the Tension Out of Traumatic Pneumothoraxes.” Nursing 29 (April 1999): 41. Pettinicchi, Theodore A. “Trouble Shooting Chest Tubes.” Nursing 28 (March 1998): 58.

Deanna M. Swartout-Corbeil, R.N.

A chest x ray may be ordered by a physician to check for possible tumors of the lungs, thyroid, lymph nodes, or even the displacement of an organ by a tumor, if present. Chest x rays can oocasionally be used to check for secondary spread of cancer from one organ to another. Cardiac disorders Although less sensitive than echocardiography to evaluate the heart, chest x ray is preferred to check for disorders such as congestive heart failure or pulmonary edema. Pericardial effusion (fluid surrounding the heart), if present, and cardiac size will also be noted on the chest x ray. Other Chest x rays can be used to see foreign bodies that may have been swallowed or inhaled, and to evaluate response to treatment for various diseases. The chest x ray is also used to verify correct placement of chest tubes or catheters in acutely ill patients.

Chest x ray Definition

Precautions

A chest x ray is a procedure used to evaluate organs and structures within the chest for symptoms of disease. Chest x rays include views of the lungs, heart, small portions of the gastrointestinal tract, and the bones of the chest area. X rays are a form of radiation that can penetrate the body and produce an image on an x ray film. Another name for the x ray image is radiograph.

Purpose Chest x rays are ordered for a wide variety of diagnostic purposes. In fact, this is probably the most frequently performed x ray exam. In some cases, chest x rays are ordered for a single check of an organ’s condition, and at other times, serial x rays are ordered to compare to previous studies. Some common reasons for chest x rays include: Pulmonary disorders Chest films are frequently ordered to diagnose or rule out pneumonia, bronchitis, pleurisy, tuberculosis, and other acute illnesses. Other pulmonary disorders such as emphysema or pneumothorax (presence of air or gas in the chest cavity outside the lungs) may be detected or evaluated through the use of chest x ray. It might also show vascular damage in the lung, which would require further evaluation. 490

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Pregnant women, particularly those in the first or second trimester, should not have chest x rays unless absolutely necessary. If the exam is ordered, women who are, or could possibly be, pregnant must wear a protective lead apron, with the full coverage adjusted for the direction of the x-ray beam. Because the procedure involves radiation, care should always be taken to avoid overexposure, particularly for children. However, the amount of radiation from one chest x ray procedure is minimal.

Description Routine chest x rays consist of two views: the frontal view (referred to as posterior-anterior or PA) and the lateral (side) view, with the left side against the x-ray board. It is preferred that the patient stand for this exam. The patient must remain motionless, and will be asked to take in a big breath for each x ray. Filling the lungs with air expands the lung fields, and shows the anatomy at its most optimum. In addition, the deep inspiration of air also helps the patient remain motionless, which is critically important in such a short x-ray exposure. The chest x ray may be performed in a physician’s office or referred to an outpatient radiology facility or hospital radiology department. In some cases, particularly for bedridden patients, a portable chest x ray may be taken. Portable films are sometimes of poorer quality than those taken with permanent equipment, but are the

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best choice for some patients or situations. Bedridden patients may be placed in as upright a position as possible to get the best possible image.

Preparation There is no advance preparation necessary for chest x rays. Once the patient arrives at the exam area, the patient will undress to the waist, and wear a gown or drape as provided by the facility. All necklaces will be removed as well.

Aftercare No aftercare is required by patients who have chest x rays.

Complications The only risk associated with chest x ray is minimal exposure to radiation, particularly for pregnant women and children. Those patients should use protective lead aprons during the procedure. Technologists are cautioned to carefully check possible dislodging of any tubes or monitors in the chest area from the patient’s placement during the exam, if IVs (intravenous lines) or chest tubes are in place.

Results A radiologist, or physician specially trained in the technique and interpretation of x rays, will evaluate the results. A normal chest x ray will show normal structures for the age and medical history or the patient. Findings, whether normal or abnormal, will be provided to the referring physician in the form of a written report. Abnormal findings on chest x rays are used in conjunction with a physician’s physical exam, medical history and other diagnostic tests to reach a final diagnosis. Often a patient can have normal appearing x rays and still have underlying diseases or conditions. Interpretation of chest x rays is most accurate when compared to previous chest studies. The patient may be asked to help the radiology facility in locating previous chest radiographs from other facilities. Pulmonary disorders Pneumonia shows up on radiographs as a patchy white area of density, as a result of fluid in the lung(s). If the bronchi, which are usually not visible, can be seen, a diagnosis of bronchial pneumonia may be made. Widening of the spaces between ribs, or very large, dark lung fields, also can be a radiographic sign of emphyse-

A chest x ray of normal, healthy adult lungs. (Photograph by John Smith, Custom Medical Stock Photo. Reproduced by permission.)

ma. Other pulmonary diseases may also be detected or suspected through chest x ray. Cancer In nearly all patients with lung cancer, some sort of abnormality can be seen on a chest radiograph. Hilar masses (enlargements at that part of the lungs where vessels and nerves enter) are one of the more common signs, as are abnormal masses and fluid buildup on the outside surface of the lungs or surrounding areas. Interstitial lung disease, which is a large category of disorders, many of which are related to exposure to substances (such as asbestos fibers), may be detected on a chest x ray as fiberlike deposits, often in the lower portions of the lungs. Other Congestive heart failure and other cardiac diseases may be diagnosed on the view of the heart and lung in a chest radiograph. Fractures of the sternum and ribs are

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KEY TERMS Bronchi—Plural of bronchus. The air passages in the lungs through which inhaled air passes on its way to the lungs. Diaphragm—The large muscle that is located between the abdomen and the chest area. The diaphragm aids in breathing. Gastrointestinal—The digestive organs and structures, including the stomach and intestines. Interstitial lung disease—About 180 diseases fall into this category of breathing disorders. Injury or foreign substances in the lungs, (such as asbestos fibers) as well as infections, cancers, or inherited disorders may cause the diseases. They can lead to breathing or heart failure. Lymphoid—Tissues relating to the lymphatic system. A thin yellowish fluid, called lymph fluid, travels throughout the body. The lymphatic system helps control fluids in the body. Portable chest x ray—An x ray procedure taken by equipment that can be brought to the patient. The resulting radiographs may not be as high in quality as stationary x ray radiographs, but allow a technologist to come to the bedridden patient. Pulmonary—Refers to the lungs and the breathing system and function. Serial x rays—A number of x rays performed over time in the disease progression or treatment intervals. The radiographs will be compared to one another to track changes. Sternum—Also referred to as the breast bone, this is the long flat bone in the middle of the chest.

The technologist performing the chest x ray is a highly trained professional and provides films for the radiologist to interpret. The technologist should be able to be versatile, should the patient have any physical challenges in complying with the x ray. In performing bedside, or portable chest x rays, often the assistance of nursing staff becomes necessary due to the condition of the patient. It should be the goal of both the technologist and/or nurse to ensure patient comfort, while getting the best possible radiograph. Patient education The technologist will explain the exam to the patient so that they feel comfortable with the procedure. Most adult patients are familiar with a chest x ray, nevertheless, a brief discussion between technologist and patient is important. Keeping the patient immobile during the exposure will limit having to repeat the x ray. Resources ORGANIZATIONS

American Lung Association. 432 Park Avenue South, New York, NY 10016. (212)889-3370. . Emphysema Anonymous, Inc. P.O. Box 3224, Seminole FL 34642. (813)391-9977. The National Heart, Lung and Blood Institute. Building 31, Room 4A21, Bethesda MD 20892. (301)496-4236. . OTHER

Pulmonary Perpectives. The American College of Chest Physicians, 3300 Dundee Road, Northbrook IL 60062. (847) 498-1400. . RSNA Radiology Info Online. . (June 6, 2001).

Thorax—The chest area, which runs between the abdomen and neck and is encased in the ribs. X ray—A form of electromagnetic radiation with shorter wavelengths than normal light. X rays can penetrate most structures.

sometimes also detected as breaks in the bone visible on the film. In some instances, the view of the diaphragm may indicate an abdominal problem. Foreign bodies which may have been swallowed or inhaled can usually be located by the radiologist as they will see the object either in the esophagus, or the upper part of the stomach, and will look different from any other tissue or structure in the chest. Serial chest x rays may be ordered to track changes in the position of an object over a period of time. 492

Debra Novograd, B.S.,R.T.(R)(M)

Chigong see Qigong

Child abuse Definition Child abuse is a blanket term for four types of child mistreatment: physical abuse, sexual abuse, emotional abuse, and neglect. In many cases children are the victims of more than one type of abuse. The abusers can be parents or other family members, caretakers such as

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Description Prevalence of abuse Child abuse was once viewed as a minor social problem affecting only a handful of children in the United States. In recent years, however, it has received close attention from the media, law enforcement, and the helping professions, and with this has come a sharp rise in the number of reported cases. But because abuse is often hidden from view and its victims too young or fearful to speak out, some experts suggest that its true prevalence may be much greater than the official data indicate. In 1999, Child Protective Service (CPS) agencies investigated 3 million reports that involved the maltreatment of approximately 4 million children. The CPS ranks neglect as the most common form of child maltreatment, comprising an estimated 54% of investigations in 1997. Physical abuse accounted for 24%; sexual abuse, 13%; emotional maltreatment, 6%; and medical neglect, 2%. Many children suffer more than one type of maltreatment. Although experts are quick to point out that abuse occurs among all social, ethnic, and income groups, reported cases usually involve poor families with little education. Young mothers, single-parent families, and parental alcohol or drug abuse are also common in reported cases. According to recent statistics, more than 90% of abusing parents have neither psychotic nor criminal personalities. Rather, they tend to be lonely, unhappy, angry, young, single parents who do not plan their pregnancies. About 10%, or perhaps as many as 40%, of abusive parents were themselves physically abused as children, but most abused children do not grow up to be abusive parents. Additional factors that contribute to child abuse include lack of parenting skills, unrealistic expectations about children’s behavior and capabilities, social isolation, and frequent family crises. Child abuse is a symptom that parents are having difficulty coping with their situation. In 1999, the majority of child abusers (75%) were parents, and another 10% were other relatives of the victim. About 13% of all perpetrators were classified as noncaretakers or unknown. People who were in other caretaking relationships to the victim (e.g., child care providers, foster parents, and facility staff) accounted for only 2% of perpetrators. In many states, perpetrators of child maltreatment by definition must be in a caretaking role.

Types of abuse PHYSICAL ABUSE. Physical abuse is the nonaccidental infliction of physical injury to a child. The abuser is usually a family member or other caretaker, and is more likely to be male. In 1996, 24% of the confirmed cases of child abuse in the United States involved physical abuse. A rare form of physical abuse is Munchausen syndrome by proxy, in which a caretaker (most often the mother) seeks attention by making the child sick or appear to be sick. SEXUAL ABUSE. Child sexual abuse is defined as any activity with a child under the age of legal consent that is for the sexual gratification of an adult or a significantly older child. It includes, among other things, sexual touching and penetration, persuading a child to expose his or her sexual organs, and allowing a child to view pornography. In most cases the child is related to or knows the abuser, and about one in five abusers are themselves underage. Sexual abuse was present in 12% of the confirmed 1996 abuse cases. An estimated 20–25% of females and 10–15% of males report that they were sexually abused by age 18. EMOTIONAL ABUSE. Emotional abuse, according to Richard D. Krugman, director of the Kempe Center in Denver, “has been defined as the rejection, ignoring, criticizing, isolation, or terrorizing of children, all of which have the effect of eroding their self-esteem.” Emotional abuse usually expresses itself in verbal attacks involving rejection, scapegoating, belittlement, and so forth. Because it often accompanies other types of abuse and is difficult to prove, it is rarely reported. NEGLECT. Neglect—failure to satisfy a child’s basic needs—can assume many forms. Physical neglect is the failure (beyond the constraints imposed by poverty) to provide adequate food, clothing, shelter, or supervision for a child. Emotional neglect is the failure to satisfy a child’s normal emotional needs, or behavior that damages a child’s normal emotional and psychological development (such as permitting drug abuse in the home). Failing to see that a child receives proper schooling or medical care is also considered neglect. Neglect was found in 52% of 1996 abuse cases.

Causes and symptoms Physical abuse Physical abuse, which can be triggered be such normal child behavior as crying or dirtying a diaper, often occurs when a parent loses control and lashes out at a child. Unlike nonabusive parents, who may become angry at or upset with their children from time to time but

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teachers and babysitters, acquaintances (including other children), and (in rare instances) strangers.

Child abuse

CHILD ABUSE: SIGNS AND SYMPTOMS Although these signs do not necessarily indicate that a child has been abused, they may help adults recognize that something is wrong. The possibility of abuse should be investigated if a child shows a number of these symptoms, or any of them to a marked degree: Sexual Abuse Being overly affectionate or knowledgeable in a sexual way inappropriate to the child’s age Medical problems such as chronic itching, pain in the genitals, venereal diseases Other extreme reactions, such as depression, self-mutilation, suicide attempts, running away, overdoses, anorexia Personality changes such as becoming insecure or clinging Regressing to younger behavior patterns such as thumb sucking or bringing out discarded cuddly toys Sudden loss of appetite or compulsive eating Being isolated or withdrawn Inability to concentrate Lack of trust or fear someone they know well, such as not wanting to be alone with a babysitter Starting to wet again, day or night/nightmares Become worried about clothing being removed Suddenly drawing sexually explicit pictures Trying to be “ultra-good” or perfect; overreacting to criticism Physical Abuse Unexplained recurrent injuries or burns Improbable excuses or refusal to explain injuries Wearing clothes to cover injuries, even in hot weather Refusal to undress for gym Bald patches Chronic running away Fear of medical help or examination Self-destructive tendencies Aggression towards others Fear of physical contact—shrinking back if touched Admitting that they are punished, but the punishment is excessive (such as a child being beaten every night to “make him/her study”) Fear of suspected abuser being contacted Emotional Abuse Physical, mental, and emotional development lags Sudden speech disorders Continual self-depreciation (“I’m stupid, ugly, worthless, etc.”) Overreaction to mistakes Extreme fear of any new situation Inappropriate response to pain (“I deserve this”) Neurotic behavior (rocking, hair twisting, self-mutilation) Extremes of passivity or aggression Neglect Constant hunger Constant tiredness Emaciation

Poor personal hygiene Poor state of clothing Untreated medical problems

No social relationships Compulsive scavenging Destructive tendencies

A child may be subjected to a combination of different kinds of abuse. It is also possible that a child may show no outward signs and hide what is happening from everyone.

Source: Kidscape, http://www.solnet.co.uk/kidscape/kids5.htm. Reprinted by permission.

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Unexplained or suspicious bruises or other marks on the skin, such as burns, are common signs of physical abuse. Skull and other bone fractures are often seen in young children, and in fact, head injuries are the leading cause of death from abuse. Children less than a year old are particularly vulnerable to injury from shaking. This is called shaken baby syndrome or shaken impact syndrome. Not surprisingly, physical abuse also causes a wide variety of behavioral changes in children. Sexual abuse According to psychological experts, the two prerequisites for this form of maltreatment include sexual arousal to children and the willingness to act on this arousal. Factors that may contribute to this willingness include alcohol or drug abuse, poor impulse control, and the mistaken belief that such sexual behaviors are acceptable and not harmful to the child. The chances of abuse are higher if the child is developmentally handicapped or vulnerable in some other way. Genital or anal injuries or abnormalities (including the presence of sexually transmitted diseases) can be signs of sexual abuse, but often there is no physical evidence. In fact, physical examinations of children in cases of suspected sexual abuse supply grounds for further suspicion only 15–20% of the time. Anxiety, poor academic performance, and suicidal tendencies are some behavioral signs of sexual abuse, but these are also found in children suffering other kinds of stress. Excessive masturbation and other unusually sexualized kinds of behavior are more closely associated with sexual abuse itself. Emotional abuse Emotional abuse can happen in many settings: at home, at school, on sports teams, and so on. Some of the possible symptoms include loss of self-esteem, sleep disturbances, head- or stomachaches, school avoidance, and running away from home. Neglect Many cases of neglect occur because the parent experiences strong negative feelings toward the child. At other times, the parent may truly care about the child, but lacks the ability or strength to provide for the child’s needs adequately because they are handicapped by depression, drug abuse, mental retardation, or some other problem.

Neglected children often do not receive adequate nourishment or emotional and mental stimulation. As a result, their physical, social, emotional, and mental development is hindered. They may, for instance, be underweight, develop language skills less quickly than other children, and seem emotionally needy.

Diagnosis Doctors and many other professionals who work with children are required by law to report suspected abuse to their state’s CPS agency. Abuse investigations are often a group effort involving medical personnel, social workers, police officers, teachers, and others. Some hospitals and communities maintain child-protection teams that respond to cases of possible abuse. Careful questioning of the parents is crucial, as is interviewing the child (if he or she can speak). The investigators must ensure, however, that their questioning does not further traumatize the child. A physical examination for signs of abuse or neglect is, of course, always necessary, and may include x rays, blood tests, and other procedures.

Treatment Notifying the appropriate authorities, treatment of the child’s injuries, and protecting the child from further harm are the immediate priorities in abuse cases. If the child does not require hospital treatment, protection often involves placing him or her with relatives or in foster care. Once the immediate concerns are dealt with, it becomes essential to determine how the child’s long-term medical, psychological, educational, and other needs can best be met, a process that involves evaluating not only the child’s needs but also the family’s (such as drug abuse counseling or parental skills training). If the child has brothers or sisters, the authorities must determine whether they have been abused as well. On investigation, signs of physical abuse are discovered in about 20% of the brothers and sisters of abused children.

Prognosis Child abuse can have lifelong and devastating consequences. Research has shown that abused children and adolescents are more likely, for instance, to do poorly in school, suffer emotional problems, develop an antisocial personality, become promiscuous, abuse drugs and alcohol, and attempt suicide. As adults they may have trouble establishing intimate relationships. Whether professional treatment is able to moderate the long-term psychological effects of abuse is a question that remains unanswered.

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are genuinely loving, abusive parents tend to harbor deep-rooted negative feelings toward their children.

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Resources

KEY TERMS

BOOKS

Child maltreatment—Another name for child abuse or neglect. Munchausen syndrome by proxy—A rare form of physical abuse wherein a caretaker (most often the mother) seeks attention by making the child sick or appear to be sick. Perpetrator—Any person who inflicts abuse of any form on a child, including neglect.

Health care team roles Nursing staff and allied health professionals can assist in the treatment of child abuse by being aware of physical symptoms and emotional reactions caused by abuse or neglect. During the diagnosis and treatment phase, nursing staff and allied health professionals can help patients and perpetrators by providing appropriate educational materials, and referrals to community and individual supportive programs.

Krugman, Richard D. “Child Abuse & Neglect.” In Pediatric Diagnosis & Treatment. Edited by William W. Hay, Jr., et al. Stamford, CT: Appleton & Lange, 1997. ORGANIZATIONS

Childhelp USA/IOF Foresters National Child Abuse Hotline. (800) 422-4453. National Clearinghouse on Child Abuse and Neglect Information. PO Box 1182, Washington, DC 20013-1182. (800) 394-3366. . National Committee to Prevent Child Abuse. 200 S. Michigan Avenue, 17th Floor, Chicago, IL 60604. (312) 663-3520. . National Parents Anonymous. 675 W. Foothill Blvd., Suite 220, Claremont, CA 91711. (909) 621-6184. . OTHER

Bethea, Lesa. “Primary Prevention of Child Abuse.”. American Family Physician (March 15, 1999). .

Bethanne Black

Prevention Government efforts to prevent abuse include homevisitor programs aimed at high-risk families, and schoolbased efforts to teach children how to respond to attempted sexual abuse. When children reach age three, parents should begin teaching them about “bad touches” and about confiding in a trusted adult if they are touched or treated in a way that makes them uneasy. Parents also need to exercise caution in hiring babysitters and other caretakers. Anyone who suspects abuse should immediately report those suspicions to the police or his or her local CPS agency, which will usually be listed in the blue pages of the telephone book under Rehabilitative Services or Child and Family Services, or in the yellow pages. Round-the-clock crisis counseling for children and adults is offered by the Childhelp USA/IOF Foresters National Child Abuse Hotline. The National Committee to Prevent Child Abuse is an excellent source of information on the many support groups and other organizations that help abused and at-risk children and their families. One of these organizations, National Parents Anonymous, sponsors 2,100 self-help groups throughout the United States, Canada, and Europe. Telephone numbers for its local groups are listed in the white pages of the telephone book under Parents Anonymous or can be obtained by calling the national headquarters. 496

Childbirth Definition Childbirth includes both labor (the process of birth) and delivery (the birth itself); it refers to the entire process as an infant makes its way from the womb down the birth canal to the outside world.

Description Childbirth usually begins spontaneously, following about 280 days after conception, but it may be started by artificial means if the pregnancy continues past 42 weeks gestation, or if complications develop. Labor may also begin prematurely. The average length of labor is about 14 hours for a first pregnancy and about eight hours in subsequent pregnancies. However, many women experience a much longer or shorter labor. Labor can be described in a series of phases. First phase of labor During the first phase of labor, the cervix dilates (opens) from 0–10 cm (0–4 in). This phase has an early, or latent, phase and an active phase. During the latent phase, progress is usually very slow. It may take quite a

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As labor begins, the muscular wall of the uterus contracts and relaxes as the cervix thins and expands. As a portion of the amniotic sac surrounding the baby is pushed into the opening, it bursts under the pressure, releasing amniotic fluid (water breaking). Sometimes the amniotic sac breaks before labor begins. During this first phase the birth attendant or nurse will do periodic pelvic exams to determine how the labor is progressing. If the contractions aren’t forceful enough to open the cervix, a drug called oxytocin (Pitocin) may be given to make the uterus contract. As pain and discomfort increase, women may be tempted to request pain medication or anesthetics. If possible, though, these should be delayed until the active phase of labor begins—at which point the medication will not slow down or stop the labor. The active stage of labor is faster and more efficient. In this phase, contractions are longer and more regular, usually occurring about every two to three minutes. These stronger contractions are also more painful. Women who use the breathing exercises learned in childbirth classes find that these can help them cope with the pain experienced during this phase. Many women also receive some pain medication at this point—either a short-term narcotic or epidural anesthesia. As the cervix dilates to 8–9 cm (3.15–3.54 in), the transition phase begins. This refers to the progression from the first phase, during which the cervix dilates, to the second phase, during which the baby is pushed out through the birth canal. As the cervix dilates completely and the baby’s head begins to descend, women feel the urge to push or bear down. Second stage of labor When the top of the baby’s head appears at the opening of the vagina, the birth is nearing completion. First the head passes under the pubic bone. It fills the lower vagina and stretches the perineum. This position is called “crowning,” since only the crown of the head is visible. When the entire head is out, the shoulders follow. The attending practitioner may suction the baby’s mouth and nose to ease its first breath. The rest of the baby usually slips out easily, and the umbilical cord is cut. Episiotomy As the baby’s head appears, the perineum may be stretched so tightly that the baby’s progress is slowed. If

there is risk of tearing the mother’s tissue, the doctor or midwife may make a small incision, called an episiotomy, into the perineum to enlarge the vaginal opening. If the woman has not had an epidural or pudendal block, she will get a local anesthetic to numb the area. Once the episiotomy is made, the baby is born with a few pushes. Third stage In the final stage of labor, the placenta is pushed out of the vagina by the continuing uterine contractions. The placenta is pancake shaped and about 10 in (25.4 cm) in diameter. During the pregnancy it was attached to the uterine wall and conveyed nourishment from the mother to the fetus. Continuing uterine contractions release it from the uterus at this point. It is important that all of the placenta be removed from the uterus. If it is not, the uterine bleeding that is normal after delivery may be much heavier, and uterine infection may occur. Breech presentation Approximately 4% of babies are in what is called a “breech” position when labor begins. In breech presentation, the baby’s bottom or legs press against the cervix and are positioned to enter the birth canal. An obstetrician may attempt to turn the baby to a head-down position using a technique called version before labor begins. This is only successful approximately half the time. The risks of vaginal delivery with breech presentation are much higher than with a head-first presentation. In these cases the mother and attending practitioner will need to weigh the risks and decide whether to deliver via cesarean section or attempt a vaginal birth. The extent of the risk depends to a great extent on the type of breech presentation, of which there are three: • Frank breech—the baby’s legs are folded up against its body. This is the most common and the safest for vaginal delivery. • Complete breech—the baby’s legs are crossed under and in front of the body. • Footling breech—one or both legs are positioned to enter the birth canal. Vaginal delivery with this presentation is considered unsafe. Several factors should be considered before attempting a vaginal breech birth. An ultrasound examination should be done to be sure the baby’s head is not unusually large, and that it is flexed (tilted forward) rather than hyperextended (tilted back). Fetal monitoring and close observation of the progress of labor are also important. If labor slows or there is any sign that it will be difficult for the baby to pass through the pelvis it may be safer to consider a cesarean section.

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while and many contractions before the cervix dilates the first few centimeters. Contractions increase in strength and frequency as labor progresses. Most women are relatively comfortable during the latent phase.

Childbirth

Placenta Umbilical cord Uterus

Vagina Cervix

Stage 1: Dilation of the cervix

(Illustration by Hans & Cassidy.)

The vacuum extractor is not as likely as forceps to injure the mother, and it leaves more room for the baby to pass through the pelvis. However, there may be problems in maintaining the suction with this method, and there is the potential for brain damage if repeated attempts are made, so forceps may be a better choice if it is important to remove the baby quickly. Cesarean sections

Forceps delivery If the labor is not progressing as it should, the baby appears to be in distress, or the mother is too exhausted to push, the doctor may opt for a forceps delivery. A forceps is a spoon-shaped device that resembles a set of salad tongs. It is placed around the baby’s head so the doctor can pull the baby gently out of the vagina. Forceps can be used after the cervix is fully dilated. Before placing the forceps around the baby’s head, pain medication or anesthesia may be given to the mother. The doctor may use a catheter to empty the her bladder, and may clean the perineal area with soapy water. Often an episiotomy is done before a forceps birth, although tears can still occur. The obstetrician slides half of the forceps at a time into the vagina and around the side of the baby’s head to gently grasp the head. When both halves are in place, the doctor pulls on the forceps to help the baby through the birth canal as the uterus contracts. Sometimes the baby can be delivered this way after the very next contraction. When used by an experienced physician, forceps can save the life of a baby in distress. Complications from this type of delivery include nerve damage or bruises to the baby’s face. The frequency of forceps delivery varies from one hospital to the next, depending on the experience of staff and the types of anesthesia offered at the hospital. Some obstetricians accept the need for a forceps delivery as a way to avoid cesarean birth. Others don’t use forceps at all. Vacuum-assisted birth This method of helping a baby out of the birth canal was developed as a gentler alternative to forceps. As with forceps, vacuum-assisted birth can only be used after the cervix is fully dilated and the head of the fetus has begun 498

to descend through the pelvis. In this procedure, the doctor uses a device called a vacuum extractor, placing a large rubber or plastic cup against the baby’s head. A pump creates suction that gently pulls on the cup to gently ease the baby down the birth canal. The force of the suction may cause a bruise on the baby’s head, but it fades in a day or so.

A cesarean section, also called a C-section, is a surgical procedure in which incisions are made through a woman’s abdomen and uterus to deliver her baby. The procedure is used to deliver nearly 25% of babies born in the United States; the rate can be as high as 60% for mothers who have had a previous C-section. Cesarean sections are performed whenever abnormal conditions complicate labor and vaginal delivery, threatening the life or health of the mother or the baby. Labor complications include: abnormalities in the mother’s birth canal; abnormalities in the fetus’s position; an unusually large baby; and abnormalities in the labor, including weak or infrequent contractions. Another complication is fetal distress, a condition in which the fetus does not get enough oxygen. This can lead to fetal brain damage. The mother’s health can also influence the decision to deliver by C-section, especially if she has vaginal herpes, pregnancy-induced hypertension, or diabetes.

Causes and symptoms One of the earliest signs of approaching labor is loss of the “mucous plug,” the thick secretion that covers the cervix during the nine months of pregnancy to protect the fetus from infection. Another is the “bloody show,” which is produced by broken capillaries in the cervix. Both the mucous plug and the bloody show appear as the cervix begins to expand and dilate in preparation for labor. The most common indication that labor has begun is the onset of contractions. Sometimes women have trouble telling the difference between early contractions and and false labor pains, but the biggest distinction is that true labor pains develop a regular pattern, with contractions coming closer together.

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Another less common sign that labor is beginning is the breaking of the amniotic sac that cushioned the baby during the pregnancy. When it breaks, it releases water in a trickle or a gush. Only about 10% of women actually experience this water flow in the beginning of labor, however. Most of the time, the rupture occurs sometime later in labor. If the amniotic sac doesn’t rupture on its own, the birth-attendant may break it during labor. A few women have diarrhea or nausea as labor begins. Others notice a sudden surge of energy and the urge to clean or arrange things right before labor begins; this is known as “nesting.”

Stage 2: Expulsion of the fetus

(Illustration by Hans & Cassidy.)

Diagnosis The progression of labor can be determined by measuring how much the cervix has dilated. The degree of dilation is estimated by feeling the opening cervix during a pelvic exam. Dilation is measured in centimeters, from 0–10 cm (0–4 in). Contractions that cause the cervix to dilate are the sign of true labor. Fetal monitoring Fetal monitoring is a process in which the baby’s heart rate is monitored for indicators of stress during labor and birth. There are several types of fetal monitoring. A special stethoscope called a fetoscope may be used. This is a simple and noninvasive method. The Doppler method uses ultrasound; it involves a handheld listening device that transmits the sounds of the heart rate through a speaker or into an attached ear piece. It can usually pick up the heart sounds 12 weeks after gestation. This method offers intermittent monitoring. It allows the mother freedom to move about and is also useful during contractions. Electronic (external) fetal monitoring, in which a monitor is strapped to the mother’s abdomen, uses ultrasound to measure the fetal heartbeat in relation to the mother’s contractions. It is often used in high-risk pregnancies, and is not always recommended for low-risk ones because it renders the mother immobile. External monitoring can be done intermittently, as needed. Internal monitoring provides continuous monitoring for the high-risk mother. It requires the mother’s water to be broken and that she be 2–3 cm (0.75–1.25 in) dilated. An electrode is attached to the baby, usually on the head, and a pressure catheter records the strength of uterine contractions. Internal monitoring is more accurate than external fetal monitoring, because external monitors are more likely to slip off. Internal monitoring is continuous.

Telemetry monitoring, the newest type, is similar to electronic monitoring, but uses radio waves beamed from a transmitter worn by the mother to measure the fetal heartbeat. The mother is able to remain mobile while still being monitored continuously. FETAL MONITORING RESULTS. The results of internal and external fetal monitoring are both displayed and printed. Most interpretations are based on the printed tracing. The top tracing reflects fetal heart rate; the bottom tracing measures contractions. Baseline fetal heart rate is considered normal if it is between 120 and 160 beats per minute (bpm). Monitoring of contractions with an external fetal monitor gives the frequency and duration of the contractions. Internal monitoring of contractions can provide contraction intensity values.

Treatment Childbirth options Most women choose some type of pain relief during childbirth, ranging from relaxation and imagery to powerful drugs. The specific choice may depend on what’s available, the woman’s preferences, her doctor or midwife’s recommendations, and how the labor is proceeding. All drugs have some risks and some advantages. REGIONAL ANESTHETICS. Regional anesthetics include epidurals and spinals. Depending on the type of medication used, these types of anesthesia can block nerve signals, causing temporary pain relief, or a loss of sensation from the waist down. An epidural or spinal block can provide complete pain relief during cesarean birth.

An epidural is placed with the woman lying on her side or sitting up in bed with the back rounded to allow more space between the vertebrae. Her back is scrubbed with antiseptic, and a local anesthetic is injected in the skin to numb the site. The needle is inserted between two

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Placenta being detached Umbilical cord

Stage 3: Expulsion of the placenta

(Illustration by Hans & Cassidy.)

vertebrae and through the tough tissue in front of the spinal column. A catheter is threaded through the needle and the needle is then removed. The anesthetic then drips continuously through the catheter. Epidurals provide complete pain relief and can help conserve a woman’s energy, allowing her to relax or even sleep during labor. This method requires an IV and fetal monitoring. It may be harder for a woman to bear down when it comes time to push, although the amount of anesthesia can be adjusted as this stage nears. Spinal anesthesia is used primarily for C-section delivery. Unlike epidural anesthesia, which is administered continuously in the space around the spinal column, spinal blocks are one-time injections of anesthetic that go directly into the fluid that surrounds the spine. Although this method disables motor nerves, preventing women who use it from pushing during delivery, this is not an issue during a C-section. Spinals provide quick and strong anesthesia and permit major abdominal surgery with minimal pain. NARCOTICS. Short-acting narcotics can ease pain

and do not interfere with a woman’s ability to push. However, they can cause sedation, dizziness, nausea, and vomiting. Narcotics cross the placenta and may slow down a baby’s breathing. For this reason they can not be given too close to the time of delivery. METHODS OF PREPARATION. Health care providers often use psychoprophylaxis to help expectant mothers prepare for childbirth. These techniques use relaxation and breathing exercises along with other methods to diminish the discomfort and fear many women experience in childbirth. Although several distinct methods have evolved since the 1930s, when psychoprophylaxis first gained acceptance in the medical community, most doctors, nurses, and midwives today use a combination of approaches to instruct their patients.

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The Read method is named for Dr. Grantly DickRead, the English obstetrician who developed it in the 1930s. This method aims to decrease the fear and tension surrounding childbirth by educating the mother about the birth process, and using relaxation and deep breathing techniques. Lamaze, or Lamaze-Pavlov, is probably the bestknown method in the United States today, although the pure Lamaze method is rarely used. It first became widely popular in the 1960s. The Lamaze method combines breathing exercises with concentration on a focal point to allow mothers to control pain while maintaining consciousness. This also allows the flow of oxygen to the baby and to the muscles in the uterus to be maintained. A partner coaches the mother throughout the birthing process. The LeBoyer method stresses a relaxed delivery in a quiet, dim room that prevents overstimulation of the baby. Mother-child bonding is fostered by placing the baby on the mother’s abdomen and by having the mother massage the baby immediately after delivery. Then the father washes the baby in a warm bath. The Bradley method is called father-coached childbirth because it encourages the father to serve as coach throughout the labor. It encourages normal activities during the first stages of labor. A newer method, called water birthing, allows mothers to labor and sometimes deliver—provided a doctor, nurse, or midwife is at hand—in a pool of warm water. The water supports and relaxes the mother, making labor more comfortable.

Prognosis National U.S. health goals are to reduce the maternal mortality rate to no more than 3.3 deaths per 100,000 live births. The baseline in 1998 was 7.1 maternal deaths per 100,000 live births. The target for fetal and infant death reduction during the perinatal period (28 weeks of gestation to seven days or more after birth) is no more than 4.5 per 1,000 live births plus fetal deaths. The baseline in 1997 was 7.5 per 1,000.

Health care team roles The nurse or nurse-midwife caring for the patient during labor and delivery will perform the following: • Obtain an initial history and perform a physical examination upon admission. • Determine the position of the baby. • Assess for rupture of membranes.

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• Monitor vital signs. • Monitor baby’s heartrate and measure frequency and duration of contractions. Apply fetal monitoring apparatus if ordered. Observe tracing and record results in patient’s record. • Encourage involvement of the father and provide explanations to him as requested. • Insert IV if ordered. Obtain laboratory specimens; evaluate results. • Provide comfort measures through emotional support, changing pads, giving ice chips if allowed, giving back massages, assisting with breathing during contractions, administering pain medications, and assisting with regional anesthesia administration. • Implement emergency measures if necessary. • Assist with vaginal exams, rupturing the membranes (amniotomy) and other procedures as indicated. • Prepare for delivery by setting up instruments, transporting to delivery room or readying birthing bed, and preparing equipment for initial newborn care. • Provide coaching during pushing and delivery.

KEY TERMS Amniotic sac—The membranous sac that surrounds the embryo and fills with watery fluid as pregnancy advances. Breech birth—Birth of a baby bottom- or feet-first, instead of the usual head first delivery. This can add to labor and delivery problems because the baby’s bottom doesn’t mold a passage through the birth canal as well as the head. Cervix—A small cylindrical organ, about an inch (2.54 cm) or so long and less than an inch around, that makes up the lower part and neck of the uterus. The cervix separates the body and cavity of the uterus from the vagina. Embryo—The unborn child during the first eight weeks of its development following conception. Gestation—The period from conception to birth, during which the developing fetus is carried in the uterus. Perineum—The area between the thighs that lies behind the genital organs and in front of the anus. Placenta—The organ that develops in the uterus during pregnancy and that links the blood supplies of mother and baby.

• Receive the baby after delivery and perform initial newborn care. • Administer medications as ordered. • Assess the mother and baby frequently after delivery. • Provide perineal care for the mother. • Monitor mother’s and baby’s vital signs.

Association of Women’s Health, Obstetric, and Neonatal Nurses. 2000 L Street, NW, Suite 740, Washington, D. C. 20036. (800) 673-8499 U.S., (800) 245-0231 Canada. www.awhonn.org. International Childbirth Education Association. PO Box

• Assist mother with breastfeeding.

20048, Minneapolis, MN 55420. (612) 854-8660.

• Facilitate bonding of baby with mother, father, and other family members.

www.icea.org.

Resources BOOKS

Cunningham, F. Gary, et.al. Williams Obstetrics. 20th ed. Stamford, CT: Appleton & Lange, 1997. Pillitteri, Adele. Maternal & Child Health Nursing. 3rd ed. Philadelphia: Lippincott, 1999. ORGANIZATIONS

American Academy of Husband-Coached Childbirth. PO Box 5224, Sherman Oaks, CA 91413. (800) 423-2397; in California (800) 422-4784. www.bradleybirth.com. The American College of Nurse-Midwives. 818 Connecticut Ave. NW, Suite 900, Washington, D.C. 20006. (202) 7289860. www.acnm.org.

OTHER

Burgess, Traci. “Benefiting from Childbirth Education.” . Department of Health and Human Services. “Healthy People 2010” <www.health.gov/healthypeople/default.htm>. Hargett, Dave, “Anesthesia and the Apnea Patient.” . McKesson HBOC Clinical Reference Systems: Adult Health Advisor. “Anesthesia.” .

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• Determine the cervical dilation, effacement, and level of descent (station), and confirm presenting part through vaginal exam.

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Childbirth education Definition Childbirth education prepares the mother and usually her partner for labor and birth. It may also include information on cesarian birth, breastfeeding, maternal postpartum issues, and neonatal care. Special classes may be available for adolescent mothers, vaginal birth after cesarian birth, siblings, and grandparents. Classes may consist of lectures, slides, videos, demonstration, and practice.

Description Based on the goals of the facility or instructor, childbirth education classes can vary considerably in terms of content. For example, some classes may focus primarily on the childbirth process, while others provide information on wellness behaviors during the different trimesters of pregnancy. Classes offered by some facilities may not include information on postpartum contraceptive choices. Some classes provide information on fetal growth and development and maternal changes during pregnancy. These classes are usually offered earlier in a woman’s pregnancy while classes that focus primarily on labor and delivery are offered later. Some obstetric practices may provide gestational-appropriate information at each prenatal visit; others may focus primarily on the mother’s questions or concerns. Some practices may offer classes that complement the information given during prenatal visits or they may have on hand a list of classes that pregnant women may want to contact. Content areas that may be included in childbirth education classes are: • maternal changes in early pregnancy: physical and emotional • fetal growth and development • risks of certain environmental factors on fetal development • maternal self-care: nutrition, rest, exercise, work accommodations • common discomforts in pregnancy and safe/unsafe relief measures • sexuality and pregnancy • signs and symptoms of complications of pregnancy • signs of preterm labor • signs of the initiation of labor • symptoms which require a call to the obstetric provider • what to expect during labor and delivery 502

A midwife meets with a pregnant patient. (Photograph by Cliff Moore. Science Source/Photo Researchers. Reproduced by permission.)

• labor and delivery analgesia/anesthesia options • breathing and relaxation techniques • role of certified nurse midwife versus obstetrician • role of the coach • making a birth plan; hiring a doula • episiotomy issues • breastfeeding versus formula • breastfeeding techniques, normal/abnormal problems, and relief measures • neonatal care and safety issues • postpartum contraception • tour of labor and delivery area of affiliated health care center

Viewpoints Childbirth education classes are offered based on the premise that knowledge about what to expect during labor and delivery prepares a woman for the process. For example, fear of the unknown is associated with increased pain and muscle tension. Childbirth classes traditionally teach breathing and relaxation techniques for women to use during labor and delivery. It is believed that these techniques enable the mother to better manage the pain of childbirth, feel more in control, have a better birth experience, and bond more readily with her newborn. Some childbirth classes promote a particular method and philosophy, such as the Lamaze and the Bradley methods. The Lamaze method is supported by the American Society for Psychoprophylaxis in Obstetrics (ASPO) and was popularized by the French physician Ferdinand Lamaze. Classes focus on breathing, movement and posi-

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• Birth is normal, natural, and healthy. • The birth experience profoundly affects women and their families. • Women’s inner wisdom guides them through birth. • Women’s confidence and ability to give birth is either enhanced or diminished by the care provider and place of birth. • Women have the right to give birth free from routine medical interventions. • Birth can safely take place in birth centers and homes. • Childbirth education empowers women to make informed choices in health care, to assume responsibility for their health, and to trust their inner wisdom. The Bradley method was designed by Robert Bradley, an obstetrician. During the 12 sessions, Bradley classes emphasize a special pregnancy diet, maternal changes during pregnancy, the coach’s role, special coaching techniques, the importance of natural childbirth, sex during pregnancy, the first, second, and third stages of labor, pushing during labor, making a birth plan, labor rehearsal, postpartum information, breastfeeding, and newborn care. The Bradley method’s goals are: • natural childbirth • active participation of the husband coach

Questions to consider when making a birth plan How have you tried to prepare yourself for labor? How has your partner or support person been involved? What do you think labor will be like? How much pain do you think you will have in labor? Why do you think it will be like that? Do you want pain medications, or do you want to avoid them? Which pain medications would you prefer? How long do you think your labor will last? Why do you think it will be that long? Which support people will be with you during labor? How is each related to you? Who is welcome to be at the birth? What do you want your support person to do for you when you are in labor? What is most scary to you about being in labor and giving birth? What is most important to you about this birth? How do you feel about: monitoring the baby during labor? mobility during labor? positions during labor? an IV? having your bag of water broken? using breathing and relaxation techniques to help you through the contractions? medication to relieve pain during labor? an epidural anesthetic to take away the pain of labor? episiotomy procedure? If a cesarean becomes necessary, do you have any special requests? If the birth is planned at home or at a birth center, what are your plans in case of transport? What are your preferences for baby care, feeding, and rooming? If you had a baby before, did anything happen that might affect you during labor this time? SOURCE: Wheeler, L. Nurse-Midwifery Handbook: A Practical Guide to Prenatal and Postpartum Care. Philadelphia: Lippincott-Raven Pub., 1997.

• excellent nutrition as the foundation of a healthy pregnancy • avoidance of drugs during pregnancy, birth, and breastfeeding unless absolutely necessary • relaxation and natural breathing • tuning in to the body • responsibility of parents for the safety of the birth place, procedures, attendants, and emergency backup • immediate and continuous contact with the newborn • initiation of breastfeeding at birth • preparation of parents for unexpected situations such as emergency childbirth and cesarian delivery Childbirth education classes provide information to pregnant women in an environment of their peers, where they meet with other women or couples at the same stage of pregnancy. By educating women about the childbirth process, these classes enable women to focus on their particular issues during prenatal visits, while still receiving general pregnancy and childbirth information. Issues raised during the classes allow women time to reflect on

the choices they want for their birth experience. In addition, these classes often are a springboard for new groups where mothers get together postpartum with their newborns. Friendships formed during class time can help avoid the isolation sometimes existing in the postpartum period.

Professional implications While some women benefit from choosing a particular method of childbirth education, many women prefer using a more eclectic approach. The more nurses and other health care professionals are informed of various methods, the better equipped they are to assist women to have the type of childbirth they choose. The various breathing and focusing techniques provide relief from or a decrease in pain through distraction and muscle relaxation. There are many ways to achieve these goals. It is important for nurses to provide options while allowing women to make their own choices. Taking a series of

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tioning during labor, use of massage and relaxation techniques, the role of labor support, use of heat and cold, and water therapy. The ASPO/Lamaze philosophy is:

Chorionic villus sampling

Spencer, Paula. Parenting Guide to Pregnancy & Childbirth. New York: Ballantine Books, 1998.

KEY TERMS

ORGANIZATIONS

Doula—A doula is someone who undergoes special training to enable them to support women during childbirth and into the postpartum period. Episiotomy—A surgical incision made to enlarge the perineal area for delivery, to avoid tearing of the tissues, especially with a large neonate or during a difficult birth. Many women request the avoidance of a routine episiotomy. To avoid performing an episiotomy, certified nurse midwives may stretch the perineum with perineal massage. Perineum—The area encompassing the anus and the vagina.

The Bradley Method. American Academy of Husband-Coached Childbirth(r). Box 5224, Sherman Oaks, CA, 91413-5224. (800) 4-A-Birth. . International Childbirth Education Association (ICEA). P.O. Box 20048. Minneapolis, MN 55420. (952) 854-8660. . Lamaze International. 2025 M Street, Suite 800, Washington DC, 20036-3309. (202) 367-1128. (800) 368-4404. .

Esther Csapo Rastegari, R.N., B.S.N., Ed.M.

Chloride test see Electrolyte tests Choking see Foreign bodies

classes and doing the required homework requires time, effort, and motivation. Many women come into childbirth virtually unprepared. Labor and delivery nurses may choose to select different aspects of a variety of methods and incorporate them into their own practice. It is helpful for office obstetric nurses to be aware of the various classes in their areas, even classes not listed by their own facility. One may be able to request permission to sit in on some classes or to view the class content list. This enables the provider to know what information, accurate or otherwise, is available to pregnant women and to address issues as needed during prenatal visits. If not provided during the classes, obstetric providers may wish to offer instruction on exercises women can do at home that will facilitate the birth process: abdominal and back exercises for strength and flexibility, Kegel (pelvic floor muscle) exercises to promote perineal healing and to counteract stress incontinence, tailor sitting and squatting to stretch perineal and pelvic floor muscles, and pelvic rocking to relieve lower backache. Nurses also need to be culturally sensitive. While most husbands may wish to participate in the birth process, this may be an uncomfortable practice in some cultures. In addition, some men, regardless of their cultural background, may not want to participate in the birth process. The birthing woman may wish instead to have a female relative or friend as a support person. As long as a practice is medically safe, nurses need to respect the choices of the birthing woman and her family. Resources BOOKS

Pillitteri, Adele. Maternal & Child Health Nursing: Care of the Childbearing and Childrearing Family. Philadelphia: Lippincott, 1999. 504

Cholangiocarcinoma see Liver cancer Cholecalciferol see Vitamin D Cholecystography see Gallbladder x rays Cholesterol tests see Lipid tests Chorea see Movement disorders

Chorionic villus sampling Definition Chorionic villus sampling (CVS) is a prenatal procedure for the removal by needle of chorionic villi and culture and examination of the fetal cells obtained. The cells are used in tests for genetic and chromosomal abnormalities of a fetus as early as 10 to 12 weeks of gestation.

Purpose Women who are at risk of carrying a fetus with a genetic or chromosomal defect may be counseled to have a prenatal screening test such as CVS or amniocentesis. CVS, which is performed at 10 to 12 weeks after a woman’s last menstrual period, may be offered as an alternative to amniocentesis, the more commonly used test for prenatal diagnosis of genetic disorders, which is performed usually at 15 to 18 weeks. Earlier diagnosis of congenital defects is especially beneficial in cases where the parents’ desire to know the results as early in pregnancy as possible, for instance, when therapeutic abortion is being considered, as the risks associated with abortion increase with gestational age.

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• Women age 35 and older. The chance of having a child with certain chromosomal birth defects increases with maternal age. The most common chromosomal disorder is Down syndrome, a combination of mental and physical abnormalities caused by the presence of an extra copy of chromosome 21. The occurrence of Down syndrome in children born to women in their 20s is approximately 1 in 1,250, but increases to 1 in 400 by age 35, and to 1 in 100 at age 40. • A child or previous pregnancy with a birth defect, or a history of miscarriages. A woman who has already had a child or pregnancy diagnosed with a genetic birth defect or chromosomal abnormality, or who has had multiple miscarriages, is at increased risk of having a child with a genetic disorder. • Determination of the sex of a fetus when the mother is known to be a carrier of a sex-linked genetic disease (for example, hemophilia A). • Other family history of genetic disease. Couples who do not have an affected child but who have family medical histories of genetic or chromosomal abnormalities or are known through genetic screening to be carriers of an inherited disease are at increased risk of having an affected child. Prenatal testing is offered only when the suspected condition can be diagnosed before birth.

Precautions Chorionic villus sampling usually is not recommended for: • A woman whose pregnancy has progressed further than about 12 weeks, counted from the first day of the last menstrual period. • A woman who is experiencing bleeding or spotting. • In the presence of certain vaginal infections. • When there are uterine abnormalities, such as a bicornuate (double) uterus or uterine fibroids. • Women who would not consider intervening in a pregnancy where a genetic abnormality is detected. Women who are concerned about the risk of miscarriage associated with CVS can be offered amniocentesis or a noninvasive alternative. One such alternative is a maternal blood test called triple marker screening or multiple marker screening, which is performed no sooner than 15 weeks but no later than 20 weeks of pregnancy. A sample of the pregnant woman’s blood is analyzed for three substances produced by the fetus and passed into the

mother’s blood: alpha fetoprotein (AFP), human chorionic gonadotropin (HCG), and unconjugated estriol (UE3). Elevated AFP may indicate the presence of anencephaly or spina bifida; HCG is increased and AFP and UE3 are decreased in Down syndrome. This screening test, however, does not definitively diagnose a genetic defect and has a relatively high rate of false negatives, but it can help to identify an unborn baby at increased risk for these birth defects. A pregnant woman whose triple marker results are indicative of a fetus at risk would be encouraged to undergo further screening, such as ultrasound and/or amniocentesis (the timing of the triple marker screening rules out CVS) to provide a definitive diagnosis. Since only cells and not fluid are collected, CVS does not allow evaluation of AFP to indicate the presence of neural tube defects. AFP is then generally measured by a maternal blood test at 15–20 weeks, but with less accuracy than would be obtained with an amniotic fluid sample. A CVS sample may be obtained either via the vagina and cervix (transcervical CVS) or through the abdomen (transabdominal CVS). Woman who have a retroverted (tipped) uterus should be sampled transabdominally, since studies have shown the risk of miscarriage to be lower than when the procedure is done transcervically. In cases where the location of the placenta contraindicates transabdominal CVS, amniocentesis should be offered as an alternative screening test. Amniocentesis, however, is only rarely performed in the first trimester. Although CVS is over 99% accurate in ruling out certain chromosomal birth defects and specific genetic problems, it is slightly more likely than amniocentesis to give inconclusive results. Amniocentesis, then, may be used as a back-up screening procedure. However, the patient should be cautioned that not all birth defects can be ruled out before birth and no prenatal test can guarantee the birth of a healthy baby. Because it is performed earlier in pregnancy than amniocentesis, CVS sampling is more likely to detect fatal genetic diseases that result in miscarriages after the diagnosis has been established.

Description Chorionic villus sampling has been in use increasingly since the 1980s. The CVS procedure involves taking a sample of the chorion frondosum—the part of the chorionic membrane that contains the villi, microscopic, finger-like projections that emerge from the chorionic membrane to form the placenta—for laboratory analysis. The chorion is the outermost membrane surrounding the developing fetus; the amnion is the inner membrane that contains the amniotic fluid. The cells that make up the chorionic villi are of fetal origin, and, thus, normally

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Prenatal screening can diagnose some genetic and virtually all chromosomal disorders and is advised for women who have one or more of the following risk factors:

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have the same genetic makeup as the fetus. The sample may be obtained with a catheter, a thin, plastic tube, inserted through the vagina and the cervix (transcervical CVS) or with a needle through the abdominal wall (transabdominal CVS); both sampling methods take about five minutes to perform (not including preparation time), are equally effective, and carry similar risks. Chorionic villus sampling is best performed between 10 and 12 weeks of pregnancy. Abdominal ultrasound is used to determine the position of the uterus, the position of the placenta within the uterus, and the size of the amniotic sack. The woman assumes the lithotomy position (on her back with her feet in stirrups). In transcervical CVS, the vulva, vagina, and cervix are thoroughly cleansed with antiseptic; no anesthetic is required. A speculum is inserted into the vagina and opened, then, using ultrasound as a guide, the doctor inserts a catheter through the cervix and into the uterus. The catheter is carefully advanced to the chorionic villi and suction is applied with the syringe attached to the catheter to obtain a small sample of the villi. The catheter is then carefully withdrawn. In transabdominal CVS, the appropriate area on the woman’s abdomen is cleansed thoroughly with antiseptic and a local anesthetic may be injected to numb the area. With ultrasound guidance to strictly avoid the placenta, a long needle is inserted through the woman’s abdominal wall, through the uterine wall and to the chorionic villi. Suction is applied with the syringe attached to the needle to obtain a small sample of the villi, and the needle is then carefully withdrawn. Most women report that transcervical CVS feels similar to the procedure for a Pap smear. The passage of the catheter through the cervix may cause cramping, and some women experience cramping or pinching sensations when the sample is taken. There is generally little or no discomfort associated with the transabdominal procedure. Occasionally, when insufficient villus material is obtained, a second sampling procedure must be performed. The chorionic villus sample is immediately placed into a sample dish containing nutrient medium for transport to the cytogenetics laboratory. At the laboratory, the sample is examined under the microscope so that any contaminating cells or material may be carefully removed. The villi can be analyzed immediately, or incubated for a day or more to give the cells time to undergo division. When the cells are in the midst of dividing, they are spread onto a slide and examined under a microscope. Cells that have clearly separated chromosomes are photographed to allow analysis of the type and number of chromosomes. The chromosomal images are collected in a report called a karyotype, which shows the number, 506

shape, size, and arrangement of chromosomal pairs. For biochemical studies, deoxyribonucleic acid (DNA) is extracted from cultured chorionic villus cells. Depending upon which tests are performed, results may be available as early as two days or up to ten days after the procedure. The chorionic villus sampling procedure costs about $3,000, including ultrasound, laboratory, and counseling charges. Some insurance plans may provide some level of coverage for this test.

Preparation Thorough pre-CVS counseling is strongly recommended to give the couple the opportunity to make informed decisions about prenatal diagnosis. The couple should be provided with literature about CVS and genetic screening options to read prior to the counseling conference, so that any questions or concerns they may have can be addressed at that time. Prior to the procedure, the woman will likely be asked to sign a consent form. For the procedure itself, the woman will be instructed to drink fluids and refrain from urinating so that the bladder is partly filled; excessive and uncomfortable bladder filling is not necessary. A filled bladder can help to properly position the uterus and create a better ultrasound picture for guiding the CVS procedure.

Aftercare After the sample is taken, the fetal heartbeat is checked by ultrasound before the woman leaves the examination room. A follow-up ultrasound procedure may be scheduled two to four days after CVS to ascertain the health of the fetus. Most physicians recommend that the woman have someone drive her home after the CVS procedure and that she limit strenuous activity for the remainder of the day. A women who experiences excessive bleeding, vaginal discharge, fever, or abdominal pain after the procedure should consult her doctor. Women with Rh negative blood may receive a Rho (D) immune globulin (RhoGAM) injection to avoid Rh incompatibility. Advances in prenatal treatment have made it possible to treat some genetic defects diagnosed by prenatal screening before birth. Congenital adrenal hyperplasia (CAH), for example, is an inherited birth defect in which an enzyme deficiency causes a female fetus to develop abnormal external genitalia by the 16th week of pregnancy. Prenatal diagnosis by CVS in pregnancies known to be at risk of CAH allows the fetus to be treated with hormones during the critical period of development from 10 to 16 weeks of gestation and can circum-

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Complications Of women who undergo transcervical CVS, one third experience minimal vaginal spotting and 7–10% experience vaginal bleeding; bleeding that is heavier than during a normal menstrual period should be reported to the doctor. One out of five women experience cramping following the procedure. Rupture of the amniotic membranes is a rare but serious complication that can lead to infection and/or miscarriage. The risk of miscarriage after CVS is 1–3%, compared to 0.5–1% for amniocentesis. A woman with Rh negative blood who is carrying an Rh positive fetus may be at an increased risk for developing Rh incompatibility following CVS and should be treated with Rho immune globulin. In the early 1990s, there were several reports linking babies born with missing or shortened fingers or toes and abnormalities of the tongue and lower jaw with CVS performed before the tenth week of pregnancy. These reports raised concerns about the safety of CVS, although this type of limb defect is known to occur in approximately 1 out of every 1,700 babies. Subsequent studies of the risk of limb defects following CVS have produced conflicting results, and CVS safety studies continue. A study by the World Health Organization’s CVS Registry, which performs ongoing assessment of CVS, reported in 1999 that the risk of these limb defects in babies born to more than 200,000 women who had CVS was not significantly increased compared to the norm. CVS is now generally performed only at ten weeks or later, and all women being offered CVS should be advised of the limited risk of limb defects. There is risk with CVS of getting a “placental mosaicism” artifact in which the cultured cells contain some abnormal chromosomes that originate in the placenta and are not related to the fetus. Mosaicism occurs when cells have two or more distinct chromosome counts. This occurs when nondisjunction (failure of chromatids to separate) occurs in germ line cells (after fertilization). The fetus may be normal, and the only way to rule out actual mosaicism is to follow up with amniocentesis. There is also a risk that insufficient chorionic villi are collected for analysis, or that the cells collected are contaminated with cells of maternal origin. In this case, a second sampling procedure is performed

about a week later, or amniocentesis may be offered as an alternative.

Results The chorionic villus cells are cultured and photographed through a microscope during cell division to obtain images of the chromosomes. The images are sorted, identified, and reported in a karyotype. Humans have 23 pairs of chromosomes, including the sex chromosomes. The karyotype allows detection of aneuploidies (extra copies of chromosomes), chromosomal deletions, and gross chromosomal translocations. The gender of the fetus is identified from the sex chromosomes, and can be reported to the parents upon request. DNA studies are performed when indicated by a family history of genetic disorders. DNA is the biochemical molecule that stores genetic information in the chromosomes. The DNA is extracted from the chorionic villus cells, and analysis of the DNA allows prenatal diagnosis of over 200 diseases, including Tay-Sachs disease, cystic fibrosis, sickle-cell anemia, and muscular dystrophy.

Health care team roles The genetic counselor, physician, or other health care provider will provide information to the couple considering CVS and explain the procedure and its risks, and alternative procedures. Counselors can also advise parents of their options when they learn that their unborn child has an inherited disorder and/or help them prepare emotionally for the delivery of a child with a birth defect. The obstetrics team carries out the ultrasound and CVS procedure, and ensures that the chorionic villus cells are properly handled for transport to a cytogenetics laboratory. The team of physician(s) and nurses also provide practical and psychological support for the couple undergoing prenatal diagnosis. Technologists in the cytogenetics laboratory perform cell culture on the chorionic villus cells, fix a sample of cells during cell division, prepare the cells on a slide for microscopic analysis, and make photographs of the chromosomes of dividing cells to be collated in a karyotype. Cytogenetic technologists are also involved in the extraction of DNA from the cells and the biochemical testing of the DNA. Training The obstetrician receives special training in the procedure for collecting the chorionic villus specimen. Cytogenetic laboratory technologists, CLSp(CG) are specially trained in sterile techniques for cell culture,

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vent the need for surgery after birth. For conditions in which prenatal treatment is not available, prenatal diagnosis can allow parents the opportunity to discuss their options with genetic counselors or other health care providers, to plan the delivery, and to prepare emotionally for the birth.

Chorionic villus sampling

KEY TERMS Alpha fetoprotein—A serum protein produced by the fetus during pregnancy and passed to the mother’s blood, useful in the prenatal diagnosis of multiple births or birth defects.

Muscular dystrophy—An inherited disease in which muscles become gradually wasted and are replaced by scar tissue and fat, sometimes also affecting the heart.

Amniocentesis—A prenatal screening procedure in which a sample of amniotic fluid from the amniotic sac in the uterus of a pregnant woman is obtained by inserting a needle through the abdominal wall.

Neural tube defect—Any of a group of inherited abnormalities of brain and spinal cord development, including spina bifida and anencephaly, caused by failure of the neural tube to close properly during development.

Aneuploidy—An irregular number of chromosomes caused by the loss or addition of one or more chromosomes or parts of chromosomes. Chromosomes—Tightly compressed rod-like structures that carry DNA; humans have 23 pairs of chromosomes including the sex chromosomes. Cystic fibrosis—An inherited chronic disease of the exocrine glands, characterized by the production of viscous mucus that obstructs the pancreatic ducts and bronchi, leading to infection and fibrosis. Down syndrome—Also called trisomy 21, a genetic disorder, associated with the presence of an extra copy or a rearrangement of chromosome 21, characterized by mild to severe mental retardation, weak muscle tone, a low nasal bridge, and epicanthic folds at the eyelids; formerly called mongolism. Human chorionic gonadotropin—A hormone produced by the developing placenta that stimulates the production of estrogen and progesterone; its presence in maternal blood or urine is used to diagnose pregnancy. Karyotype—A report in which photographic images of the chromosomes of a cell are displayed as a systematized arrangement of pairs in descending order of size.

photomicrography, construction of the karyotype report, and biochemical analysis of DNA. Resources BOOKS

Carlson, Karen J., Stephanie A. Eisenstat, and Terra Ziporyn. The Harvard Guide to Women’s Health. Cambridge, MA and London: Harvard University Press, 1996. PERIODICALS

“Evaluation of chorionic villus sampling safety: WHO/PAHO Consultation on CVS.” Prenatal Diagnosis 19, No. 2 (February 1999): 97–99. 508

Rh incompatablility—An Rh negative person who is exposed to Rh positive red blood cells. When an Rh negative mother becomes pregnant with an Rh positive fetus, the fetal red blood cells may enter the maternal circulation and stimulate production of Rh antibodies. This process can be prevented by administration of Rho immune globulin prior to or during the pregnancy. Sickle-cell anemia—An inherited chronic blood disease that occurs primarily among persons of African descent characterized by abnormal hemoglobin that causes red blood cells to become sickle-shaped and nonfunctional, leading to an enlarged spleen, chronic anemia, weakness, joint pain, and formation of blood clots. Tay-Sachs disease—A rare and fatal inherited disease occurring chiefly in persons of eastern European Jewish origin, characterized by a red spot on the retina, gradual blindness, and paralysis. Ultrasound—Also called ultrasonography, a diagnostic imaging technique that uses reflected highfrequency sound waves to visualize internal body structures or organs, especially useful as a noninvasive prenatal diagnostic tool.

OTHER

Arnot Ogden Medical Center website. Information About Chorionic Villi Sampling. 1995–1998. Arnot Ogden Medical Center. . Holbrook, R. Harold Jr., M.D. Chorionic Villus Sampling (CVS). . March of Dimes website. Chorionic Villus Sampling (CVS). 2001. March of Dimes Birth Defects Foundation, . Olney, Richard S., Cynthia A. Moore, Muin J. Khoury, J. David Erickson, Larry D. Edmonds, Lorenzo D. Botto. “Chorionic Villus Sampling and Amniocentesis:

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Patricia L. Bounds, Ph.D.

Chromosome studies see Genetic testing

Chronic kidney failure Definition Chronic kidney failure occurs when disease or disorder damages the kidneys so that they can no longer adequately remove fluids and wastes from the body or maintain proper levels of kidney-regulated chemicals in the bloodstream.

Description Chronic kidney failure, also known as chronic renal failure, affects over 250,000 Americans annually. It may be caused by a number of diseases and inherited disorders, but the progression (end result) of chronic kidney failure is always the same. The kidneys, which serve as the body’s natural filtration system, gradually lose their ability to remove fluids and waste products (urea) from the bloodstream. They also fail to regulate certain chemicals in the bloodstream and allow protein to leak into the urine. Chronic kidney failure is irreversible and eventually leads to total kidney failure, known as end-stage renal disease (ESRD). Without treatment and intervention to remove wastes and fluids from the bloodstream, ESRD is inevitably fatal.

Causes and symptoms Kidney failure is caused by acquired disease or hereditary disorders in the kidneys. The four most common causes of chronic kidney failure include: • Diabetes. Diabetes mellitus (DM), both insulin dependant (IDDM) and non-insulin dependant (NIDDM), occurs when the body cannot produce and/or use insulin, the hormone necessary for the body to process glucose. Long-term diabetes may cause the glomeruli, the filtering units located in the nephrons of the kidneys, to gradually lose function.

• Hypertension. High blood pressure is both a cause and a result of kidney failure. The kidneys can become stressed and ultimately sustain permanent damage from blood pushing through them at excessive pressures over long periods of time. • Glomerulonephritis. Glomerulonephritis is an inflammation of the glomeruli, or filtering units of the kidney. Certain types of glomerulonephritis are treatable, and may only cause a temporary disruption of kidney functioning. • Polycystic kidney disease. Polycystic kidney disease is an inherited disorder that causes cysts to form in the kidneys. These cysts impair the regular functioning of the kidney. Less common causes of chronic kidney failure include kidney cancer, obstructions such as kidney stones, pyelonephritis, reflux nephropathy, systemic lupus erythematosus, amyloidosis, sickle cell anemia, Alport syndrome, and oxalosis. Initially, symptoms of chronic kidney failure develop slowly. Even individuals with mild to moderate kidney failure may have few symptoms in spite of increased urea in their blood. Among signs and symptoms that may be present at this point are frequent urination during the night and high blood pressure. Most symptoms of chronic kidney failure are not apparent until kidney disease has progressed significantly. Common symptoms include: • Anemia. The kidneys are responsible for the production of erythropoietin (EPO), a hormone that stimulates red cell production. If kidney disease causes shrinking of the kidney, this red cell production is hampered. • Bad breath or a bad taste in mouth. Urea in the saliva may cause an ammonia-like taste in the mouth. • Bone and joint problems. The kidneys produce vitamin D, which aids in the absorption of calcium and keeps bones strong. In patients with kidney failure, bones may become brittle, and in children, normal growth may be stunted. Joint pain may also occur as a result of unchecked phosphate levels in the blood. • Edema. Puffiness or swelling around the eyes and legs. • Frequent urination. • Foamy or bloody urine. Protein in the urine may cause it to foam significantly. Blood in the urine may indicate bleeding from diseased or obstructed kidneys, bladder, or ureters. • Headaches. High blood pressure may trigger headaches.

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Recommendations for Prenatal Counseling.” CDC WONDER Web publication MMWR 44(RR-9) (07/21/1995): 1-12, . University of Maryland website. Chorionic Villus Sampling. 1998. A.D.A.M. Software, Inc., .

Chronic kidney failure

• Hypertension, or high blood pressure. The retention of fluids and sodium causes blood volume to increase, which, in turn, causes blood pressure to rise. • Increased fatigue. Toxic substances in the blood and the presence of anemia may cause feelings of exhaustion. • Itching. Phosphorus, which is typically eliminated in the urine, accumulates in the blood of patients with kidney failure. This heightened phosphorus level may cause itching of the skin. • Low back pain. Pain where the kidneys are located, in the small of the back below the ribs. • Nausea, loss of appetite, and vomiting. Urea in the gastric juices may cause upset stomach. This can lead to malnutrition and weight loss.

Diagnosis Kidney failure is typically diagnosed and treated by a nephrologist, a physician specializing in kidney disease. The patient suspected of having chronic kidney failure will undergo an extensive blood work-up, usually performed by a laboratory technologist or technician. Blood tests will assess the levels of creatinine, blood urea nitrogen (BUN), uric acid, phosphate, sodium, and potassium in the blood. Urine samples will also be collected, usually over a 24-hour period, to assess protein loss. Uncovering the cause of kidney failure is critical to proper treatment. A full assessment of the kidneys is necessary to determine if the underlying disease is treatable and if the kidney failure is chronic or acute. X ray, MRI, computed tomography scan, ultrasound, renal biopsy, and/or arteriogram of the kidneys may be employed to determine the cause of kidney failure and level of remaining kidney function. X rays and ultrasound of the bladder and/or ureters may also be taken. Most imaging studies are performed by radiology technicians.

Treatment

Peritoneal dialysis In peritoneal dialysis (PD), the peritoneum, (lining of the abdomen) acts as a blood filter. A catheter is surgically inserted into the patient’s abdomen. During treatment, the catheter is used to fill the abdominal cavity with liquid dialysate. Waste products and excess fluids move from the patient’s bloodstream into the dialysate solution. After a waiting period of 6 to 24 hours, depending on the treatment method used, the waste-filled dialysate is drained from the abdomen, and replaced with clean dialysate. There are three types of peritoneal dialysis, which vary by treatment time and administration method: continuous ambulatory peritoneal dialysis (CAPD), continuous cyclic peritoneal dialysis (CCPD), and intermittent peritoneal dialysis (IPD). Kidney transplantation

Chronic kidney failure is an irreversible condition. Hemodialysis, peritoneal dialysis, or kidney transplantation must be employed to replace the lost function of the kidneys if the failure progresses to ESRD. In addition, dietary changes and treatment to relieve specific symptoms such as anemia and high blood pressure are critical to the treatment process. Hemodialysis Hemodialysis is the most frequently prescribed type of dialysis treatment in the United States. Most hemodialysis patients require treatment three times a week, for an average of three to four hours per dialysis 510

“run” depending on the type of dialyzer used and their current physical condition. The treatment involves circulating the patient’s blood outside of the body through an extracorporeal circuit (ECC), or dialysis circuit. The dialysis circuit consists of plastic blood tubing, a two-compartment filter known as a dialyzer, or artificial kidney, and a dialysis machine that monitors and maintains blood flow and administers dialysate, a chemical bath used to draw waste products out of the blood. The patient’s blood leaves and enters the body through two needles inserted into the patient’s vein, called an access site, and is pushed through the blood compartment of the dialyzer. Once the patient’s blood is inside the dialyzer, excess fluids and toxins are pulled out of the bloodstream and into the dialysate compartment, where they are carried out of the body. At the same time, electrolytes and other chemicals in the dialysate solution move from the dialysate into the bloodstream. The purified, chemically balanced blood is then returned to the body. Specially trained nurses and dialysis technicians supervise and monitor patients during treatment.

Kidney transplantation involves surgically implanting a functioning kidney, known as a graft, from a brain dead organ donor (a cadaver transplant), or from a living donor, to a patient with ESRD. Patients with chronic renal disease who need a transplant and do not have a living donor register with UNOS (United Network for Organ Sharing), the federal organ procurement agency. UNOS places patients on a waiting list for a cadaver kidney transplant. Kidney availability is based on the patient’s health status. When the new kidney is transplanted, the patient’s diseased kidneys may or may not be removed, depending on the circumstances surrounding the kidney failure. A regimen of immunosuppressive

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Dietary management A diet low in sodium, potassium, and phosphorous, three substances that healthy kidneys excrete, is critical in managing kidney disease. Other dietary restrictions, such as a reduction in protein, may be prescribed depending on the cause of kidney failure and the type of dialysis treatment employed. Patients with chronic kidney failure also need to limit their fluid intake. Patients may receive instruction about appropriate dietary measures from registered dietitians, nutritionists, nurses, or health educators. Medications and dietary supplements Kidney failure patients with hypertension typically take medication to control their high blood pressure. Epoetin alfa, or EPO (Epogen), a hormone therapy, and intravenous or oral iron supplements are used to manage anemia, especially if the kidneys have been surgically removed. A multivitamin may be prescribed to replace vitamins lost during dialysis treatments. Vitamin D, which promotes the absorption of calcium, along with calcium supplements, may also be prescribed. Since 1973, Medicare has reimbursed up to 80% of ESRD treatment costs, including the costs of dialysis and transplantation as well as the costs of some medications. To qualify for benefits, a patient must be insured or eligible for benefits under Social Security, or be a spouse or child of an eligible American. Private insurance and state Medicaid programs often cover the remaining 20% of treatment costs.

Prognosis Early diagnosis and treatment of kidney failure is critical to improving length and quality of life in chronic kidney failure patients. Patient outcome varies; it depends on the cause of chronic kidney failure and the method chosen to treat it. Overall, patients with chronic kidney disease leading to ESRD have a shortened life span. According to the United States Renal Data System (USRDS), the life span of an ESRD patient is 18-47% of the life span of the age-sex-race matched general population. ESRD patients on dialysis have a life span that is 16-37% of the general population. The demand for kidneys to transplant continues to exceed supply. Cadaver kidney transplants have a 50% chance of functioning nine years, and living donor kidneys that are well-matched (have two matching antigen pairs) have a 50% chance of functioning for 24 years.

KEY TERMS End-stage renal disease (ESRD)—Total kidney failure; chronic kidney failure is diagnosed as ESRD when kidney function falls to 5-10% of capacity. Nephrotic syndrome—Characterized by protein loss in the urine, low protein levels in the blood, and fluid retention. Ureters—The two ducts that pass urine from each kidney to the bladder.

However, some transplant grafts have functioned for more than 30 years.

Health care team roles Patients with chronic kidney failure are treated by a team that includes nephrologists, dialysis technicians, nurses, radiology technicians, and laboratory technicians. Patients undergoing kidney transplant are cared for by a transplant team headed by a transplant surgeon. Registered dietitians, nutritionists, and nurses instruct patients about dietary changes to manage their disease. Resources BOOKS

Brenner, Barry M. and Floyd C. Rector, Jr., eds. The Kidney, 5th edition. Philadelphia: W.B. Saunders Company, 1996. Cameron, J. S. Kidney Failure: The Facts. New York: Oxford Univ. Press, 1996. Ross, Linda M., ed. Kidney and Urinary Tract Diseases and Disorders Sourcebook. Vol. 21. Health Reference Series. Detroit: Omnigraphics, 1997. U.S. Renal Data System. USRDS 1997 Annual Data Report. Bethesda, MD: The National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, 1996. (Available in paper and microfiche versions from National Technical Information Service (NTIS), Springfield, VA.) The Washington Manual of Medical Therapeutics, 30th Edition. Philadelphia PA: Lippincott Williams & Wilkins, 2001, pp. 267-270. PERIODICALS

Friedman, Elia A. “End-stage Renal Disease Therapy: An American Success Story.” Journal of the American Medical Association 275 (April 1996): 1118-22. Taylor, Judy H. “End-stage Renal Disease in Children: Diagnosis, Management, and Interventions.” Pediatric Nursing 22 (Nov-Dec 1996): 481-92.

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(anti-rejection) medication is required after transplantation surgery.

Classification of teeth

ORGANIZATIONS

American Association of Kidney Patients (AAKP). 100 S. Ashley Drive, Suite 280, Tampa, FL 33602. (800)7492257. . American Kidney Fund (AKF). Suite 1010, 6110 Executive Boulevard, Rockville, MD 20852. (800)638-8299. . National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Natcher Building - 6AS-13K, 45 Center Drive, Bethesda, MD 20892-6600. . National Kidney Foundation (NKF). 30 East 33rd Street, New York, NY 10016. (800)622-9020. . United States Renal Data System (USRDS). USRDS Coordinating Center, 315 W. Huron, Suite 240, Ann Arbor, MI 48103. (313)998-6611. .

Barbara Wexler

Chronic leukemias see Leukemias, chronic Chronic obstructive pulmonary disease see Emphysema Chylomicron test see Lipoproteins test Circulation support see Mechanical circulation support

Classification of teeth Definition Classification of teeth refers to the position of the first molars, and how they bite together.

Description In 1844 J.F. Cravens, a dentist from Indianapolis, discussed the first dental deformities. He studied the first molar biting relationship and how the molars should line up with each other on the upper and lower jaws. Cravens called the first molar the “patriarch of the mouth,” meaning the first molar determined the bite relationship for the entire mouth. J.N. Farrar, a leading dentist, in 1880 discussed the teeth relationship as an irregularity in his book “A Treatise on the Irregularities of the Teeth and Their Corrections.” In 1905 at the 4th Annual Meeting of American Society of Orthodontics the subject was again broached, but this time by Edward H. Angle, a dentist who dis512

agreed with the other leading dentists and their terms and names of bite relationships. Angle had devised a simple and logical classification system for the teeth irregularities and deformities, which he didn’t believe were irregularities or deformities at all, but rather malocclusions. He felt the first molar was “king of the mouth” and the basis for the classification of malocclusion of the teeth. Angle had studied Cravens’s work and knew he could prove the theories. Angle’s classification system refers to the position of first molars and how they bite together and is broken into three main categories: Class I, II, III. • Class I: The normal biting relationship between the upper and lower teeth and jaw, also known as a balanced bite. The front teeth may be spaced apart or crowding of the anterior teeth may be seen, but the biting relationship of the first molars is balanced. • Class II: The lower first molar is posterior or more towards the back of the mouth than the upper first molar. In this abnormal biting relationship the upper front teeth of the jaw protrude further than the lower jaw, commonly called “buck teeth.” There is a convex appearance in the profile of the patient with a receding chin and lower lip. Class II problems can be due to insufficient growth of the lower jaw or an over growth of the upper jaw, or a combination of the two. Class II cases are commonly genetically inherited and can be aggravated by environmental factors such as thumb sucking. • Class III: The lower first molar is anterior or more towards the front of the mouth than the upper first molar. In this abnormal relationship the lower teeth and jaw project further forward than the upper teeth and jaws. There is a concave appearance in the profile with a prominent chin. Class III problems are commonly due to an overgrowth in the lower jaw or undergrowth of the upper jaw or a combination of the two. Like Class II, Class III is genetically inherited. Orthodontia may help relieve the class III biting relationship, but often surgery is required to shorten the lower jaw.

Viewpoints The classification system founded by Angle represented a milestone in the dental profession, because for the first time the concept of diagnostic arrangement based on science was discussed and it opened the way to etiological research of malocclusions. Angle was firmly persuaded that the upper first molars always erupted in a fixed, constant position on the facial bulk, “Upper first molar as basis of diagnosis in orthodontia,” thereby making a set classification system that could be used univer-

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Anterior—Towards the front. Etiology—The study of the origin.

Robert S. Quinn, Orthodontic Specialist. 450 Sutter Street #1715, San Francisco, CA 94108. (415) 433-4045. . Gumshield. Orthodontics: Dental History. .

Malocclusion—The relationship of the molars is not right, known as a “bad bite.”

Cindy F. Ovard, RDA

Orthodontia—The science of studying malocclusions of the mouth.

Climacteric see Menopause

Posterior—Towards the back.

Clinical laboratories see Medical laboratories

sally. This viewpoint was not accepted by a few other dentists, primarily J.N. Farrar, who refused to think this system was correct or would work in dentistry. Many other American dentists grasped this new idea of classification and a new age in orthodontia began. It took some years for other nations of the world to grasp this system, but American universities began teaching it soon after it was introduced, with the first school of orthodontics established in 1905 by Edward Angle. Many Italian universities have yet to employ this basic system. Japan, England, and many other countries use this method of classification of the teeth, making it an international system for malocclusion in dentistry.

Professional implications The classification of the teeth for malocclusion has given dentists and orthodontists a much simpler way to diagnose malocclusions. Using this classification system of the teeth universally keeps dentists and orthodontists from getting confused about bite relationships and malocclusion, and facilitates the sharing of information concerning these subjects. Resources PERIODICALS

Electronic Journal Of Orthodontics 4 (July 2000). . The Virtual Journal of Orthodontics 3.3 (February 2000) . ORGANIZATIONS

American Association of Orthodontists. 401 North Lindbergh Boulevard St. Louis, MO 63141-7816. (314) 993-1700. . The American Board of Orthodontics. 401 N. Lindbergh Blvd., Ste. 308, St. Louis, MO 63141. (314) 432-6130. E-Mail: [email protected]. .

Clinical laboratory science see Medical laboratory technology

Clinical nurse specialist Definition Clinical nurse specialists (CNSs) are licensed registered nurses with additional master’s or doctorate level training in CNS. These advanced practice nurses are clinical experts in theory-based or research-based nursing, focusing on specific specialty areas.

Description A CNS is an advanced practice nurse. There are four categories of advanced practice nurses: nurse practitioners, certified nurse-midwives (CNMs), clinical nurse specialists, and certified registered nurse anesthetists. Advanced practice nurses typically are registered nurses (RNs) who have gone on to complete master’s degree programs. CNSs have broadened patient care roles because of their advanced training and often provide direct patient care without supervision by a doctor. Sometimes, they have the authority to prescribe medications. This authority is granted on the state level and varies from state to state. CNSs assume many roles within the health care delivery system. While many are in the clinical setting, others also work as educators, administrators, consultants, researchers, change agents, and case managers. CNSs can become specialized in the areas of adult psychiatry, child psychology, community health, home health, gerontology, and medical-surgical, as well as oncology, perinatal critical care, critical care, and rehab. Some in areas of specialty certification classify themselves as CNSs, and others use the umbrella term of advanced practice nursing. There are all kinds of other

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OTHER

KEY TERMS

Clinical nurse specialist

KEY TERMS Certified nurse-midwives (CNMs)—Advanced practice nurses who provide prenatal and gynecological care to healthy women. These nurses deliver babies in all types of settings and offer postpartum care. Certified registered nurse anesthetists—An advanced practice nurse who administers anesthesia as sole providers or as part of health care teams. Charge agents—Nurses who work to make changes within systems to improve the delivery of clinical care. Nurse practitioner—An advanced practice nurse delivering front-line primary and acute care.

certifications, including those of wound care nurses, case managers, and administrators, that CNSs might earn in addition to the certification as CNS. In March 2000, the number of RNs prepared to practice in at least one advanced practice role was estimated to be 196,279, which is about 7.3% of the total RN population. The largest group among the advanced practice nurses was the nurse practitioners, followed by the CNSs. These two groups together made up about 80% of all advanced practice nurses. There were about 54,374 CNSs (up from 53,500 in 1996), which does not include those who were certified as both nurse practitioners and CNSs. While about 36.9% of the CNSs were employed in nursing, only about 24% were practicing under the position title of CNS. Nearly a quarter of CNSs reported working in nursing education positions.

Work settings The work settings of CNSs include all those settings where one would find nurses and other health care providers. CNSs work in the acute care, long-term care, and intermediate care settings. They work in clinical education within health care facilities, as well as in nursing education programs as faculty teaching nursing. Other settings in which CNSs work include outpatient and ambulatory care, private practice, home health, physician office practice, subacute care, government or military service, community health centers, health care administration, private industry (working for drug companies or manufacturers, in managed care, and other areas of the private sector), and nurse-managed centers, which are health centers completely run by nurses. Within these 514

categories, CNSs work in assisted living facilities; specialized hospital areas, such as cardiac catheterization labs; correctional facilities; dialysis units; parish nursing; and psychiatric hospitals.

Education and training First of all, nurses must have a baccalaureate degree, or its equivalent, to enroll in a CNS program. To use the title of CNS, the nurse must have a minimum of a master’s degree from an education program that prepares CNSs. The training is graduate-level education. Some universities have a fast track program whereby they will accept individuals who do not have a baccalaureate and move them into a master’s program. CNSs also take a certification exam in a specialty, offered by one of the nationally recognized certification entities. CNS students go through advanced theory and practice training, revolving around the three areas of influence, that impact on direct patient care, others supervising direct patient care, and patient care systems. The general areas of learning that are included in this graduate education are theoretical foundations; phenomena of concern; assessment and intervention/design and development; clinical inquiry; technology, products, and devices; teaching and coaching; change, persuasion, influence, and negotiation; systems thinking, consultation theory; measurement; and evaluation methodologies. Under the umbrella of theory, CNSs learn to understand health, illness, and wellness as subjective experiences. They also learn to understand health behavior and health behavior change, as well as the theories of learning, stress, consultation, and organizational development. On the clinical side, CNSs focus on awareness, knowledge, and skill in cognitive work in the three spheres of influence. They learn about technology, products, and devices, as well as how to teach and coach patients and other health care providers. The American Nurses Credentialing Center certifies CNSs as adult psychiatric, child psychology, community health, home health, gerontology, and medical-surgical CNSs. There also are other certifying bodies, including the rehabilitation nursing certification board, oncology nursing certification corporation, and American association of critical care nurses certification.

Advanced education and training The master’s-prepared clinical specialist can go on to get a doctorate. Each certifying body has its own requirements for recertification. State licensing boards may also have continuing education requirements.

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Future outlook The outlook is good for all types of nurses, especially those at the RN level or higher. It is projected that if current trends continue, demand will exceed supply of RNs by about 2010. It is possible that as many as 114,000 jobs for full-time-equivalent RNs are going to go unfilled nationwide by 2015. This is due to a growing elderly population with mounting health care needs, an aging RN workforce, the expansion of primary care, and technological advances that require more highly trained nurses.

Coagulation tests Definition Hemostasis has been described as “a process by which the body spontaneously stops bleeding and maintains blood in the fluid state within the vascular compartment.” There are at least four major systems that are involved in this complex process: the vasculature system, the platelets, the fibrin-forming system, and the fibrinlysing system. Hemostasis has also been further segregated into stages or steps. These are primary hemostasis, which is the interaction of the injured blood vessel and platelets; secondary hemostasis, which is referred to historically as the blood coagulation process; and tertiary hemostasis, which is the process of fibrinolysis (clot destruction). The first two stages are assessed by blood coagulation tests that evaluate platelets, circulating coagulation factors, and blood vessels.

Resources

Purpose

BOOKS

Occupational Outlook Handbook. U.S. Department of Labor. Bureau of Labor Statistics. Division of Information Services. 2 Massachusetts Ave., NE, Room 2860. Washington, D.C. 20212. (202) 691-5200. .

Coagulation tests are performed to aid in the diagnosis of bleeding disorders, monitor the effectiveness of anticoagulant therapy, and confirm a patient’s blood clotting status prior to surgery.

Precautions

ORGANIZATIONS

American Association of Colleges of Nursing. One Dupont Circle, NW, Suite 530. Washington, DC 20036. (202) 463-6930. . National Association of Clinical Nurse Specialists. 3969 Green Street. Harrisburg, PA 17110-1575. (717) 2346799. . OTHER

The Registered Nurse Population National Sample Survey of Registered Nurses—March 2000. U.S. Department of Health and Human Services, Health Resources and Services Administration. Bureau of Health Professions. Division of Nursing. .

Lisette Hilton

Cloning see Genetic engineering Clotting disorders see Bleeding disorders CNS stimulants see Central nervous system stimulants Coagulation disorders see Bleeding disorders

Before administering the test, the patient should be asked to list the medications he or she is taking, and whether or not he or she has recently experienced active bleeding, acute infection or illness, or undergone a blood transfusion, as these factors could adversely affect their coagulation test results. Some of the medications that can affect coagulation results include antacids, antibiotics, anticoagulants, antihistamines, aspirin, diuretics, nicotine, nonsteroidal anti-inflammatory drugs, oral contraceptives, steroids, tranquilizers, and vitamins C and K. If a patient is currently being medicated, the testing facility should be contacted to determine the acceptability of the blood sample. From the moment the blood specimen is drawn until the test is completed, the handling of the specimen is critical in coagulation studies. Assuming that the specimen is drawn correctly, the following procedures should be followed. Collection of blood for coagulation tests There is a generally held belief that the first tube in a case where multiple specimens are drawn should never be used for any hemostasis assay, because tissue thromboplastin from the initial venipuncture may affect coagulation test results. In addition, the tube(s) for coagulation

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The CNS at the doctoral level typically focuses on research. Although there is a research component to the masters, the doctorate training, more often than not, is a research degree.

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testing should be filled before any tubes containing EDTA. If coagulation tests are the only studies ordered, a discard tube should be drawn before filling the bluestoppered citrate tube used for the tests. Anticoagulant for coagulation tests The anticoagulant of choice for coagulation testing is sodium citrate, which reversibly chelates calcium. Evacuated blue-top tubes containing sodium citrate are available commercially with a 3.8% (129 mmol/L) or 3.2% (109 mmol/L) citrate concentration. Blue-stoppered tubes are manufactured to draw nine parts of whole blood to one part of liquid sodium citrate already present in the tube. Thus, when using an evacuated system, blood must be allowed to flow into the tube until it stops automatically. This provides for the 90% fill ratio required for coagulation testing. Ideally the plasma specimen is tested within four hours of collection. If this is not possible then the samples should be frozen until testing. Gross hemolysis is usually a criterion for sample rejection.

Description The first or primary event that stops bleeding from a very small wound is the formation of a platelet plug, which seals the hole in the vessel wall. This is followed by arteriolar vasoconstriction. The plug in turn is strengthened by fibrin strands. Exposure to collagen and subendothelial components is thought to be the trigger that causes the platelets to aggregate and form the primary plug. Aggregation has been proven to be dependent on the Von Willebrand factor and other plasma factors, such as ADP release from lysed red cells or platelets after exposure to collagen. A defect in one of these plasma factors, a qualitative defect in platelets, a reduced number of platelets (thrombocytopenia), or a defect in the blood vessel wall can result in failure of the primary hemostatic stage, causing spontaneous bleeding or purpura. The blood clotting or coagulation system is a proteolytic cascade. Each enzyme of the pathway is present in plasma in an inactive (zymogen) form, which, when activated, releases the active factor from the precursor molecule. An active factor then “switches on” the next factor. The mechanism functions as a series of positive and negative feedback loops to effectively control the process. The main aim of this process is to produce thrombin, which can convert soluble fibrinogen into insoluble fibrin, thus forming the clot. There are three phases of coagulation, the intrinsic and extrinsic (tissue factor) pathways that provide alternative routes for the generation of factor X and the final common pathway that results in thrombin formation. The distinction between the intrinsic and extrinsic pathways 516

is important for understanding the laboratory tests of coagulation. It is not relevant for the real-life process of blood clotting in the body, which may involve both pathways to different extents. Experts are unclear as to which pathway is involved in venous thromboembolic diseases such as deep vein thrombosis and pulmonary embolism. Bleeding disorders According to the cascade theory, each coagulation factor is converted to its active form by the preceding factor in a series of biochemical chain reactions. If there is a deficiency of any one of the factors, coagulation cannot proceed at a normal rate, initiation of the next reaction is delayed, and the time required for clotting is prolonged, resulting in bleeding from injured vessels for a longer time. Bleeding disorders can be either acquired or inherited (congenital). Von Willebrand’s disease is the most common hereditary coagulation disorder; it results in problems with platelet quality and can cause mild to moderately severe bleeding. Inherited disorders also include hemophilia A and B, which are associated with a decrease in factor VIII or IX activity, respectively. Because the liver produces many of the coagulation factors, diseases that affect the liver may be associated with clotting abnormalities. Disseminated intravascular coagulation (DIC), anticoagulant therapy, and thrombocytopenia also increase bleeding tendencies. There are several tests available to aid in the diagnosis of bleeding disorders and monitor anticoagulation therapy, and the most common are listed below. Platelet count Platelets are disk-shaped structures formed by the detachment of cytoplasm from megakaryocytes. They aid in the coagulation process by attaching or adhering to the walls of injured blood vessels, where they stick together to form the initial platelet plug. A low platelet count may occur in patients with AIDS, viral infections, lymphoma, and lupus erythematosus, or in patients taking certain drugs, most notably quinine and quinidine. Decreased platelet production is also a cause of thrombocytopenia, and may be due to aplastic anemia, leukemia, lymphoma, or bone marrow fibrosis. When collecting a specimen for a platelet count, EDTA is the anticoagulant of choice. The test is most commonly performed on an automated instrument which employs impedence measurement to count platelets, red blood cells, and white blood cells. Impedence counting is also known as the Coulter principle. According to Beckman Coulter, a major manufacturer of cell counters, the methodology works as follows: “A small opening (aperture) between electrodes is the sensing zone through

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Thrombin time This test is used to screen for abnormalities in the conversion of fibrinogen to fibrin. These may be caused by qualitative or quantitative abnormalities of fibrinogen or by inhibitors, such as heparin or fibrin/fibrinogen split products. The principle of the thrombin time test is that the exogenous addition of thrombin to plasma converts fibrinogen to fibrin and bypasses both the intrinsic and extrinsic pathways. The time it takes for the patient’s plasma to clot on addition of thrombin, referred to as the thrombin time, is a function of fibrinogen concentration. The test procedure involves adding one part of a known concentration of thrombin to one part of the patient’s citrated plasma and the clotting time is recorded. A reference range should be established by each testing facility, but a range of 14.0 to 20.0 seconds is considered normal. Prothrombin time (PT) The PT measures the function of the extrinsic and common pathways of the coagulation cascade. A reagent containing tissue thromboplastin (factor III) of rabbit brain origin and calcium is commonly used as an activating substance. Factor III (thromboplastin) initiates the

extrinsic pathway by forming a complex with factor VII. Calcium is needed to replace the plasma calcium that was chelated by the citrate in the blood collection tube. The PT is timed from the moment that the reagent is added to the plasma until the sample clots. As the factor VII-tissue thromboplastin complex activates factor X, the coagulation cascade proceeds into the common pathway. After formation of thrombin, fibrin will form at a normal rate only if factors involved in the extrinsic pathway (VII) and common pathway (X, V, II, I) are present in adequate amounts. If the PT is normal, then the sample contains adequate levels of factors VII, X, V, II, and I. The PT test is used to (1) screen for hereditary or acquired factor deficiencies in the extrinsic/common pathway (i.e., VII, X, V, II, I), (2) screen for specific factor or non-specific inhibitors (such as the lupus anticoagulant), (3) monitor anticoagulant therapy with vitamin K antagonists such as Coumadin and warfarin, and (4) assess the effect of vitamin K deficiency, which is an index of liver damage in patients with chronic liver disease. The results of the PT depend on the source and preparation of the thromboplastin reagent used, the instrumentation selected to perform the test, and the handling of the patient’s sample. The PT may be reported as the clotting time in seconds or as the INR (international normalized ratio). The INR is preferred to the clotting time measured in seconds because different thromboplastin reagents have different sensitivities to warfarininduced changes in levels of clotting factors. Since the potency of different commercially prepared calciumthromboplasin reagents varies, the International Sensitivity Index (ISI) was developed to describe the relative strength of each reagent. This index is a measure of the sensitivity of the thromboplastin used in PT assays. The higher the ISI, the less sensitive the thromboplastin. The INR is calculated by dividing the patient PT value by the established mean PT value of the normal population in each testing facility. This value is then raised to the power of the ISI. Use of the INR eliminates the interlaboratory variation seen with prothrombin times measured in seconds. Activated partial thromboplastin time (aPTT) The aPTT measures the function of the intrinsic and common pathways of the coagulation cascade. To begin the test, a reagent containing a contact activator (cephalin) and a phospholipid substitute for platelet factor III is incubated with the patient’s platelet-poor plasma. During this incubation period, the intrinsic pathway is initiated by conversion of XII to XIIa, which then converts XI to XIa. The cascade does not proceed any further, since the subsequent conversion of IX to IXa

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which suspended particles pass. In the sensing zone each particle displaces its own volume of electrolyte. Volume displaced is measured as a voltage pulse; the height of each pulse being proportional to the volume of the particle. Several thousand particles per second are individually counted and sized with great accuracy.” Automated cell counters also report the Mean Platelet Volume (MPV) or Platelet Distribution Width (PDW), two indices used to determine the relative size of the platelets being counted. Since a variety of factors can affect results (e.g., fibrin clots in EDTA blood, platelet clumping in capillary samples), a platelet estimate can also be performed to verify count accuracy. This is done by counting the platelets seen on a blood film by microscopic examination. Each platelet seen per field is estimated to be equivalent to 20,000 platelets/µL. This means 10 platelets per field would correspond to a platelet count of 200,000/µL. When results are questionable, manual platelet counts may performed using light or phase contrast microscopy. The procedure is as follows: the sample is first treated with 1% ammonium oxalate counting fluid, then charged into a Neubauer hemacytometer chamber. The chamber is placed in a moist Petri dish for 10 minutes to allow the cells to settle. The chamber is then placed on the microscope platform and the platelets in the 25 small center squares of the chamber grid are systematically counted. The number obtained is multiplied by 1,000 to give the platelet count per microliter of blood.

Coagulation tests

requires calcium ions. At this point, calcium is added as a second reagent. After recalcification, fibrin will form at a normal rate only if the factors involved in the intrinsic pathway (prekallikrein, high molecular weight kininogen [HMWK], XII, XI, IX, VIII) and common pathway (V, X, II, I) are present in adequate amounts. This rate of clotting measures the overall coagulant activity. The term “partial” in aPTT is used because platelet substitutes (the phospholipid emulsion) are not capable of activating the extrinsic pathway. This requires “complete” thromboplastin (tissue factor). Thus, the aPTT bypasses the extrinsic pathway and is unaffected by any abnormalities of factor VII. The aPTT is used to (1) screen for hereditary or acquired deficiencies of factors in the intrinsic/common pathway (i.e., all factors except VII and XIII), (2) screen for specific factor or non-specific inhibitors (such as the lupus anticoagulant), and (3) monitor anticoagulant therapy with parenteral heparin. Intrinsic coagulation disorders are apparent when the aPTT is prolonged and the prothrombin time is normal. For screening purposes, the aPTT is usually done in combination with other tests, such as the prothrombin time, which evaluates the factors of the extrinsic pathway. The combination of tests narrows the list of possible missing or defective factors. Results of the aPTT are prolonged by factor VIII deficiency (Hemophilia A) and factor IX deficiency (Hemophilia B). When the aPTT test is being used to monitor the effect of heparin, the test is done before the first dose of heparin and then as necessary to monitor therapeutic dosage. The activated clotting test (ACT) may be used in place of the aPTT to monitor heparin therapy. This test is performed by adding kaolin, (a clay that activates factor XII), or other clotting activator to the patient’s plasma and measuring the time required for clot formation. Bleeding time test The bleeding time (BT) is defined as the time between making a small incision through a skin capillary and the moment the bleeding stops. It is an in vivo measurement of platelet participation in small blood vessel hemostasis, and is one of the simplest and best tests of overall platelet function. This test is used to determine how well platelets interact with the blood vessel wall to form a blood clot. The test is usually performed on patients who have a history of prolonged bleeding after cuts, or who have a family history of bleeding disorders, or as a preoperative test to determine a patient’s likely bleeding response during and after surgery. There are four methods used: the Ivy method, template, modified template, and Duke method. With all methods the skin is cut in an area void of visible veins. The time from when the incision is made until all bleeding has stopped is 518

measured and recorded as the bleeding time. Every 30 seconds, filter paper or a paper towel is used to draw off the blood. The test is finished when bleeding has stopped completely. Fibrinogen The fibrinogen test aids in the diagnosis of suspected clotting or bleeding disorders caused by fibrinogen abnormalities which include the absence of fibrinogen, low fibrinogen concentration, or functionally abnormal fibrinogen. Reduced fibrinogen levels can be found in liver disease, prostate cancer, lung disease, bone marrow lesions, malnutrition, and certain bleeding disorders. Obstetric complications or trauma may also cause low levels. Patients who have received multiple blood transfusions may exhibit low fibrinogen levels because banked blood does not contain fibrinogen. Fibrinogen levels are also decreased in approximately 50% of patients with disseminated intravascular coagulation (DIC). In this condition the coagulation process is triggered by malignancy, severe injury, sepsis (and other conditions) and continues unabated, causing systemic clots to form until coagulation factors and platelets are depleted. This process is followed by internal hemorrhage. The fibrinogen test is performed by adding thrombin to specific dilutions of the patient’s plasma and measuring the amount of time it takes for the sample to clot. Anticoagulation therapy with low molecular weight heparin (LMWH) The anticoagulating effects of LMWH (heparin of smaller chain length) are easier to predict than standard heparin, and LMWH is associated with a lower risk of excessive bleeding and heparin induced thrombocytopenia. However, the effects of LMWH cannot be measured using the aPTT or activated clotting test (ACT). LMWH therapy is monitored by the anti-factor Xa assay. The antifactor Xa activity of heparin has been considered important because it is relatively unaffected by the molecular weight of heparin and therefore less influenced by the effect of potent heparin antagonists which can be released from platelets. The anti-factor Xa assay measures the antiXa effect of LMWH whereby heparin in a citrated plasma sample combines with antithrombin, forming a complex that inhibits an excess of purified factor Xa. Measurement of the clotting activity of residual factor Xa is done by the addition of phospholipids and calcium in the presence of a substrate plasma. This substrate plasma brings to the assay an excess of AT-III and other coagulation factors, thus eliminating interferences by the factors that are already present in the plasma being tested.

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Anticoagulant—A substance that suppresses or counteracts coagulation of the blood. Coagulation—The process of blood clotting. Coagulation cascade—The sequence of biochemical activities, involving clotting factors, that stops bleeding by forming a clot. Coagulation factors—Substances in the blood that act in sequence to stop bleeding by forming a clot. Coumadin—An anticoagulant taken to prevent blood clots. Fibrin—The insoluble protein formed by the action of thrombin on fibrinogen and stabilized by the action of factor XIIIa. Fibrin forms strands that add bulk to a forming blood clot to hold it in place and help “plug” an injured blood vessel wall. Fibrinogen—A type of blood protein called a globulin that interacts with thrombin to form fibrin. Fibrinolytic (thrombolytic) therapy—The intravenous administration of a drug to break up a blood clot. Hemostasis—The process the body uses to stop the flow of blood when the vascular system is damaged. Heparin—A medication that prevents blood clots by enhancing the activity of antithrombin. The heparin-antithrombin complex inhibits the activity of factor Xa, thrombin, and other clotting factors.

Complications Other than potential bruising at the puncture site, and/or dizziness, there are no complications associated with this test.

Results The absolute numbers that are considered normal vary from one laboratory to another. Any results reported should come with information regarding the testing facility’s normal range. The values listed below are representative of normal values. The patient’s physician is the best person to consult about a specific test level. • Platelets: A normal platelet count ranges between 150,000 and 400,000/µL. Platelet counts under 50,000/µL put a patient at risk for severe bleeding, while counts below 30,000/µL are considered critical.

International Normalized Ratio (INR)—A measurement system that standardizes the prothrombin time to help monitor anticoagulant activity for clients receiving warfarin (Coumadin) therapy. It is recommended by the World Health Organization (WHO) for more consistent reporting of prothrombin time results, as it eliminates variation in PT results between laboratories caused by differences in the sensitivity of thromboplastin reagents. Partial thromboplastin time—A test that measures the function of the clotting factors of the intrinsic pathway. Platelet—An irregularly shaped cell-like particle in the blood that is an important part of blood clotting. Platelets are activated when an injury causes a blood vessel to break. They change shape from round to spiny, “sticking” to the broken vessel wall and to each other to begin the clotting process. Prothrombin—A protein in blood plasma that is converted to thrombin during the clotting process. Thrombin—An enzyme in blood plasma that converts fibrinogen to fibrin during the last stage of the clotting process. Thromboplastin—A tissue substance that initiates the intrinsic coagulation pathway. Thrombus—A solid mass of blood constituents (blood clot) formed in the heart or vessels.

• Thrombin time: Reference values for the thrombin time are 14 to 15 seconds or within five seconds of the control. • Prothrombin time: PT results are reported in seconds and/or the International Normalized Ratio (INR). The normal range for the prothrombin time reported in seconds is between 11 and 13 seconds. Therapeutic levels for patient receiving Coumadin therapy generally are between 1.5 and 2-fold normal, or in terms of the INR, between 2.0 and 3.0. • Activated partial thromboplastin time: The normal range is between 20 and 36 seconds. If a patient is being anticoagulated with heparin, a result approximately 1.5 to 2.5 times the normal control value is usually a therapeutic goal. • Bleeding time: A normal bleeding time for the Ivy method is less than five minutes from the time of the incision until all bleeding from the wound has stopped.

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KEY TERMS

Code of ethics for nurses

Some texts extend the normal range to eight minutes. The normal value for the template method is eight minutes or less, while for the modified template method, up to 10 minutes is considered normal. Normal for the Duke method is three minutes or less. • Fibrinogen: Normal reference values for fibrinogen are 200 mg/dL-400 mg/dL for adults and 125 mg/dL-300 mg/dL for newborns.

Health care team roles Coagulation tests are ordered and interpreted by physicians (in some cases pharmacists). The samples may be collected by a nurse, physician assistant, phlebotomist, or technician. Testing is preformed by a clinical laboratory scientist, CLS(NCA)/medical technologist, MT(ASCP) or by a clinical laboratory technician, CLT(NCA)/medical laboratory technician, MLT(ASCP). Resources BOOKS

Berkow, Robert (ed), et al. Merck Manual of Medical Information. Whitehouse Station, NJ: Merck Research Laboratories, 1997. Chernecky, Cynthia C. and Barbara Berger. Lab Tests and Diagnostic Processes. 3rd ed. Philadelphia: W. B. Saunders Company, 2001. Kee, Joyce LeFever. Handbook of Laboratory and Diagnostic Tests. 4th ed. Upper Saddle River, NJ: Prentice Hall, 2001. Pagana, Kathleen D. and Timothy J. Pagana. Mosby’s Diagnostic and Laboratory Test Reference. St. Louis: Mosby, Inc., 1998. PERIODICALS

Reddy, N.M., S.W. Hall, and R.F. MacKintosh. “Partial Thromboplastin Time: Prediction of Adverse Events and Poor Prognosis by Low Abnormal Values.” Archives of Internal Medicine 159 (13 December 1999): 2706. OTHER

Beckman Coulter, Inc. . Copyright 1998, 1999, 2000, 2001. Columbia University College of P & S. Disorders of Blood Coagulation . Emergency Nursing World. .

Victoria E. DeMoranville

Cobalain see Vitamin B12 520

Code of ethics for nurses Definition A code of ethics is a guide for an individual or group to follow in making decisions regarding ethical issues.

Description In the broadest sense, ethics are the principles that guide an individual, group, or profession in conduct. Although nurses do make independent decisions regarding patient care, they are still responsible to the profession as a whole in how those decisions are made. From the earliest concept of nursing, the proper behavior and conduct of a nurse was closely scrutinized. Florence Nightingale wrote of specific issues of conduct and moral behavior. The Nightingale pledge that was composed in 1893 by nursing instructor Lystra Gretter includes the vow “to abstain from whatever is deleterious and mischievous and will not take or knowingly administer any harmful drug.” Over the last 100 years, nursing has evolved into a very complex professional field. Nurses are now faced with life and death decisions, sometimes on an hourly basis. Medical care has advanced to the point that new technology with its potential benefit or harm to a patient changes constantly. Although the private conduct of a nurse is no longer controlled by the employer, the effects of that lifestyle on the nurse’s ability to think and respond to patients while on duty falls under the code of ethics.

Viewpoints The study of ethics is actually a branch of philosphy. The word ethics is derived from the Greek term ethos which means customs, habitual usage, conduct, and character. The study of ethics has led to the identification of basic concepts including rights, autonomy, beneficence, nonmaleficence, justice, and fidelity. Understanding these concepts assists the nurse with making decisions during difficult situations. Rights Webster defines a right as “something to which one has a just claim or the power or priviledge to which one is justly entitled.” Patient rights have evolved to the point that federal legislation has been passed in the United States to protect a patient’s individual rights. A Patient’s Bill of Rights was initially developed by the American Hospital Association in 1973 and revised in 1992. All hospitals are now required by law to inform patients of these rights upon admission to the hospital.

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Autonomy comes from the latin auto meaning “self” and nomy which means “control.” Individuals must be given the rights to assist in their own decision making. This ethical concept has led to the need for informed consent. Sometimes patients’ religious or cultural beliefs lead them to make decisions regarding their own care that may seem controversial or even dangerous. However, the concept of autonomy gives them the right to make those decisions unless they are mentally impaired. Beneficence and nonmaleficence Beneficence means to do good, not harm, to other people. Nonmaleficence is the concept of preventing intentional harm. Both of these ethical concepts relate directly to patient care. In the American Nurses Association Code for Nurses, there is a specific charge to protect patients by specifying that nurses should report unsafe, illegal, or unethical practices by any person. Nurses are often faced with making decisions about extending life with technology, which might not be in the best interest of the patient. Often the concept of weighing potential benefit to the patient against potential harm is used in making these difficult decisions, along with the patient’s own stated wishes. Justice The word justice is closely tied with the legal system. However, the word refers to the obligation to be fair to all people. In 2001, healthcare economics have hospitals and other providers stretching their resources to their limits. Economic decisions about healthcare resources have to be made based on the number of patients who would benefit. The potential of rationing care to the frail elderly, poor, and disabled creates an ethical dilemma that is sure to become even more complicated in the future. Fidelity Fidelity refers to the concept of keeping a commitment. Although the word is more closely used to describe a marital relationship, fidelity is the concept of accountability. What is the nurse’s responsibility to his or her patient, employer, society, or government? Privacy and confidentiality are concepts that could be challenged under the concept of fidelity. If a nurse is aware of another healthcare giver who is impaired, but the circumstances are private or confidential, how is the conflict resolved?

Professional implications As a general rule, nurses are employed by a hospital, clinic, or private practice. Decisions that are made about patient care are not totally independent. Every decision creates a ripple effect and touches someone else in the health care field. One of the purposes of a code of ethics is to help nurses keep perspective and a balanced view regarding decisions. One way to study a code of ethics is to look at a case study. J. L. presents herself to the emergency room with lower right abdominal pain. J. L. is a 17-year-old white female and is accompanied by her mother. J. L.’s mother is a nurse and works in another department of the hospital. The mother signed all of J. L.’s admission paperwork and received the Patient Bill of Rights. Although J. L.’s pain does not seem severe enough for appendicitis, she does have a history of fever for 24 hours and her temperature in the hospital is 100.8°F (38°C). An ultrasound that did not show appendicitis had been done earlier in the day. She was told to report to emergency room if the fever rose. After J. L. reports her symptoms to both a nurse and a physician assistant, she is examined briefly by emergency department physician. The staff assumes that J. L.’s mother wants to stay in the room and does not seek the patient’s permission. As a part of her history, J. L. informs them she is not sexually active and is on the second day of her menstrual cycle. The mother can tell by the tone of questioning that the staff does not believe J. L. is still a virgin. After a two-hour delay, including having to repeat the urinalysis because of a lost specimen, the emergency physician decides a pelvic exam needs to be done. The pelvic exam is traumatic for the patient, despite her mother’s best efforts to calm her. J. L. is told in a condescending tone that the exam hurts because of her failure to relax. Following the exam, the physician tells J. L. and mother that her blood count is normal, the urinalysis was inconclusive because of menstrual blood, and the patient was uncooperative in giving a catheterized specimen. J. L. and her mother were informed a pregnancy test was done, because the staff have experienced “immaculate conceptions” in their department. The only time that J. L. and her mother had contact with an RN during this time was when she was initially triaged and when the discharge instructions were handed to her mother. J. L. and her mother were sent home with instructions. Her pain subsided without treatment. Although this case study is not one of life and death decision making, there were numerous violations of the patient’s rights and of the nursing code of ethics. The patient’s right to privacy was violated. It is questionable whether the patient (J. L.) ever saw the Patient’s Bill of

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Autonomy

Cognitive-perceptual rehabilitation

KEY TERMS Beneficence—The obligation to do good, not harm, to other people. Ethics—A specific area of study of morality, which concentrates on conduct and human values. Maleficence—The act of intentionally doing harm or evil. Nonmaleficence is the principle of purposefully not doing harm.

Rights, since it was given to her mother. J. L. was sexually inactive and a virgin, so the question of nonmaleficence is raised by the traumatic pelvic exam. The question of abandonment is also raised due to lack of nursing attention. If J. L. had asked her mother to leave during the exams, could confidentiality have been breached by the mother the next day by checking the hospital computer for reports? The answer to all of the above questions is yes; areas of nursing code of ethics could have been broken. No one died, but there must be constant reeducation of staff regarding the importance of these issues. In an attempt to keep the concept of ethical care in the forefront of nurses, physicians, and other healthcare worker’s minds, hospitals have ethics committees or even an ethicist on staff. Special educational seminars may be offered or actual case studies reviewed. Some hospitals have protocols for requesting an ethics consult at the bedside. These type of consults are usually seen in ICU or trauma situations where ceasing life support is being discussed. A new area of potential ethical dilemma was discussed in the July 2, 1999, Online Journal of Issues in Nursing. Silva and Ludwick discussed the pros and cons of interstate practice laws. As new laws are passed that allow more fluid movement of nurses between states, new issues of ethical behavior may arise. The initial reaction of most people in the health care field is that a nurse practices the same way everywhere, but there are subtle differences in the laws between states. For example, there are different definitions of minors and when minors can be emancipated to make their own decisions. Are there differences in state laws regarding patients with impaired decision-making capabilities? What if the nurse is not aware of the subtle differences in each state’s law? Communication technology such as the Internet is also complicating ethical issues. Do web sites that encourage patients to describe symptoms to on-line nurses expose too great a risk? What backup mechanisms are 522

in place if a patient talking to a triage nurse gets disconnected or loses consciousness? How can there be assurances of confidentiality in a telenursing setting? Silva and Ludwick encouraged their readers to “be proactive and stimulate critical thinking about ethics and interstate practice.” A nursing code of ethics cannot remain a stagnant document. As new issues arise in nursing and healthcare practice, they must be addressed and possibly included in a formal statement. The American Nurses Association (ANA) Code for Nurses with Interpretive Statements was approved in 1985 and was still being used in mid-2001. A task force met in 1996 and began the process of reviewing and revising the code. A draft of the new code is anticipated to be approved and released in 2001. The new code is more comprehensive than the 1985 code. It is the responsibility of all professional nurses to be aware of the Code for Nurses and any changes that may be made in the future. It is also the responsibility of each individual nurse to practice ethical care on a daily basis. Resources BOOKS

Ellis, Janice R. and Celia L. Hartley. Nursing In Today’s World: Challenges, Issues and Trends, 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins Publishing, 2001. PERIODICALS

Silva, Mary C. and Ruth Ludwick. “Interstate Nursing Practice and Regulation: Ethical Issues for the 21st Century.” Online Journal of Issues in Nursing July 1999. . ORGANIZATIONS

American Nurses Association. 600 Maryland Ave. SW, Ste 100 West, Washington, DC 20024-2571. (800) 2744ANA. . OTHER

“Florence Nightingale: Her Writings.” 16 April 2001. .

Gayle G. Wilkins, RN, BSN, OCN

Cognitive-perceptual rehabilitation Definition Cognitive-perceptual rehabilitation addresses the impairments, functional limitations, and disabilities that result from a deficit in cognition or perception. Cognition

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Purpose Individuals who have neurological insult (trauma to the brain), whether mild or severe, may experience cognitive and perceptual difficulties. Researchers have found that 75–90% of children with learning disabilities present with motor difficulties, which often are accompanied by perceptual deficits. In one study, over half of patients admitted for cognitive rehabilitation due to head injury also presented with visual perceptual impairments. In addition, individuals who have experienced strokes or inflammatory or infectious brain diseases, such as meningitis or encephalitis, are at risk for perceptual and cognitive disorders. Cognitive and perceptual rehabilitation is indicated when a patient or client presents with deficits in these areas during the medical, physical therapy, or occupational therapy assessment. Difficulties may appear in equilibrium and vestibular functions, automatic postural reactions, fine and visual motor performance, motor planning abilities, and/or sensory integration. The individual may remember events incorrectly and have difficulty perceiving new information. In addition, he or she may have inappropriate responses to sensory input due to deficits in sensory processing. Unilateral spatial inattention, a visual perceptual dysfunction occurring most frequently in patients who have had a stroke, traumatic brain injury, or tumor, may be detected by asymmetries in performance. For example, in drawing a clock, the individual may place all of the numbers on the right half of the clock only. When an individual has visual, auditory, or tactile agnosia, he or she is unable to recognize and name a common object using one of the senses of sight, hearing, or touch, respectively. Visuospatial disorders are manifested by the inability to discern spatial relationships. Visuoconstructive disabilities occur when an individual is unable to synthesize parts into a whole, such as building a tower from blocks or copying a line drawing. Vestibular impairments may present as dizziness or imbalance with certain movements or head positions. Many standardized tests exist to assess perceptual performance in children or adults.

Description Intervention is found in either direct therapy or indirect therapy. Direct therapy usually focuses on the par-

ticular tasks or skills to be learned, with compensatory behaviors filling in for abilities that are missing. In contrast, indirect therapy focuses on rehabilitating the underlying dysfunction of the central nervous system (CNS), in hopes that improvement of the dysfunction will transfer to skill attainment. Sensory integration and motor control approaches are considered indirect therapies. Sensory integration is an approach, used often with children, in which sensory input is provided within the context of a meaningful activity, usually play-related. The goal is that the child will display appropriate responses and gain experience in organization of sensory input. When using the motor control approach, task-oriented behavior is practiced to enhance perceptual information from the feedback and feedforward mechanisms in the CNS. Verbal and visual cues, in addition to varying the practice situation, are all used to assist in facilitating appropriate performance that can be applied to a variety of situations. An example of direct therapy is functionally relevant motor skill training. Balance, locomotion, body awareness, and eye-hand coordination tasks are practiced in the context of activities of daily living, e.g., tying a shoe. Tasks are broken down into simple parts, then as a whole, and practiced in a variety of ways for carryover to different situations. Visual perceptual rehabilitation usually takes the form of direct therapy as well. Clients are trained to use eye and head movements along with visual markers to scan their environment, compensating for unilateral spatial inattention. Clients with visuospatial and visuoconstructive disorders are trained by progressing from simple to more complex tasks, using verbal, proprioceptive, and vestibular input to aid in performing the tasks. Treatment of vestibular impairments takes place in a similar fashion. The patient is habituated to certain head movements through practice, then is progressed to more complex ones as tolerance increases. Cognitive prosthetics, another form of direct therapy, may be used in the rehabilitation of an individual with impairments in brain processes. Prosthetics, in the form of computer technology, are used to compensate for the individual’s impairments by altering the environment for optimum function. Highly individualized computer software is used to provide an individual with the support necessary to successfully perform tasks of daily living. For example, it may sequence steps of a task, or convert written words to pictures or speech. Regardless of the interventions selected, the underlying strategies for working with an individual who has cognitive-perceptual dysfunction are similar. Goals should be clear and relevant to the patient to reduce con-

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refers to the mental processes of comprehension, judgment, memory, and reasoning. Perception is part of the cognitive process, and is characterized by the conscious recognition and interpretation of sensory stimuli for knowledge or motivation of action.

Cold injuries

Resources

KEY TERMS

BOOKS

Feedback—Peripheral sensory input which indicates a need for correction of errors. Feedforward—The use of previous motor learning to anticipate errors in movement planning, allowing for advance correction.

Shumway-Cook, Anne, and Marjorie Woollacott. Motor Control: Theory and Practical Applications. Baltimore, MD: Williams & Wilkins, 1995. Umphred, Darcy A. Neurological Rehabilitation. 3rd ed. St. Louis, MO: Mosby Yearbook, Inc, 1995. PERIODICALS

Proprioceptive—Pertaining to sensations of body movements and position.

Cole, Elliot. “Cognitive Prostethics: An Overview to a Method of Treatment.” NeuroRehabilitation 12 (1999): 39-51.

Sensory integration—The processing and organization of sensory input.

Peggy Campbell Torpey, MPT

Unilateral spatial inattention—Perceptual unawareness of stimuli on one side of the body, associated with a cortical or subcortical lesion in the opposite side of the brain. Vestibular—Pertaining to the inner ear structures associated with balance and position sense.

fusion and increase motivation. In the beginning, the complex should be broken down into simple parts with verbal, visual, tactile, or other cues provided as necessary. Distractions in the environment should be decreased at first. As progress is made, tasks then move toward more complexity.

Results Progress may be slow, depending upon the severity of disability, individual motivation, family support, etc. The desired outcome, however, is that the individual learns to better modulate and discriminate sensory input in order to process it and respond to it appropriately. This may occur as an actual change in neural function, or through the use of compensatory measures. An increase in functional ability and reduction in disability are the ultimate goals.

Cold injuries Definition Cold injuries include frostbite and frostnip. Frostbite is the term for damage to skin and other tissues caused by freezing. Frostnip is a milder form of cold injury.

Description In North America, frostbite is largely confined to Alaska, Canada, and the northern states. However, it can occur whenever people are exposed to sustained cold temperatures without proper protection. Recent years have witnessed a substantial decline in the number of cold injury cases, probably for several reasons, including better winter clothing and footwear and greater public understanding of how to avoid cold-weather dangers. At the same time, the nature of the at-risk population has changed. Increased numbers of homeless people have made frostbite an urban as well as a rural public health concern. The growing popularity of outdoor winter activities has also expanded the at-risk population.

Causes and symptoms Frostbite

Health care team roles Cognitive-perceptual rehabilitation truly requires a transdiciplinary approach. Any or all of the following individuals may be involved, depending upon the specific needs of the individual: family physician, neurologist, psychiatrist, ophthalmologist, otologist, psychologist, occupational therapist, physical therapist, speech and language pathologist, recreational therapist, and vocational education specialist. 524

Skin exposed to temperatures slightly below the freezing mark can take hours to freeze, but very cold temperatures can freeze skin in minutes or seconds. Air temperature, wind speed, and moisture all affect how rapidly skin becomes cold. A strong wind can lower skin temperature considerably by dispersing the thin protective layer of warm air that surrounds human bodies. Wet clothing readily draws heat away from skin because water is a potent conductor of heat. The evaporation of moisture from the surface of skin also produces cooling. For these reasons,

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The extent of any permanent injury, however, is determined not by how cold skin and underlying tissues become but by how long they remain frozen. Consequently, homeless people and others whose selfpreservation instincts may be clouded by alcohol or psychiatric illness face a greater risk of frostbite-related health effects because they are more likely to stay out in the cold when prudence dictates seeking shelter or medical attention. Alcohol and smoking also affect blood circulation in the extremities in a way that can increase the severity of injury. A review of 125 Saskatchewan frostbite cases found a tie to alcohol in 46% and to psychiatric illness in 17%. Other risk factors identified by researchers include inadequate clothing, previous cold injury, fatigue, wound infection, atherosclerosis, and diabetes. Driving in poor weather can also be dangerous. Vehicular failure was a predisposing factor in 15% of the Saskatchewan cases. Three nearly simultaneous physiological processes underlie frostbite injury: tissue freezing, tissue hypoxia, and the release of inflammatory mediators. Tissue freezing causes the formation of ice crystals and other changes that damage and eventually kill cells. Much of this harm occurs because the ice produces pressure changes that cause water (crucial for cell survival) to flow out of cells. Tissue hypoxia (oxygen deficiency) occurs when blood vessels in the hands, feet, and other extremities narrow in response to cold. Among its many tasks, blood transfers body heat to skin, which then dissipates the heat into the environment. Blood vessel narrowing is the body’s way of protecting vital internal organs at the expense of the extremities by reducing heat flow away from the core or center portions of the body. However, blood also carries life-sustaining oxygen to skin and other tissues, and narrowed vessels result in oxygen starvation. Narrowing also causes acidosis (an increase in tissue acidity) and increases blood viscosity (thickness). Ultimately, blood stops flowing through capillaries (tiny blood vessels that connect arteries and veins), and blood clots form in the arterioles and venules (the smallest arteries and veins). Damage also occurs to endothelial cells that line blood vessels. Hypoxia, blood clots, and endothelial damage lead, in turn, to the release of inflammatory mediators (substances that act as links in the inflammatory process), which promote further endothelial damage, hypoxia, and cell destruction. Frostbite is classified by degree of injury (first, second, third, or fourth), or simply divided into two types, superficial (corresponding to first- or second-degree injury) and deep (corresponding to third- or fourthdegree injury). Most frostbite injuries affect the feet or

hands. The remaining 10% of cases typically involve ears, nose, cheeks, or penis. Once frostbite sets in, an affected part begins to feel cold and usually becomes numb. This is followed by a feeling of clumsiness. Skin turns a white or yellowish color. Many individuals experience severe pain in the affected part during rewarming treatment. This is often followed by an intense throbbing pain that arises two or three days later and can last for days or weeks. As skin begins to thaw during treatment, edema (excess tissue fluid) often accumulates, causing swelling. In second- and higher-degree frostbite, blisters appear. Third-degree frostbite cases produce deep, bloodfilled blisters and, during the second week, a hard black eschar (scab). Fourth-degree frostbite penetrates below the skin to the muscles, tendons, nerves, and bones. In severe cases of frostbite the dead tissue can mummify and drop off. Infection is also a possibility. Frostnip Like frostbite, frostnip is associated with ice crystal formation in tissues, but no tissue destruction occurs and any crystals dissolve as soon as the skin is warmed. Frostnip affects areas such as the earlobes, cheeks, nose, fingers, and toes. The skin turns pale and one experiences numbness or tingling in the affected part until warming begins.

Diagnosis Frostbite diagnosis relies on a physical examination and may also include conventional radiography (x rays), angiography (x-ray examination of the blood vessels using an injected dye to provide contrast), thermography (use of a heat-sensitive device for measuring blood flow), and other techniques for predicting the course of injury and identifying tissue that requires surgical removal. During the initial treatment period, however, a physician cannot judge how a case will progress. Diagnostic tests only become useful between three and five days after rewarming, once the blood vessels have stabilized.

Treatment Frostbite Emergency medical help should always be summoned whenever frostbite is suspected. While waiting for help to arrive, one should, if possible, remove wet or tight clothing and put on dry, loose clothing or wraps. A splint and padding are used to protect an injured area. Rubbing an injured area with snow or anything else is dangerous. The key to prehospital treatment is to avoid partial thawing and refreezing, which releases more

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wet skin or clothing on a windy day can lead to frostbite even if the air temperature is above the freezing mark.

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applications are repeated three times each, ending with the cold compress. Nutritional therapy to promote tissue growth in damaged areas may also be helpful. Homeopathic and botanical therapies may also assist recovery from frostbite. Homeopathic Hypericum (Hypericum perforatum) is recommended when nerve endings are affected (especially in the fingers and toes) and Arnica (Arnica montana) is prescribed for shock. Cayenne pepper (Capsicum frutescens) can enhance circulation and relieve pain. Drinking hot ginger (Zingiber officinale) tea also aids circulation. Other possible approaches include acupuncture to avoid permanent nerve damage and oxygen therapy. Human hand with frostbite. (Photo Researchers, Inc. Reproduced by permission.)

Frostnip

inflammatory mediators and makes an injury substantially worse. For this reason, the affected part must be kept away from heat sources such as campfires and car heaters. Experts advise rewarming in the field only when emergency help will take more than two hours to arrive and refreezing can be prevented. Because the outcome of a frostbite injury cannot be initially predicted, all hospital treatment follows the same protocol. Treatment begins by rewarming the affected part for 15–30 minutes in water at a temperature of 104–108°F (40–42.2°C). This rapid rewarming halts ice crystal formation and dilates narrowed blood vessels. Aloe vera (which acts against inflammatory mediators) is applied to the affected part, which is then splinted, elevated, and wrapped in a dressing. Depending on the extent of injury, blisters may be debrided (cleaned by removing foreign material) or simply covered with aloe vera. A tetanus shot and possibly penicillin are used to prevent infection, and the injured person is given ibuprofen to combat inflammation. Narcotics are needed in most cases to reduce the excruciating pain that occurs as sensation returns during rewarming. Except when injury is minimal, treatment generally requires a hospital stay of several days, during which hydrotherapy and physical therapy are used to restore health to the affected body parts. Experts recommend a cautious approach to tissue removal, and advise that 22–45 days must pass before a decision on amputation can safely be made. Alternative practitioners suggest several kinds of treatment to speed recovery from frostbite after leaving a hospital. Bathing the affected part in warm water or using contrast hydrotherapy may help enhance circulation. Contrast hydrotherapy involves a series of hot and cold water applications. A hot compress (as hot as the patient can stand) is applied to the affected area for three minutes followed by an ice cold compress for 30 seconds. These 526

Frostnipped fingers are helped by blowing warm air on them or holding them under one’s armpits. Other frostnipped areas can be covered with warm hands. The injured areas should never be rubbed.

Prognosis The rapid rewarming approach to frostbite treatment, pioneered in the 1980s, has proved to be much more effective than older methods in preventing tissue loss and amputation. A study of 56 first-, second-, and thirddegree frostbite patients treated with rapid rewarming in 1982–85 found that 68% recovered without tissue loss, 25% experienced some tissue loss, and only 7% needed amputation. In a comparison group of 98 patients, treatment using older methods resulted in a tissue loss rate of 35% and an amputation rate of nearly 33%. Although the comparison group included a higher proportion of second- and third-degree cases, the difference in treatment results was determined to be statistically significant. The extreme throbbing pain that many frostbite sufferers endure for days or weeks after rewarming is not the only prolonged symptom of frostbite. During the first weeks or months after a cold injury, people often experience tingling, a burning sensation, or a sensation resembling shocks from an electric current. Other possible consequences of frostbite include skin-color changes, nail deformation or loss, joint stiffness and pain, hyperhidrosis (excessive sweating), and heightened sensitivity to cold. For everyone, a degree of sensory loss lasting at least four years—and sometimes a lifetime—is inevitable.

Health care team roles The head of most health care teams is a physician. A physician determines a plan for treatment, provides guidance, assigns tasks for other members of the team, and monitors progress. Paramedics or other persons render-

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Prevention With appropriate knowledge and precautions, frostbite can be prevented even in the coldest and most challenging environments. Appropriate clothing and footwear are essential. To prevent heat loss and keep blood circulating properly, clothing should be worn loosely and in layers. Covering the hands, feet, and head is also crucial for preventing heat loss. Outer garments need to be wind and water resistant, and wet clothing and footwear must be removed and replaced as quickly as possible. Alcohol and drugs should be avoided because of their harmful effects on judgment and reasoning. Experts also warn against alcohol use and smoking in the cold because of the circulatory changes they produce. Paying close attention to weather reports before venturing outdoors and avoiding unnecessary risks such as driving in isolated areas during a blizzard are also important. Resources BOOKS

McCauley, Robert L., et al. “Frostbite and Other ColdInduced Injuries.” In Wilderness Medicine: Management of Wilderness and Environmental Emergencies. edited by Paul S. Auerbach. St. Louis: Mosby, 1995. Petty, Kevin J. “Hypothermia.” In Harrison’s Principles of Internal Medicine, 14th ed. edited by Anthony S. Fauci et al. New York, McGraw Hill, 1998. Yoder, Ernest L. “Disorders due to heat and cold.” In Cecil Textbook of Medicine, 21st ed. edited by Goldman, Lee, Bennett, J. Claude. Philadelphia, Saunders, 2000. PERIODICALS

Graham, C.A., and Stevenson, J. “Frozen chips: an unusual cause of severe frostbite injury.” British Journal of Sports Medicine (October 2000): 382-383. Hall, Christine B. Cold Hurts: Frostbite, Frostnip, and Immersion Foot. Anchorage, AL: University of Alaska Sea Grant, 1995. Hamlet, M.P. “Frostbite.” International Journal of Circumpolar Health 59 (2000): 1-130. ORGANIZATIONS

Rocky Mountain Survival Group. P. O. Box 2572; Dillon, Colorado 80435. [email protected].

OTHER

eMedicine.com. . University of Illinois. McKinley Health Center. “Frostbite.” . Urgent Care at Home. . Your Health.com. .

L. Fleming Fallon, Jr., MD, PhD, DrPH

Cold sore Definition A cold sore is a clear, fluid-filled blister, which often appears on the lips or nose. Cold sores, also referred to as fever blisters, are caused by a viral infection, herpes simplex virus Type 1 (HSV-1).

Description Cold sores are painful, unsightly, and often recurrent. HSV-1 often occurs on the lower face but can occur on the genitals or buttocks. Though rarely fatal, HSV-1 can be serious if cold sores occur in newborns, the chronically ill, or the elderly. Other names for cold sores are oral herpes, labial herpes, herpes labialis, and herpes febrilis. They are different from common canker sores because they usually are on the lips, whereas canker sores usually occur inside the mouth, on the tongue, or inside the cheeks. Cold sores rarely occur inside the mouth except during the initial episode. While there are eight types of herpes viruses, cold sores are only caused by HSV-1 or herpes simplex virus Type 2 (HSV-2). It is commonly believed that herpes simplex virus type 1 infects above the waist and herpes simplex virus type 2 infects below the waist. This is not completely true. HSV-1 does appear on the genitals and sometimes on other areas of the body. Nurses and other health care workers have been known to get herpetic sores after the virus has entered a break in the skin of their fingers. Oral herpes is very common. About 50-80% (some estimates are as high as 90%) of Americans are thought to carry antibodies for HSV-1. Most people who are exposed to HSV-1 become infected but only 10% of

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ing first aid are also members of the team by providing immediate or early assistance to persons with frostbite or frostnip. Nurses may provide treatment alongside physicians. Physical therapists may become involved with rehabilitation of serious cases of frostbite. Occasionally, surgeons are called upon to amputate (remove) portions of bodies that have become too severely damaged to recover from frostbite.

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those people have symptoms, such as sores, and experience recurring outbreaks of the infection. Of the 50 million Americans thought to be infected with HSV-1, most acquired the virus when they were children and only about 5% are bothered enough by HSV-1 to consider it a medical problem. Anyone can become infected by the herpes virus, and once a person is infected the virus remains latent for life. Herpes viruses are spread from person to person by direct skin-to-skin contact and, sometimes, by respiratory transmission (coughing or sneezing). The highest risk for spreading the virus is the time period beginning with the appearance of blisters and ending with scab formation. However, infected persons need not have visible blisters to spread the infection to others, since the virus may be present in the saliva without obvious oral lesions. Viruses are different from bacteria. While bacteria are independent and can reproduce on their own, viruses enter human cells and force the cells to make more of the virus. The infected human cell is usually killed and releases thousands of new viruses. The cell death and resulting tissue damage causes the actual cold sores. In addition, the herpes virus can infect a cell and instead of making the cell produce new viruses, it hides inside the cells of the nervous system. This is called “latency.” A latent virus can wait inside the nervous system for days, months, or even years. At some future time, the virus “awakens” and causes the cell to produce thousands of new viruses which cause an active infection. This process of latency and active infection is best understood by considering the cold sore cycle. An active infection is obvious because cold sores are present. The first infection is called the “primary” infection. This active infection is then controlled by the body’s immune system and the sores heal. In between active infections the virus is latent. At some point in the future, latent viruses become activated and once again cause sores. These are called “recurrent” infections. Although it is not known what triggers the latent virus to activate, several conditions seem to bring on infections. These include stress, illness, tiredness, exposure to sunlight, menstruation, fever, and diet.

Causes and symptoms While anyone can be infected by the herpes virus, not everyone will show symptoms. The first symptoms of herpes occur within 2-20 days after contact with an infected person. Symptoms of the primary infection are usually more severe than those of recurrent infections. The primary infection can cause symptoms like other viral infections, including tiredness, headache, fever, and swollen lymph nodes in the neck. 528

People who experience outbreaks might have one or several blisters. Typically, 50-80% of persons who have outbreaks experience prodrome symptoms of oncoming disease of pain, burning, itching, or tingling at the site where blisters will form. This prodrome stage may last from a few hours, to one or two days. The herpes infection prodrome occurs in both the primary infection and recurrent infections. In 95% of people with cold sores, the blisters occur at the outer edge of the lips, which is called the “vermilion border.” Less often, blisters form on the nose, chin, or cheek. Following the prodrome, the disease process is rapid. First, small red bumps appear which quickly form fluid-filled blisters. The painful blisters may either burst and form a scab or dry up and form a scab. Within two days of the first red bumps, all the blisters have formed scabs. The skin heals completely and without scarring within six to ten days. The virus then moves to nerve cells and remains in its resting state until the next outbreak, which can occur in the same or a nearby site. Some children have a very serious primary (first episode) herpes infection called “gingivostomatitis.” This causes fever, swollen lymph glands, and numerous blisters inside the mouth, lips, and tongue that may form large, open sores. These painful sores may last up to three weeks and can make eating and drinking difficult. Because of this, young children with gingivostomatitis are at risk from dehydration (excessive loss of water from the body). Most people experience fewer than two recurrent outbreaks of cold sores each year. Some people never experience outbreaks, while some have very frequent outbreaks, as often as every few weeks. In most people, the blisters form in the same area each time and are triggered by the same factors (such as stress, sun exposure, etc.).

Diagnosis The typical appearance of HSV-1 often makes it an easy visual diagnosis. Health care professionals who are uncertain of the diagnosis can swab the infected area and send it to a lab for analysis. HSV-1 can be diagnosed and treated by family doctors, dermatologists (doctors who specialize in skin diseases), and infectious disease specialists. Sometimes, dentists or nurses are the first to see the signs of HSV-1. Other laboratory tests, including scrapings and blood tests, might be performed to look for the virus. These tests produce valid results only in the early stages of an outbreak and, sometimes, more than one test is needed. Oral herpes may resemble a bacterial infection called “impetigo.” This skin infection is most commonly seen in

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Treatment There is no cure for herpes virus infections. There are antiviral drugs available, which have some effect in lessening the symptoms and decreasing the length of herpes outbreaks. There is evidence that some may also prevent future outbreaks. These antiviral drugs work by interfering with the replication of the viruses and are most effective when taken as early in the infection process as possible. For the best results, drug treatment should begin during the prodrome stage before blisters are visible. Depending on the length of the outbreak, drug treatment could continue for up to ten days or be used on an on-going basis as a method of prevention. Acyclovir, famciclovir, and valacyclovir are oral antiviral medications developed to effectively treat herpes infections. In June 2000, the United States Food and Drug Administration approved the first over-the-counter ointment, called docosanol 10% cream, as a topical treatment for cold sores. During an outbreak of cold sores, salty foods, citrus fruits (oranges, etc.), and other foods which irritate the sores should be avoided. The sores should be washed once or twice a day with warm, soapy water and patted gently dry. Over-the-counter lip products which contain the chemical phenol (such as Blistex Medicated Lip Ointment) and numbing ointments (Anbesol) help to relieve cold sores. Sometimes applying ice at the first sign of a cold sore diminishes the outbreak. A band-aid may be placed over the sores to protect them and prevent spreading the virus to other sites on the lips or face. Acetaminophen (Tylenol) or ibuprofen (Motrin, Advil) may be taken if necessary to reduce pain and fever. Alternative treatment Vitamin and mineral supplements and diet may have an effect on the recurrence and duration of cold sores. In general, cold sore sufferers should eat a healthy diet of unprocessed foods such as vegetables, fruits, and whole grains. Alcohol, caffeine, and sugar should be avoided. An imbalance in the amino acids lysine and arginine is thought to be one contributing factor in herpes virus outbreaks. A diet that is rich in the amino acid lysine may help prevent recurrence of cold sores. Foods which con-

tain high levels of lysine include most vegetables, legumes, fish, turkey, and chicken. In one study, patients taking lysine supplements had milder symptoms during an outbreak, a faster healing time, and had fewer outbreaks than patients who did not take lysine. Patients should take 1,000 mg of lysine three times a day during a cold sore outbreak and 500 mg daily on an ongoing basis to prevent recurrences. Intake of the amino acid arginine should be reduced. Foods rich in arginine that should be avoided are chocolate, peanuts, almonds, and other nuts and seeds. Vitamin C and bioflavonoids (a substance in fruits that helps the body to absorb and use vitamin C) have been shown to reduce the duration of a coldsore outbreak and reduce the number of sores. The vitamin B complex includes important vitamins that support the nervous system where viruses can hide out. B complex vitamins also can help manage stress, an important contributing factor to the outbreak of herpes viruses. Applying the oil in vitamin E capsules directly to cold sores may provide relief. Zinc lozenges appear to affect the reproduction of viruses and also enhance the immune system. Ointments containing lemon balm (Melissa officinalis) or licorice (Glycyrrhiza glabra) and peppermint (Menthapiperita) have been shown to help heal cold sores.

Prognosis Oral herpes can be painful and embarrassing but it is not a serious condition. There is no cure for oral herpes but outbreaks usually occur less frequently with time. The spread of the herpes virus to the eyes is very serious. Herpes virus can infect the cells in the cornea and cause scarring which may impair vision. Those who are seriously ill, with compromised immune systems, are vulnerable to more severe and dangerous outbreaks.

Health care team roles Registered nurses are often involved in helping to identify oral herpes. It is important that nurses then educate patients that cold sores caused by herpes simplex are highly contagious. Nurses need to teach patients not to touch their mouths and then other parts of their bodies, such as the eyes, because they can spread the virus to other parts of their bodies. Nurses should also inform patients that if the sore is indeed herpetic, patients might experience intense symptoms when the infection first appears and the sores and symptoms could last up to two weeks. Normally, subsequent outbreaks, if they occur, are shorter because people generally build up some immunity to the virus. Nurses should let patients know about factors, such as sun exposure, that can stimulate outbreaks, and educate them about over-the-counter and

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children and causes herpes-like blisters around the mouth and nose. Also, because oral herpes can occur inside the mouth, the blisters could be mistaken for common canker sores. Therefore, the doctor would need to determine whether the blisters are oral herpes, canker sores, or impetigo. The diagnosis and treatment of herpes infections should be covered by most insurance providers.

Cold sore

• Herpes can be transmitted via respiratory secretions, such as coughing or sneezing, so avoiding these situations is advised.

KEY TERMS Latent—A non-active virus that is in a dormant state within a cell. Herpes virus is latent in the nervous system. Prodrome—Symptoms that warn of the beginning of disease. The herpes prodrome consists of pain, burning, tingling, or itching at a site before blisters are visible. Recurrence—The return of an active infection following a period of latency.

prescription options, as well as things patients can do to alleviate their symptoms, such as applying ice at the first signs of an outbreak. While RNs educate patients about cold sores, nurse practitioners often diagnose and treat them just as a physician would. Nurses can direct patients to many sites on the Internet that can help to answer their questions. For example, the American Academy of Dermatology at www.aad.org, www.herpes.org and www.herpeszone.com. The Herpes Resource Center, a public service of the American Social Health Association, provides educational pamphlets and a counseling line at 919-361-8488.

• Washing hands frequently. Persons with oral herpes should wash their hands carefully before touching others. An infected person can spread the virus to others, even when he or she has no obvious blisters. • Avoid contact with others during active infection. Infected persons should avoid kissing and sexual contact with others until after the cold sores have healed. • Wear gloves when applying ointment to a child’s sore. • Be especially careful with infants. Never kiss the eyes or lips of a baby who is under six months old. • Be watchful of infected children. Do not allow infected children to share toys that may be put into the mouth. Toys that have been mouthed should be disinfected before other children play with them. • Maintain good general health. A healthy diet, plenty of sleep, and exercise help to minimize the chance of getting a cold or the flu, which are known to bring on cold sores. Also, good general health keeps the immune system strong, which helps to keep the virus in check and prevents outbreaks. Resources BOOKS

Prevention The only way to prevent oral herpes is to avoid contact with those who are infected. This is not an easy solution because as many as 60% of those who are infected don’t realize or admit that they may have herpes. As of 2001, there are no herpes vaccines available, although herpes vaccines, which will function to prevent infection in new patients, are being tested. The belief is that an effective vaccine is about three to five years away. Researchers are also attempting to reduce the rate of asymptomatic viral shedding to prevent transmission of the virus. Many say that a cure for herpes won’t come for another seven to 10 years. Several practices can reduce the occurrence of cold sores and the spread of virus to other body locations or people. These practices are: • Avoidance of sun exposure to the face. Before getting prolonged exposure to the sun, apply sunscreen to the face and especially to the lips. Wearing a hat with a large brim is also helpful. • Avoid touching cold sores. Squeezing, picking, or pinching blisters can allow the virus to spread to other parts of the lips or face, and infect those sites. 530

Gorbach, Sherman, John Bartlett, and Neil Blacklow, editors. Infectious Diseases. Philadelphia: W.B. Saunders Co., 1998. PERIODICALS

Emmert, David. “Treatment of Common Cutaneous Herpes Simplex Virus Infections.” American Family Physician 61 (March 15, 2000): 1697. “FDA Approves Docosanol to Treat Cold Sores.” Virus Weekly August 8, 2000. Vance, Holly. “Soothe the Common Cold Sore.” Pediatrics for Parents 19 (March 2001): 3. ORGANIZATIONS

American Academy of Dermatology. 930 N. Meacham Road, Schamburg, IL 60168-4014. (847) 330-0280. . OTHER

“FDA Approves Cold Sore Treatment Docosanol 10% Cream, Over-the-Counter.” Doctor’s Guide. . June 1, 2000. (March 29, 2001). Herpes. (March 28, 2001). Herpes.org. (March 28, 2001). Herpesite. (March 28, 2001).

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Phone interview with Ellis Quinn Youngkin, PhD, RNC (Certified Women’s Healthcare Nurse Practitioner), ARNP. Florida Atlantic University College of Nursing. 777 Glades Road, Boca Raton, Fla. 33431. (561) 2973887. .

Lisette Hilton

Cold therapy see Cooling treatments Colds see Common cold Colon cancer see Colorectal cancer

Colonoscopy Definition Colonoscopy is an endoscopic (to visualize a hollow organ’s interior) medical procedure that uses a long, flexible, tubular instrument called a colonoscope to view the rectum and the entire inner lining of the colon (large intestine).

Purpose A colonoscopy is generally recommended when the patient complains of rectal bleeding or has a change in bowel habits and other unexplained abdominal symptoms. The test is frequently used to look for colorectal cancer, especially when polyps or tumor-like growths have been detected by a barium enema examination and other diagnostic imaging tests. Polyps can be removed through the colonoscope, and samples of tissue (biopsies) can be taken to detect the presence of cancerous cells. In addition, colonoscopy can also be used to remove foreign bodies, control hemorrhaging, and excise tumors. The test also enables physicians to check for bowel diseases such as ulcerative colitis and Crohn’s disease and is an essential tool for monitoring patients who have a past history of polyps or colon cancer. Colonoscopy is being used increasingly as a screening tool in both asymptomatic patients and patients at risk for colon cancer. It has been recommended as a screening test in all people 50 years or older.

Precautions Patients who regularly take aspirin, nonsteroidal anti-inflammatory drugs (NSAIDS), blood thinners, or insulin should be sure to inform the physician prior to the colonoscopy. Patients with severe active colitis, extremely dilated colon (toxic megacolon), or severely inflamed bowel may not be candidates for colonoscopy. Patients requiring continuous ambulatory peritoneal dialysis are generally not candidates for colonoscopy due to a higher risk of developing intraperitoneal bleeding.

Description Colonoscopy can be performed either in a physician’s office or in an endoscopic procedure room of a hospital. An intravenous (IV) line is inserted into a vein in the patient’s arm to administer, in most cases, a sedative and a pain-killer. During the colonoscopy, patients are asked to lie on their sides with their knees drawn up towards the abdomen. The doctor begins the procedure by inserting a lubricated, gloved finger into the anus to check for any abnormal masses or blockage. A thin, well-lubricated colonoscope is then inserted into the anus and gently advanced through the colon. The lining of the intestine is examined through the colonoscope. Images are viewed by the physician on a television monitor, and the procedure can be documented using a video recorder. Still images can be recorded and saved on a computer disk or printed out. Occasionally air may be pumped through the colonoscope to help clear the path or open the colon. If excessive secretions, stool, or blood obstructs the viewing, they are suctioned out through the scope. The doctor may press on the abdomen or ask the patient to change position in order to advance the scope through the colon. The entire length of the large intestine can be examined in this manner. If suspicious growths are observed, tiny biopsy forceps or brushes can be inserted through the colon and tissue samples can be obtained. Small polyps can also be removed through the colonoscope. For excising tumors or performing other types of surgery on the colon during colonoscopy, an electrosurgical device or laser system may be used in conjunction with the colonoscope. After the procedure, the colonoscope is slowly withdrawn and the instilled air is allowed to escape. The anal area is then cleansed with tissues. The procedure may take anywhere from 30 minutes to two hours depending on how easy it is to advance the scope through the colon. Colonoscopy can be a long and uncomfortable procedure, and the bowel cleansing preparation may be tiring and can produce diarrhea and

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“Herpes simplex.” KidsHealth. (March 28, 2001).

Colonoscopy Endoscopic view of a colonic polyp. (G-I Associates/Custom Medical Stock Photo. Reproduced by permission.)

cramping. During the colonoscopy, the sedative and the pain medications will keep the patient drowsy and relaxed. Some patients complain of minor discomfort and pressure from the colonoscope. However, the sedative and pain medication usually causes most patients to dose off during the procedure.

Preparation The physician should be notified if the patient has allergies to any medications or anesthetics, bleeding problems, or is pregnant. The doctor should also be informed of all the medications that the person is currently taking and if the patient has had a barium enema x-ray examination recently. If the patient has had heart valves replaced, the doctor should be informed so that appropriate antibiotics can be administered to prevent infection. The risks are explained to the patient beforehand, and the patient is asked to sign a consent form. The colon must be thoroughly cleansed before performing colonoscopy. Hence, for two or more days before the procedure, considerable preparation is necessary to clear the colon of all stool. The patient is asked to refrain from eating any solid food for 24 to 48 hours before the test. Only clear liquid such as juices, broth, 532

and Jello are allowed. Red or purple juices should be avoided, since they can cause coloring of the colon that may be misinterpreted during the colonoscopy. The patient is advised to drink plenty of water to avoid dehydration. A day or two before the colonoscopy, the patient is prescribed liquid, tablet, and/or suppository laxatives by the physician. In addition, commercial enemas may be prescribed. The patient is given specific instructions on how and when to use the laxatives and/or enemas. On the morning of the colonoscopy, the patient is not to eat or drink anything. Unless otherwise instructed by the physician, the patient should continue to take all current medications. However, vitamins with iron, iron supplements, or iron preparations should be discontinued for a few weeks prior to the colonoscopy because iron residues in the colon can inhibit viewing during the procedure. These preparatory procedures are extremely important to ensure a thoroughly clean colon for examination. After the procedure, the patient is kept under observation until the medications’ effects wear off. The patient has to be driven home and can generally resume a normal diet and usual activities unless otherwise instructed. The

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For a few hours after the procedure, the patient may feel groggy. There may be some abdominal cramping and considerable amount of gas may be passed. If a biopsy was performed or a polyp was removed, there may be small amounts of blood in the stool for a few days. If the patient experiences severe abdominal pain or has persistent and heavy bleeding, it should be brought to the physician’s attention immediately. For patients with abnormal results, such as polyps, the gastroenterologist will recommend another colonoscopy, usually in another year or so.

Complications The procedure is virtually free of any complications and risks. Rarely (two in 1000 cases) a perforation (a hole) may occur in the intestinal wall. Heavy bleeding due to the removal of the polyp or from the biopsy site occurs infrequently (one in 1000 cases). Some patients may have adverse reactions to the sedatives administered during the colonoscopy, but severe reactions are very rare. Infections due to a colonoscopy are also extremely rare. Patients with artificial or abnormal heart valves are usually given antibiotics before and after the procedure to prevent an infection.

Results The results are normal if the lining of the colon is a pale reddish pink and there are no masses that appear abnormal in the lining. Abnormal results indicate polyps or other suspicious masses in the lining of the intestine. Polyps can be removed during the procedure, and tissue samples can be biopsied. If cancerous cells are detected in the tissue samples, then a diagnosis of colon cancer is made. A pathologist analyzes the tumor cells further to estimate the tumor’s aggressiveness and the extent of the disease. This is crucial before deciding on the mode of treatment for the disease. Abnormal findings could also be due to inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease. A condition called diverticulosis, which causes many small fingerlike pouches to protrude from the colon wall, may also contribute to an abnormal result in the colonoscopy.

Health care team roles For otherwise healthy patients, colonoscopy is generally performed by a gastroenterologist in an office setting. It may also be performed in the endoscopy depart-

KEY TERMS Barium enema—An x-ray test of the bowel after giving the patient an enema of a white chalky substance that outlines the colon and the rectum. Biopsy—Removal of a tissue sample for examination under the microscope to check for cancer cells. Colonoscope—A thin, flexible, hollow, lighted tube that is inserted through the anus and into the rectum and into the colon to enable the doctor to view the entire lining of the colon. Crohn’s disease—A chronic inflammatory disease that generally starts in the gastrointestinal tract and causes the immune system to attack one’s own body. Diverticulosis—A condition that involves the development of sacs that bulge through the large intestine’s muscular walls but are not inflamed. It may cause bleeding, stomach distress, and excess gas. Electrosurgical device—A medical device that uses electrical current to cauterize or coagulate tissue during surgical procedures. Often used in conjunction with laparoscopy. Pathologist—A doctor who specializes in the diagnosis of disease by studying cells and tissues under a microscope. Polyps—An abnormal growth that develops on the inside of a hollow organ such as the colon. Ulcerative colitis—A chronic condition where recurrent ulcers are found in the colon. It is manifested clinically by abdominal cramping and rectal bleeding.

ment of a hospital, where patients with other medical conditions requiring hospitalization, more intensive physiologic monitoring, or general anesthesia can be better examined. Depending on the patient’s condition, the colonoscopy may also be performed by a colorectal surgeon. In the gastroenterologist’s office, a nurse and/or nurse anesthetist are necessary to provide patient sedation and analgesic medication, monitor the patient during the procedure, and assist the physician during the colonoscopy. In the hospital, colonoscopy performed under general anesthesia requires an anesthesiologist. Biopsied tissue samples are sent to a clinical laboratory, where they are analyzed by a pathologist.

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patient is advised to drink lots of fluids to replace those lost by laxatives and fasting.

Color blindness

Resources BOOKS

Beers, Mark H. and Berkow, Robert, eds. Merck Manual of Diagnosis and Therapy 17th edition. Merck Research Laboratories, 1999. Segen, Joseph C. and Joseph Stauffer. The Patient’s Guide to Medical Tests. Facts On File, 1998. PERIODICALS

Lieberman, David A., Weiss, David G., Bond, John H., Ahnen, Dennis J., Garewal, Harinder, Chejfec, Gregorio. “Use of Colonoscopy to Screen Asymptomatic Adults for Colorectal Cancer.” New England Journal of Medicine. 343, no. 3 (July 20, 2000): 162-168. ORGANIZATIONS

Colorectal Cancer Network (CCNetwork). PO Box 182, Kensington, MD 20895-0182. (301)879-1500. . National Digestive Diseases Information Clearinghouse. 2 Information Way, Bethesda, MD 20892-3570. . Society of American Gastrointestinal Endoscopic Surgeons(SAGES). 2716 Ocean Park Boulevard, Suite 3000, Santa Monica, CA 90405. (310) 314-2404. . Society of Gastroenterology Nurses and Associates Inc. 401 North Michigan Avenue, Chicago, IL 60611-4267. (800) 245-7462. . OTHER

Glaser, Vicki. “Colorectal Cancer Screening: New Directions, Evolving Guidelines.” Patient Care. (February 28, 2001). . Society of American Gastrointestinal Endoscopic Surgeons. “Colonoscopy.” .

Jennifer E. Sisk, M.A.

Color blindness

the back of the eye on the retina. Most of us are trichromats, which means that we have three types of cones, commonly called red, green, and blue cones. They are long, medium, and short wavelength receptors, respectively. The interplay among these cones enables us to see a large spectrum of colors. A defect in any of these types of cones will result in deficient color vision. Most colordeficient individuals are dichromats. They are not entirely blind to color, rather they get some colors confused with each other. For example, they may see certain colors (like red and green) as very similar, whereas people without the deficiency would easily be able to differentiate these colors. The following are three basic types of color deficiency: • Protanopia and deuteranopia (commonly called red/green color blindness). Red/green color blindness is the most common deficiency, affecting about 10% of Caucasian males and 0.5% of females. People with protanopia have fewer red cones; blue-green and redpurple appear gray to them. Deuteranopes have fewer green cones; green and purple-red appear gray to them. • Tritanopia (commonly called Blue color blindness). People with tritanopia have fewer blue cones; blue and yellow appear as white or gray to them. Such people are very rare and have poor blue and/or yellow perception. As many females as males have this deficiency. It usually appears in people who have physical disorders, such as liver disease or diabetes mellitus. • Achromatopsia (commonly called total color blindness). Total color blindness—vision only in black, white, and shades of gray—can be caused by monochromacy (a retina that has only one type of receptor) or from acquired brain damage. Monochromacy is a very rare hereditary disorder. It affects one person in 33,000 in the United States, males and females equally. They usually have poor visual acuity and extreme sensitivity to light. Their vision is significantly impaired and they protect their light-sensitive eyes by squinting in even ordinary light.

Definition The term color blindness describes a deficiency in discriminating various colors. It is a misnomer because most color-blind people do, in fact, see colors. The deficiency is a lack of perceptual sensitivity to certain colors. A rare few may not see colors at all.

The key symptom of color blindness is the long-term inability to distinguish colors or notice some colors entirely. Most cases of color blindness (in particular red/green) are inherited, and affect males almost exclusively. Color blindness can be acquired by the following:

Description Normal color vision requires the use of special cells, called cones. They are wavelength receptors located at 534

Causes and symptoms

• Chronic illness. Illnesses that can lead to color blindness are: Alzheimer’s disease, diabetes, glaucoma, leukemia, liver diseases, chronic alcoholism, macular

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• Trauma. Accidents or strokes that damage the eye can lead to color blindness. • Medications. Some frequently used medications may cause color blindness. Some antibiotics, barbiturates, anti-tubercular drugs, high blood pressure medications, and a number of medications used to treat nervous disorders and psychological problems may lead to color blindness. • Industrial toxins. Strong chemicals can cause color vision loss. Some include carbon monoxide, carbon disulfide, fertilizers, styrene, and lead-based chemicals.

KEY TERMS Acuity—Acuity is the clarity or sharpness of vision. Cone cells—Cone cells are special cells in the retina and are responsible for color vision and fine visual discrimination. Retina—The retina is the innermost lining of the eye, containing light sensitive nerve tissue composed of rod and cone cells. Stereoscopic—Stereoscopic refers to vision in which things have a three-dimensional appearance.

• Aging. After age 60, changes occur in people’s capacity to discriminate colors.

Diagnosis Some of the tests available to detect color vision in the general public include: • American Optical/Hardy, Rand, and Ritter (AO/ H.R.R.) Pseudoisochromatic test. This is the test used most often to detect color blindness. A person with full color vision looking at a sample plate from this test would see a number, composed of blobs of one color, clearly located somewhere in the center of a circle of blobs of another color. A colorblind person is not able to distinguish the number. • Ishihara test. The Ishihara test is made up of eight test plates similar to the AO/H.R.R. pseudoisochromatic test plates. The person being tested looks for numbers made up of various colored dots on each test plate. • Titmus II Vision Tester Color Perception test. During this test, a person looks into a stereoscopic machine. The chin rests on a base, and the image comes on only when the forehead touches a pad on the top of the unit. Either a series of plates, or only one plate, can be used to test for color vision. The one most often used in doctors’ offices is one that has six samples on it. Six different designs or numbers are on a black background, framed in a yellow border. While Titmus II can test one eye at a time, its value is limited because it only tests for red/green deficiencies and is not highly accurate.

Treatment There is no treatment or cure for color blindness. Most color deficient persons compensate well for their defect and may even discover instances in which they can discern details and images that would escape normal-sighted persons. Colorblind people tend to look for outlines, not colors. Consequently, they are not easily confused by camou-

flage. (Some colorblind people were used in World War II spy planes to spot camouflaged German camps.) Also, their night vision may be much better than average.

Health care team roles Color blindness can be tested for and diagnosed by a general physician, ophthalmologist, or optometrist. Questions about color blindness may be addressed by nurses or optometry assistants.

Prognosis Color blindness that is hereditary is present in both eyes and remains constant over time. Some cases of acquired color vision loss are not severe and last for only a short time. Other cases tend to be progressive, becoming worse over time.

Prevention Hereditary color blindness cannot be prevented. In the case of acquired color blindness, if the cause of the problem is removed, the condition may improve with time. If not, damage may become permanent. Resources BOOKS

Newell, Frank. Ophthalmology Principles and Concepts. Boston, MA: Mosby, 1996. Rosenthal, Odeda, and Robert H. Phillips. Coping with ColorBlindness. Garden City Park, NY: Avery Publishing Group, 1997. ORGANIZATIONS

Achromatopsia Network. C/O Frances Futterman, P.O. Box 214, Berkeley, CA 94701-0214. .

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degeneration, multiple sclerosis, Parkinson’s disease, sickle cell anemia, and retinitis pigmentosa.

Colorectal cancer

American Academy of Ophthalmology. 1533 Shattuck Avenue, Berkeley, CA 94701. (847) 845-1059. and . National Society to Prevent Blindness. 500 East Remington Road, Schaumburg, IL 60173. (708) 843-2020 or (800) 331-2020. .

Lorraine T. Steefel Timothy E. Moore, PhD

ly begins as a benign growth (polyp) in the lining of the intestine. Although most polyps are not cancerous, virtually every colorectal cancer case begins with these polyps. There are two kinds of polyps: hyperplastic polyps, which are small, completely benign, and never develop into cancers, and adenomas, which are polyps that do have the potential to become cancerous.

Causes and symptoms Causes The current consensus among the medical community is that most colorectal cancers have a genetic link. Abnormal genes have been found in all inherited colorectal cancers and in most sporadic colon cancers. Dietary and environmental factors also seem to play a role in colorectal incidence.

Colorectal cancer Definition The digestive system is made up of the esophagus (food pipe), stomach, and the small and large intestines. The upper 5–6 feet (1.5–1.8 m) of the large intestine is the colon, and the last 6–8 inches (15–20 cm) of the colon is the rectum. Colorectal cancer is a disease in which the cells of the tissues lining the colon and the rectum start to grow uncontrollably and form tumors.

Description Colorectal cancer is the second most common cancer for both men and women, and the second leading cause of cancer deaths. There are 150,000 new cases each year, with more than 55,000 people dying annually. The average age at first diagnosis is between 60 and 65 and appears to be a disease that affects the latter years of life. Since it is slow growing, it may take years before the disease manifests. The primary function of the colon is to absorb water and the nutrients from the food that is already digested by the stomach and the small intestine. The waste material that remains moves into the rectum. From there, it is excreted out of the body through the anus. The colon has four sections. The ascending colon moves upward to the hepatic flexure. It then becomes the transverse colon, moving across to the liver. When it reaches the spleen, the colon continues as the descending colon and moves down to the pelvic area. It is then called the sigmoid colon and extends to the rectum. Cancer can develop in any of the four sections or in the rectum. Cancers beginning in the different sections have different symptoms. Colorectal cancers have a very high cure rate if found early. Unfortunately, most colorectal cancers are silent tumors, which means they grow slowly and often do not produce symptoms until they reach a large size. Therefore, diagnosis is often delayed. The cancer usual536

Several risk factors may make a person more susceptible to colorectal cancer. They include: • Family history: Some conditions such as familial adenomatous polyps (FAP) and Lynch syndrome (a genetic condition that predisposes certain families to colon cancer, even when polyps are not present) occur in certain families and may make an individual more likely to develop cancer of the colon or the rectum. • History of colorectal cancer: Even when colorectal cancer has been completely removed, new cancers may still develop in other areas of the colon and the rectum. The incidence of recurrence is every 10 years. • Recurrent intestinal polyps: These are polyps that increase the risk of colorectal cancer, especially if they are large and there are many of them. • Inflammatory bowel disease: Chronic ulcerative colitis, a condition in which the colon is inflamed over a long period of time and causes ulcers in the lining, can increase the risk of colon cancer. • Age: About 90% of colorectal cancers are found in people over the age of 50. • Diet: Eating foods that are high in fat and low in fiber may increase the risk of colorectal cancer. It is estimated that diet accounts for 35%–45% of disease incidence. • Physical inactivity: A sedentary lifestyle and not enough physical activity has been reported to be associated with a higher risk of colorectal cancer. • Gender factors: Women have a 38% higher risk of having upper-colon cancer than men. • Smoking: There is strong evidence that smoking increases the risk of colorectal cancer, possibly causing 12% of all colorectal cancer deaths. The frequency,

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Colorectal cancer

amount, and duration of smoking over a lifetime are positively correlated with colon cancer. The more a person smokes over a long period of time, the greater the incidence of colon cancer. • Ethnicity: Black, non-Hispanic people may have as much as a 24% increased risk in upper-colon cancer than other groups. • Co-morbid illnesses: The presence of serious, lifethreatening diseases like congestive heart failure, peptic ulcer, and diabetes mellitus may contribute up to a 28% increase in risk of colorectal cancer. Symptoms The earliest sign of colon cancer may be bleeding, though the amount is usually quite small. Blood can be detected by the fecal occult blood test (FOBT), which is a chemical testing of the feces for hidden (occult) blood. When tumors grow to a large size, they may cause a change in bowel habits. Stools may be very narrow in diameter, and there may be diarrhea or constipation. Other symptoms of general stomach discomfort may be present, such as a feeling of fullness or bloating, stomach cramps, or gas pains. Sometimes, the patient complains of a feeling that the bowel does not empty completely. Constant tiredness and weight loss with no known reason may be other warning signs. Even though many of these symptoms can be caused by conditions other than cancer, they must be evaluated by a doctor without delay. Usually, there are no signs of colorectal cancer at all. That is why screening is essential. Polyps may be detected before they develop into cancers, and are easily removed.

Diagnosis Regular screenings can identify colorectal cancer before symptoms manifest. Routinely, depending on the screening method used, this is done every one to five years, beginning at age 50. With higher risk populations (a family history of colorectal cancer or polyps, previous ulcerative colitis, or a specific ethnicity), screening may be initiated at an earlier age and conducted more often. Screening methods include a digital rectal examination, fecal occult blood testing (FOBT), a sigmoidoscopy, a colonoscopy, and a double-contrast barium enema. If the physician suspects colon cancer, then a thorough physical examination will be conducted to check all symptoms and a complete medical history will be taken to assess any risk factors. A digital rectal examination will be done during the physical. In this procedure,

An endoscopic view of a colorectal tumor. (Custom Medical Stock Photo. Reproduced by permission.)

the physician inserts a gloved finger into the rectum to feel for anything abnormal. This simple test can help to detect many rectal cancers. A fecal occult blood test may be ordered, in which a sample of stool is examined for blood. The test kit can be purchased at any local pharmacy. The test involves taking a sample of stool and smearing it on a slide. This is then sent to the laboratory or to the doctor’s office to be chemically examined for the presence of red blood cells. A sigmoidoscopy may be done to enable the physician to look inside the rectum and the lower half of the colon. In this procedure, a thin, flexible, hollow, lighted tube (sigmoidoscope) is inserted into the rectum. The physician then looks inside the scope for polyps. Since they may become cancerous, they are usually removed with the sigmoidoscope and examined for cancer cells. About half of all colon and rectal cancers are found using this procedure. A colonoscopy will be ordered if the doctor wishes to examine the entire colon lining. A colonoscope is longer than a sigmoidoscope and is inserted through the rectum into the colon. It is connected to a video camera and a video display unit so that the physician can look at the inside of the colon. If a suspicious mass is detected, then the physician may cut out a small piece to examine it under a microscope for cancer cells. This procedure is called a biopsy. Another test that is used to diagnose colon cancer is known as a double-contrast barium enema. The patient is given a barium sulfate enema through the anus. This is a chalky substance that partially fills and opens the colon. When the colon is about half full of barium, the patient is turned on the x-ray table so that the barium spreads throughout the colon. Air is then inserted into the colon to make it expand and x-ray films are taken. Usually, this procedure is done if the patient cannot tolerate a sigmoi-

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doscopy, or a suspected mass prevents the penetration of the sigmoidoscope or the colonoscope.

Treatment Treatment for colon and rectal cancers depends on the stage of the cancer, which refers to the extent to which it has spread (metastasized). The standard modes of treatment are surgery, radiation therapy, and chemotherapy. Surgery is the primary treatment for colon cancer. If the cancer is found at a very early stage, the physician may be able to remove the cancer without cutting into the abdomen. Instead, the physician may insert a tube through the rectum into the colon and cut the tumor out. This procedure is called a local excision. If the cancer is found in a polyp, however, the operation is called a polypectomy. When the cancer is large but confined to a portion of the colon, the abdomen is opened up and the cancerous growth and a small piece of normal tissue from either side of the cancer are removed. This procedure is called segmental resection. If there is any likelihood of the cancer having metastasized to the nearby lymph nodes, they may be removed as well. The remaining sections of the colon are then reattached. When the physician is unable to reattach the colon, an opening called a stoma will be surgically created on the outside of the body for the waste material to pass from the body. This procedure is called a colostomy. Sometimes, the colostomy is temporary, lasting until the colon is healed, and then the colostomy can be reversed. However, if the surgery involves taking out the entire lower colon, a permanent colostomy is required. The patient will need to wear a special bag to collect body wastes. The disposable bag attaches to the body around the opening (stoma). Hospital personnel will teach patients how to take care of the stoma and maintain colostomy bags. In the case of rectal cancer, different surgical methods are used. When the cancer is found in polyps, a polypectomy is performed. Local excision is a procedure that can be used to remove small superficial cancers. A small amount of adjoining tissue is also removed from the inner layer of the rectum. If the cancer is in the deeper layers of the rectum, local full thickness resection is used. A cut is made through all the layers of the rectum to remove the invasive cancer as well as some surrounding normal rectal tissue. Electrofulguration is a procedure in which the cancer is burned away by passing an electric current through it. All of these methods may be done without cutting through the abdomen. However, a colostomy may still be necessary if the cancer is too 538

close to the anus, necessitating the removal of the sphincter muscles. Radiation therapy involves the use of high-energy radiation to kill cancer cells. It can be applied to both colon and rectal cancers. External-beam radiation uses radiation from an external source that is focused on the tumor. Internal radiation therapy uses a small pellet of radioactive material that is implanted directly into the cancer. Radiation therapy is generally used as adjuvant therapy, that is, it is used after the surgery to destroy any cancerous material that may not have been removed during surgery. If the tumor is in a place that makes surgery difficult, then radiation may be used before surgery to shrink the tumor. In advanced cancers, in which surgery is not an option, radiation may be used to ease the symptoms such as pain, blockage, or bleeding. In colorectal cancers, chemotherapy is generally used after surgery to destroy any cancerous cells that may have migrated from the original site and spread to other parts. The anti-cancer drugs are either given intravenously (through a vein) in the arm or orally in the form of pills. In the case of advanced cancers, chemotherapy may be given to alleviate symptoms.

Prognosis The death rate from colorectal cancer has been going down for the past 20 years. This is due to advanced methods of early detection and improved treatment modes. If colorectal cancer is detected at an early stage and is treated appropriately, 92% of patients will survive five years or more. However, only a third of colorectal cancers are found at that early stage. Once the cancer has metastasized to nearby organs or lymph nodes, the five-year survival rate plummets to 64%. If the disease has metastasized to distant sites such as the liver or the lung, the outlook is bleak, with only 7% of the patients surviving five years after initial diagnosis. The American Cancer Society also notes that once colorectal cancer is detected and removed, another occurrence is highly probable in 10 years.

Health care team roles Physicians, nurse practitioners, nurses, lab technicians, and radiology technicians all participate in the screening, diagnosing, and treating of colorectal cancers. Physicians and their nursing staff must educate patients in the necessity and urgency of complying with colorectal screening guidelines. Colorectal cancer, for many people, is a totally preventable disease. By exercising regularly, eating a high-fiber diet, and avoiding smoking many colorectal cancers can be prevented. For those with

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Cancer

Polyp

Subsequently, all members of the medical health team will need to educate patients about early screening, the procedures involved, and any possible side effects. They will also need to provide information about diet and exercise and anti-smoking support groups. Physicians may need to prescribe medications to cope with nicotine withdrawal.

Submucosa Muscularis Serosa Class A colorectal cancer

When cancer is detected, the entire medical team will need to educate the patient about treatment options and procedures, outcomes, and aftercare. Physicians and radiology technicians will perform additional tests. The gastroenterologist and surgeon will prepare the patient physically and psychologically for surgery. The surgeon will remove the cancer and prepare a stoma, if necessary. The gastroenterologist will recommend radiation and/or chemotherapy as a preventative. The nursing staff will educate the patient on the care of the stoma and the colostomy equipment.

Cancer

Class B colorectal cancer

Cancer

Prevention Many colon and rectal cancers may be prevented by avoiding risk factors and following screening guidelines. The number of colorectal cancer cases can be lowered and, by detecting the disease at an earlier stage, the death rate can be reduced. The American Cancer Society recommends that, beginning at age 50, both men and women follow a screening schedule for the early detection of colorectal cancer. One or more of the following tests should be performed: a yearly fecal occult blood test and a digital rectal examination, a flexible sigmoidoscopy every five years, a colonoscopy every five to 10 years (depending on the patient’s risk factors), or a barium enema x ray every five to 10 years. Proper diet and exercise go a long way in preventing colorectal cancer. The American Cancer Society recommends eating at least five servings of fruits and vegetables every day and six servings of food from plant sources that contain fiber, such as breads, cereals, grain products, rice, pasta, or beans. Reducing the consumption of high-fat, low-fiber foods such as red meat and processed foods is also advised. Achieving and maintaining an ideal body weight are recommended, and participating in at least 30 minutes of physical activity every day is advocated. The addition of mineral supplements may also be helpful in preventing colorectal cancer. Copper, selenium,

Lymph nodes with cancer Class C colorectal cancer

Classes of colorectal cancer: class A, class B, and class C. (Delmar Publishers, Inc. Reproduced by permission.)

and calcium seem to be factors in colorectal cancer prevention. Eating foods rich in these minerals is recommended. It is also recommended that individuals over 50 quit smoking as soon as possible. Besides the risks of other forms of cancer, there seems to be a correlation between the incidence of colorectal cancer and the amount of tobacco smoked and for how long. It may not be possible to control risk factors such as a strong family history of colorectal cancer. However, by getting information about prevention and early detection, one can still beat the odds. People with a family history of colorectal cancer should start screening at a younger age, and the tests should be done more frequently. Certain genetic tests are now available that can help determine which members of certain families have inherited a high risk for developing colorectal cancer.

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a family history of polyps or colorectal cancer, participation in a screening program can detect polyps, and they can have them removed before they turn into cancerous growths.

Colorectal cancer

KEY TERMS Adenomas—Polyp-like growths in the colon or the rectum that have the potential to turn cancerous. Barium enema—An x-ray test of the bowel after receiving an enema of a white chalky substance that outlines the colon and the rectum, making them more visible in an x ray. Benign—Tested tissue that is not cancerous and does not invade surrounding tissue or spread to other parts of the body. Biopsy—Removal of a tissue sample for examination under the microscope to check for cancer cells. Chemotherapy—Treatment with drugs that destroy cancerous tissue. Colonoscopy—A medical procedure in which the physician looks at the colon through a flexible lighted instrument called a colonoscope.

Familial adenomatous polyps (FAP)—An inherited condition in which hundreds of polyps develop in the colon and rectum. Fecal occult blood test (FOBT)—A test in which the stool sample is chemically tested for hidden blood. Flexible sigmoidoscopy—An examination in which the physician looks at the lower half of the colon. Hyperplastic polyps—Benign polyps found in the colon or the rectum. Lynch syndrome—A genetic condition that predisposes certain families to colon cancer, even when polyps are not present. Polyp—An abnormal growth that develops on the inside of a hollow organ such as the colon. Polypectomy—A surgical procedure that involves removal of the polyp.

Colostomy—An opening is created to provide a path for waste material to leave the body after the colon has been removed.

Radiation therapy—Treatment using high-energy radiation from x-ray machines, cobalt, radium, or other sources.

Crohn’s disease—A chronic inflammatory disease in which the immune system starts attacking one’s own body. The disease generally starts in the gastrointestinal tract.

Segmental resection—Surgical removal of a portion of the colon.

Digital rectal examination—An exam to detect rectal cancer.

Ulcerative colitis—A chronic condition in which recurrent ulcers are found in the colon.

Resources BOOKS

American Cancer Society. American Cancer Society Guide to Complementary and Alternative Cancer Methods. Atlanta, GA: American Cancer Society, 2000. Murphy, Gerald P. Informed Decisions: The Complete Book of Cancer Diagnosis, Treatment and Recovery. Atlanta, GA: American Cancer Society, 1997. PERIODICALS

Author unspecified. “New Studies Identify Patients at High Risk for Advanced Disease or Best Suited for Surgery.” Cancer Weekly (March 13, 2001): pNA. Author unspecified. “Screening Should Begin Earlier for Certain Ethnic Groups.” Cancer Weekly (March 20, 2001): pNA. Author unspecified. “Trends in Screening for Colorectal Cancer: United States, 1997 and 1999.” Journal of the American Medical Association 285 no. 12 (March 28, 2001): 1570. 540

Stoma—The opening established in the abdominal wall by the colostomy procedure.

Desmono Pinkowish, Mary. “Strong Evidence Links Smoking, Colon Cancer.” Patient Care 35 no. 4 (February 28, 2001): 9. Glaser, Vicki. “Colorectal Cancer Screening: New Directions, Evolving Guidelines.” Patient Care 25 no. 4 (February 28, 2001): 24. ORGANIZATIONS

American Cancer Society (National Headquarters). 1599 Clifton Road, N.E., Atlanta, GA 30329. (800) 227-2345. . Cancer Research Institute (National Headquarters). 681 Fifth Avenue, New York, NY 10022. (800) 992-2623. . National Cancer Institute. Public Inquiries Office, Building 31, Room 10A03, 31 Center Drive, MSC 2580, Bethesda, MD 20892. (800) 422-6237. . Oncolink. University of Pennsylvania Cancer Center. .

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NCI/PDQ Patient Statement. “Colon Cancer.” National Cancer Institute. NCI/PDQ Patient Statement. “Rectal Cancer.” National Cancer Institute.

Janie F. Franz

Colostomy Definition A colostomy is a surgical procedure that brings a portion of the large intestine through the abdominal wall to carry feces out of the body.

• Double-barrel colostomy: This colostomy involves the creation of two separate stomas on the abdominal wall. The proximal (nearest) stoma is the functional end that is connected to the upper gastrointestinal tract, and will drain stool. The distal stoma, connected to the rectum, drains small amounts of mucus material. This is most often a temporary colostomy, performed to rest an area of bowel and to be later closed. • Loop colostomy: This colostomy is created by bringing a loop of bowel through an incision in the abdominal wall. The loop is held in place outside the abdomen by a plastic rod placed beneath it. An incision is made in the bowel to allow the passage of stool through the loop colostomy. The supporting rod is removed approximately seven to 10 days after surgery, after healing has occurred that will prevent the loop of bowel from retracting into the abdomen. A loop colostomy is most often performed for the creation of a temporary stoma to divert stool away from an area of intestine that has been blocked or ruptured.

Purpose A colostomy is created as a means to treat various disorders of the large intestine, including cancer, obstruction, inflammatory bowel disease, ruptured diverticulum, ischemia (compromised blood supply), or traumatic injury. Temporary colostomies are created to divert stool from injured or diseased portions of the large intestine, allowing rest and healing. Permanent colostomies are performed when the distal bowel (bowel at the farthest distance) must be removed or is blocked and inoperable. Although colorectal cancer is the most common indication for a permanent colostomy, only about 10–15% of patients with this diagnosis require a colostomy.

Description Surgery will result in one of three types of colostomies: • End colostomy: The functioning end of the intestine, the section of bowel that remains connected to the upper gastrointestinal tract, is brought out onto the surface of the abdomen to form a stoma (an artificial opening) by cuffing the intestine back on itself and suturing the end to the skin. The surface of the stoma is actually the lining of the intestine, usually appearing moist and pink. The distal portion of bowel (now connected only to the rectum) may be removed or sutured closed and left in the abdomen. An end colostomy is usually a permanent colostomy, resulting from trauma, cancer, or another pathological condition.

Preparation The physician will outline the procedure, possible side effects, and what the patient may experience after surgery. The physician or an enterostomal therapist will explain the general aftercare to the patient before surgery, so the patient has all of the information necessary to make an informed decision about surgery and medical care. Blood and urine studies, along with various x rays and an electrocardiograph (EKG), may be ordered as necessary. If possible, the patient should visit an enterostomal therapist, who makes the decision about the appropriate place on the abdomen for the stoma and who offers pre-operative education on colostomy management. To empty and cleanse the bowel, the patient may be placed on a low-residue diet for several days prior to surgery. A liquid diet may be ordered for at least the day before surgery. A series of enemas and/or oral preparations (GoLytely or Colyte) may be ordered to empty the bowel of stool. Oral anti-infectives (neomycin, erythromycin, or kanamycin sulfate) may be prescribed to decrease bacteria in the intestine and help prevent postoperative infection. On the day of surgery or during surgery, a nasogastric tube is inserted into the nose to connect it to the stomach to remove gastric secretions and prevent nausea and vomiting. A urinary catheter may also be placed to keep the bladder empty during surgery, giving more space in the surgical area and decreasing the risk of accidental injury.

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United Ostomy Association, Inc. (UOA). 36 Executive Park, Suite 120, Irvine, CA 92612. (800) 826-0826.

Colostomy

KEY TERMS Diverticulum—Pouches that project off the wall of the intestine. Embolism—Blockage of a blood vessel by any small piece of material traveling in the blood. Enema—Insertion of a tube into the rectum to infuse fluid into the bowel and encourage a bowel movement. Intestine—Commonly called the bowels, divided into the small and large intestine, they extend from the stomach to the anus. The small intestine is about 20 feet (6 m) long; the large intestine is about 5 feet (1.5 m) long. Ischemia—A compromise in blood supply delivered to body tissues that causes tissue damage or death. Ostomy—A surgically created opening in the abdomen for elimination of waste products (urine or stool).

Complications Potential complications of colostomy surgery include: • excessive bleeding • surgical wound infection • thrombophlebitis (inflammation and blood clot in veins in the legs) • pneumonia • pulmonary embolism (blood clot or air bubble in the lungs’ blood supply) • cardiac stress due to allergic reaction to the general anaesthetic • if the colostomy becomes blocked

Preparation Post-operative care for the patient with a new colostomy involves monitoring of blood pressure, pulse, respirations, and temperature. The patient is instructed how to support the operative site during deep breathing and coughing, and given pain medication as necessary. Fluid intake and output is measured, and the operative site is observed for color and amount of wound drainage. The nasogastric tube will remain in place, attached to low-intermittent suction until bowel activity resumes. For the first 24 to 48 hours after surgery, the colostomy will drain bloody mucus. Fluids and electrolytes are infused intravenously until the patient’s diet can gradually be resumed, beginning with liquids. Usually within 72 hours, passage of gas and stool through the stoma begins. Initially the stool is liquid, gradually thickening as the patient begins to take solid foods. The patient is usually out of bed in eight to 24 hours after surgery and discharged in two to four days. A colostomy pouch or bag will generally have been placed on the patient’s abdomen, around the stoma, during surgery. During the hospital stay, the patient and the caregivers will be educated on how to care for the stoma and the colostomy bag. Determination of appropriate pouching supplies and a schedule of how often to change the pouch should be established. Regular assessment and meticulous care of the skin surrounding the stoma is important to maintain an adequate surface on which to 542

apply the pouch. Patients will be instructed in daily irrigation of the stoma about seven to 10 days after surgery. This results in the regulation of bowel function. Some patients with colostomies may need only a dressing or cap over the stoma and do not wear a colostomy pouch. Often, an enterostomal therapist will visit the patient at home after discharge to help with the patient’s resumption of normal daily activities.

• if the stoma extends too far out from the abdomen, presenting the potential for physical damage or infection The physician should be made aware of any of the following problems after surgery: • increased pain, swelling, redness, drainage, or bleeding in the surgical area • flu-like symptoms such as headache, muscle aches, dizziness, or fever • increased abdominal pain or swelling, constipation, nausea or vomiting, or black, tarry stools Stomal complications to be monitored include: • Necrosis (death) of stomal tissue. Caused by inadequate blood supply, this complication is usually visible 12 to 24 hours after the operation and may require additional surgery. • Retraction (stoma is flush with the abdomen surface or has moved below it). Caused by insufficient stomal length, this complication may be managed by the use of special pouching supplies. Elective revision of the stoma is also an option. • Prolapse (stoma increases length above the surface of the abdomen). Most often, this results from an overly large opening in the abdominal wall or inadequate fixation of the bowel to the abdominal wall. Surgical correction is required when blood supply is compromised.

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• Parastomal hernia (bowel-causing bulge in the abdominal wall next to the stoma). Usually, this is due to placement of the stoma where the abdominal wall is weak or the creation of an overly large opening in the abdominal wall. The use of a colostomy support belt and special pouching supplies may be adequate. If severe, the defect in the abdominal wall should be repaired surgically, and the stoma moved to another location. Psychological complications may result from colostomy surgery because of the fear of the social stigma attached to wearing a colostomy bag. Patients also may be depressed and have feelings of low self-worth because of the change in their lifestyle and their appearance. Some patients may feel sexually unattractive and may worry that their spouse or significant other will no longer find them desirable. Counseling and education regarding surgery and the inherent lifestyle changes are often necessary.

Nettina, Sandra M. The Lippincott Manual of Nursing. Philadelphia: J. B. Lippincott, 2001. PERIODICALS

Author unspecified. “Colostomy.” Clinical Reference Systems (Annual 2000): 359. De Marquiequi, Asun, and Margot Huish. “A Woman’s Sexual Life after an Operation.” British Medical Journal 318 (7177) (January 16, 1999): 178. National Digestive Diseases Information Clearinghouse. Ileostomy, Colostomy, and Ileoanal Reservoir Surgery. (February 1, 2000): 1. ORGANIZATIONS

United Ostomy Association, Inc. 19772 MacArthur Blvd., Suite 200, Irvine, CA 92612-2405. (714) 660-8624. (800) 826-0826. (714) 660-9262. [email protected]. . Wound Ostomy and Continence Nurses Society. 2755 Bristol Street, Suite 110, Costa Mesa, CA 92626. (714) 476-0268. . OTHER

“Colostomy.” (20 April 1998).

Janie F. Franz

Results Complete healing is expected without complications. The period of time required for recovery from the surgery may vary, depending on the patient’s overall health prior to surgery. The colostomy patient, without other medical complications, should be able to resume all daily activities once recovered from the surgery.

Health care team roles A team of doctors, surgeons, specialists, technicians, and nurses are involved in the care of a patient who has a colostomy. While the skills of each health care provider are necessary, it is education and support that may be the most critical in affecting a successful outcome for the patient. Understanding what is involved in the procedure, what the results will be, and the ramifications of the surgery outcome are all considerations for the patient in order to make informed decisions. A thorough understanding of the implications of the surgical procedure and trust in the medical team enable the patient to face the change in lifestyle in a more positive fashion. Resources BOOKS

Monahan, Frances. Medical-Surgical Nursing. Philadelphia: W. B. Saunders Company, 1998.

Colostomy care Definition A colostomy is a surgically created opening in the abdominal wall through which digested food passes. It may be temporary or permanent. The opening is called a stoma from the Greek word meaning mouth. Stool passes through the stoma into a pouch attached to the stoma on the outside of the abdomen. The pouch, stoma, and skin surrounding the stoma require care and maintenance by the patient or caregiver.

Purpose A pouch is worn over a colostomy to collect the stool passed through the stoma. There are a variety of pouches available for use with a colostomy. Over time the patient can determine which pouch type best suits his or her needs. A colostomy pouch is normally emptied one or more times daily. The pouch itself usually needs to be changed every four to six days. The stoma and surrounding skin need to be kept clean and sanitary.

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• Stenosis (narrowing at the opening of the stoma). Often, this is associated with infection around the stoma or scarring. Mild stenosis can be removed under local anesthesia, while severe stenosis may require surgery for reshaping the stoma.

Colostomy care Colostomy care and colostomy pouch replacement in a hospital. (Delmar Publishers, Inc. Reproduced by permission.)

Precautions The nurse attending to a colostomy should wash his or her hands before and after the procedure, as well as wear latex gloves while performing care.

Description A pouching system is normally worn over a colostomy stoma. Pouches can be obtained from several different manufacturers in both disposable and reusable varieties. The enterostomal therapy ET nurse can be an invaluable resource when helping patients select a pouch system. Colostomy pouches may be either open ended or closed. Open-ended pouches require a clamp for closure. They can be drained simply and reused after they are emptied. Closed pouches are sealed at the bottom and are usually used by patients who irrigate their colostomies or who have a regular bowel elimination pattern. Two-piece pouch systems consist of a separate flange and pouch. The pouch has a closing ring that attaches to a matching piece on the flange. One-piece systems have a connected wafer and pouch that do not separate. The portion of the pouch that is applied to the abdomen is called a skin barrier wafer. Both two-piece and one-piece systems can be either closed or open ended. 544

Some patients with colostomies can irrigate their stomas using a procedure similar to an enema. This cleans the stool out of the colon through the stoma. A special irrigation system is used. Sometimes a special lubricant is used to prepare for the irrigation. Irrigating often leads to increased control over the timing of bowel movements. Removing the colostomy appliance requires gently pushing away the skin surrounding the stoma and pulling the appliance downwards. Adhesive remover wipes are available to help in the removal of the wafer. The bag is then discarded in an appropriate waste container. The stoma should be cleaned with lukewarm water and dried with a soft towel. The stoma and surrounding skin should be assessed. The stoma should be pink or red and moistlooking, and may bleed slightly when cleansed. The stoma normally decreases in size slightly during the first weeks after surgery. The opening in the wafer should fit snugly around the stoma. An opening that is too large will allow intestinal contents to leak onto the skin. Measuring guides come with the colostomy wafers so that the hole can be cut to the proper size. Skin barrier paste can be used to help create a better seal between the wafer and the patient’s abdomen. Various skin preparation products are

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Stoma—Surgically constructed mouth or passage between the intestine and the outside of the patient’s body.

Thomason, Susan S. “Promoting Outcomes for Patients with Spinal Cord Impairments and Ostomies.” MedSurg Nursing 9 (April 2000): 77. ORGANIZATIONS A colostomy creates a stoma (opening) in the abdominal wall to which a section of the large intestine is attached. The surface of the stoma is the inside lining of the intestine, so it appears moist and pink or red. (Custom Medical Stock Photo. Reproduced by permission.)

United Ostomy Association. 19772 MacArthur Blvd., Suite 200, Irvine, CA 92612. (800) 826-0826. .

Deanna M. Swartout-Corbeil, R.N.

also available to help protect the skin under the wafer and around the stoma. They also aid in the adhesion of the wafer. Using the fingertips, gentle pressure should be applied to put the wafer in place. After the application of the barrier, the bag should be applied (if it is a two-piece system). If it is an open system, apply a clamp to the bottom of the new pouch.

Preparation The nurse should instruct the patient and caregiver(s) about the procedure before it is performed. Many people feel anxious and nervous when first dealing with an ostomy. Encourage the patient to ask questions, and explain all steps as they are performed.

Aftercare The nurse should assess the patient’s tolerance of the procedure and response to teaching or education about the appliance.

Health care team roles Although most members of the health care team will come into contact with patients having ostomies, it is the nurse who has the responsibility for providing ostomy care and instructing the patient and/or caregiver how to provide care independently. An enterostomal therapy (ET) nurse is specially educated in all aspects of ostomy care. Resources PERIODICALS

Bryant, Diane. “Changing an Ostomy Appliance.” Nursing 2000 (November 2000).

Colposcopy Definition Colposcopy is a procedure that allows a physician to examine a woman’s cervix and vagina using a special microscope called a colposcope. It is used to check for precancerous or abnormal areas.

Purpose Colposcopy is used to identify or rule out the existence of any precancerous conditions in the cervical tissue. If a PAP test shows abnormal cell growth, a colposcopy is usually the first follow-up test performed. The physician will attempt to find the area that produced the abnormal cells and remove it for further study (biopsy) and diagnosis. Colposcopy may also be performed if the cervix looks abnormal during a routine examination. It may also be suggested for women with genital warts and for DES daughters (women whose mothers took DES when pregnant with them). Colposcopy is also used in the emergency department to examine victims of sexual assault and abuse and document any physical evidence of vaginal injury.

Precautions Women who are pregnant, or who suspect that they are pregnant, must tell their doctor before the procedure begins. Pregnant women can, and should, have a col-

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KEY TERMS

Colposcopy

poscopy if they have an abnormal PAP test. However, special precautions must be taken during biopsy of the cervix.

Description A colposcopy is usually performed in a physician’s office and is similar to a regular gynecologic exam. An instrument called a speculum is used to hold the vagina open, and the gynecologist looks at the cervix and vagina using a colposcope, a low-power microscope designed to magnify the cervix 10–40 times its normal size. Most colposcopes are connected to a video monitor, which displays the area of interest. Photographs are taken during the examination to document abnormal areas. The colposcope is placed outside the patient’s body and never touches the skin. The cervix and vagina are swabbed with dilute acetic acid (vinegar). The solution highlights abnormal areas by turning them white (instead of a normal pink color). Abnormal areas can also be identified by looking for a characteristic pattern made by abnormal blood vessels. If any abnormal areas are seen, the doctor will take a biopsy of the tissue, a common procedure that takes about 15 minutes. Several samples might be taken, depending on the size of the abnormal area. A biopsy may cause temporary discomfort and cramping, which usually go away within a few minutes. If the abnormal area appears to extend inside the cervical canal, a scraping of the canal may be done. The biopsy results are usually available within a week. If the tissue sample indicates abnormal growth (dysplasia) or is precancerous, and if the entire abnormal area can be seen, the doctor can destroy the tissue using one of several procedures, including ones that use high heat (diathermy), extreme cold (cryosurgery), or lasers. Another procedure, called a loop electrosurgical excision (LEEP), uses low-voltage, high-frequency radio waves to excise tissue. If any of the abnormal tissue is within the cervical canal, a cone biopsy (removal of a conical section of the cervix for inspection) will be needed.

Preparation Patients should be instructed not to douche or have sexual intercourse for 24 hours before the colposcopy. Patients should empty their bladder and bowels before colposcopy for comfort. Colposcopy does not require any anesthetic medication because pain is minimal. If a biopsy is done, there may be mild cramps or a sharp pinching when the tissue is removed. To lessen this pain the doctor may recommend 800 mg of ibuprofen (Motrin) taken 546

A colposcopy makes it possible for a physician to view this healthy cervix without surgery. (Photograph by Dr. P. Marazzi, Custom Medical Stock Photo. Reproduced by permission.)

the night before and the morning of the procedure (no later than 30 minutes before the appointment). Patients who are pregnant or allergic to aspirin or ibuprofen can take two tablets of acetaminophen (Tylenol) instead.

Aftercare If a biopsy was done, there may be a dark vaginal discharge afterwards. After the sample is removed, the doctor applies Monsel’s solution to the area to stop the bleeding. When this mixes with blood it creates a black fluid that looks like coffee grounds. This fluid may be present for a couple of days after the procedure. It is also normal to have some spotting after a colposcopy. Painrelieving medication can be taken to lessen any postprocedural cramping. Patients should not use tampons or put anything else in the vagina for at least a week after the procedure, or until the doctor says it’s safe. In addition, women should not douche or have sex for at least a week after the procedure because of the risk of infection.

Complications Occasionally, patients may have bleeding or infection after biopsy. Bleeding is usually controlled with a topical medication prescribed by the physician or health care provider. A patient should call her doctor right away if she notices any of the following symptoms: • heavy vaginal bleeding (more than one sanitary pad an hour) • fever, chills, or an unpleasant vaginal odor • lower abdominal pain

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The colposcopy may be performed by a gynecologist or other qualified health care provider. Such examinations will normally be performed in the presence of a female nurse. In cases of sexual assault, a nurse practitioner or registered nurse may perform the procedure. If a biopsy is performed, a pathologist examines the tissue samples under a powerful microscope in the laboratory and sends the results to the health care provider who, in turn, informs the patient of the results.

Results If visual inspection shows that the surface of the cervix is smooth and pink, this is considered normal. Areas that look abnormal may be normal variations; a biopsy will indicate whether the tissue is normal or abnormal. Abnormal conditions that can be detected using colposcopy and biopsy include precancerous tissue changes (cervical dysplasia), cancer, and cervical warts (human papilloma virus). Resources BOOKS

Carlson, Karen J., Stephanie A. Eisenstat, and Terra Ziporyn. The Harvard Guide to Women’s Health. Cambridge: Harvard University Press, 1996. Ryan, Kenneth J., Ross S. Berkowitz, and Robert L. Barbieri. Kistner’s Gynecology, 7th ed. St. Louis: Mosby, 1999. PERIODICALS

Holmes, Melisa M., and Deborah Kaplan, eds. “Clinical Management of Rape in Adolescent Girls.” Patient Care (April 30, 1999). . ORGANIZATIONS

American College of Obstetricians and Gynecologists. 409 12th St., SW, PO Box 96920, Washington, DC 200906920. . American Society for Colposcopy and Cervical Pathology. 20 W. Washington St., Ste. #1, Hagerstown, MD 21740. (301) 733-3640. . Association of Women’s Health, Obstetric, and Neonatal Nurses (AWHONN). 2000 L St., NW, Ste. 740, Washington, DC 20036. (800) 673-8499. . DES Action USA. 610 16th St., Ste. 301, Oakland, CA 94612. (510) 465-4011. . Society of Gynecologic Oncologists. 401 North Michigan Ave., Chicago, IL 60611. (312) 644-6610. .

KEY TERMS Biopsy—Removal of sample of abnormal tissue for more extensive examination under a microscope. Cervix—The neck of the uterus. Cryosurgery—Freezing and destroying abnormal cells. DES—The abbreviation for diethylstilbestrol, a synthetic form of estrogen that was widely prescribed to women from 1940 to 1970 to prevent complications during pregnancy. It was linked to several serious birth defects and disorders of the reproductive system in daughters of women who took DES. In 1971 the FDA suggested it not be used during pregnancy and banned its use in 1979 as a growth promoter in livestock. Diathermy—Also called electrocautery, this is a procedure that heats and destroys abnormal cells. It is gradually being replaced by cryosurgery, lasers, or LEEP. Dysplasia—Development of abnormal tissue. Human papilloma virus (HPV)—A virus that causes common warts of the hands and feet, as well as lesions in the genital and vaginal area. More than 50 types of HPV have been identified, some of which are linked to cancerous and precancerous conditions, including cancer of the cervix. Loop electrosurgical excision (LEEP)—A procedure that can help diagnose and treat cervical abnormalities using a thin wire loop that emits a low-voltage high-frequency radio wave that can excise tissue. It is considered better than either lasers or electrocautery because it can both diagnose and treat precancerous cells or early stage cancer at the same time. Mousel’s solution—An aqueous solution of Monsel’s salts with valuable styptic properties. PAP test—The common term for the Papanicolaou test, a simple smear method of examining stained cells to detect cancer of the cervix. Speculum—A retractor used to separate the walls of the vagina to make visual examination easier.

Jennifer E. Sisk, M.A. G A L E E N C Y C L O P E D I A O F N U R S I N G A N D A L L I E D H E A LT H

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Health care team roles

Coma

• the presence of certain substances such as drugs, alcohol, carbon dioxide, and ketones that disrupt the functioning of neurons

Coma Definition Coma, from the Greek word koma, meaning deep sleep, is a state of extreme unresponsiveness, in which an individual exhibits no voluntary movement or behavior. Furthermore, in a deep coma, even painful stimuli (actions which, when performed on a healthy individual, result in reactions) are unable to cause any response, and normal reflexes may be lost.

Description The important characteristics of the conscious state is defined by two fundamental elements: awareness and arousal. Awareness allows one to receive and process all the information communicated by the five senses. Awareness has both psychological and physiological components. The psychological component refers to an individual’s mind and mental processes. The physiological component refers to the functioning of an individual’s brain, and the physical and chemical condition of the brain. Awareness is regulated by cortical areas within the cerebral hemispheres, the outermost layer of the brain. Arousal is regulated solely by physiological functioning and consists of more primitive responsiveness to the world, as demonstrated by predictable reflex (involuntary) responses to stimuli. Arousal is maintained by the reticular activating system (RAS), a network of brain structures, including the brainstem, the medulla, and the thalamus, and nerve pathways that function together to produce and maintain arousal.

Causes and symptoms Coma is the result of something that interferes with the functioning of the cerebral cortex and/or the functioning of the structures that comprise the RAS. Several conditions can result in coma. Anatomic causes of coma are those conditions that disrupt the brain structures responsible for consciousness, either at the level of the cerebral cortex or the brainstem, while metabolic causes of coma consist of those conditions that change the chemical environment of the brain, thereby adversely affecting function. There are many metabolic causes of coma, including: • a decrease in the delivery to the brain of substances necessary for appropriate brain functioning, such as oxygen, glucose (sugar), and sodium 548

• changes in chemical levels in the brain caused by seizures

Diagnosis History and examination form the cornerstone of diagnosis when an individual is in a coma. However, history must be obtained from family, friends, or emergency medical service personnel. The Glasgow Coma Scale is a system of examining a comatose person. It evaluates the depth of the coma, tracks the person’s progress, and predicts the ultimate outcome of the coma. The Glasgow Coma Scale assigns a different number of points for exam results in three different categories: opening the eyes, verbal response, and motor response (moving a part of the body). Fifteen is the largest possible number of total points, indicating the highest level of functioning, which would be demonstrated by individuals who spontaneously open their eyes, give appropriate answers to questions about their situations, and can carry out a command such as moving a specific limb when ordered. Three is the least possible number of total points, and would be given to a person for whom not even a painful stimulus is sufficient to provoke a response. In the middle are those people who may be able to respond, but who require an intense or painful stimulus, and whose response may demonstrate some degree of brain malfunctioning. When performed as part of the admission examination, a Glasgow score of three to five points often suggests that an individual has likely suffered fatal brain damage, while eight or more points indicates that the person’s chances for recovery are good. Expansion of the pupils and respiratory pattern are also important. Metabolic causes of coma are diagnosed from blood work and urinalysis to evaluate blood chemistry, drug screen, and blood cell abnormalities that may indicate infection. Anatomic causes of coma are diagnosed from computed tomography (CT) or magnetic resonance imaging (MRI) scans.

Treatment Coma is a medical emergency, and attention must first be directed to maintaining an individual’s respiration and circulation, using intubation and ventilation, administration of intravenous fluids or blood as needed, and other supportive care. If head trauma has not been excluded, the neck should be stabilized in the event of fracture. It is extremely important for a physician to quickly determine

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Various metabolic disorders can be addressed by supplying an individual with the correct amount of oxygen, glucose, or sodium, by treating the underlying problem in liver disease, asthma, or diabetes, and by halting seizures with medication. Because of their low incidence of side effects and potential for prompt reversal of coma in certain conditions, glucose, the B-vitamin thiamine, and Narcan (to counteract any narcotic-type drugs) are routinely given.

Prognosis Some conditions that cause coma can be completely reversed, restoring an individual to an original level of functioning. However, if areas of the brain have been sufficiently damaged due to the severity or duration of the condition that led to the coma, an individual may recover with permanent disabilities, either physical or mental, or may never regain consciousness. Short of death, the most severe types of brain injury result in states in which an individual loses all ability to function and remains deeply unresponsive. An individual who has suffered such a severe brain injury may remain in a coma indefinitely. This condition is termed a persistent vegetative state. Outcome from a coma is therefore quite variable and depends a great deal on the cause and duration of the coma. In the case of drug poisonings, extremely high rates of recovery can be expected following prompt medical attention. Persons who have suffered head injuries tend to do better than do those whose coma was caused by medical illness. Besides those people whose coma results from drug poisoning, only about 15% of individuals who remain in a coma for more than just a few hours make a good recovery. Adult patients who remain in a coma for more than four weeks have almost no chance of eventually regaining their previous level of functioning. On the other hand, children and young adults have regained functioning after two months in a coma.

Health care team roles Emergency medical team members are often first on the scene to provide a preliminary assessment of unconsciousness. In the hospital, a physician makes the diagnosis of coma, often with assistance from radiologists and laboratory technicians. Nurses provide supportive

Coma

the cause of a coma, so that potentially reversible conditions are immediately treated. These conditions may include an infection that can be treated with antibiotics, a brain tumor that can be removed, or brain swelling that can be reduced with certain medications.

KEY TERMS Anatomic—Related to the physical structure of an organ or organism. Metabolic—Refers to the chemical processes of an organ or organism. Narcan—A drug that reverses the effects of narcotics. Neuron—The cells within the body which comprise the nervous system. Reticular activating system (RAS)—A network of structures, including the brainstem, medulla, and thalamus, and nerve pathways, which function together to produce and maintain arousal. Stimulus—Action performed on an individual that predictably provokes a reaction.

care throughout the duration of a coma. Physical therapists provide range of motion and other therapeutic movements designed to preserve normal muscular functioning.

Prevention Medical conditions known to cause comas should be monitored and promptly treated. Applicable safety precautions and rules should be followed when engaging in any activity that has the potential for serious head injury. Resources BOOKS

Adams, Raymond D., Maurice Victor, and Allan H. Ropper. Adam’s & Victor’s Principles of Neurology, 6th ed. New York: McGraw Hill, 1997. Mindell, Amy, and Robert King. Coma, A Healing Journey: A Guide for Family Friends and Helpers. Portand, OR: Lao Tse Press, 1999. O’Farrell, Maggie. After You’d Gone. New York: Viking Press, 2001. Ropper, Allan H., and Joseph B. Martin. “Acute Confusional States and Coma.” In Harrison’s Principles of Internal Medicine, 14th ed., edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, pp. 125-34. Simon, Roger P. “Brain Death.” In Cecil Textbook of Medicine, 21st ed., edited by Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, pp. 2027-8. Simon, Roger P. “Coma and Disorders of Arousal.” In Cecil Textbook of Medicine, 21st ed., edited by Lee Goldman

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and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, pp. 2023-6. Simon, Roger P. “Persistent Vegetative State.” In Cecil Textbook of Medicine, 21st ed., edited by Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, pp. 2026-7.

Combat neurosis see Post-traumatic stress disorder Community fluoridation see Water fluoridation

PERIODICALS

Lodi, J. R. “When a Coma Isn’t One.” Time 157 no. 12 (March 26, 2001): 62. Namen A. M., et al. “Predictors of Successful Extubation in Neurosurgical Patients.” American Journal of Respiratory and Critical Care Medicine 163 no. 3 Pt 1 (2001): 658-64. Palmer S., et al. “The Impact on Outcomes in a Community Hospital Setting of Using the AANS Traumatic Brain Injury Guidelines.” Journal of Trauma 50 no. 4 (2001): 657-64. Wallace B.E., A. K. Wagner, E. P. Wagner, and J. T. McDeavitt. “A History and Review of Quantitative Electroencephalography in Traumatic Brain Injury.” Journal of Head Trauma Rehabilitation 16 no. 2 (2001): 165-90. Wilkins I. A., D. K. Menon, and B. F. Matta. “Management of Comatose Head-Injured Patients: Are We Getting Any Better?” Anesthesia 56 no. 4 (2001): 350-69. ORGANIZATIONS

American Academy of Neurology. 1080 Montreal Avenue, St. Paul, Minnesota 55116. (651) 695-1940. (651) 695-2791. . [email protected]. Brain Injury Association. 105 North Alfred Street, Alexandria, VA 22314. (800) 444-6443. (703) 236-6000. (703) 2366001. . [email protected]. International Brain Injury Association. 1150 South Washington Street, Suite 210, Alexandria, VA 22314. (703) 683-8400. (703) 683-8996. . [email protected]. National Center for Injury Prevention and Control. Centers for Disease Control and Prevention, Mailstop F41, 4770 Buford Highway NE, Atlanta, GA 30341-3724. (770) 488-4031. (770) 488-4338. . [email protected]. OTHER

Coma Recovery Association. . Glasgow Coma Score. . National Academy of Child Development. . National Institute of Neurological Disorders and Stroke. . Neurology Channel. .

L. Fleming Fallon, Jr., M.D., Dr.P.H. 550

Common cold Definition The common cold is a viral infection of the upper respiratory system, including the nose, throat, sinuses, eustachian tubes, trachea, larynx, and bronchial tubes. Although over 200 different viruses can cause a cold, 30–50% are caused by a group of viruses known as rhinoviruses. Almost all colds clear up in less than two weeks without complications.

Description Colds, sometimes called rhinovirus or coronavirus infections, are common, frequently occurring illnesses. It is estimated that the average person has more than 50 colds during a lifetime. Anyone can get a cold, although preschool and grade school children catch them more frequently than adolescents and adults because they have not been exposed to the cold viruses and developed immunity. Repeated exposure to the viruses that cause colds creates partial immunity. Although most colds resolve on their own without complications, they are a leading cause of visits to the doctor and of time lost from work and school. Treating symptoms of the common cold has given rise to a multimillion dollar industry in over-the-counter medications. Cold season in the United States begins in early autumn and extends through early spring. Colds occur more frequently during this period because people tend to spend more time indoors where it is easier for viruses to spread from one person to another. Although it is not true that getting wet or being in a draft causes a cold (a person has to come in contact with the virus to catch a cold), certain conditions may lead to increased susceptibility. These include: • fatigue and overwork • emotional stress • poor nutrition • smoking • living or working in crowded conditions

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Causes and symptoms Colds are caused by more than 200 different viruses. The most common groups are rhinoviruses and coronaviruses. Different viruses are more infectious at different seasons of the year, but determining the exact virus causing the cold is not important for purposes of treatment. People with colds are contagious during the first two to four days of the infection. Colds pass from person to person in several ways. When an infected person coughs, sneezes, or speaks, tiny fluid droplets containing the virus are expelled. If these are inhaled by others, the virus may establish itself in their noses and airways. Colds can also be passed through direct contact. If a person with a cold touches his runny nose or watery eyes, then shakes hands with another person, the virus is transferred to the uninfected person. When the uninfected person touches his mouth, nose, or eyes, the virus is transported to an environment where it can reproduce and produce symptoms of illness. Finally, cold viruses can be spread through inanimate objects such as doorknobs, telephones, or toys that become contaminated with the virus. This is a common method of viral transmission in childcare centers. When a child with a cold touches his runny nose, then plays with a toy, the virus may be transferred to the toy. When another child plays with the toy a short time later, he may pick up the virus on his hands. When the second child touches his contaminated hands to his eyes, nose, or mouth the virus is once again in an environment conducive to replication. Once acquired, the cold virus attaches itself to the mucosal lining of the nasal passages and sinuses. This causes the infected cells to release a chemical called histamine. Histamine increases blood flow to the infected cells, causing swelling, congestion, and increased mucus production. One to three days following infection, the affected individual begins to experience cold symptoms. The first cold symptoms are sore throat, runny nose, and sneezing. The initial discharge from the nose is clear and thin. Later it changes to a thick yellow or greenish discharge. Most adults do not develop a fever when they contract a cold. Young children may develop fevers to 102°F (38.9°C).

Along with a runny nose and fever, symptoms of a cold include coughing, sneezing, nasal congestion, headache, myalgias (muscle aches), chills, sore throat, hoarseness, watery eyes, fatigue, and loss of appetite. The cough that accompanies a cold is usually intermittent and nonproductive (dry). Most people begin to feel better four to five days after cold symptoms become noticeable. All symptoms are generally gone within ten days, except for a dry cough that may linger for up to three weeks. Colds increase susceptibility to bacterial infections such as strep throat, middle ear infections, and sinus infections. Individuals with symptoms that do not begin to improve within a week; or those with chest pain, persistent fever (fever for longer than a few days), difficulty breathing, productive cough, skin rash, swollen glands, or whitish spots on the tonsils or throat should consult a health care practitioner. The health care practitioner will determine if these patients have acquired secondary bacterial infections that require treatment with antibiotics. People who have emphysema, chronic pulmonary disease, diabetes, or a weakened immune system—either from diseases such as AIDS or leukemia, or as the result of immunosuppressive medications (corticosteroids, chemotherapy drugs)—should consult a health care practitioner when they experience cold symptoms. Patients with these chronic health problems are at greater risk for secondary infections.

Diagnosis Colds are readily diagnosed using a focused history and physical examination. There are no laboratory tests readily available to detect or isolate the causative virus. When patients seek medical care, the health care practitioner (physician or mid-level practitioner) may perform a throat culture or blood test to rule out a secondary bacterial infection. Though viruses cause both colds and influenza (flu), influenza is usually a more serious viral illness. A cold develops gradually over the course of a day or two. Patients may have a runny nose, sneezing, mild sore throat, headache and body aches, but usually they do not have fever or feel completely exhausted. Influenza symptoms develop suddenly. They are similar to cold symptoms, but usually more severe. Patients with influenza generally feel sicker than those with colds because the influenza virus produces symptoms throughout the body—muscle aches, weakness, fever, and chills. Allergies also produce rhinitis (runny nose). Symptoms of allergic rhinitis—sneezing, nasal congestion, and itchy, runny nose—are commonly caused by

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Colds make the upper respiratory system less resistant to bacterial infection. Secondary bacterial infection may lead to otitis media (middle ear infection), bronchitis, pneumonia, sinus infection, or strep throat. Patients with chronic lung disease, asthma, diabetes, or a weakened immune system are more likely to develop these complications.

Common cold

dust mites, animal dander, or indoor molds. Other environmental irritants such as smoke, pollen, pollutants, pesticides, and perfumes may also trigger allergic rhinitis. Allergies are usually more persistent than the common cold. An allergist can perform tests to determine if the persistent cold-like symptoms are attributable to an allergic reaction. Also, some people get a runny nose when they go outside in winter and breathe cold air. This type of runny nose, called vasomotor rhinitis, is not a symptom of a cold.

Treatment There are no medicines that will cure the common cold. Given time, the body’s immune system will make antibodies to fight the infection, and the cold will resolve without any intervention. Antibiotics are useless against a cold. There are, however, medications to provide symptom relief. Pharmaceutical companies in the United States promote an array of products designed to relieve cold symptoms. Most products contain antihistamines, decongestants, and/or pain relievers. Antihistamines block the action of the chemical histamine that is produced when the cold virus invades the cells lining the nasal passages. Histamine increases blood flow and causes the cells to swell. Antihistamines relieve the symptoms of sneezing, runny nose, itchy eyes, and congestion. Side effects are dry mouth and drowsiness, especially with the first few doses. Patients should be advised against taking antihistamines if they intend to drive or operate dangerous equipment. The brand names of common over-the-counter antihistamines are ChlorTrimeton, Dimetapp, Tavist, and Actifed. The generic names of two common antihistamines are chlorpheniramine and diphenhydramine. Decongestants work to constrict the blood flow to the vessels in the nose. This can shrink the tissue, reduce congestion, and open inflamed nasal passages, making breathing easier. Decongestants can cause patients to feel jittery or prevent them from sleeping. They should not be prescribed for or used by patients with heart disease, high blood pressure, or glaucoma. The brand names of some common decongestants are Neo-Synepherine, Novafed, and Sudafed. The generic names of common decongestants are phenylephrine, phenylpropanolamine, pseudoephedrine, and in nasal sprays naphazoline, oxymetazoline, and xylometazoline. Many over-the-counter medications are combinations of antihistamines and decongestants. They also may include an ache and pain reliever, such as acetaminophen (Datril, Tylenol, Panadol) or ibuprofen (Advil, Nuprin, Motrin, Medipren), and a cough suppressant (dextromethorphan). Common combination 552

medications include Tylenol Cold and Flu, Triaminic, Sudafed Plus, and Tavist D. Aspirin should not be given to children with colds because of its association with a risk of Reye’s syndrome. Nasal sprays and nose drops also are promoted to relieve nasal congestion. These usually contain a decongestant, but the decongestant can act more quickly and strongly than ones found in pills or liquids because it is applied locally, directly in the nose. Congestion usually returns after a few hours. Patients may become dependent on nasal sprays and nose drops. If used for a long time, users may suffer withdrawal symptoms when the products are discontinued. This withdrawal condition is called rhinitis medicamentosa. Nasal sprays and nose drops should not be used for more than a few days. Patients should be instructed to adhere to product-specific recommendations about duration and frequency of use. Individuals have varied reactions to different cold medications and may find some more helpful than others. A medication may be effective initially, then lose some of its effectiveness. Children sometimes react differently from adults. Patients should be cautioned against giving over-the-counter cold remedies to infants without first consulting a health care professional. Care should be taken not to exceed the recommended dosages, especially when combination medications or nasal sprays are used. Individuals should determine whether they wish to use any of these medications based on their need for symptom relief, since none of them shorten the duration of a cold. Patients confused about the use of over-the-counter cold remedies should be encouraged to seek counsel from a health care practitioner, such as a physician, mid-level practitioner, nurse, or pharmacist. Along with the optional use of over-the-counter cold remedies, there are some self-care steps that patients can take to ease their discomfort. These include: • Drinking plenty of fluids, but avoiding acidic juices, which may irritate the throat. • Gargling with warm salt water (made by adding one teaspoon of salt to 8 oz of water) for a sore throat. • Not smoking. • Getting plenty of rest. • Using a cool-mist room humidifier to ease congestion and sore throat. • Rubbing Vaseline or other lubricant under the nose to prevent irritation from frequent nose blowing. • For babies too young to blow their noses, the mucus should be suctioned gently with an infant nasal aspira-

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tor. It may be necessary to soften the mucus first with a few drops of salt water. Many alternative health care practitioners believe that people contract colds because their immune systems are weak. They observe that everyone is exposed to cold viruses, but not everyone becomes ill. The difference seems to be in the ability of the immune system to fight infection. Prevention focuses on strengthening the immune system by eating a healthy diet low in sugars and high in fresh fruits and vegetables, practicing meditation to reduce stress, and getting regular moderate exercise. There is some scientific evidence that phytochemicals, nutrients found in fruits and vegetables, may act to prevent viral infections such as colds. An herb, Echinacea purpurea, is widely used to prevent and treat colds. It is believed to act as a transient (brief) immunostimulant, however, patients with autoimmune diseases should not use it since continuous use had been linked to immunosuppression. The use of zinc lozenges every two hours along with high doses of vitamin C is another an alternative therapy. Some alternative practitioners also suggest eliminating dairy products for the duration of the cold because they contend that dairy products encourage production of mucus. The use of zinc lozenges to treat cold symptoms remains controversial. Some studies evaluating the effectiveness of zinc gluconate lozenges found that using zinc in the first 24 hours after cold symptoms occurred shortened the duration of symptoms. Other studies refuted these findings.

Prognosis Given time, the body will generate antibodies to the cold. Most colds last a week to ten days, and patients start feeling better within four or five days. Occasionally, a cold will lead to a secondary bacterial infection that causes strep throat, bronchitis, pneumonia, sinus infection, or a middle ear infection. These conditions usually resolve rapidly when treated with the appropriate antibiotic.

Health care team roles Nearly all health care professionals encounter patients seeking advice about, or treatment for, cold symptoms. Physicians, mid-level practitioners, nurses, pharmacists, and health educators are often called upon to evaluate symptoms, instruct patients in self-care techniques, and reassure them that colds are self-limiting disorders that generally resolve without treatment.

Rhinovirus magnified 100,000 times. Rhinovirus causes the common cold. (CHSP/Custom Medical Stock Photo. Reproduced by permission.)

Patient education Along with strategies to prevent the spread of cold viruses, it is vitally important for health care professionals to teach patients that antibiotics have no role in the treatment of the common cold. Antibiotics should not be prescribed for colds because, as of 2001, there are no antibiotics effective against the viruses that cause colds. Further, antibiotics should not be prescribed unnecessarily because they can produce side effects such as rash and diarrhea. Another dangerous public health consequence of overuse of antibiotics is the emergence of strains of bacteria that are resistant to these medications.

Prevention It is not possible to prevent colds because the viruses that cause colds are common and highly infectious. There are, however, steps individuals can take to reduce their spread. These include: • Washing hands well and frequently, especially after touching the nose and before handling food. • Covering the mouth and nose when sneezing. • Disposing of used tissues properly. • Avoiding close contact with an infected individual during the first two to four days of their infection. • Not sharing food, eating utensils, or cups with others. • Avoiding crowded places where cold germs can spread. • Eating a healthy diet and getting adequate sleep. Resources BOOKS

Castleman, Michael. “Cold and Flu Therapy.” In Nature’s Cures. Emmaus, PA: Rodale Press, 1996.

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Description

KEY TERMS Bronchial tubes—The major airways to the lungs and their main branches. Coronavirus—A type of virus that causes respiratory disease and gastroenteritis. Corticosteroids—A group of hormones produced naturally by the adrenal gland or manufactured synthetically. They are often used to treat inflammation. Examples include cortisone and prednisone. Eustachian tube—A thin tube between the middle ear and the pharnyx. Its purpose is to equalize pressure on either side of the ear drum. Rhinovirus—A virus that infects the upper respiratory system and causes the common cold.

“Colds and Flu.” In Alternative Medicine: The Definitive Guide, compiled by the Burton Goldeberg Group. Puyallup, WA: Future Medicine Publishing, 1994. Pelletier, Kenneth R. The Best Alternative Medicine What Works? What Does Not? New York: Simon & Schuster, 2000. Silverstein Alvin, et al. Common Cold and Flu (Diseases and People). Springfield, MA: Enslow Publishers, 1996. OTHER

“Zinc: A Weapon Against the Commmon Cold?” Mayo Health Oasis. . (9 September 1997).

Barbara Wexler

Community health programs Definition Community health programs are locally based education and treatment programs available typically to individuals who are living in poverty and/or do not have health insurance coverage. Community health programs are usually non-profit and seek funding through health department programs, donations, and government grants. Community-based health programs are typically found in communities where the services are needed the most, and the services are tailored to the populations of residents. 554

Community health programs and clinics provide treatment, special clinics, education, and media campaigns that target a variety of issues affecting the health of a community. Many poor populations would have no other options for treatment without such neighborhood clinics and community health programs. Typical services include testing and treatment of sexually transmitted diseases; gynecological and obstetrical services; well-baby checks and immunizations; treatment of chronic diseases such as diabetes and high blood pressure; substance abuse programs; and general health promotion of good nutrition and weight management. U.S. populations Community-based programs will continue to be in demand to serve all populations from newborns to the elderly. Such programs are likely to become increasingly necessary to serve the growing number of immigrants moving to and living in the United States, the aging of the baby boomer generation, and the overall expansion of the population. In the 21st century, the United States is expected to become increasingly diverse as the proportion of immigrants grows. In the next 25 years, the number of nonHispanic white people living in the United States is expected to decrease from 72% to 62% due mostly to the increase in Hispanic populations. Immigration also affects fertility rates because women in some immigrant populations tend to have more children. The need for reproductive health care and pregnancy prevention services are expected to increase at the community level. The demand for services for the elderly will also increase as baby boomers age. As the health status of the elderly population improves, older adults are increasingly choosing to stay in their own homes and live independently. Senior citizens who live on a fixed income or who have limited health care coverage may be hardpressed to pay for medications, monitoring, and treatment of age-related, chronic conditions such as diabetes, high blood pressure, declining eye sight, hearing loss, and heart disease.

Viewpoints One point of debate within community health programs is the maximum income a person may earn and still be eligible for community health benefits. With limited funding, these agencies must follow guidelines for whom to offer services. In addition to those clearly living in poverty, the working poor and those with fixed

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The American Public Health Association (APHA) emphasizes that health care for all individuals is a basic human right. Every individual should be able to participate in his or her own health and wellbeing, and it is every citizen’s responsibility to contribute to the wellbeing of all. Community-based health programs offers the opportunity to empower the community to enable all citizens to have access to optimum health. Community health directors can take the lead to promote these ends. In collaboration with the APHA, the American Medical Association (AMA) has implemented seven goals, known as the Medicine/Public Health Initiative. They include: working to change the attitude within academic health centers; community health programs, insurance companies, and other heath care delivery providers having a more health-centered approach; creating interdisciplinary teams to establish research-based programs that focus on relevant health problems; expanding the public’s understanding of medicine, and, in turn, helping those in medicine understand public health; developing a common research agenda for public health; and developing a framework for integrating health promotion into clinical and community settings.

Professional implications The AMA emphasizes that the success of health education and promotion lies with many disciplines collaborating and working cooperatively. Health care professionals, such as physicians, social workers, nurses, health educators, environmental health engineers, and behavioral health professionals, have their own unique training, skills, and tools. Public health is a multidisciplinary field. By contributing a population-based perspective on health and disease, public health practitioners can collaborate with medical professionals to optimize resources and ideas and contribute more effectively to improving the health of the community. Community-based health clinics and centers are in need of professionals who can lobby legislators to support funding for programs, in addition to lobbyists who can work with government agencies such as the Health Care Financing Administration (HCFA), which oversees Medicaid funding. Resources BOOKS

Maxcy, Kenneth Fuller, M.J. Rosenau, John M. Last, et. al., eds. Public Health and Preventive Medicine. McGrawHill Professional Publishing, 1998.

Swanson, Janice M., Mary A. Nies, and Ilde Rader Albrecht, eds. Community Health Nursing: Promoting the Health of Aggregates, 2nd ed. Philadelphia: WB Saunders, 1996. ORGANIZATIONS

American Public Health Association. 800 I Street, NW, Washington, D.C. 20001. (202) 777-2742. . The Center for Community-Based Health Strategies. 1825 Connecticut Ave., NW, Washington, D.C. 20009. (202) 884-8862. . U.S. Department of Health and Human Services, Offices of Disease Prevention and Health Promotion. 200 Independence Ave., SW, Washington, D.C. 20201. (202) 401-6295. .

Meghan M. Gourley

Complementary nursing therapies Definition Complementary therapies are treatment modalities originating outside of Western medical practices that are used in addition to traditional Western medical practices. Alternative therapies are treatment modalities used in place of traditional Western medicine. The two terms are sometimes used interchangeably. The term integrative therapy may be used to describe the use of complementary and alternative (CAM) therapies with traditional Western medical practice. The National Center for Complementary and Alternative Medicine (NCCAM) at the National Institutes of Health defines complementary and alternative medical practices as “practices that are not currently an integral part of conventional medicine.”

Description The NCCAM groups CAM practices into five categories: • Alternative medical systems. This category includes acupuncture and traditional Chinese medicine (TCM), the ancient Indian practice of Ayurveda, homeopathy, naturopathy, and practices considered traditional to other cultures. The term medical system means that these practices incorporate the use of dietary recommendations, exercise, meditation, and/or herbal remedies as part of the total treatment plan. • Mind-body interventions. These include biofeedback, prayer, meditation, hypnosis, dance, music and art ther-

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incomes may not otherwise be able to afford health care services.

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apies, guided imagery, progressive muscle relaxation, and visualization. Many of these techniques aid in stress-reduction and can be taught to patients, either individually or in groups. • Biologically based therapies. Included in this category are herbal remedies and supplements, special diets such as Dr. Dean Ornish’s program (low-fat, vegetarian, meditation, exercise, and support group) for cardiac rehabilitation patients, vitamin therapy, or the use of laetrile or shark cartilage. • Manipulative and body-based methods. Osteopathy, chiropractic, massage, and reflexology are considered manipulative therapies. • Energy therapies. These practices are based on the philosophy that an energy field exists around the body. The goal of practices such as reiki, qi gong, and therapeutic touch (TT) is to reestablish a healthy energy field so that the body can then work to heal itself. The use of magnets to manipulate the energy field is another example. Describing CAM practices using the vocabulary of Western medicine is often a challenge, as the concept of life force, or chi, does not exist. However, a health practitioner who has been with a dying patient will recognize that, when the patient has died, there is a physical difference in how the patient looks. They do not just look asleep, for that which made them alive is now gone. It is this rather ephemeral quality that is described as chi. Acupuncture has existed for thousands of years. Treatment is based on the belief that the acupuncture points connect a system of meridians, or energy pathways, to the internal organs. When energy flows freely, health is experienced. Disease or illness represents a blockage of the flow of energy throughout the body. TCM uses acupuncture along with herbal remedies and diet to reestablih balanced energy. Acupuncture may use an herb called moxa to enhance the stimulation of the acupuncture points. Acupressure involves the stimulation of the meridian points by manual pressure rather than with the fine acupuncture needles. Acupuncture has been successfully used to treat dental pain and the nausea associated with pregnancy, postsurgical anesthesia, and chemotherapy. According to the NCCAM, the World Health Organization lists about 40 conditions for which acupuncture may be beneficial. Ayurveda is a traditional Indian medical system based on the belief that disease and illness result when there is an imbalance of the three doshas, which represent qualities governing body type, as well as the seasons and the different times of day. Each body type is susceptible to its own set of illnesses. Treatment to reestablish balance involves diet, herbal supplements, yoga, meditation, and massage with certain herbal oils. 556

Homeopathy functions on the philosophy that substances causing illness can be used in very dilute quantities to reestablish health. The more the substance is diluted, the more potent it becomes. Homeopathic remedies come in tablet, liquid, and cream form, and are used for children as well as for adults. The Food and Drug Administration (FDA) regulates the manufacture of homeopathic remedies. Mind-body therapies emphasize the healing power intrinsic within the human body. Biofeedback uses a machine that both records physical measurements, such as skin temperature and blood pressure, as well as giving visual or auditory cues to teach the individual to control these factors usually considered involuntary. Patients suffering from migraines may use biofeedback to learn to warm their hands and cool their foreheads, thus providing relief on demand. Patients may learn a meditation technique in order to control the effect of stress on the body, perhaps to decrease their high blood pressure. Many meditation techniques exist. In meditation, the individual tries to focus on a word, feeling, breathing pattern, or state of being in order to free the mind of other thoughts. Guided imagery is a technique encouraging individuals to utilize all their senses to create a peaceful, calming image in their mind. This technique works well with children, and can be used to distract from pain or anxiety. In progressive muscle relaxation, the individual tightens then relaxes the muscles of the body, starting with the feet and moving towards the head. This process helps the person become more aware of the feeling of tight versus relaxed muscles, and enables the body to achieve greater physical relaxation. Nurses can teach these techniques to their patients, empowering them with ways to manage the stress in their daily lives. Herbal remedies and supplements are used for therapeutic purposes and may be a part of an alternative system, such as Chinese medicine or naturopathy. They may be taken in tablet form, drunk as a tea, applied in a carrier cream, or inhaled in a vapor. Aromatherapy uses essential oils to stimulate the brain through the sense of smell to bring about a physiological effect such as relaxation or mood elevation. While individual herbal remedies are being investigated, such as the use of garlic to reduce cholesterol levels, or the use of saw palmetto for benign protastic hyperplasia (enlarged prostate), the interaction of herbs with standard medications has often not been thoroughly researched. Infant massage can be taught to new parents to facilitate bonding, and to teach them how to soothe their newborn. Infant massage has been used with infants in the intensive care unit to reduce their level of stress from being in an over-stimulating, noisy environment, address

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Reflexology involves a directed massage of the feet or hands. Points on the hands and feet are believed to correspond with internal organs, similar to the connection between acupuncture points, meridians, and internal organs. In reflexology, the practitioner applies pressure to specific points on the feet or hands to stimulate or remove energy blockages, thereby promoting healing and restoring health. Prayer and the use of support groups are other important methods that can have an impact on an individual’s health. Individuals with cancer who attended support groups were found to live longer than those who did not attend a support group. Therapeutic touch (TT) is an energy technique developed by a registered nurse and university professor, Dr. Dolores Kreiger. Practitioners use their hands to sense the energy around a patient, feeling for areas where the energy is stagnant, or blocked. The patient may feel a sense of warmth or tingling while the practitioner is working to rebalance the energy. The goal is to promote the patient’s innate ability to self-heal by reestablishing free-flowing energy. TT has been used to decrease pain, allowing a patient to prolong the time period between pain medication, to accelerate the rate of wound healing, and to promote relaxation.

Viewpoints A 1998 study reported that in 1997 an estimated $21.2 billion was spent on CAM services, of which $12.2 billion was spent out-of-pocket. This figure is greater than the amount spent for all hospitalizations in the United States in 1997. Nurses may choose to believe in the validity of CAM or to believe that these, or some of these, practices represent medical quackery. Regardless of their personal belief, nurses need to recognize that many of their patients will believe and/or follow these practices. Respect for a patient’s belief system is fundamental to the practice of nursing. Because of this, nurses must become knowledgeable about CAM practices in order to provide better nursing care to their patients. As research studies using CAM practices report beneficial outcomes, the definition of which therapies are considered alternative and which are considered mainstream changes. For this reason, it may be best not to label a therapy as CAM in discussing its use with a patient. In addition, patients’ cultural backgrounds affect which therapies are mainstream to them.

Professional implications As patient interest in and use of CAM increases, nurses need to be aware of these practices, regardless of whether or not they have been scientifically proven to be effective. CAM and nursing intersect at many points, including: • History and assessment. As the nurse documents the patient’s pertinent medical history, CAM practices need to be included. Asking open-ended questions, such as “What do you use to help your migraine pain?”, may elicit a different response from the patient than the question, “Do you use alternative medicine for your migraine pain?” A 1999 study of women with breast cancer reported that while 72% of the women were engaged in at least one form of complementary medicine, only 54% informed their health care professional of their CAM use, although 94% told their alternative practitioner what medical treatments they were receiving. Reasons cited included concern of ridicule and perceived lack of interest from the professional. Patients requiring surgery may take herbal remedies that could interact with anesthesia medications. Knowledge of all the medications and supplements that the patient is taking could be critical. • Triage. Nurses may receive telephone calls from patients who want to know if a particular herbal remedy is effective for their or their child’s condition. In addition, patients may call after taking a remedy and experiencing an adverse side effect. Knowledge of herbal remedies could facilitate proper diagnosis. • Nurse as practitioner. Nurses may choose to study CAM practices, become proficient in their use, and integrate their use into an existing nursing practice. However, nurses must keep in mind the legal implications of adding CAM therapies to their existing practice, to ensure they continue to practice within the legal boundaries of their license. Resources BOOKS

Ellis, Janice Rider, and Celia Love Hartley. Nursing in Today’s World, 7th Edition. Philadelphia, PA: Lippincott, 2001. Milton, Doris, and Samuel Benjamin. Complementary and Alternative Therapies: An Implementation Guide to Integrative Health Care. Chicago: Health Forum, Inc., 1999. PERIODICALS

Adler, S. R., and J. R. Fosket. “Disclosing Complementary and Alternative Medicine Use in the Medical Encounter: A Qualitative Study in Women with Breast Cancer.” Journal of Family Practice 48(6) (June 1999): 453-8.

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their emotional needs, foster weight gain, and enable earlier discharge.

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cell count, hemoglobin and hematocrit that aid in the diagnosis and classification of anemia.

KEY TERMS Chi, qi—Life-force energy existing in and around the body. Osteopathy—A practice of medicine that focuses on the care of the toal person with an emphasis on the musculoskeletal system.

Eisenberg, D. M., et al. “Trends in Alternative Medicine Use in the United States, 1990-1997: Results of a Follow-Up National Survey.” JAMA 280(18) November 1997: 1569-75. Griffin, Teresa M. “Introduction of a Positive Touch Programme: The Value of Infant Massage.” Journal of Neonatal Nursing 6(4) (July 2000): 112-116. Hodge, Peggy, and Susan Ullrich. “Does Your Assessment Include Alternative Therapies?” RN 62(6) (June 1999): 47. Jones, Kristy. “Clinical Aromatherapy and Touch: Complementary Therapies for Nursing Practice.” ANNA Journal 26(5) (October 1999): 527. ORGANIZATIONS

American Holistic Nurses Association (AHNA). P.O. Box 2130, Flagstaff, AZ 86003-2130. (800) 276-2462. . OTHER

National Center for Complementary and Alternative Medicine. NCCAM Clearinghouse, P.O. Box 8218, Silver Spring, MD 20907-8218. (888) 644-6226. .

Esther Csapo Rastegari, R.N., B.S.N., Ed.M.

Complete blood count Definition A complete blood count (CBC) is a series of tests used to evaluate the composition and concentration of the cellular components of blood. It consists of the following tests: red blood cell (RBC) count, white blood cell (WBC) count, and platelet count; measurement of hemoglobin and mean red cell volume; classification of white blood cells (WBC differential); and calculation of hematocrit and red blood cell indices. The hematocrit is the percentage of blood by volume that is occupied by the red cells (i.e., the packed red cell volume). Red blood cell indices are calculations derived from the red blood 558

Purpose The CBC provides valuable information about the blood and to some extent the bone marrow which is the blood-forming tissue. The CBC is used for the following purposes: • As a preoperative test to ensure both adequate oxygen carrying capacity and hemostasis. • To identify persons who may have an infection. • To diagnose anemia. • To identify acute and chronic illness, bleeding tendencies, and white blood cell disorders such as leukemia. • To monitor treatment for anemia and other blood diseases. • To determine the effects of chemotherapy and radiation therapy on blood cell production.

Precautions The CBC requires a sample of blood collected from a vein. The nurse or phlebotomist performing the venipuncture should observe universal precautions for the prevention of transmission of bloodborne pathogens. The collection tube must be filled completely, as under-filling increases the anticoagulant (EDTA) to blood ratio, which will crenate red blood cells. The tourniquet should be removed from the arm as soon as the blood flows to prevent hemoconcentration. If a fingerstick is used to collect the blood, care must be taken to wipe away the first drop, and not to squeeze the finger excessively as this causes the blood to be diluted by tissue fluid. The tests should be performed within four hours of collection or the sample must be refrigerated. Samples stored at 35-46°F (2-8°C) may be measured for up to 18 hours. Samples must be thoroughly mixed prior to measurement. Many drugs affect the results by causing increased or decreased RBC, WBC, and/or platelet production. Medications should be taken into account when interpreting results.

Description The CBC is commonly performed on an automated hematology analyzer using well mixed whole blood anticoagulated with EDTA. A CBC is a group of tests used to quantify the number of RBCs, WBCs, and platelets, provide information about their size and shape, measure the hemoblobin content of RBCs, determine the percentage and absolute number of the five white blood cell types, and identify early and abnormal blood cells. These tests are

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Electronic cell counting Electronic blood cell counting is based upon the principle of impedance (i.e., resistance to current flow). Some hematology analyzers combine impedance counting with light scattering to measure platelets. A small sample of the blood is aspirated into a chamber (the WBC counting bath) and diluted with a balanced isotonic saline solution that is free of particles. The diluted blood sample is split into two parts, one for counting RBCs and platelets and the other for counting WBCs. The RBC portion is transferred to the RBC/platelet counting bath where it is diluted further. The other portion remains in the WBC bath and a detergent (lysing agent) is added to destroy (hemolyze) the red blood cells. A small portion of the diluted fluid in each bath is allowed to flow past a small aperture. An electrical current is produced in each aperture by two electrodes, one on the inside and the other on the outside of the aperture. The saline solution is responsible for conducting current between the electrodes. The cells move through the aperture one at a time. When a cell enters the aperture, it displaces a volume of electrolyte equal to its size. The cell acts as an electrical resistor, and impedes the flow of current. This produces a voltage pulse the magnitude of which is proportional to the size of the cell. Instrument electronics are adjusted to discriminate voltage pulses produced by different cells. These adjustments are called thresholds. For example, the threshold for counting a RBC is equivalent to a cell volume of 36 femtoliters or higher. Voltage pulses that are equivalent to volumes between 2-20 femtoliters are counted as platelets. This process is repeated two more times so that the RBC, WBC, and platelet counts are performed in triplicate. Each time frame for counting is several seconds and many thousands of cells are counted. The computer processes the counting data first by determining the

agreement between the three counts. If acceptable criteria are met the counts are accepted and used to calculate the result. The computer mathematically corrects the count for the random chance of two cells entering the aperture simultaneously. The voltage pulses for each cell type are sorted and displayed. The RBC and platelet sizes are plotted as a histogram, and the WBC sizes are plotted as a scattergram. This process produces cell counts with coefficients of variation that are on the order of tenfold lower than can be achieved by manual cell counting. The hemoglobin concentration is measured optically using the solution in the WBC bath. The lysing agent contains potassium cyanide that reacts with the hemoglobin to form cyanmethemoglobin. The optical density of the cyanmethemoglobin is proportional to hemoglobin concentration. Source light from a small tungsten lamp or an LED that produces monochromatic light is directed through the sample contained in a small tube behind the bath. An interference filter on the other side of the tube transmits unabsorbed monochromatic light (e.g., 525 nm) to a photodiode. The photodiode current is proportional to the light it receives. This electronic signal is converted to an inverse log voltage that is proportional to the optical density of the solution. The optical density reading for the diluent is subtracted from the sample and the value is multiplied by a calibration factor (determined by measuring a calibrating solution) in order to calculate hemoglobin concentration. The voltage pulses produced by the white blood cells depend upon the size of the cell and its nuclear density. Therefore, the pulses may be analyzed to differentiate between the types of WBCs found. For example, lymphocytes are the smallest WBCs and comprise the lower end of the size scale. Monocytes, prolymphocytes, and immature granulocytes comprise the central area of the WBC histogram, and mature granulocytes comprise the upper end. In addition to cell sizing, automated instruments may use any of three other methods to distinguish between subpopulations. These are radio frequency conductance, forward and angular light scattering, and fluorescent staining. Red blood cell count The red cells, the most numerous of the cellular elements, carry oxygen from the lungs to the body’s tissues. They are released from the bone marrow into the blood in an immature form called the reticulocyte that still retains much of the cellular RNA needed for hemoglobin production. Reticulocytes may be counted on some automated analyzers and are an index to recovery from anemia. The average life span of RBCs in the circulation is approximately 110 days.

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performed simultaneously, (usually in less than one minute), using an automated hematology analyzer. When the performance limit of the automated hematology analyzer is exceeded, sample dilution or pretreatment, manual smear review, or manual cell counts may be required. Such conditions include very low or elevated cell counts, and the presence of cold agglutinins, lipemia, and cell fragments. For example, a manual WBC count may be performed when the automated WBC count is below 500 per microliter. A manual microscopic evaluation of a stained blood film is performed when an abnormal cell population is encountered. Each laboratory has established rules for determining the need for manual smear review based upon specific CBC parameters. For example, a manual differential is always performed when nucleated red blood cells are found on an electronic cell count.

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The red blood cell (RBC) count determines the total number of red cells (erythrocytes) in a sample of blood. Most anemias are associated with a low RBC count, hemoglobin, and hematocrit. Common causes include excessive bleeding; a deficiency of iron, vitamin B12, or folic acid; destruction of red cells by antibodies or mechanical trauma; bone marrow malignancy and fibrosis; and structurally abnormal hemoglobin. The RBC count is also decreased due to cancer, kidney diseases, and excessive IV fluids. An elevated RBC count may be caused by dehydration, hypoxia, or polycythemia vera. Hypoxia may result from high altitudes, chronic obstructive lung diseases, and congestive heart failure. Hematocrit and cell indices The hematocrit is a test that measures the volume of blood in percent that is comprised of the red blood cells. Automated cell counters calculate the hematocrit by multiplying the RBC count by the mean red cell volume (see MCV below). A decrease in the number or size of red cells also decreases the amount of space they occupy, resulting in a lower hematocrit. Conversely, an increase in the number or size of red cells increases the amount of space they occupy, resulting in a higher hematocrit. Thalassemia minor is an exception in that it usually causes an increase in the number of red blood cells, but because they are small, it results in a decreased hematocrit. The three RBC indices are used to determine the average size and hemoglobin content of the RBCs and they help determine the cause of anemia. The three indices are described below: • Mean corpuscular volume (MCV)—the average size of the red blood cells expressed in femtoliters. MCV is calculated by dividing the hematocrit (as percent) by the RBC count in millions per microliter of blood, then multiplying by 10. • Mean corpuscular hemoglobin (MCH)—the average amount of hemoglobin inside an RBC expressed in picograms. The MCH is calculated by dividing the hemoglobin concentration in grams per deciliter by the RBC count in millions per microliter, then multiplying by 10. • Mean corpuscular hemoglobin concentration (MCHC)—the average concentration of hemoglobin in the RBCs expressed in percent. It is calculated by dividing the hemoglobin in grams per deciliter by the hematocrit, then multiplying by 100. The mechanisms by which anemia occurs will alter the RBC indices in a predictable manner. Therefore, the RBC indices permit the physician to narrow down the 560

possible causes of an anemia. The MCV is an index of the size of the RBCs. When the MCV is below normal, the RBCs will be smaller than normal and are described as microcytic. When the MCV is elevated, the RBCs will be larger than normal and are termed macrocytic. RBCs of normal size are termed normocytic. Failure to produce hemoglobin results in smaller than normal cells. This occurs in many diseases including iron deficiency anemia, thalassemia (an inherited disease in which globin chain production is deficient), and anemias associated with chronic infection or disease. Macrocytic cells occur when division of RBC precursor cells in the bone marrow is impaired. The most common causes of marcocytic anemia are vitamin B12 deficiency, folate deficiency, and liver disease. Normocytic anemia may be caused by decreased production (e.g., malignancy and other causes of bone marrow failure), increased destruction (hemolytic anemia), or blood loss. The RBC count is low, but the size and amount of hemoglobin in the cells is normal. White blood cell count The majority of CBCs include both a WBC count and an automated differential. A differential determines the percentage of each of the five types of mature white blood cells. An elevated WBC count occurs in infection, allergy, systemic illness, inflammation, tissue injury, and leukemia. A low WBC count may occur in some viral infections, immunodeficiency states, and bone marrow failure. The WBC count provides clues about certain illnesses, and helps physicians monitor a patient’s recovery from others. The differential will reveal which WBC types are affected most. For example, an elevated WBC count with an absolute increase in lymphocytes having an atypical appearance is most often caused by infectious mononucleosis. The differential will also identify early WBCs which may be reactive (e.g., a response to acute infection) or the result of a leukemia. When the electronic WBC count is abnormal or a cell population is flagged, meaning that one or more of the results is atypical, a manual differential is performed. In that case, a wedge smear is prepared. This is done by placing a drop of blood on a glass slide, and using a second slide to pull the blood over the first slide’s surface. The smear is air dried, then stained with Wright stain and examined under a microscope using oil immersion (1000x magnification). One hundred white cells are counted and identified as either neutrophils, lymphocytes, monocytes, eosinophils, or basophils based on the shape and appearance of the nucleus, the color of cytoplasm, and the presence and color of granules. The purpose is to determine if these cells are present in a normal distribution, or if one cell type is increased or decreased. Any atypical or immature cells also are counted.

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Complete blood count

In addition to determining the percentage of each mature white blood cell, the following tests are performed as part of the differential: • Evaluation of RBC morphology is performed. This includes grading of the variation in RBC size (anisocytosis) and shape (poikioocytosis); reporting the type and number of any abnormal RBCs such as target cells, sickle cells, stippled cells, etc.; reporting the presence of immature RBCs (polychromasia); and counting the number of nucleated RBCs per 100 WBCs. • An estimate of the WBC count is made and compared to the automated or chamber WBC count. An estimate of the platelet count is made and compared to the automated or chamber platelet count. Abnormal platelets such as clumped platelets or excessively large platelets are noted on the report. • Any immature white blood cells are included in the differential count of 100 cells, and any inclusions or abnormalities of the WBCs are reported. WBCs consist of two main subpopulations, the mononuclear cells and the granulocytic cells. Mononuclear cells include lymphocytes and monocytes. Granulocytes include neutropohils (also called polymorphonuclear leukocytes or segmented neutrophils), eosinophils, and basophils. Each cell type is described below: • Neutrophils are normally the most abundant WBCs. They measure 12-16 µm in diameter. The nucleus stains dark purple-blue, and is divided into several lobes (usually three or four) consisting of dense chromatin. A neutrophil just before the final stage of maturation will have an unsegmented nucleus in the shape of a band. These band neutrophils may be counted along with mature neutrophils or as a separate category. The cytoplasm of a neutrophil contains both primary (azurophilic) and secondary (specific) granules. The secondary granules are lilac in color and are more abundant, almost covering the pink cytoplasm. Neutrophils are phagocytic cells and facilitate removal of bacteria and antibody-coated antigens. The neutrophilic granules are rich in peroxidase, and aid the cell in destroying bacteria and other ingested cells. • Eosinophils are 14-16 µm in diameter and contain a blue nucleus that is segmented into two distinct lobes. The cytoplasm is filled with large refractile orange-red granules. The granules contain peroxidase, hydrolases, and basic proteins that aid in the destruction of phagocytized cells. Eosinophils are increased in allergic reactions and parasitic infections. • Basophils, like eosinophils, are 14-16 µm in diameter and have a blue nucleus that is bilobed. The cytoplasm

Wright’s stain of normal red blood cells and platelets. (Delmar Publishers, Inc. Reproduced by permission.)

of the basophil is filled with large dark blue-black granules that may obscure the nucleus. These contain large amounts of histamine, heparin, and acid mucopolysaccharides. Basophils mediate the allergic response by releasing histamine. • Lymphocytes are the second most abundant WBCs. They may be small (7-9 µm in diameter) or large (1216 µm in diameter). The nucleus is dark blue and is nearly round or slightly indented and the chromatin is clumped and very dense. The cytoplasm is medium blue and usually agranular. An occasional lymphocyte will have a few azurophilic granules in the cytoplasm. Lymphocytes originate in the lymphoid tissues and are not phagocytic. They are responsible for initiating and regulating the immune response by the production of antibodies and cytokines. • Monocytes are the largest WBCs, measuring 14-20 µm in diameter. They have a large irregularly shaped and folded blue nucleus with chromatin that is less dense than other WBCs. The cytoplasm is gray-blue, and is filled with fine dust-like lilac colored granules. Monocytes are phagocytic cells that process and present antigens to lymphocytes, an event required for lymphocyte activation. Platelet count Platelets are disk-shaped structures formed by the detachment of cytoplasm from megakaryocytes. They aid in the coagulation process by attaching or adhering to the

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walls of injured blood vessels, where they stick together to form the initial platelet plug. A low platelet count may occur in patients with AIDS, viral infections, lymphoma, and lupus erythematosus, or in patients taking certain drugs, most notably quinine and quinidine. Decreased platelet production is also a cause of thrombocytopenia, and may be due to aplastic anemia, leukemia, lymphoma, or bone marrow fibrosis. A low platelet count can occur due to increased destruction. This can result from alloantibody production which is often drug-induced (heparin treatment being a prominent cause). Increased destruction also results from autoantibody production as occurs in idiopathic thrombocytopenic purpura (ITP) and thrombotic eipisodes that consume platelets such as occur in thrombotic thrombocytopenic purpura (TTP), disseminated intravascular coagulation (DIC), and hemolytic-uremic syndrome (HUS). Inherited (congenital) thrombocytopenia can be caused by Glanzmann’s thrombasthenia, von Willebrand’s disease, Fanconi syndrome, and Wiskott-Aldrich syndrome. Thrombocytosis, an increased platelet count, is most often caused by a reaction to injury or inflammation. In these cases the platelet count increases transiently and is usually within the range of 400,000-800,000 per microliter. Persistent or higher counts are usually associated with myeloproliferative disease (malignant disease involving blood forming cells) such as chronic granulocytic (myelogenous) leukemia, polycythemia vera, or primary (essential) thrombocythemia. The platelet count is most often measured by impedance counting but is performed manually when the platelet count is very low, platelet clumping is observed, or abnormally large (giant) platelets are present. Often these abnormalities and others such as cryoglobulinemia, cell fragmentation (hemolysis), and microcytic RBCs are signaled by abnormal RBC and platelet indices and abnormal population flags. An abnormal mean platelet volume or platelet histogram indicates that morphological platelet abnormalities are present and the platelets should be observed from a stained blood film to characterize the abnormality. The platelet count can be estimated using the Wright-stained blood smear used for a differential WBC count by multiplying the average number of platelets per oil immersion field by 20,000. Platelet estimates should correlate with actual counts. When they disagree, the platelet count should be repeated and a manual count performed if necessary.

Preparation

Discomfort or bruising may occur at the puncture site. Applying pressure to the puncture site until the bleeding stops helps to reduce bruising; warm packs relieve discomfort. Some people feel dizzy or faint after blood has been drawn and should be treated accordingly.

Complications Other than potential bruising at the puncture site, and/or dizziness, there are no complications associated with this test.

Results CBC values vary by age and sex. Normal values are ultimately determined by the laboratory performing the test. As a guide, the normal values for men and non-pregnant women are as follows: • WBCs: 4500 to 11,000 per microliter for women and men, with neutrophils representing 50-70%, lymphocytes 25-35%, monocytes 4-6%, eosinophils 1-3%, basophils 0.4-1%, and bands 0-5%. • RBCs: 4.2 to 5.0 million per microliter for women; 4.5 to 6.2 million per microliter for men. • Hemoglobin: 12-15 g/dL for women; 13.6 to 17.2 g/dL for men. • Hematocrit: 35-47% for women; 42-52% for men. • Platelets: 150,000 and 350,000 per microliter. • Reticulocyte count: 0.5-1.5%. Normal adult results for red blood cell indices are as follows: • MCV: 80-98 fl (femtoliters). • MCHC: 32-36%. • MCH: 27-31 pg (picograms). • RDW: 11.5-14.5%. In addition to normal values, critical values (alert, panic values) are established for hemoglobin (and hematocrit), WBC count, and platelet count. Precipitously low hemoglobin is associated with hypoxia that can have lifethreatening complications. Extremely low WBCs indicates an inability to fight infection and a high risk of sepsis. A severely reduced platelet count predisposes the patient to spontaneous internal bleeding. Representative critical values are shown below. • Hemoglobin: less than 5.0 g/dL.

The CBC does not require fasting or any special preparation. 562

Aftercare

• Hematocrit: less than 15%. • Platelet count: less than 30,000 per microliter.

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Anemia—A diminished oxygen carrying capacity caused by a decrease in the size, number, or function of red blood cells. Capillaries—The smallest of the blood vessels that bring oxygenated blood to tissues. EDTA—A colorless compound used to keep blood samples from clotting. Its chemical name is ethylenediaminetetraacetic acid. EDTA functions by binding the calcium in the blood sample. Hematocrit—The volume of blood occupied by the red blood cells expressed in percent. Hemoglobin—A protein inside red blood cells that carries oxygen to body tissues. Hypochromic—A descriptive term applied to a red blood cell with a decreased concentration of hemoglobin. Macrocytic—A descriptive term applied to a larger than normal red blood cell. Mean corpuscular hemoglobin (MCH)—A measurement of the average weight of hemoglobin in a red blood cell. Mean corpuscular hemoglobin concentration (MCHC)—The measurement of the average concentration of hemoglobin in a red blood cell.

• WBC count: less than 2,500 per microliter and greater than 30,000 per microliter. Abnormal blood count results are seen in a variety of conditions. One of the most common is anemia, which is characterized by a low RBC count, hemoglobin, and hematocrit. The category into which a person’s anemia is placed is in part based upon the red blood cell indices provided. The indices provide a significant clue as to the cause of the anemia, but further testing is needed to confirm a specific diagnosis. The most common causes of macrocytic anemia (high MCV) are vitamin B12 and folic acid deficiencies. Lack of iron in the diet, thalassemia (a type of hereditary anemia), and chronic illness are the most common causes of microcytic anemia (low MCV). Normocytic anemia (normal MCV) can be caused by kidney and liver disease, bone marrow disorders, leukemia, excessive bleeding, or hemolysis of the red blood cells. Iron deficiency and thalassemia are the most common causes of hypochromic anemia (low MCHC). Normocytic anemias are usually also normochromic and share the same causes. The red cell distribution width (RDW) is increased in anemias caused by deficiencies of

Mean corpuscular volume (MCV)—A measure of the average volume of a red blood cell. Mean platelet volume (MPV)—A measure of the average volume of a platelet. Microcytic—A descriptive term applied to a smaller than normal red blood cell. Normochromic—A descriptive term applied to a red blood cell with a normal concentration of hemoglobin. Normocytic—A descriptive term applied to a red blood cell of normal size. Red blood cell indices—Measurements that describe the size and hemoglobin content of red blood cells. Red cell distribution width (RDW)—A measure of the variation in size of red blood cells. Thrombocyte—Another name for platelet. Thrombocytopenia—An abnormally low platelet count. Thrombocytosis—An abnormally high platelet count. It occurs in polycythemia vera and other disorders in which the bone marrow produces too many platelets.

iron, vitamin B12, or folic acid. Abnormal hemoglobins, such as in sickle cell anemia, can change the shape of red blood cells as well as cause them to hemolyze. The abnormal shape and the cell fragments resulting from hemolysis increase the RDW. Conditions that cause more immature cells to be released into the bloodstream, such as severe blood loss, will increase the RDW. The larger size of immature cells creates a distinct size variation. Infections and leukemias are associated with increased numbers of WBCs. Increases or decreases in the percentage of each white cell can be associated with a number of diseases or conditions, including cancer, leukemia, anemia, multiple sclerosis, allergies, parasitic and viral diseases, infections, and tissue damage.

Health care team roles The CBC is ordered by a physician. A nurse or phlebotomist usually draws the blood to be used for the test. A clinical laboratory scientist/medical technologist or clinical laboratory technician/medical laboratory technician performs the test. The laboratory personnel are

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responsible for notifying the physician when a critical limit is encountered. A clinical pathologist may be consulted when abnormal findings that indicate a serious blood disease are noted, such as early cells or cells containing inclusions. Resources BOOKS

Chernecky, Cynthia C, and Berger, Barbara J. Laboratory Tests and Diagnostic Procedures. 3rd ed. Philadelphia, PA: W. B. Saunders Company, 2001. Henry, John B. Clinical Diagnosis and Management by Laboratory Methods. Philadelphia: W. B. Saunders Company, 1996. Kee, Joyce LeFever. Handbook of Laboratory and Diagnostic Tests. 4th ed. Upper Saddle River, NJ: Prentice Hall, 2001. Merck Manual of Medical Information, edited by Robert Berkow, et al. Whitehouse Station, NJ: Merck Research Laboratories, 1997. Mosby’s Diagnostic and Laboratory Test Reference, edited by Kathleen Deska Pagana, and Timothy James Pagana. St. Louis: Mosby-Year Book, Inc., 1998.

Victoria E. DeMoranville

Computed radiography Definition Computed radiography, or CR, is a digital image acquisition and processing system for radiography that uses computers and laser technology. It was developed in the mid-1980s. CR images can be recorded on laserprinted film or transmitted and stored digitally. This technological change has a significant impact on hospital operating costs and efficiency because radiography is the most common method of diagnostic imaging. It accounts for 70% of all imaging procedures, in comparison to 10% for CT scans and 6% for MRIs.

Purpose

In addition to providing clear diagnostic images that can be adjusted before printing, CR simplifies the process of transmission for purposes of consultation. CR images can easily be sent to other physicians or facilities for consultation via computer networks. Furthermore, CR systems permit considerable reductions in the cost of storage space for diagnostic images. Given the rapid rise in operating costs of full-service radiology departments, many newer facilities and some larger hospitals have installed CR systems.

Precautions Radiation levels One problematic aspect of CR is that it requires a higher dose of radiation to produce an image comparable to those produced by the film-screen method. The higher dose is necessary because the plate speed is approximately half that of the current screens used in film-screen combinations. The speed of the plate is directly related to the amount of radiation needed to create the x-ray image. Keeping the patient’s exposure to radiation “ALARA,” or “as low as is reasonably achievable,” has always been one of the goals of radiologic imaging. On the other hand, some radiologists note that patients may receive lower total dosages of radiation from CR imaging because fewer repeat exposures are required. Performance considerations A second problematic aspect of CR is that although its contrast resolution is better than that of conventional radiographic films, its spatial resolution is not as good. This drawback is especially apparent in mammograms and chest radiographs. One study that compared six different systems for chest radiography found that the CR system performed the least well, even though it was tested under the normal operating conditions for its setting.

Description

The purpose of CR is to produce accurate radiographic images without the use of film, thereby streamlining the storage, display, and transmission of patient data. Because CR allows the radiographer to correct images immediately following exposure, the need for retake exposures is dramatically reduced. In a CR system, corrections made in the image are relayed to the radiographer through an s number. This value tells the 564

radiographer whether the system had to brighten or darken the image, and to what degree, in order to produce a usable image. The adjusted image can then be printed on a film by a laser printer.

Computed radiography is an imaging technology in which a phosphor imaging plate replaces the older combination of film-screen radiography. Phosphors are substances that become luminescent (emit light) when they are excited by ultraviolet light or other forms of radiation. The imaging plate consists of either aluminum or a steel frame with honeycombed carbon fiber on one side. This side is the x-ray attenuating side. Inside is the phosphor

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The radiographer positions the patient and inserts the imaging plate cassette with the carbon-fiber side facing the x-ray tube. When the phosphor inside the imaging plate is exposed to x rays, its electrons are excited to higher energy levels. The radiographer then places the plate in a scanner, in which a helium-neon laser irradiates the excited electrons in the phosphor. The electrons emit light and return to a lower energy level. The light given off is converted first to an analog electrical signal which is then digitized, or converted into numerical data. The data can be recorded as an image on laser-printed film or transmitted and stored digitally. Picture-archiving communications systems (PACS) Picture-archiving communication systems, or PACS, are computer systems that allow several physicians to view radiographic images from multiple locations at the same time, whether in different departments of the same hospital or from remote facilities. CR images can be scanned, reviewed by the technologist for accuracy, and made available within three minutes to both the radiologist and the admitting physician. PACS improve hospital efficiency by eliminating the risk of losing or misplacing x-ray films as well as minimizing the need for storage space.

Complications Systems conversion One of the major challenges in the implementation of computed radiography in any institution is acceptance by the clinical staff. The task of retraining radiologists and technologists as well as ancillary staff can be daunting. Lastly, the increasing complexity of radiographic equipment requires greater cooperation between the engineers and scientists who develop the equipment and the health care personnel who use them. Gradual introduction of CR, along with smooth coordination of the technology experts and the clinical staff, is usually the best way of moving toward full departmental conversion.

KEY TERMS Cassette—The thin container that holds the film or the laser plate during radiographic exposure. Digital radiography (DR)—A newer form of filmless imaging that produces digital images on a computer monitor without the use of cassettes. Digital recording—A method of recording audio or visual data in which an input wave form is sampled thousands of times per second, and each sample is given a binary numerical value. Film-screen—The combination of x-ray film and screens used in current conventional methods of radiographic imaging. Phosphor—A substance that emits light when it is struck by light of a certain wavelength. Some phosphors are luminescent only when struck by ultraviolet light. Picture-archiving communication system (PACS)—A digitized system for storing CR or DR images that replaces older film storage, manual filing, and manual routing systems. Screen—The layer lining the cassette that changes the x-ray into light

resembles CR in that it transmits, displays, and stores images without the use of film, but it differs from CR in that it is strictly digital and does not use cassettes at all. While the advantages of CR include its portability and its lower production cost, DR offers superior contrast resolution, immediate image readout, and considerable time savings. The first productivity studies comparing the two imaging systems have found that a CR examination takes between three and four times as long as an examination using digital radiography. In one hospital near Boston, the average two-view chest radiograph required 9.9 minutes with a CR system but only 2.5 minutes with DR. Most of the time difference appears to be due to the steps required to process the CR cassettes. While some hospitals are using both CR and DR systems, others are concerned that CR technology may not have a long enough future in spite of its lower initial costs to justify implementing it at all.

Newer technology An additional complication to implementing CR systems is that they no longer represent cutting-edge imaging technology. Within the past few years, a system called digital radiography, or DR, has been introduced. It

Results CR does, however, offer significant advantages in diagnostic quality over conventional film-screen methods. The latest enhancements for CR include energy sub-

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imaging plate, which replaces the older film-screen cassette. The plate is contained in standard-size radiographic cassettes that can be used in existing radiographic tables and stands.

Computers in health care

traction, which makes it possible to view bone-only and soft tissue-only images of the chest, and dynamic range control, which makes it possible to study both bone and soft tissue on the same image. Another benefit of the CR system is that the images are available immediately on the monitor for evaluation and post-processing enhancement. In addition, the images can be evaluated by an offsite radiologist with a monitor hooked up to the hospital’s system. Lastly, CR is a portable system that can be used at the patient’s bedside or in the emergency room as well as in a radiology clinic.

Health care team roles With computed radiography as with conventional film-screen technology, the exposures can be made by a radiologic technologist or a radiologist. The radiologist will interpret the images as part of the process of differential diagnosis. A PACS system will allow the radiologist to consult with colleagues in other parts of the hospital or other institutions. Resources

Computed tomography equipment see CT imaging equipment Computerized axial tomography see CT scans

Computers in health care Definition Once used primarily as back-office record keepers and financial calculators, computers and their networks now play increasingly significant roles in patient care. They are increasingly used by health-care practitioners for patient information, record keeping, communicating with colleagues, devising strategies for patient care, interpreting lab results, and research. The fast processors and large memory capacity of today’s computers, along with the Internet and other networks, have expanded the role of computers into virtually every aspect of health care.

PERIODICALS

DeMaster, Dean R. “Digital radiography offers major productivity gains over computed radiography: Results of a time-motion study.” Applied Radiology 30, no. 3 (March, 2001): 28-31. Manning, D. J., et al. “An ROC evaluation of six systems for chest radiography.” Radiography 5, no. 4 (November 1999): 201-209. ORGANIZATIONS

Association of Educators in Radiological Sciences (AERS). P. O. Box 90204, Albuquerque, NM 87199-0204. (505) 823-4740. Web site: . Radiological Society of North America, Inc. 820 Jorie Boulevard, Oak Brook, IL 60523-2251. (630) 571-2670. Fax: (630) 571-7837. Web site: . Society for Computer Applications in Radiology (SCAR). 10105 Cottesmore Court, Great Falls, VA 22066-3540. (703) 757-0054. Fax: (703) 757-0454. Web site: htpp://www.scarnet.org. The Society has published the Journal of Digital Imaging since 1988. OTHER

Page, Douglas. “Point-counterpoint: Direct and computed radiography coexist, but for how long?” Presentation at SCAR2000, annual meeting of the Society for Computer Applications in Radiology. Van Metter, Richard, Ph.D. “The Technology Behind Digital Radiography: All Systems are Not Created Equal.” (January/February 2001).

Debra Novograd, B.S.,R.T.(R)(M) 566

Description From the moment a patient walks into a hospital, doctor’s office or clinic, computers are involved in his or her care. Patient information is often entered electronically to generate an electronic chart. Some organizations integrate this information with practice management software, helping staff schedule patient procedures and manage the financial matters. Computer workstations in exam rooms can now allow clinicians to access patient information, lab results, and educational material. Electrocardiograms and other lab and radiology tests are often analyzed initially by computer programs to save staff time. Some radiology departments have begun to use digital “filmless” imaging technologies, and computers are even slowly entering the chaotic environment of the operating room, where perioperative nurses use workstations to document procedures. Computers are being used to help avert medical errors—a critical need, since, according to an Institute of Medicine report important, an estimated 44,000 to 98,000 Americans die each year from preventable errors. Computer systems in some hospitals monitor patients in intensive-care units or operating rooms, alerting clinicians to anything abnormal, such as a sharp decrease in hemoglobin levels, for example. Instead of writing prescriptions on paper, some clinicians now use computerbased systems that not only suggest drug dosages but

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Computers can be used to view patient information, help with diagnoses, and communicate with colleagues at other facilities. (Custom Medical Stock Photo. Reproduced by permission.)

check for allergies and interactions as well. Some clinicians also use handheld computers to enter patient notes and check medical references. In addition to computerizing individual hospital departments, computers are being used to tie disjointed departments together and to standardize health care information over the entire industry. Aside from promising monetary savings and improved efficiency, such departmental integration is expected to help hospitals adhere to insurance company and government requirements. The federal Health Insurance Portability and Accountability Act (HIPAA), designed to protect confidential health care information, has pushed health care organizations to use consistent standards in their dealings with patients and insurers. Such standardization also promises to improve research by allowing scientists to track public health records more accurately and to better identify both treatments for, and causes of, disease. The Internet has quickly become an integral part of health care. Patients can check their medical records, research drug interaction information, or find information on clinical trials and experimental medical treatment. Health care practitioners use the Internet for research, to

gain continuing medical education (CME) credits, and to check patient information. To help manage this information overload, several websites provide customized health information and access to research tools such as the National Library of Medicine’s Medline/PubMed, a search engine that provides access to millions of citations from research journals. The Internet can also educate people about disease prevention and help them adopt a healthy lifestyle. Specialty websites, whose topics range from mental health to infectious diseases, allow individuals to conduct disease screenings and lifestyle and quality-of-life assessments. In addition, government health organizations, such as the Centers for Disease Control and Prevention, use the web to provide public health information to state and local health departments, health professionals, and the general public. The World Health Organization (WHO) and its member organizations have created a vast global computer network called the Library and Information Networks for Knowledge (LINK); the agency also supports an electronic database called WHOLIS. Both the library and the database support the WHO’s mission to improve international public health. Once a communica-

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ble disease outbreak has been confirmed, for example, information is placed on the web for the general public.

Resources

Several Internet applications can even provide telemedical services, such as long-distance mammograms to underserved women. Other applications help patients suffering from chronic diseases such as asthma, diabetes, and heart disease to monitor their conditions. Still another computer program allows diabetics to download data from a blood glucose meter, enter information about their medications, diet, and symptoms, and transmit this data to healthcare providers.

Ball, M. and K. Hannah, eds. Nursing Informatics: Where Caring and Technology Meet. New York: SpringerVerlag, 2000. Saba, Virginia K., Kathleen A. McCormick, eds. Essentials of Computers for Nurses: Informatics for the New Millennium. New York: McGraw-Hill, 2001. Shortliffe, E., and L. Perreault, eds. Medical Informatics: Computer Applications in Health Care and Biomedicine. New York: Springer-Verlag, 2001. PERIODICALS

Pravikoff, D. “On the Information Highway, Or Sitting on the Curb?” Journal of Nursing Education vol. 39, no. 3 (2000): 99-100.

Viewpoints Although computers have improved patient care, administrative efficiency, and disease tracking, their increasing use also poses several challenges. Consistent, standardized data coding is one example. Maintaining patient privacy is another concern. In an electronic world of integrated departments and shared databases, patient confidentiality can be difficult to maintain unless great care is taken with sensitive patient information (like HIV status or drug-abuse history), and staff is trained to protect the confidentiality and security of patient information. Another consideration: making sure technology is reliable enough to be trusted. Poorly designed pharmaceutical software could result in drug errors, for example.

Professional implications Nurses, who have traditionally gathered, stored, and maintained patient information, have an especial need for computer training. Even beginning nurses should have basic word processor, database, spreadsheet, and E-mail skills, according to a panel of researchers affiliated with the American Nurses Association (ANA). As computers become ever-more integrated into patient care, disease prevention, and health promotion, as well as into medicine’s administrative processes, nurses need information literacy as much as they need computer literacy. This means that they must be able to recognize when information is needed and know how to track down and use it appropriately, according to the ANA panel. Reflecting this shift, some nurses have chosen to augment their training with courses in nursing informatics, a field that was officially recognized as a specialty for registered nurses by the American Nurses Association in 1992. This specialty is a combination of nursing science, information processing theory, and computer science. 568

BOOKS

ORGANIZATIONS

American Association of Critical-Care Nurses (AACN), 101 Columbia, Aliso Viejo, CA 92656. (949) 362-2000. . American Association of Nurse Anesthetists (AANA), 222 South Prospect Avenue, Park Ridge, IL 60068. (847) 6927050. . The American Health Information Management Association. 233 N. Michigan Avenue, Suite 2150, Chicago, IL 60601. (312) 233-1100. . American Nurses Association (ANA), 600 Maryland Avenue, SW, Suite 100 West, Washington, DC 20024. (800) 2744ANA. . AORN, Association of Perioperative Registered Nurses, 2170 South Parker Road, Suite 300, Denver, CO 80231. (800) 755-2676. . Emergency Nurses Association (ENA), 915 Lee Street, Des Plaines, IL 60016. (800) 900-9659. . National Student Nurses Association (NSNA), 555 West 57th Street, New York, NY 10019. (212) 581-2211. . OTHER

Gawande, A., and D. Bates. “The Use of Information Technology in Improving Medical Performance.” Medscape General Medicine. 2000, vol. 2, no.1. . Kohn, L., J. Corrigan, and M. Donaldson, eds. To Err Is Human: Building a Safer Health System. Committee on Quality of Health Care in America, Institute of Medicine 2000. . Legal Issues for Physicians. American Medical Association, Office of General Counsel, Division of Health Law. . Scope of practice of nursing informatics and the standards of practice and professional performance for the informatics nurse specialist. American Nurses Association Expert Panel. .

Ann Quigley

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Definition Concussion is a trauma-induced change in mental status, associated with confusion and amnesia, that may or may not be accompanied by a brief loss of consciousness.

Description A concussion occurs when the head hits or is hit by an object, or when the brain is jarred against the skull with sufficient force to cause temporary loss of function in the higher centers of the brain. The injured person may remain conscious or briefly lose consciousness and become disoriented for some minutes after the blow. According to the Centers for Disease Control and Prevention, approximately 300,000 people sustain mild to moderate sports-related brain injuries each year, most of them young men between the ages of 16 and 25. While a concussion usually resolves on its own without lasting effect, it can set the stage for a much more serious condition. “Second impact syndrome” occurs when a person with a concussion, even a very mild one, suffers a second blow before fully recovering from the first. The brain swelling and increased intracranial pressure that can result is potentially fatal. More than 20 such cases have been reported since the syndrome was first described in 1984.

A concussion is usually accompanied by another area of brain injury on the opposite side of the head from the initial blow. This is called a contrecoup injury. It is caused by to the impact of the brain on the opposite side of the skull after the initial blow. Concussion and lasting brain damage is an especially significant risk for boxers, since the goal of the sport is, in fact, to deliver a concussion to the opponent. For this reason, the American Academy of Neurology has called for a ban on boxing. Repeated concussions over months or years can cause cumulative head injury. The cumulative brain injuries suffered by most boxers can lead to permanent brain damage. Multiple blows to the head can cause “punch-drunk” syndrome or dementia pugilistica, as evidenced by Muhammed Ali, whose Parkinson’s disease is a result of his career in the ring. Young children are likely to suffer concussions from falls or collisions on the playground or around the home. Child abuse is, unfortunately, another common cause of concussion. Symptoms Symptoms of concussion include: • headache • disorientation relative to time, date, or place • amnesia for the events immediately preceding the blow • confusion

Causes and symptoms

• dizziness

Causes

• vacant stare or confused expression

Most concussions are caused by motor vehicle accidents and sports injuries. In motor vehicle accidents, concussion can occur without an actual blow to the head. Instead, concussion occurs because the skull suddenly decelerates or stops, which causes the brain to be jarred against the skull. Contact sports, especially football, hockey, and boxing, are among those most likely to lead to concussion. Other significant causes include falls, collisions, or blows due to bicycling, horseback riding, skiing, and soccer. The risk of concussion from football is extremely high, especially at high school level. Studies show that approximately one out of every five players suffers a concussion or more serious brain injury during their brief high-school careers. The rate at the collegiate level is approximately one person in 20. Rates for hockey players are not known with certainty but are believed to be similar.

• incoherent or incomprehensible speech • incoordination or weakness • nausea or vomiting • double vision • ringing in the ears (tinnitus) These symptoms may last from several minutes to several hours. More severe or longer-lasting symptoms may indicate more severe brain injury. A person with a concussion may or may not lose consciousness from the blow. If consciousness is lost, the duration is usually brief, for several minutes at most. More prolonged unconsciousness indicates more severe brain injury. The severity of concussion is graded on a three-point scale. This is used as a basis for treatment decisions. • Grade 1: no loss of consciousness, transient confusion, and other symptoms that resolve within 15 minutes.

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• Grade 2: no loss of consciousness, transient confusion, and other symptoms that require more than 15 minutes to resolve.

should be discontinued and not resumed until there have been no symptoms, during both rest and activity, for one week.

• Grade 3: loss of consciousness for any period of time.

A person with a grade 2 concussion (no loss of consciousness, transient confusion, and other symptoms that require more than 15 minutes to resolve) must discontinue sports activity for the day, should be evaluated by a trained professional, and should be observed closely throughout the day to make sure that all symptoms have completely cleared. Worsening of symptoms, or continuation of any symptoms beyond one week, indicates the need for a CT or MRI scan. Return to contact sports should only occur after one week with no symptoms, both at rest and during activity, and following examination by a physician. Following a second grade 2 concussion, the person should remain symptom-free for two weeks before resuming contact sports.

Days or weeks after the accident, a person may show signs of: • headache • poor attention and concentration • memory difficulties • anxiety • depression • sleep disturbances • light and noise intolerance The occurrence of such symptoms is called “postconcussion syndrome.”

Diagnosis It is very important for those attending a person with a concussion to pay close attention to the person’s symptoms and progression immediately after the accident. The duration of unconsciousness and degree of confusion are very important indicators of the severity of the injury and help guide the diagnostic process and subsequent treatment decisions. A trained health professional may make an immediate assessment based on the severity of the symptoms; a neurological exam of the pupils, coordination and sensation; and brief tests of orientation, memory, and concentration. Persons with very mild concussions may not need to be hospitalized or have expensive diagnostic tests. Questionable or more severe cases may require a computed tomography scan (CT) or magnetic resonance imaging (MRI) scan to look for brain injury.

Treatment The symptoms of concussion usually clear quickly and without lasting effect, if no further injury is sustained during the healing process. Guidelines for returning to sports activities are based on the severity of a concussion. A grade 1 concussion (no loss of consciousness, transient confusion, and other symptoms that resolve within 15 minutes) can usually be treated with rest and continued observation alone. The person may return to sports activities the same day, but only after examination by a trained professional, and after all symptoms have completely resolved. If the person sustains a second concussion of any severity that same day, contact sports 570

A person with a grade 3 concussion (involving any loss of consciousness, no matter how brief) should be examined by a medical professional either on the scene or in an emergency room. More severe symptoms may warrant a CT or MRI scan, along with a thorough neurological and physical exam. The person should be hospitalized if any abnormalities are found or if confusion persists. Prolonged unconsciousness and worsening symptoms require urgent neurosurgical evaluation or transfer to a trauma center. Following discharge from professional care, a person should be closely monitored for neurological symptoms that may arise or worsen. If headaches or other symptoms worsen or last longer than one week, a CT or MRI scan should be performed. Contact sports should be avoided for one week following unconsciousness of only seconds, and for two weeks following unconsciousness of a minute or more. A person receiving a second grade 3 concussion should avoid contact sports for at least a month after all symptoms have cleared, and then resume them only with the approval of a physician. If signs of brain swelling or bleeding are seen on a CT or MRI scan, an athlete should not return to the sport for the rest of the season at the earliest, if not indefinitely. For someone who has sustained a concussion of any severity, it is critically important to avoid the possibility of another blow to the head until well after all symptoms have cleared to prevent second-impact syndrome. The guidelines above are designed to minimize the risk of this syndrome.

Prognosis A concussion usually leaves no lasting neurological problems. Nonetheless, symptoms of post-concussion syndrome may last for weeks or even months.

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Health care team roles A doctor, nurse, athletic trainer, or emergency medical technician may provide an initial evaluation at the time of the concussion. These health care team members can usually evaluate a grade 1 or 2 concussion. A neurologist, neurosurgeon, or trauma specialist should evaluate a concussion in a hospital. A neurologist or neurosurgeon should provide follow-up for grade 3 concussions. A nurse may provide post-concussion supportive care. Radiologists may obtain and interpret CT or MRI scans.

Prevention Many cases of concussion can be prevented by using appropriate protective equipment. This includes using seat belts and air bags in automobiles, and wearing helmets in all contact sports. Helmets should also be worn when bicycling, skiing, or horseback riding. Soccer players should avoid heading the ball when it is kicked at high velocity from close range. Playground equipment should be underlaid with soft material, either sand or special matting. The value of high-contact sports such as boxing, football, or hockey should be weighed against the high risk of brain injury during a young person’s participation in the sport. Steering a child’s general enthusiasm for sports into activities less apt to produce head impacts may reduce the likelihood of brain injury. Resources BOOKS

Adams, Raymond D, Victor, Maurice and Ropper, Allan H. Adam’s & Victor’s Principles of Neurology, 6th ed. New York: McGraw Hill, 1997. Bailes, Julian E, Lovell, Mark R and Maroon, Joseph C. Sports Related Concussion. St. Louis, MO: Quality Medical Pub, 1998. Parker, Rolland S. Concussive Brain Trauma: Neurobehavioral Impairment and Maladaptation. Boca Raton, FL: Lewis Publishers, 2000. Rizzo, Matthew and Tranel, Daniel. Head Injury and Postconcussive Syndrome. London: Churchill Livingstone, 1996. Wrightston, Philip and Gronwall, D.M.A. Mild Head Injury: A Guide to Management. New York: Oxford, 1999. PERIODICALS

Bailes, J.E. and Cantu, R.C. “Head Injury in Athletes.” Neurosurgery 48(1): 26-45, 2001.

KEY TERMS Amnesia—A loss of memory that may be caused by brain injury, such as concussion; the loss may be temporary or permanent. Contrecoup injury—An injury, usually involving the brain, in which the tissue damage is on the side opposite the site of the trauma. Parkinson’s disease—A neurological disorder that includes a fine tremor, muscular weakness and rigidity, and an altered way of walking. Tinnitus—A sensation of ringing in the ears in the absence of external sources of noise.

Centers for Disease Control and Injury. Facts about Concussion and Brain Injury and Where to Get Help. Order electronically at: . Guskiewicz, K.M., Weaver, N.L., Padua, D.A. and Garrett, W.E. “Epidemiology of concussion in collegiate and high school football players.” American Journal of Sports Medicine 28(5): 643-650, 2000. Maroon, J.C., et al. “Cerebral concussion in athletes: evaluation and neuropsychological testing.” Neurosurgery 47(3): 659-669, 2000. Proctor, M.R. and Cantu, R.C. “Head and neck injuries in young athletes.” Clinics in Sports Medicine 19(4): 693-715, 2000. Reece, R.M. and Sege, R. “Childhood head injuries: accidental or inflicted?” Archives of Pediatric and Adolescent Medicine 154(1): 11-15, 2000. ORGANIZATIONS

American Academy of Neurology, 1080 Montreal Avenue, St. Paul, Minnesota 55116. (651) 695-1940. Fax: (651) 6952791. . [email protected]. American College of Sports Medicine, 401 W. Michigan St., Indianapolis, IN 46202-3233. (317) 637-9200. Fax: (317) 634-7817. [email protected]. Brain Injury Association, 105 North Alfred Street, Alexandria, VA 22314. (800) 444-6443 or (703) 236-6000. Fax: (703) 236-6001. . [email protected]. International Brain Injury Association, 1150 South Washington Street, Suite 210, Alexandria, VA 22314. (703) 683-8400. Fax: (703) 683-8996. . [email protected]. National Center for Injury Prevention and Control, Centers for Disease Control and Prevention, Mailstop F41, 4770 Buford Highway NE, Atlanta, GA 30341-3724. (770) 488-4031. Fax: (770) 488-4338.

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Studies of concussion in contact sports have shown that the risk of sustaining a second concussion is even greater than for the first, if the person continues to engage in the sport.

Consciousness, levels of

els of consciousness that have been studied extensively by psychologists. A few of them are described below.

. [email protected]. OTHER

American Academy of Family Physicians. . Head Injury Hotline. . Pashby Sport Concussion Safety. . University of California Los Angeles. . University of Missouri Health Center. .

L. Fleming Fallon, Jr., MD, PhD, DrPH

Confidentiality see Patient confidentiality Consciousness disorders see Coma

Consciousness, levels of Definition The everyday meaning of the word “consciousness” corresponds fairly closely to how most psychologists use the term. To be conscious is to be aware.

Perhaps the most frequent and conspicuous altered state of consciousness is experienced during sleep. Sleep is typically studied by means of an electroencephalograph. It produces a visual record (called an EEG) of the changes in electrical activity in the brain that occur during sleep. Changes in muscle activity and eye movements are also monitored. There are four major stages of sleep that are distinguished from one another on the basis of the electrical activity associated with each. There is also a distinctive fifth stage, known as REM (rapid eye movement) sleep. During this phase the brain’s electrical activity is similar to that of the waking state. The sleeper’s eyes dart about rapidly, even though the lids remain closed. Apart from the occasional twitch, there is a total suppression of muscle movement. The sleeper is essentially paralyzed. Because the brain’s motor cortex is active during this stage, REM sleep is sometimes referred to as “paradoxical sleep.” There is considerable internal activity, but an external calmness. REM sleep is the stage during which almost all dreaming occurs. REM sleep is usually accompanied by genital arousal in both males and females, although such arousal is unrelated to dream content. Regardless of the stage of sleep, there is no evidence that any substantive learning can take place during sleep. Despite extravagant claims, listening to a foreign language while sleeping is not going to make someone bilingual. Hypnosis

Description Most of the time, we are aware of whatever activity happens to be at the center of our current attentional focus. For example, in order to read this sentence the readers need to focus their attention on the appropriate line on the page, and concentrate on extracting meaning from what they are reading. Such conscious attention is, however, very selective. Research has demonstrated that a great deal of our mental activity is performed outside of conscious awareness. Consciousness is like the tip of an iceberg. It allows us to exert purposeful control over our current activities, and to communicate our mental states to others. We selectively attend to only a small fraction of the stimulation to which we are constantly exposed. We ignore many sources of external information, but can be made instantly aware of them. Upon reflection, it is obvious that we are operating at various levels of consciousness throughout the day. Do students daydream in class, and later wonder what the teacher said? When people brush their teeth, are they thinking about how clean they are getting them? There are a variety of states or lev572

Sleep

Most of us have seen Hollywood movies in which a hypnotist puts somebody in a trance and then ostensibly induces them to perform silly and sometimes dangerous activities. There are reports of criminal investigations having been assisted by witnesses whose memories have been hypnotically enhanced. “Age regression” demonstrations show hypnotized subjects apparently reliving experiences from their childhood. Are these memories accurate? Does hypnotism produce an altered state of consciousness? Can hypnosis cause people to act against their will? There are two competing explanations of what goes on during hypnosis. The social-cognitive approach views hypnosis as a social phenomenon. According to this perspective, hypnosis is not a unique physiological state and the behaviors produced by hypnosis can also be produced by other means. Hypnotized people are simply in a heightened state of suggestibility. Most people know what is supposed to happen during a hypnosis session. If the hypnotist’s suggestions are believed to be irresistible,

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The dissociation approach views hypnosis as a procedure that produces a split between two basic functions of consciousness—the executive function that we use for controlling our own behavior, and the monitoring function that is used for observing it. Hypnosis is assumed to disconnect these two components of consciousness, thereby preventing hypnotic experiences from entering normal consciousness. The two approaches are not necessarily contradictory. Certainly there is abundant evidence that social scripts play a role in many hypnotically induced behaviors. Numerous studies have shown that normal subjects who are asked to pretend to be hypnotized produce behaviors that are indistinguishable from those of hypnotized subjects. In another study, hypnotized subjects were given what they were told was a blank piece of paper. In reality, the number 8 was written on it. After hypnosis, those who reported that the paper was blank were told that only fakers would say that. They were then asked to draw what had been on the paper. Almost all drew the number 8. As far as hypnotically enhanced memories are concerned, such testimony is rarely admissible in court. The problem is that hypnotically revived memories often combine fact with fiction. Under hypnosis, people are more likely to use their imagination to construct or retrieve their recollections. Consequently, there is a danger that people will confidently assert having a memory of something they never experienced. Hypnosis continues to be an active area of research. It is used in psychotherapy and is sometimes useful in alleviating chronic pain. Regardless of what the underlying mechanism might be, there is no evidence that hypnosis produces exceptional psychological feats or behaviors. Automatic and controlled processing It’s not easy for us to talk on the phone while simultaneously carrying on a conversation with somebody else in the same room. Such difficulty illustrates a fundamental principle of cognition, namely that our cognitive resources are limited. We simply do not have the mental wherewithal to focus on several different tasks at once. If so, how do we manage to execute two activities at the same time, for example reading the newspaper and listening to the radio? The answer is that there are two different levels of conscious control over our behavior. The first is referred to as “automatic processing” because it

requires relatively little conscious awareness, and makes little demand on limited attentional capacity. When a person drives a car while mentally reviewing the previous days’ events, he is demonstrating automatic processing. Automatic processing develops with practice as the component parts of the activity become well learned. “Controlled processing” refers to behaviors that require effortful and deliberate concentration. It requires substantial use of cognitive resources. Consequently tasks requiring controlled processing can usually only be performed one at a time. Automatic processing is rapid and effortless, but somewhat inflexible. Controlled processing is slower, effortful, but adaptable. This distinction between automatic and controlled processing is directly relevant to the current controversy about the use of cell phones while driving. There is good evidence to suggest that such behavior poses significant risks. For most adults, driving a car is a relatively automatic activity. For this reason, talking on the phone while driving may seem like a victimless crime. However, driving is not always automatic. When the unexpected happens, concentration is required. A driver in the midst of an animated conversation may not recognize an impending emergency and/or may not be able to respond with appropriate speed when it is recognized. Subliminal perception To what extent can we be influenced by stimuli whose presence we are not even aware of? There are numerous laboratory studies that show that individual words can be processed, even when presented so quickly that the viewer has no awareness of the word’s identity. There is also evidence that patients under general anesthesia can apparently remember information (i.e., words) presented while they are unconscious. But what about more extraordinary claims? Can we be induced to buy a product or change our behavior on the basis of images or directives that are presented outside of conscious awareness? In a word, no. Before changing one’s habitual response to a stimulus, one would have to be aware of perceiving it. There is no evidence to suggest that people initiate actions on the basis of subliminally presented stimuli. Resources BOOKS

Merikle, P. M., & Joordens, S. “Measuring unconscious influences.” In Scientific Approaches to Consciousness. Ed. by J. D. Cohen & J. W. Schooler. Mahwah NJ: Erlbaum, 1997.

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then people will comply with them. It’s not that people are being deliberately deceptive. Their behaviors are genuine enough but they reflect beliefs about hypnosis and the role of hypnotized subjects, rather than the skills of the hypnotist or an altered state of consciousness.

Contact lenses

PERIODICALS

Greenwald, A. W. “New look 3: Unconscious cognition reclaimed.” American Psychologist 47 (1992): 766-779. Moore, T. E. “Subliminal perception: facts and fallacies.” Skeptical Inquirer 16 (1992): 273-281.

Timothy E. Moore, PhD

People employed in certain occupations may be prohibited from wearing contact lenses, or may be required to wear safety eyewear over the contact lenses. Physicians and employers should be consulted for recommendations.

Description

Consumption see Tuberculosis

Ophthalmologists (M.D.s) or optometrists (O.D.s) dispense contact lenses. The prices for lenses vary for the different types. Some physicians offer a “global fee” to their patients that includes the contact lens fitting, lenses, and follow-up visits.

Contact lenses

Over 32 million people in the United States wear contact lenses. These lenses provide a field of view unobstructed by eyeglass frames. They do not fog-up or get splattered and are less noticeable than any eyeglass style. On the other hand, they take time to get accustomed to; require more measurements for fitting; require many follow-up visits to the eye doctor; can lead to complications such as infections and corneal damage (but only if not cared for properly or replaced as prescribed); and may not correct astigmatism as well as eye glasses.

Definition Contact lenses are small, light-weight plastic devices worn on the eye that correct refractive errors in vision. While they appear to be worn in direct contact with the cornea, they actually float on a layer of tears that separates them from the cornea.

Purpose Contact lenses correct or improve the vision of people with nearsightedness (myopia), farsightedness (hyperopia), presbyopia, and astigmatism. In recent years, some people also wear contact lenses not for medical reasons, but rather to change their eye color.

Precautions People allergic to certain plastics should not wear contact lenses manufactured from that type of material. Patients with dry eye or severe seasonal allergies may find contact lenses uncomfortable and may prefer eye glasses. A careful patient history needs to be taken by the physician or contact lens technician to make sure these problems are addressed. Eye care professionals should ensure that contact lens patients who have disposable or planned replacement lenses keep strictly to their replacement schedules. Contact lenses wear out over time and can damage patients’ eyes. Deposits also can build up on the lenses, leading to lid and eye infections. Patients who have lenses they can sleep in (extended wear lenses) also are advised not to keep their contact lenses in their eyes for longer periods than directed by their physician. Adherence to the schedules recommended by their physicians helps patients avoid infection and long-term damage to the cornea. 574

Originally, hard contact lenses were made of a material called PMMA. Although still available, it is rarely used because it does not allow oxygen to pass through the lens. The more common types of contact lenses are: • Rigid gas-permeable (RGP) daily-wear lenses are made of plastic that does not absorb water, but does allow oxygen to permeate from the atmosphere to the cornea. (This is important because the cornea has no blood supply and needs to acquire oxygen from the atmosphere through the film of tears that moves beneath the lens.) They must be removed and cleaned each night. • Rigid gas-permeable (RGP) extended-wear lenses are made from plastic that also does not absorb water and is more permeable to oxygen than the plastic used for daily-wear lenses. They can be worn for up to a week, then cleaned, and reinserted. • Daily wear soft lenses are made of plastic that is permeable to oxygen and absorbs water; therefore, they are soft and flexible. These lenses must be removed and cleaned each night, and they do not correct all vision problems. Many patients find it easier to become accustomed to soft lenses, but these lenses are more prone to ripping and do not last as long as rigid lenses. • Extended-wear soft lenses are highly permeable to oxygen, are flexible by virtue of their ability to absorb water, and can usually be worn for up to one week. They do not correct all vision problems.

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• One type of disposable soft lenses are worn for one day and then discarded by the patient. Doctors believe these lenses reduce the risk of infection due to poor cleaning habits or over-wearing lenses. They can be price prohibitive for some patients at $1 a day. • Planned-replacement soft lenses are daily wear lenses that are replaced on a regular schedule, most commonly every two weeks, monthly, or quarterly. They must also be cleaned. Soft contact lenses come in a variety of materials. High Dk materials provide high oxygen permeability and allow greater comfort for patients. Advances in toric contact lenses also allow individuals with astigmatism to achieve better visual correction from contact lenses with more comfort. There are also different kinds of RGP and soft multifocal contact lenses available. There are five basic designs and over one hundred brands that offer variations of these designs. The optics of bifocal contact lenses are improving dramatically, as baby boomers move into presbyopia and more research dollars are devoted to this area. Monovision, where one contact lens corrects for distance vision while the other corrects for near vision, also may be an option for presbyopic patients. However, monovision may affect depth perception and may not be appropriate for everyone. Contact lenses also come in a variety of tints. Soft contact lenses are available that can change eye color. Even though such lenses have no prescription, they must still be fitted and checked to ensure that an eye infection does not occur. People should never wear someone else’s contact lenses. This can lead to infection or damage to the eye.

Preparation Before contact lenses are prescribed, the patient’s eyes are examined by an optometrist or an ophthalmologist. Contact lens technicians, ophthalmic nurses, and ophthalmic technicians also may assist with the exam, although frequently their findings are verified by the physician. Eyeglass prescriptions, if necessary, are then given to patients. A separate contact lens-fitting exam is necessary if the patient wants contact lenses. This is sometimes performed by the doctor, but in many cases is completed by a contact lens technician. Before prescribing contact lenses, a technician performs an evaluation. He or she conducts a written and oral interview with the patient to determine if the patient

is a viable contact lens candidate. The technician then assesses the technical aspects of the patient’s ocular status, since good eye health is required to wear lenses. The patient’s palpebral aperture and visual iris diameter is measured to determine the appropriate diameter for the contact lens. The technician also tests the patient’s tear quantity. A poor tear film is a contraindication for contact lenses use. Using instrumentation and information gained from the patient’s eye exam, the technician determines what type of lens is best for the patient. For example, RGPs are commonly given to astigmatic patients because they provide clearer vision for these patients. The contact lens technician selects the lens material and design, then determines the best trial lens. Based on the patient’s experience with the trial lenses, the technician then determines the lens parameters. The physician reviews these findings to make the recommendation for the proper contact lenses. He or she ascertains the proper fit, and measures visual acuity and over-refraction to determine the proper lens prescription. Because a contact lens is an FDA-approved medical device placed directly onto the eye (unlike eye glasses), it cannot be issued until the eye’s proper health has been ascertained via a followup examination. Unlike eyeglass prescriptions, a contact lens prescription includes not only the prescription, but also the contact lens material, diameter, brand, and curvature. Before the patient is sent home with the lenses, the technician will give a detailed demonstration of inserting, removing, and cleaning the lenses. A written list of detailed instructions is usually dispensed with the lenses.

Aftercare The doctor and technician schedule several return visits for the patient to evaluate the lens fit and performance. At these visits, eye care professionals determine whether the lens design or material needs to be modified. Patients may be allergic to certain solutions that are used to clean or lubricate the lenses. For that reason, physicians instruct patients not to change solutions without prior approval. Contact lens wearers also are advised to seek immediate attention if they experience eye pain, a burning sensation, red eyes, intolerable sensitivity to light, cloudy vision, or an inability to keep the eyes open. To avoid infection, it is important for contact lens wearers to exactly follow the instructions for lens insertion, removal, and cleaning. Soft contact lens wearers should never use tap water to rinse their lenses or to make up solutions. All contact lens wearers should always carry a pair of glasses and a contact lens case with them,

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• Extended-wear disposable lenses are soft lenses worn continually for up to six days and then discarded, with no need for cleaning.

Contact lenses

worn as instructed and cared for properly. Dry eye and seasonal allergy symptoms may be exacerbated by wearing contact lenses.

KEY TERMS Astigmatism—A vision condition that occurs when the cornes is slightly irregular in shape. This irregularity prevents light from focusing properly on the retina. Cornea—The clear outer covering of the front of the eye. Index of refraction—A constant number for any material that is an indicator of the degree of the bending of the light caused by that material. Lens—A device that bends light waves. Permeable—Capable of allowing substances to pass through. Polycarbonate—A very strong type of plastic often used in safety glasses, sport glasses, and children’s eye glasses. Polycarbonate lenses have approximately 50 times the impact resistance of glass lenses. Polymer—A substance formed by joining smaller molecules. Examples of polymers include plastic, acrylic, cellulose acetate, cellulose propionate, nylon, etc. Presbyopia—A condition affecting people over the age of 40 where the system of accommodation that allows focusing of near objects fails to work because of age-related hardening of the lens of the eye. Retina—The inner, light-sensitive layer of the eye containing rods and cones; transforms the image it receives into electrical messages sent to the brain via the optic nerve. Ultraviolet (UV) light—Part of the electromagnetic spectrum with a wavelength just below that of visible light. It is damaging to living material, especially eyes and DNA.

in case the contact lenses have to be removed due to eye irritation.

Complications Wearing contact lenses increases the risk of corneal damage and eye infections, if the lenses are not properly cleaned, if the lenses are inserted or removed with dirty hands, or if the lenses are worn for a longer period of time than recommended. However, there is little increased risk of eye infection or damage if the lenses are 576

Results The normal expectation is that people will achieve 20/20 vision while wearing corrective lenses.

Health care team roles Nursing and allied health professionals play an important role in contact lens examination and fitting. With advances in technology, technicians now have duties that formerly only a physician performed. Contact lens technicians take the lead role in the contact lens fitting by recording the pertinent patient history, measuring the eye for the proper lens fit, and testing the tear quantity. Advanced and intermediate level ophthalmic technicians perform refractions and determine the patient’s depth perception. These professionals also may perform corneal topography (mapping). Some of these professionals seek certification through the American Board of Opticianry and the National Contact Lens Examiners or other organizations. These organizations offer seminars and testing that helps professionals keep current with technological advances. Physicians have become increasingly dependent on these technicians and assistants as managed care dictates they see more patients per day. By delegating these task to qualified personnel, the physicians can see more patients per day without jeopardizing patients’ ocular health. Patient education Technicians emphasize the importance of cleaning contact lenses and adhering to any planned replacement schedule. They stress that while patients may save money by wearing lenses longer or skimping on cleaning solution, these actions increase the risk of eye infections or damage. Younger patients also are cautioned that sharing colored contact lenses with others can lead to eye infections. The importance of inserting and removing contact lenses with clean hands also is emphasized to all contact lens wearers. Training Optometrists and ophthalmologists receive training in optometry schools or medical residencies for these procedures. Contact lens technicians may complete special training courses or be trained by the physician.

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Continuous ambulatory electrocardiography see Ambulatory electrocardiography

BOOKS

Silbert, Joel, ed. Anterior Segment Complications of Contact Lens Wear. New York: Churchill Livingstone, 1994. Zinn, Walter J., and Herbert Solomon. Complete Guide to Eyecare, Eyeglasses & Contact Lenses. 4th ed. Hollywood, FL: Lifetime Books, 1997.

Continuous passive motion device

PERIODICALS

Gromacki, Susan. “Satisfying Baby Boomers and Their Boomlets with Contact Lenses.” Optometric Management 35(October 2000): 52-56. ORGANIZATIONS

American Academy of Ophthalmology. P.O. Box 7424, San Francisco, CA 94120-7424. (415) 561-8500. . American Optometric Association. 2420 North Lindbergh Boulevard, St. Louis, MO 63141. (800) 365-2219. . Contact Lens Council. 8201 Corporate Drive, Suite 850, Landover, MD 20785. (800) 884-4CLC. . Optician Association of America. 10341 Democracy Lane, Fairfax, VA 22030-2521. (800) 443-8997. <www.opticians.org>. OTHER

Hall, Brenda, and Stephen Jones. “Clinical Performance of a Monthly Lens and Patient Comfort.” Contact Lens Spectrum 5(December 2000). . Jameson, Mary. “Education: The Key to Delegation.” Contact Lens Spectrum (1996). (September 1996). “Lenses Through Time: A Fascinating Historical Look at Eyeglass Trivia.” . Polycarbonate Lens Council. “New Developments in Polycarbonate.” . “Polymer Scientists Engineer Better Remedies.” . Pustareri, Thomas J. “Contact Lenses for Today’s Lifestyles.” Ophthalmology Management (2001). (January 2001). West, Walter D. “Delegating Technical Tasks to Your Technicians.” Contact Lens Spectrum (1997). (October 1997).

Mary Bekker

Definition Continuous passive motion (CPM) is a modality of postoperative treatment intended to assist recovery following joint surgery or injuries of upper or lower extremities. CPM equipment covers a range of mechanical devices designed to move the patient’s joint or extremity without the use of the patient’s muscles through a prescribed range of motion over extended periods of time. These devices were first introduced in the 1980s by Dr. Robert Salter, an orthopedic surgeon.

Purpose CPM is used to reduce the adverse effects of trauma or immobilization following surgery. In physiological terms, synovial fluid is diffused without hindering tissue repair; the joint receives nutrition, the flow of venous blood is increased, and the cartilage is prevented from deteriorating. From a clinical perspective, joint swelling (edema) is decreased, range of motion (ROM) is maintained, tissue repair is accelerated, and the patient experiences less pain. CPM devices are used as alternatives and adjuncts to conventional physical therapy following surgery or injury. CPM devices may also be used in bedridden surgical patients to reduce the incidence of deep vein thrombosis, to treat abnormal muscle shortening that occurs due to prolonged immobilization, and in patients with burns or joint sepsis.

Description Typical CPM devices consist of a limb support resembling a splint or brace, a motor drive, and a control unit. CPM devices for the lower limb are used primarily after total knee replacement and ligament repair to provide flexion and extension of the joint. Configurations for exercising the hip, ankle, or toes are also available. Larger lowerlimb CPM devices are typically designed to rest directly on the patient’s bed; some are designed with the limb support suspended from an overhead traction frame. Upperlimb CPM devices are available mounted on stands that

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Resources

Continuous passive motion device

discomfort, pain, and chafing. Most manufacturers offer accessories or configurations to adjust for variations in patient limb size.

KEY TERMS Edema—An abnormal buildup of fluid in the tissues or joint capsules of the body, causing swelling of the involved area. Edema is a common cause of stiffness in the joints following injury or surgery. Range of motion (ROM)—The extent to which a joint can be moved. Sepsis—A local or generalized invasion of the body by disease microoganisms or their toxins. Synovial fluid—A clear, viscous fluid secreted by membranes surrounding the joints. Synovial fluid helps to lubricate the joints. Thrombosis—Coagulation or clotting of the blood inside a vein.

can be wheeled to the patient’s bedside, in tabletop configurations, and as portable battery-powered units. The motor drive of a CPM device is connected by a shaft to the limb support. The control unit contains adjustments for speed, motor reversal, and such range of motion parameters as degree of rotation, flexion, or extension. Some units are computerized and have remote control capabilities. Other units pause the continuous motion to allow for some active contraction by the patient or for the application of neuromuscular electrical stimulation.

Operation

CPM devices are low-maintenance equipment since they are designed for continuous use. They do, however, require frequent checks for wear of moving parts and malfunctioning.

Health care team roles The use of a CPM device is most often prescribed by a physician or orthopedic surgeon, and overseen by nursing, physical therapy, or rehabilitation staff.

Training Manufacturers of CPM devices provide training for clinical staff. In addition, detailed user manuals are provided for reference during operation and maintenance. Patients using CPM devices at home should be given instructions regarding proper use of the device. Resources BOOKS

Pierson, F. Principles and Techniques of Patient Care, 2nd ed. Philadelphia: W. B. Saunders Co., 1999. “Rehabilitation Treatment.” The Merck Manual of Diagnosis and Therapy, 17th edition, ed. Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 1999. PERIODICALS

The limb requiring CPM is strapped into the device’s support. The range of motion parameters, speed, cycling time, and duration are then set. Most CPM devices have mechanical safety releases, resistance sensors, and/or automatic shut-offs for safety purposes. The most advanced CPM devices use microprocessors and load cells to measure resistance and automatically adjust parameters. Hospital patients may have 24-hour CPM operation. Patients using CPM at home may use the devices from four to six hours daily in hour-long sessions. Patients on CPM devices should be monitored for problems with limb positioning and interference with device operation. For instance, bedsheets may become tangled in the device, or the patient’s limb may become trapped, resulting in injury. Patients with urinary incontinence should be monitored carefully during CPM, because body fluids are an electrical hazard. All patients on CPM devices should be monitored for unnecessary 578

Maintenance

Gassner R., et al. “Cytokine-induced nitric oxide production of joint cartilage cells in continuous passive movement. Anti-inflammatory effect of continuous passive movement on chondrocytes: in vitro study.” Mund Kiefer Gesichtschirurgie 4 (September 2000), Supp. 2: S479S484. Hazard, Rowland G. “Relief from an Aching Back: Alternative Treatments.” Orthopedic Technology Review 2, no. 11 (December 2000). . Johnson, C. “Continuous Passive Motion: Technology Advances.”Orthopedic Technology Review 2, no. 4 (April 2000). . O’Driscoll, Shawn W., and Nicholas J. Giori. “Continuous Passive Motion (CPM): Theory and Principles of Clinical Application.” Journal of Rehabilitation Research and Development 37, no. 2 (March/April 2000). .

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ORGANIZATIONS

American Academy of Orthopaedic Surgeons. 6300 North River Road, Rosemont, IL 60018-4262. (847) 823-7186. . American Academy of Physical Medicine and Rehabilitation. One IBM Plaza, Suite 2500, Chicago, IL 60611-3604. (313) 464-9700. . American Physical Therapy Association. 1111 North Fairfax Street, Alexandria, VA 22314-1488. (703) 684-2782. .

Jennifer E. Sisk, M.A.

Continuous positive airway pressure see Ventilation assistance

• Effectiveness. If this method is used as directed, what is the likelihood that it will fail to prevent a pregnancy? • Ease of use. Is this method easy or difficult to use correctly? • Timing. Is this method effective the first time it is used or put in place, or is it necessary to use it for a while before it will be effective? • Frequency. How frequently will the individual engage in sexual intercourse? • Temporary versus permanent. Does this method provide temporary birth control, or is it considered a permanent method? If permanent, could it be reversed in the future? • Ethics. Is this method acceptable within the context of the individual’s religious or ethical beliefs? • Benefits. Other than its ability to provide contraception, does its use have any benefits to the individual’s health? • Postpartum. How soon after pregnancy can this method of birth control be used? Is it safe while breastfeeding? Does fertility return?

Contraception Definition Contraception is the use of a method, device, or medication to prevent pregnancy by interfering with ovulation, fertilization, and/or implantation. Another term for contraception is birth control.

Purpose The purpose of contraception is to allow individuals to engage in sexual intercourse without it resulting in pregnancy.

Precautions There are many methods of contraception. Factors to consider in choosing a method include: • Safety. What are the risks of using this method? Can its use result in any damage to the female or male reproductive tract? Is its use associated with a higher risk of certain cancers? What are the consequences of its longterm use? Does its use affect future fertility? • Access. Is a prescription needed to gain access to this method? • Cost. How expensive is this method? • Is the cost of this method covered by my health insurance?

Description During a woman’s reproductive years, from its onset at menarche to its termination at menopause, an egg, or ovum, is released each month from one of her two ovaries, and it travels through the adjacent fallopian tube and into the uterus. If the egg is fertilized, it implants into the lining of the uterus and undergoes changes that eventually lead to the development of a fetus. In tandem with the release of the egg, the lining of the uterus, called the endometrium, undergoes changes that will enable it to support a pregnancy should the released egg become fertilized. When the egg is not fertilized, the endometrium that has built up in preparation for the pregnancy is shed. This tissue and the non-fertilized egg leave the uterus through the cervix and exit the body through the vagina in the form of menstrual secretions. Birth control methods vary in targeting different aspects of this monthly process. The primary methods of birth control are hormonal, barrier, spermicides, intrauterine devices (IUDs), surgical, and periodic abstinence. In choosing a form of birth control it is important to understand how each method works, as well as its associated risks, benefits, and side effects. • Hormonal. Hormonal methods of birth control include oral birth control pills. Birth control pills, sometimes called the Pill, come in two forms: combination, containing both estrogen and progestin, and progestin only, referred to as the mini-pill. Both forms suppress ovula-

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Worland, Richard L., et al. “Home Continuous Passive Motion Machine versus Professional Physical Therapy Following Total Knee Replacement.” Journal of Arthroplasty 13, no. 7 (October 1998): 784-787.

Contraception Various contraceptives. (Photograph by Michael Keller. The Stock Market. Reproduced by permission.)

tion, thicken cervical mucus, and prevent implantation. Both require prescriptions. The hormone doses in the pills are kept as low as possible, while still being effective as a contraceptive. For this reason it is extremely important that they are taken on a daily basis. Skipping doses can put a woman at risk of becoming pregnant and she should supplement the pill with the use of a barrier method. In the first month a woman begins oral contraception, she may not be fully protected, so a barrier method should be used as a back-up. In a survey conducted by Planned Parenthood, only 28% of women take the Pill correctly, and only 42% actually take it on a daily basis. Because of the hormones used, women who suffer from migraines, diabetes, have had breast or uterine cancer, or who smoke, may need to choose another method. Women should always mention their use of birth control pills to their primary health care provider, as some medications prescribed for other conditions may interact with oral contraceptives. Use of the Pill can make other medications less effective, or exaggerate their effectiveness. Serious potential side effects of the combined pill include the formation of blood clots, myocardial infarction, and stroke. Because oral contraceptives suppress ovulation, their use can decrease a woman’s risk of getting ovarian cancer. Some women find that their oral contraceptive improves skin problems. Hormonal contraception can be used by breastfeeding mothers, but usually not until the milk supply has been well established. In the case of the mini-pill, it can usually be started earlier, as it does not decrease milk volume. The combination pill can decrease the volume and lower the protein content of the breast milk. Oral contraceptives do not protect against any sexually transmitted diseases, so a condom should be used for that purpose in addition to taking the Pill. 580

• Depo-Provera and Lunelle are two brands of contraception given by injection. Depo-Provera is the trade name for the contraceptive depot medroxyprogesterone acetate (DMPA). Lunelle is a combination of estrogen and progesterone. They provide protection for about 12 weeks. They may be a good choice for women who have trouble remembering to take the Pill on a daily basis, for those for whom privacy of using a contraceptive is important, and for those engaging frequently in sexual intercourse. They work by suppressing ovulation, fertilization, and implantation. This method may not be a good choice for women who have had breast cancer, blood clots, heart attack or stroke, major depression, high cholesterol or blood pressure, diabetes, migraines, or abnormal results on liver function tests. If given within the first five days of a woman’s menstrual cycle, they are considered protective against pregnancy during the first month of use. Side effects include irregular vaginal bleeding, loss of menstruation after one year of use, nausea, breast tenderness, depression, weight gain, vaginal dryness, and increased facial hair. After a woman stops using DMPA, it may take 18 months before a woman is able to become pregnant. They do not provide protection against sexually transmitted disease. • Barrier methods. Barrier methods work by preventing the sperm from reaching and fertilizing the egg. Male and female condoms, diaphragms, and cervical caps work by creating a membrane through which the sperm cannot travel. Spermicides and the contraceptive sponge contain chemicals that decrease the sperm’s ability to travel towards the egg. Condoms, diaphragms and caps should be used in conjunction with spermicides to increase overall effectiveness. Spermicides come in several forms: foam, cream, gel, sponge, and vaginal suppository. Condoms provide the most protection against sexually transmitted diseases. The diaphragm and cervical cap require fitting by a health care practitioner and a prescription. The other barrier methods are available without a prescription. Barrier methods are used at the time of sexual intercourse. They are less effective than hormonal methods of contraception. Individuals who have latex allergies, or who have had an allergic reaction to bananas, avocados or chestnuts, should speak with their health care provider before trying a condom, diaphragm, or cap. The allergic reaction may be mild, with symptoms such as runny nose, itching or a rash, or may be severe, resulting in anaphylaxis in which breathing can be obstructed by swelling. Early signs of anaphylaxis include rash, flushed skin, dizziness, or a tingling sensation. Medical help should be sought right away. A condition called toxic shock syndrome (TSS) has been

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• Intrauterine devices (IUDs). The IUD is a small, plastic device that is inserted by a health care practitioner into a woman’s uterus. While in place it seems to prevent implantation by altering the endometrium. It is also thought that the consistency of the cervical mucus is changed, affecting sperm motility, preventing fertilization. It is easy to have it inserted and can be removed at any time by a practitioner. One brand contains copper and can be left in place for ten years, another contains progestin and needs to be replaced after one year. IUDs have a string attached at one end that hangs into the vagina. This not only assists in its ultimate removal, but also allows a woman to check periodically that it is still in its proper place. If the string appears to be shorter or longer than when inserted, the woman should have its placement checked by her practitioner. The string does not function as a wick, so it does not draw fluid up into the uterus. The IUD is not a good choice for a woman with a sexually transmitted disease or a history of pelvic inflammatory disease (PID). It is usually inserted during a menstrual period by a health care provider. Some practitioners may require the woman to have a negative pregnancy test done just prior to insertion. Some women may experience spotting between periods, or heavier periods with more cramping while using the copper IUD. Because the IUD was inserted through the cervix, a woman may be at a somewhat higher risk of infection, until the cervix closes tightly again (around three weeks). Two rare side effects can occur: the IUD imbedding into the uterus and the migration of the IUD into the abdominal cavity, requiring surgery to remove it. There is also a higher risk of pelvic inflammatory disease and infection of the reproductive organs, which could result in sterility, or require removal of the uterus. IUDs do not protect against sexually transmitted diseases. • Surgical sterilization. Individuals who have completed their childbearing may choose a permanent form of contraception: surgical sterilization. In the male, this is known as a vasectomy. The vasectomy blocks the sperm from mixing with the seminal fluid. Sperm continue to be produced, but are reabsorbed by the body. Vasectomy does not affect the man’s ability to have an erection, to ejaculate, nor does it affect the production

of male hormones. It is not effective immediately, as some sperm are still present in the unblocked portion of the tubes. A sperm analysis needs to be done to check for the presence of sperm. Until this process is completed, the man and his partner need to use another form of contraception to prevent a pregnancy. For the woman sterilization is known as tubal ligation, tubal sterilization, or having one’s tubes tied. In tubal ligation the fallopian tubes are cut or blocked, preventing the egg from passing through towards the uterus. The ovum will continue to be released each month, but will be reabsorbed by the body after being blocked in the fallopian tube. Menstrual cycles continue as usual, and hormone production is not affected. It is effective immediately. Surgical sterilization is considered permanent and irreversible, although some individuals have been successful at having the process reversed. In a small percentage of cases, the surgery is not successful and the woman becomes pregnant. Both surgeries are done through small incisions, and on an outpatient basis. This form of birth control is not recommended for very young individuals, or those who have not yet had families. Because they involve surgery, complications associated with surgery, such as infection, bleeding, or a reaction to the anesthesia, can occur. Tubal ligation and vasectomy do not provide protection against sexually transmitted diseases. For the individual undergoing the sterilization, the surgery must be voluntary. • Periodic abstinence. Periodic abstinence, or fertility awareness, is a technique of birth control based on abstaining from sexual intercourse on those days when a woman might become pregnant. The same techniques can be used by couples trying to conceive, by identifying the days when a woman is most likely to become pregnant. Using periodic abstinence often requires taking a class to learn the techniques used. The techniques employed are basal body temperature (BBT), cervical mucus identification, and a calendar method. The most effective use is the combination of all three techniques to predict which are the safe and which are the unsafe days for intercourse. Couples may then use this information to abstain from intercourse or use a barrier form of contraception on unsafe days. The calendar method keeps track of a woman’s menstrual cycle. The cervical mucus identification method teaches the woman the differences in the vaginal secretions at various times of her cycle, which helps to identify when ovulation is most likely taking place. The BBT method charts the first temperature of the morning. Just prior to ovulation there is a slight dip in the basal temperature, followed by a slight temperature elevation when the woman ovulates. This method requires the use of a special thermometer that is more finely calibrated than one used

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occasionally reported with diaphragm use. Signs of TSS include high fever, vomiting, diarrhea, flu-like symptoms such as aching joints or sore throat, dizziness, and rash. The diaphragm should be removed right away and the woman should call her practitioner. Diaphragm and cervical caps need to be refitted with weight gain or loss, and after a few years need to be replaced because the rubber begins to tear or decompose, rendering them ineffective.

Contraception

Preparation and aftercare

KEY TERMS Anaphylaxis—A serious allergic response that can be fatal if not treated. In anaphylaxis the individual undergoes a hypersensitive reaction to a substance. Initial signs may include itching, wheezing, coughing and shortness of breath. If left untreated, the individual’s respiratory passages may begin to swell, blocking the flow of air. Anaphylaxis is a medical emergency, and can result in death. Ectopic pregnancy—A pregnancy that implants outside of the uterus, most commonly in a fallopian tube. An ectopic pregnancy can cause the fallopian tube to rupture, causing severe internal bleeding and pain. A woman with an ectopic pregnancy must seek medical care right away. Triage—To organize or sort patients according to the degree or severity of their condition. Vaginal suppository—Medication that is bulletshaped, and is inserted into the vagina, where it melts and is absorbed.

for checking the presence of a fever. This combination of techniques requires that a woman’s menstrual cycles are quite regular, that she has the ability to keep careful records, and that she and her partner(s) can abstain from intercourse or use a barrier method for much of the month. The readings are not accurate when the woman is sick, and may be affected by certain medications. • Post-coital contraception. No method of contraception is 100% effective. If birth control was not used or if it failed during intercourse, or in the event of rape, the possibility of pregnancy exists. Some reproductive health centers and physicians offer emergency contraception that is used within 72 hours of unprotected sex, failed contraception, or rape. It involves taking oral doses of progestin or an estrogen-progestin combination, similar to that used in oral contraceptives. Some women experience dizziness or nausea and vomiting following the treatment. If a woman has had a positive pregnancy test and wishes to terminate the pregnancy, she may choose between surgical or medical abortion. Medical abortion involves the use of hormonal therapy, referred to in the United States as RU486. Planned Parenthood offers more information about these options through the telephone number listed below in Resources, and on their web site. 582

Preparation for the different contraceptive choices varies. Oral contraceptives need to be taken on a daily basis, and require a prescription, a thorough health history, and a visit to a health care provider. Injected hormonal contraception requires periodic visits for the injection. Barrier methods must be used every time there is intercourse, these methods differ in how long they may remain in the vagina, and whether ejaculation can be repeated without the use of a new barrier device. The IUD requires insertion and removal by a practitioner. Surgical sterilization is usually done in an outpatient facility. Patients will be given post-surgical instructions to follow, including which symptoms necessitate contacting their physician. Practitioners will want to be sure that this irreversible decision was made carefully and competently and that the patients are aware that there is a failure rate. Some follow-up care may be necessary. Periodic abstinence requires careful monitoring of a woman’s fertility and the ability to abstain from intercourse or use barrier methods on unsafe days.

Complications Complications of contraception vary according to the method used. Hormonal complications involve a response to the particular hormone and dosage used. Bleeding between periods or difficulty regaining regular menstruation or fertility following their discontinuance may occur. Oral contraceptives can interfere with the effectiveness of other medications. Women over 35 who smoke should not use oral contraceptives, as smoking places them at greater risk of heart attack or stroke. Barrier methods may produce a local reaction to the spermicide use. Spermicide packages should be checked for an expiration date. If used after expiration, they are not reliable. Diaphragm use is associated with the risk of toxic shock syndrome. Individuals unaware of their latex allergy may have a small allergic reaction, or could go into anaphylaxis. IUDs do have a serious but rare risk of puncturing the uterine wall, and also carry a risk of pelvic inflammatory disease with potential complications such as sterility if untreated. IUDs may be expelled from the uterus, so it is important to periodically check for the string that is attached to it. Women who become pregnant while using the IUD are at greater risk of an ectopic pregnancy. Surgical sterilization involves the risks of surgery, such as bleeding, or infection due to the anesthesia used. Vasectomy is only effective once all stored sperm has been ejaculated. Fertility awareness carries a higher risk of pregnancy, and if hands are not washed prior to checking the cervical mucus, bacteria could be introduced into the vagina and spread.

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The end result of effective contraception is prevention of pregnancy. Individuals choosing contraception must weigh the risks of the method against its ease of correct use and its success rate of preventing pregnancy. Hormonal methods are usually at least 95% effective. Barrier methods range from 60–80% effective. The IUD is considered 99% effective. Sterilization is about 99% effective. Fertility awareness is about 85% effective. Of course, effectiveness depends on consistent, careful use.

Health care team roles Pharmacists are involved in filling the prescriptions of various forms of birth control. Having prescriptions filled at the same pharmacy provides protection against the possibility of interactions between different medications. Nurses provide education to patients on the various forms of birth control the individual is considering. Nurses are also involved in the care of patients seeking surgical contraception, as well as triaging calls from patients when they call their health care providers with questions and concerns about possible side effects. If a patient suspects an IUD has been dislodged, a radiology technician may take an imaging scan to locate the IUD. Resources BOOKS

Ammer, Christine. The New A to Z of Women’s Health, 4th Edition. New York: Facts on File, Inc., 2000. Knowles, John and Marcia Ringel. Planned Parenthood. All About Birth Control: The Complete Guide. New York: Three Rivers Press, 1998. Spencer, Paula. Parenting: Guide to Pregnancy and Childbirth. New York: Ballantine Books, 1998. PERIODICALS

Croxatto H. B. “Progestin implants.”Steroids. (October/November 2000): 681-685. Massai, R., S. Diaz, T. Jackaniez, and H. B. Croxatto. “Vaginal rings for contraception in lactating women.”Steroids. (October/November 2000): 703-707. Shulman, L. P. “Contraception 2000: Lunelle, an injectable combination contraceptive option.”Journal Womens Health Gender Based Medicine (September 2000): 725729.

Conversion disorder see Somatoform disorders

Cooling treatments Definition Cooling or cold treatments are used to decrease pain, minimize swelling, and slow the inflammatory response secondary to injury (usually acute). Cold treatments slow the local physiological activity of the tissues, decrease nerve transmission, and decrease muscle guarding and spasm, thus minimizing potential damage to tissues when injury has occurred. Another name for cold or cooling treatments is cryotherapy.

Purpose The most common reasons for cooling treatments are sprains, bruises, burns, eye injuries, and muscle spasms. Cooling treatments are used to help alleviate the resulting swelling, pain, and discoloration of the skin. They also help to cool the body if fever or hyperthermia exists. The body can sustain temperatures up to 104°F (40°C) with relative safety, however temperatures above 104°F (40°C) are more likely to cause damage to the brain, muscles, blood, and kidneys. Cooling treatments slow chemical reactions within the body. For this reason, cooling tissues below normal body temperature (98.6°F [37°C]) can prevent injury from inadequate oxygen or nutrition. Interestingly, cold water drowning victims suffering from hypothermia (cooling of the body below its normal temperature) have been successfully resuscitated after long periods underwater without medical complications because of this effect. For the past 40 years, heart surgeons have been experimenting with hypothermia to protect tissues from lack of blood circulation during an operation. Neurosurgeons are also working with hypothermia to protect the very sensitive brain tissues during periods of absent or reduced blood flow. However, the major use for cooling treatments is to alleviate pain and swelling after acute injury.

ORGANIZATIONS

Planned Parenthood Federation of America. 810 Seventh Ave. New York, NY 10019. (212) 541-7800. (800) 230-PLAN (7526). (888) NOT-2-LATE.

Esther Csapo Rastegari, R.N., B.S.N., Ed.M.

Precautions Before using cryotherapy nurses and other allied health team members need to make sure patients do not have sensation deficits or circulatory problems.

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Results

Cooling treatments

Preparation Cooling treatments are prepared a number of ways: • Ice bags: Plastic bags filled with ice applied over a towel for 20 minutes. • Ice massage: Usually performed with a Styrofoam cup filled with water that has been frozen. Treatment lasts until skin is numb. • Cryo-compression units: These units provide both cooling and mechanical compression of the affected area. A large pad or cuff is placed around the area. • Vapocoolant sprays: An aerosol spray is usually used for treating trigger points (local muscular spasm with high sensitivity). • Gel packs: Reusable gel packs are stored in a freezer until gel is completely frozen. Use with caution and less time than ice bags. • Immersion: Usually, ice is frozen and placed in a bib of water, providing a very complete cold treatment. They should be used for about 15–20 minutes.

A technician uses a hose that blows cold, dry air directly onto goalkeeper Carlos Roa’s injury. (Photograph by Oscar Pipkin. AP/Wide World Photo. Reproduced by permission.)

Aftercare

Description There are many types of cooling treatments that offer relief of pain and decrease inflammation during acute injury: • Ice bags: For application of deep cold. A very simple and inexpensive method. • Ice massage: Simply rubbing ice on the skin, usually in a circular motion. • Cryo-compression units: Usually a pad that fits around the affected area. Tubes or lines provide constant (cold) fluid under pressure from a mechanical device. • Vapocoolant sprays: Either Ethel chloride or Fluoromethane type sprays that provide local pain relief and decreased muscle spasm. • Gel packs: Packs are stored in the freezer until needed, and they contain a gel that can be refrozen any time. • Immersion: Placing the limb, area, or joint in a bin of ice water. • Cold bags (chemical): Bags with separate pouches containing chemicals within. The pouches are broken by squeezing the entire bag, the chemicals mix by means of an endothermic chemical reaction, and yield cold. 584

• Cold bags (chemical): Kept at room temperature until needed with no need for freezing. They do not provide intense cold; more of a cooling treatment. Can be used for up to 30 minutes.

Nurses and other allied health professionals should realize that there are three to four stages of cold sensation perceived by the patient: The first is the feeling of cold followed by (second stage) the patient feeling a burning sensation. The third stage is a dull aching over the area and finally (fourth stage) the patient reports feeling numbness. Removal of the cold treatment occurs when the skin feels numb. Sometimes the dull aching, or third stage, is not felt.

Complications Nurses and allied health professionals also need to be aware that in instances where vaso constriction is contraindicated, cryotherapy should not be used. Furthermore, some patients may be oversensitive to cold and have an allergic type reaction. Excessive duration of cooling treatments may cause sensitivity.

Results Cold treatments are usually the optimum treatment for acute injuries such as strains, sprains, bruises, and trigger points. Cryotherapy is one of the easiest and

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Health care team roles Nurses and other allied health team members should use the RICE principle when treating an acute injury: rest the area, ice the area, apply compression, and elevate the area. Resources Books Cameron, M. H. Physical Agents in Rehabilitation. W. B. Saunders, 1999. PERIODICALS

Barone, F. C., G. Z. Feuerstein, and R. F. White. “Brain Cooling During Transient Focal Ischemia Provides Complete Neuroprotection.” Neuroscience & Biobehavioral Reviews 21 (Jan. 1997): 31-44. Imamaki M., T. Hirayama, and M. Nakajima. “SeparateHypothermia Retrograde Cerebral Perfusion.” Annals of Thoracic Surgery 63 (Feb. 1997): 54754-54758. OTHER

“Cryotherapy, Cold Therapy.” Jointhealing.com. 2000. . “Physical Rehabilitation in Managing Pain.” International Association for the Study of Pain. . Stamford B. “Giving Injuries the Cold Treatment.” The Physician and Sports Medicine Online. 1996. .

Mark Damian Rossi, Ph.D, P.T., C.S.C.S.

Coombs’ test see Antiglobin tests Coordination tests see Balance and coordination tests COPD see Emphysema

Copper Description Copper is an essential mineral that plays an important role in iron absorption and transport. It is considered a trace mineral because it is needed in very small amounts. Only 70–80 mg of copper are found in the body of a normal healthy person. Even though the body needs

very little of it, copper is an important nutrient that holds many vital functions in the body. Copper is essential for normal development of the body because it: • Participates in a wide variety of important enzymatic reactions in the body. • Is a component of or a cofactor for approximately 50 different enzymes. These enzymes need copper to function properly. • Is essential for iron absorption and transport. Iron is needed to make hemoglobin, a main component of red blood cells. Therefore, copper deficiency is often linked to iron-deficiency anemia. • Is required to build elastin and collagen, which are an important components of bones and connective tissues. Therefore, copper is believed to protect the bones and joints against degeneration and osteoporosis. • Is required for melanin production. People with copper deficiency may have pale skin and hair. • Is a key mineral for the immune system. Copper promotes wound healing. Studies show that premature infants or children with genetic copper defects are at high risk of getting infections and would significantly improve with copper supplementation. • Attacks free radicals. Copper is a strong antioxidant. It works by attaching itself to the enzyme Superoxide dismutase (SOD). Copper also binds to a protein to form ceruloplasmin, which is an antioxidant. • Helps the body produce energy. Copper participates in many oxidative reactions that break down fats in fat tissue to produce much needed energy. Copper deficiency has been associated with high cholesterol levels. • Is necessary for normal functioning of insulin. Copper deficiency is also associated with poor blood glucose control. • Is needed for normal functioning of the cardiovascular system. • Protects the structure and function of the nervous system, including the brain. Copper protects nerve fiber by maintaining myelin, the insulating sheath that surrounds nerve cells. It also aids the transmission of nerve signals in the brains.

General use Copper supplements may be beneficial in treating or preventing copper deficiency. Copper deficiency used to be relatively rare because the body requires so little of it, only about 2 mg per day. In addition, it is available naturally in a variety of foods such as whole grains, shellfish,

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effective treatments in decreasing pain, swelling, and muscle spasms.

Copper

nuts, beans, and leafy vegetables. Additional sources of copper are the copper water pipes that run through homes or the copper cookware in the kitchen. These sources leach copper into the water we drink and the food we eat. The level of copper in drinking water is sometimes so high that it becomes a public concern. However, scientists now realize that copper deficiency, especially borderline cases, is more common than once thought. Copper deficiency is currently on the rise due to a decrease of whole foods in the diet and high consumption of fatty and processed foods. Besides dietary causes, certain diseases or conditions may reduce copper absorption, transport, or increase its requirements, resulting in abnormally low copper blood levels. Increased copper intake through diet or supplementation may be necessary in the following conditions: • premature infants fed only cow’s milk • pregnant women • malnutrition • celiac disease, sprue, cystic fibrosis, or short-bowel syndrome (These diseases cause poor absorption of dietary copper.) • kidney disease • high consumption of zinc or iron (These minerals interfere with copper absorption.) • highly processed foods (Copper is stripped away during food processing.) • Menkes syndrome (In this disease, copper deficiency is caused by genetic defects of copper transport. Menkes syndrome patients cannot use copper supplied by the diet efficiently.) Symptoms of copper deficiency include: • anemia • malnourished infants

toxicity is a very serious medical problem. Acute toxicity due to ingestion of too much supplement, for example, may cause nausea, vomiting, abdominal pain, diarrhea, dizziness, headache, and a metallic taste in the mouth. Chronic toxicity is often caused by genetic defects of copper metabolism, such as Wilson’s disease. In this disease, copper is not eliminated properly and is allowed to accumulate to toxic levels. Copper is therefore present at high concentration where it should not be, such as in the liver, the lens of the eye, kidneys, or brain. Disease prevention Copper is a good antioxidant. It works together with an antioxidant enzyme, superoxide dismutase (SOD), to protect cell membranes form being destroyed by free radicals. Free radicals are any molecules that are missing one electron. Because this is an unbalanced and unstable state, a radical is desperately finding ways to complete its pair. Therefore, it reacts to any nearby molecules to either steal an electron or give away the unpaired one. In the process, free radicals initiate chain reactions that destroy cell structures. Like other antioxidants, copper scavenges or cleans up these highly reactive radicals and changes them into inactive, less harmful compounds. Therefore, it can help prevent cancer and many other degenerative diseases or conditions such as premature aging, heart disease, autoimmune diseases, arthritis, cataracts, Alzheimer’s disease, or diabetes. Osteoporosis Copper may play a role in preventing osteoporosis. Calcium and vitamin D have long been considered the mainstay of osteoporosis treatment and prevention. However, a recent study has shown that they can be even more effective in increasing bone density and preventing osteoporosis if they are used in combination with copper and two other trace minerals, zinc and manganese.

• prominently dilated veins Rheumatoid arthritis

• pale hair or skin • poorly formed bones • nervous system disorders • high cholesterol levels • heart disease • loss of taste • increased susceptibility to infections • infertility • birth defects Exceeding the daily requirement is dangerous, however, because copper toxicity commonly occurs. Copper 586

Copper has been a folklore remedy for rheumatoid arthritis since 1500 B.C. in ancient Egypt. Some people believe that wearing jewelry made of copper may relieve arthritic symptoms. To evaluate the effect of copper for the treatment of rheumatoid arthritis, Dr. Walker and his colleagues conducted a study of 77 arthritic patients. Patients were divided into two groups: treatment group wearing copper jewelry and placebo group wearing nothing or aluminum jewelry. In this study, patients who wore copper bracelets felt significantly better than those in the placebo group. In addition, patients in the treatment group reported recurrences of symptoms after the bracelets were removed. To explain the effects of the cop-

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Preparations Copper is contained in many multivitamin/mineral preparations. It is also available as a single ingredient in the form of tablets. These tablets should be swallowed whole with a whole cup of water preferably with meals to avoid stomach upset. A person may choose any of the following preparations: copper gluconate, copper sulfate, or copper citrate. However, copper gluconate may be the least irritant to the stomach. Zinc and copper compete with each other for absorption in the gastrointestinal tract. As a result, excessive copper intake may cause zinc deficiency, and vice versa. Therefore, a person should take zinc and copper supplements together in ratios of 10:1 or 15:1.

Copper

per bracelets, these researchers suggested that copper contained in the bracelets was dissolved in sweat and then absorbed through the skin. They suspected that copper’s effectiveness may be related to its role as an antioxidant. They also believe that copper may function as both an anti-inflammatory agent and as an antioxidant. Thus, it is possibly effective in reducing inflammatory response to such conditions as rheumatoid arthritis.

KEY TERMS Antioxidants—Antioxidants are nutrients that deactivate reactive molecules (free radicals) and prevent harmful chain reactions. Minerals—Inorganic chemical elements that are found in plants and animals and are essential for life. There are two types of minerals: major minerals, which the body requires in large amounts, and trace elements, which the body needs only in minute amounts.

Side effects A person should stop taking copper supplements and seek medical help immediately if having the following signs or symptoms: • anemia • nausea • vomiting • abdominal pain

Precautions

Interactions

Take heed to the following:

Factors that increase copper concentrations

• Persons who take copper supplements should inform their doctors for proper instruction and monitoring of side effects. Copper toxicity due to excessive doses of copper supplements have been reported.

Certain disorders have been known to increase copper levels. Persons with these conditions should not take copper supplements as they may cause copper toxicity.

• Although there currently is no recommended daily allowance RDA established for copper, 2 mg of copper per day is considered sufficient and safe. Nausea and vomiting may occur in persons taking more than 20 mg of copper daily.

• lupus erythematosus

• It is not known if copper supplementation may harm a growing fetus. However, as with any drugs, pregnant or nursing women should not take copper or any other supplements or drugs without first consulting their doctors.

• viral infections

• In certain areas, drinking water may contain high levels of copper. Periodic checks of copper levels in drinking water may be necessary. • Because individual antioxidants often work together as a team to defend the body against free radicals, the balance between copper, zinc, and iron must be maintained. Excessive intake of one nutrient might result in a deficiency of other minerals and decrease resistance to infections and increase risk of heart disease, diabetes, arthritis, and other diseases.

• recent heart attacks • cirrhosis of the liver • schizophrenia • leukemia and some other forms of cancer • ulcerative colitis (This inflammatory bowel disease may cause accumulation of copper in the body. Excessive amount of copper may worsen many symptoms of this disease by increasing susceptibility to infections and inhibiting wound healing.) • Wilson’s disease (This disease causes accumulation of copper in the tissues. As a result, these patients have liver disease, mental retardation, tremor, and poor muscle coordination. They also have copper deposits in the cornea of the eyes. To manage this disease, patients are put on a low-copper diet and given penicillamine, a drug that attaches itself to copper and increases its excretion.)

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Coronary artery disease

Resources BOOKS

Lieberman, Shari and Nancy Bruning. “Copper.” In The Real Vitamin & Mineral Book: Using Supplements for Optimum Health Garden City Park, NY: Avery Publishing Group, 1997. Passwater, Richard A. All About Antioxidants. Garden City Park, NY: Avery Publishing Group, 1998. PERIODICALS

Reginster, Jean-Yves, Anne Noel Taquet, and Christiane Gosset. “Therapy for Osteoporosis: Miscellaneous and Experimental Agents.” Endocrinology and Metabolism Clinics (June 1998): 453-463. Uauy, Ricardo, Manuel Olivarez, and Mauricio Gonzales. “Essentiality of Copper in Humans.” Journal of Clinical Nutrition 67 suppl (1998): 952S-959S. OTHER

“Copper.” The Merck Manual of Diagnosis and Therapy. . (9 April 2000). Rosenstein, Elliot D. and Jacques R. Caldwell. “Therapies: Trace Elements in the Treatment of Rheumatic Conditions.” In Rheumatic Diseases Clinics of North America. Part II. . (10 May 2000).

one in every five deaths in the United States was caused by coronary artery disease. About every 29 seconds one American will have a heart attack; about every minute one American will die from a heart attack. Fourteen million Americans have active symptoms of coronary artery disease. Many millions more have asymptomatic (silent) coronary disease, the first indication of which can be sudden death. Coronary artery disease occurs when the coronary arteries become partially blocked or clogged, thereby depriving the heart muscle of oxygen (myocardial ischemia). When the blockage is temporary or partial, angina (chest pain or pressure) may occur. When the blockage completely and suddenly cuts off the flow of blood, the result is myocardial infarction. Healthy coronary arteries are clean, smooth, and slick. The artery walls are flexible and can expand to let more blood through when the heart needs to work harder. Atherosclerosis is thought to begin with an injury to the linings of the inner walls of the arteries. This injury makes them susceptible to atherosclerosis and thrombosis (blood clots).

Causes and symptoms Mai Tran

Copper deficiency see Mineral deficiency Coronary angiography see Cardiac catheterization

Coronary artery disease Definition Coronary artery disease is a stenosis (narrowing) or blockage of the arteries and vessels that provide oxygenated blood to the heart. It is caused by atherosclerosis (hardening of the arteries), an accumulation of fatty plaque on the inner linings of arteries. The resulting blockage restricts blood flow through the coronary arteries. When blood flow is completely cut off, the result is myocardial infarction (heart attack).

Description Coronary artery disease, also called coronary heart disease or atherosclerotic heart disease, is the leading cause of death for men and women in the United States. According to the American Heart Association, in 1998 588

Coronary artery disease is usually caused by atherosclerosis. Cholesterol and other fatty substances accumulate on the inner wall of the arteries. This attracts fibrous tissue, blood components, and calcium, which harden into flow-obstructing plaques. If a blood clot suddenly forms on one of these plaques it can convert a partial obstruction to a total occlusion. This is known as coronary thrombosis. Congenital defects and spasms of a coronary artery may also block blood flow. There is evidence that infection from organisms such as chlamydia bacteria may be responsible for some cases of coronary artery disease. A number of major contributing factors increase the risk of developing coronary artery disease. Some risk factors can be modified and others cannot. Persons with more of these risk factors are at greater risk of developing coronary artery disease. Major risk factors Major risk factors significantly increase the chance of developing coronary artery disease. Risk factors that cannot be changed include: • Heredity. People whose parents have coronary artery disease, particularly those who develop it at younger ages, are more likely to be diagnosed with it. AfricanAmericans are also at increased risk because they expe-

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• Gender. Men under the age of 60 years of age are more likely to have myocardial infarctions than women of the same age. Over age 60, however, women have coronary artery disease at a rate equal to that of men. • Age. Men over age 45 and women over age 55 years are more likely to have coronary artery disease. Occasionally, coronary disease affects individuals in the 30s. Older adults (those over 65) are more likely to die of a myocardial infarction. Older women are twice as likely as older men to die within a few weeks of a myocardial infarction. Major risk factors that can be changed are: • Smoking. Smoking greatly increases both the risk of developing coronary artery disease and resulting mortality. Smokers have two to four times the risk of nonsmokers for sudden cardiac death and are more than twice as likely to have a myocardial infarction. They are also more likely to die within an hour of a heart attack. Second-hand smoke may also increase risk. • High cholesterol. Cholesterol is produced by the body, and obtained from eating animal products such as meat, eggs, milk, and cheese. Age, gender, heredity, and diet affect cholesterol level. Risk of developing coronary artery disease increases as blood cholesterol levels increase. When combined with other factors, the risk is even greater. Total cholesterol of 240 mg/dL or more poses a high risk, and 200–239 mg/dL a borderline high risk. For LDL (low-density lipoprotein) cholesterol, high risk starts at 130–159 mg/dL, depending on other risk factors. Low levels of HDL (high-density lipoprotein) increases the risk of coronary disease; high HDL protects against it. • Hypertension (high blood pressure). High blood pressure makes the heart work harder, and over time, weakens it. It increases the risk of myocardial infarction, stroke, kidney failure, and congestive heart failure. Blood pressure of 140 over 90 or above is considered high. When hypertension is combined with obesity, smoking, high cholesterol, or diabetes, the risk of myocardial infarction or stroke increases several times. • Sedentary lifestyle and lack of physical activity. Inactivity increases the risk of coronary artery disease. Even modest physical activity is beneficial if done regularly. • Diabetes mellitus. The risk of developing coronary artery disease is significantly increased for diabetics. More than 80% of diabetics die of some type of cardiovascular disease.

Contributing risk factors Contributing risk factors have been linked to coronary artery disease, but their precise contribution to the development of disease is not known yet. Contributing risk factors are: • Obesity. Excess weight increases the strain on the heart and increases the risk of developing coronary artery disease, even if no other risk factors are present. Obesity increases both blood pressure and blood cholesterol, and can lead to diabetes. • Stress and anger. Stress and anger can produce physiological changes that contribute to the development of coronary artery disease, in part by increasing the risk of thrombosis. Stress, the mental and physical reaction to life’s irritations and challenges, increases heart rate and blood pressure and can injure the lining of the arteries. Evidence shows that anger increases the risk of dying from heart disease. The risk of heart attack is more than double after an episode of anger. Angina (chest pain) is the main symptom of coronary heart disease but it is not always present. Symptoms of angina typically include chest pain that may be described as heaviness, tightness, a burning sensation, squeezing, or pressure behind the breastbone. This pain may radiate to the left arm, neck, or jaw. Many people have no symptoms of coronary artery disease before having a heart attack; 63% of women and 48% of men who died suddenly of coronary artery disease had no previous symptoms of the disease, according to the American Heart Association.

Diagnosis The diagnosis of coronary artery disease is made by the physician after a medical history, physical examination, and basic screening tests have been performed. The diagnostic work-up includes evaluation of body weight, blood pressure, blood lipid levels, and fasting blood glucose levels. Other diagnostic tests include resting and exercise electrocardiogram (ECG), echocardiography, radionuclide scans, and coronary angiography. A treadmill exercise (stress) test also may be used as a screening test for patients with significant risk factors but are asymptomatic. An ECG may reveal if a patient has had a previous myocardial infarction (MI) or is having a MI. An ECG taken on a patient with coronary artery disease, who is not having chest pain during the ECG and has not had a prior MI, may be completely normal. An ECG technician places electrodes on the patient’s chest, arms, and legs. These electrodes send impulses of the heart’s activity through an oscilloscope (a monitor) to a recorder that traces them on

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rience a higher rate of severe hypertension than whites.

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against the patient’s chest to obtain an image that can be displayed on a monitor. It does not visualize the coronary arteries, but can detect abnormalities in heart wall motion caused by coronary disease. Performed in a cardiology outpatient diagnostic laboratory, the test takes about 3060 minutes. Nuclear myocardial scanning enables physicians to see if the myocardium (heart muscle) is being adequately perfused by the coronary arteries. Performed by radiologists and radiology technicians, nuclear scans involve injecting a small amount of radiopharmaceutical, such as thallium or sestamibi, into a vein. A camera that uses gamma rays to produce an image of the radioactive material records pictures of the heart. A radionuclide scan is comparable, in terms of radiation exposure, to a chest x ray. The tiny amount of radioactive material used disappears from the body in a few days. Radionuclide scans cost about four times as much as exercise stress tests but provide more information. In nuclear myocardial scanning, a camera passes back and forth over the patient who lies on a table. Usually performed in a hospital’s nuclear medicine department, the procedure takes 30-60 minutes.

A fluorescent microscopy of a fresh thrombus of the coronary artery. (Photograph by J.L. Carson, Custom Medical Stock Photo. Reproduced by permission.)

paper. The test takes about 10 minutes and is performed in a physician’s office. A definite diagnosis cannot be made from electrocardiography. About 50% of patients with significant coronary artery disease have normal resting electrocardiograms. Another type of electrocardiogram, known as an exercise stress test, measures how the heart and blood vessels respond to exertion when the patient is exercising on a treadmill or a stationary bike. This test is performed in a physician’s office or an exercise laboratory. It takes 15-30 minutes. Like many medical tests, it does not have 100% accuracy. It sometimes gives a normal reading when the patient has a heart problem or an abnormal reading when the patient does not. If the electrocardiogram reveals a problem or is inconclusive, the next step is exercise echocardiography or nuclear myocardial scanning (radionuclide angiography). Echocardiography, cardiac ultrasound, uses sound waves to create an image of the heart’s chambers and valves. A technician presses a hand-held transducer 590

Nuclear myocardial scanning is usually performed in conjunction with an exercise stress test. When the stress test is completed, thallium or sestamibi is injected. The patient resumes exercise for one minute to absorb the thallium. For patients who cannot exercise, cardiac blood flow and heart rate may be increased by intravenous dipyridamole (Persantine) or adenosine. Thallium or sestamibi scanning is done twice, immediately after injecting the radiopharmaceutical and again four hours (and maybe 24 hours) later. Usually performed in a hospital’s nuclear medicine department, each scan takes about 3060 minutes. Coronary angiography is the gold standard (most accurate method) for establishing the diagnosis of coronary artery disease, but it is also the most invasive. During coronary angiography the patient is awake but sedated. ECG electrodes are placed on the patient’s chest and an intravenous line is inserted. A local anesthetic is injected into the site where the catheter will be inserted. The invasive cardiologist inserts a catheter into a groin artery and guides it into the aorta. A contrast dye is injected directly into the coronary arteries to determine whether they are obstructed. Coronary angiography is performed in a cardiac catheterization laboratory either in an outpatient or inpatient surgery unit. It takes from 30 minutes to two hours.

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Coronary artery disease can be treated many ways. The choice of treatment depends on the severity of the disease. Treatments include lifestyle changes and drug therapy, percutaneous transluminal coronary angioplasty, and coronary artery bypass surgery. Coronary artery disease is a chronic disease requiring lifelong care. Angioplasty or bypass surgery is not a “cure.” Patients with less severe coronary artery disease may gain adequate control through lifestyle changes and drug therapy. Many of the lifestyle changes that prevent disease progression—a low-fat, low-cholesterol diet, weight loss if needed, exercise, and not smoking—also help prevent the disease from developing. Drugs such as nitrates, beta-blockers, and calciumchannel blockers relieve chest pain and complications of coronary artery disease, but they cannot clear blocked arteries. Nitrates (nitroglycerin) improve blood flow to the heart. Beta-blockers (acebutelol, propranolol) reduce the amount of oxygen required by the heart during stress. One type of calcium-channel blocker (verapamil, diltiazem hydrochloride) helps keep the arteries open and reduces blood pressure. Aspirin helps prevent blood clots from forming on plaques, reducing the likelihood of myocardial infarction. Cholesterol-lowering medications are also indicated in most cases. Percutaneous transluminal coronary angioplasty and bypass surgery are invasive procedures to improve blood flow in the coronary arteries. Percutaneous transluminal coronary angioplasty, usually called coronary angioplasty or PTCA, is a non-surgical procedure. A catheter tipped with a balloon is threaded through an artery in the groin into the blocked coronary artery. The balloon is inflated, compressing the plaque to enlarge the blood vessel and open the blocked artery. The balloon is deflated, and the catheter is removed. Coronary angioplasty is performed by an invasive cardiologist in a hospital and generally requires a stay of one or two days. Coronary angioplasty is successful about 90% of the time, but onethird of the time the artery restenoses (narrows again) within six months. The procedure can be repeated. It is less invasive and less expensive than coronary artery bypass surgery. In coronary artery bypass surgery, a healthy vein from an arm, leg, or the internal mammary artery is used to build a detour (bypass) around the coronary artery blockage. Bypass surgery is appropriate for those patients with blockages in two or three major coronary arteries, those with severely narrowed left main coronary arteries, and those who have not responded to other treatments. It is performed in a hospital under general anesthesia. A heart-lung machine is used to support the

patient while the healthy vein or artery is attached past the blockage to the coronary artery. About 70% of patients who have bypass surgery experience complete relief from angina; about 20% experience partial relief. Only about 3-4% of patients per year experience a return of symptoms. Survival rates after bypass surgery decrease over time. At five years after surgery, survival expectancy is 90%; at 10 years about 80%, at 15 years about 55%, and at 20 years about 40%. Three newer surgical procedures for unblocking coronary arteries are currently being evaluated. Atherectomy is a procedure in which the cardiologist shaves off and removes strips of plaque from the blocked artery. In laser angioplasty, a catheter with a laser tip is inserted into the affected artery to burn or break down the plaque. A metal coil, called a stent, may be implanted permanently to keep a blocked artery open. Stenting is gaining popularity as an alternative to more invasive surgery.

Prognosis In many cases, coronary artery disease can be successfully treated. Advances in medicine and healthier lifestyles have caused a substantial decline in death rates from coronary artery disease since the mid-1980s. New diagnostic techniques enable doctors to identify and treat coronary artery disease in its earliest stages. New technologies and surgical procedures have extended the lives of many patients who would otherwise have died. Research on coronary artery disease continues.

Health care team roles Patients with coronary artery disease are most often treated by primary care physicians with consultation from cardiologists and cardiovascular surgeons when needed. Nurses, ECG technicians, laboratory technologists, and other allied health professionals have important roles in the diagnosis of coronary artery disease as well as in the institution of timely treatment. Nurses and other practitioners involved in triage or screening in the emergency department must accurately assess patients with chest pain or other indications of coronary artery disease. ECG technicians, radiology technicians, and laboratory technologists are responsible for performing the diagnostic imaging studies, ECG and blood chemistries, to confirm the diagnosis of coronary artery disease. During the hospitalization, nurses, dieticians, respiratory and physical therapists collaborate to plan a cardiac rehabilitation program and provide patient and family education.

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Treatment

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KEY TERMS Angina—Chest pain that happens when diseased blood vessels restrict the flow of blood to the heart. Angina is often the first symptom of coronary artery disease. Atherosclerosis—A process in which the walls of the coronary arteries thicken due to the accumulation of plaque in the blood vessels. Atherosclerosis is the cause of coronary artery disease. Beta-blocker—A drug that blocks some of the effects of fight-or-flight hormone adrenaline (epinephrine and norepinephrine), slowing the heart rate and lowering the blood pressure. Calcium-channel blocker—A drug that blocks the entry of calcium into the muscle cells of small blood vessels (arterioles) and keeps them from narrowing. Coronary arteries—The main arteries that provide blood to the heart. The coronary arteries surround the heart like a crown, coming out of the aorta, arching down over the top of the heart, and dividing into two branches. These are the arteries in which coronary artery disease occurs. HDL cholesterol—High-density lipoprotein cholesterol is a component of cholesterol that helps protect against heart disease. HDL is nicknamed “good” cholesterol. LDL cholesterol—Low-density lipoprotein cholesterol is the primary cholesterol molecule. High levels of LDL increase the risk of coronary heart disease. LDL is nicknamed “bad” cholesterol. Plaque—A deposit of fatty and other substances that accumulate in the lining of the artery wall. Triglyceride—A fat that comes from food or is made from other energy sources in the body. Elevated triglyceride levels contribute to the development of atherosclerosis.

Patient education Nurses, physical therapists and dieticians work together to educate patients and their families. Patients are taught to recognize and accurately describe symptoms such as pain, pressure, or heaviness in the chest, left arm, or jaw. Patients are advised to report any changes in the intensity or quality of their pain to nurses or other health care professionals while in the hospital. When 592

necessary, they are counseled by nursing or pharmacy technicians about the use of sublingual (under the tongue) nitroglycerin to relieve chest pain. They are instructed to seek medical attention immediately should serious symptoms return after they have been discharged. Along with instruction about medication, follow-up care, and the importance of participating in cardiac rehabilitation, patients are informed about ways to reduce their risk for myocardial infarction or other complications of coronary artery disease. This education is tailored to the individual patient’s needs. It may include referral to a smoking cessation program; nutritional counseling to reduce dietary fat and sodium and achieve a desirable body weight; and recommendations to increase physical activity. Patient education also addresses treatment of any coexisting illnesses such as diabetes; and instruction about ways to more effectively manage stress and anger.

Prevention A healthy lifestyle can help prevent coronary artery disease and help keep it from progressing. A hearthealthy lifestyle includes eating right, regular exercise, maintaining a healthy weight, no smoking, moderate drinking, no recreational drugs, controlling hypertension, and managing stress. Cardiac rehabilitation programs are excellent to help prevent recurring coronary problems for patients at risk and those with a history of coronary events and procedures. Resources BOOKS

Ahya, Shubhada N, Flood, Kellie, and Paranjothi, Subramanian. The Washington Manual of Medical Therapeutics 30th Edition. Philadelphia: Lippincott Williams & Wilkins, 2001, pp. 96-100. American Heart Association and American Cancer Society. Living Well, Staying Well. New York and Toronto: Time Books, a division of Random House, 1996. DeBakey Michael E., and Antonio M. Gotto, Jr. “Coronary Artery Disease,” and “Surgical Treatment of Coronary Artery Disease.” In The New Living Heart. Holbrook, MA: Adams Media Corporation, 1997. Notelovitz, Morris, and Diana Tonnessen. The Essential Heart Book for Women. New York: St. Martin’s Press, 1996. Texas Heart Institute. “Coronary Artery Disease, Angina, and Heart Attacks.” In Texas Heart Institute Heart Owner’s Handbook. New York, Brisbane, Toronto, Singapore: John Wiley & Sons, 1996. ORGANIZATIONS

American Heart Association. National Center. 7272 Greenville Avenue, Dallas, TX 75231-4596. (214) 373-6300. .

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Corticosteroids

National Heart, Lung, and Blood Institute. P.O. Box 30105, Bethesda, MD 20824-0105. (301) 496-4236. . Texas Heart Institute Heart Information Service. P.O. Box 20345, Houston, TX 77225-0345. (800) 292-2221. . OTHER

“Atherectomy.” American Heart Association. Accessed August 11, 2001. . “NHLBI Report of the Workshop on Research in Coronary Heart Disease in Blacks.” National Heart, Lung, and Blood Institute, Accessed August 11, 2001. .

Barbara Wexler

Coronary disease see Coronary artery disease Coronary heart disease see Coronary artery disease Coronary thrombosis see Myocardial infarction

Corticosteroids Definition A group of natural and synthetic analogues of the hormones secreted by the hypothalamic-anterior pituitary-adrenocortical (HPA) axis, more commonly referred to as the pituitary gland. These include glucocorticoids, which are anti-inflammatory agents with a large number of other functions; mineralocorticoids, which control salt and water balance primarily through action on the kidneys; and corticotropins, which control secretion of hormones by the pituitary gland.

Purpose Glucocorticoids have multiple effects, and are used for a large number of conditions. They affect glucose utilization and fat metabolism, bone development, and are potent anti-inflammatory agents. They may be used for replacement of natural hormones in patients with pituitary deficiency (Addison’s disease), as well as for a wide number of other conditions including but not limited to arthritis, asthma, anemia, various cancers, and skin inflammations. Additional uses include inhibition of nausea and vomiting after chemotherapy, treatment of sep-

Photograph of cortisone. (Michael Siegel/Phototake NYC. Reproduced by permission.)

tic shock, treatment of spinal cord injuries, and treatment of hirisutism (excessive hair growth). The choice of drug will vary with the condition. Cortisone and hydrocortisone, which have both glucocorticoid and mineralocorticoid effects, are the drugs of choice for replacement therapy of natural hormone deficiency. Synthetic compounds, which have greater anti-inflammatory effects and less effect on salt and water balance, are usually preferred for other purposes. These compounds include dexamethasone, which is almost exclusively glucocorticoid in its actions, as well as prednisone, prednisolone, betamethasone, trimacinolone, and others. Glucocorticoids are formulated in oral dosage forms, topical creams and ointments, oral and nasal inhalations, rectal foams, and ear and eye drops. Mineralocorticoids control the retention of sodium in the kidneys. In mineralocorticoid deficiency, there is excessive loss of sodium through the kidneys, with resulting water loss. Fludrocortisone (Florinef) is the only drug available for treatment of mineralocorticoid deficiency, and is available only in an oral dosage form. Corticotropin (ACTH, adrenocorticotropic hormone) stimulates the pituitary gland to release cortisone. A deficiency of corticotropic hormone will have the same effects as a deficiency of cortisone. The hormone, which is available under the brand names Acthar and Actrel, is used for diagnostic testing, to determine the cause of a glucocorticoid deficiency, but is rarely used for replacement therapy since direct administration of glucocorticoids may be easier and offers better control over dosages.

Recommended dosage Dosage of glucocorticoids varies with drug, route of administration, condition being treated, and patient. Consult specific references.

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KEY TERMS Hallucination—A false or distorted perception of objects, sounds, or events that seems real. Hallucinations usually result from drugs or mental disorders. Hormone—A substance that is produced in one part of the body, then travels through the bloodstream to another part of the body where it has its effect. Inflammation—Pain, redness, swelling, and heat that usually develop in response to injury or illness. Ointment—A thick, spreadable substance that contains medicine and is meant to be used on the outside of the body. Pregnancy category—A system of classifying drugs according to their established risks for use during pregnancy. Category A: Controlled human studies have demonstrated no fetal risk. Category B: Animal studies indicate no fetal risk, but no human studies; or adverse effects in animals, but not in well-controlled human studies. Category C: No adequate human or animal studies; or adverse fetal effects in animal studies, but no available human data. Category D: Evidence of fetal risk, but benefits outweigh risks. Category X: Evidence of fetal risk. Risks outweigh any benefits.

Fludrocortisone, for use in replacement therapy, is normally dosed at 0.1 mg/day. Some patients require higher doses. It should normally be administered in conjunction with cortisone or hydrocortisone. ACTH, when used for diagnostic purposes, is given as 10 to 25 units dissolved in 500 ml of 5% Dextrose Injection infused IV over eight hours. A long-acting form, which may be used for replacement therapy, is given by subcutaneous (SC) or intramuscular (IM) injection at a dose of 40 to 80 units every 24–72 hours.

pression is seen primarily with drugs administered systemically, it can also occur with topical drugs such as creams and ointments, or drugs administered by inhalation. Abrupt cessation of corticosteroids may result in acute adrenal crisis (Addisonian crisis) which is marked by dehydration with severe vomiting and diarrhea, hypotension, and loss of consciousness. Acute adrenal crisis is potentially fatal. Chronic overdose of glucocorticoids leads to Cushingoid syndrome, which is clinically identical to Cushing’s syndrome and differs only in that in Cushingoid, the excessive steroids are from drug therapy rather than excessive glandular secretion. Symptoms vary, but most people have upper body obesity, rounded face, increased fat around the neck, and thinning arms and legs. In its later stages, this condition leads to weakening of bones and muscles with rib and spinal column fractures. The short term adverse effects of corticosteroids are generally mild, and include indigestion, increased appetite, insomnia, and nervousness. There are also a very large number of infrequent adverse reactions, the most significant of which is drug-induced paranoia. Delerium, depression, menstrual irregularity, and increased hair growth are also possible. Consult detailed reviews for further information. Long-term use of topical glucocorticoids can result in thinning of the skin. Oral steroid inhalations may cause fungal overgrowth in the oral cavity. Patients must be instructed to rinse their mouths carefully after each dose. Corticosteroids are pregnancy category C. The drugs have caused congenital malformations in animal studies, including cleft palate. Breastfeeding should be avoided. Because fludrocortisone has glucocorticoid activity as well as mineralocorticoid action, the same hazards and precautions apply to fludrocortisone as to the glucocorticoids. Overdose of fludrocortisone may also cause edema, hypertension, and congestive heart failure. Corticotropin has all the same risks as the glucocorticoids. Prolonged use may cause reduced response to the stimulatory effects of corticotropin.

Precautions The most significant risk associated with administration of glucocorticoids is suppression of natural corticosteroid secretion. When the hormones are administered, they suppress the secretion of ACTH, which in turn reduces the secretion of the natural hormones. The extent of suppression varies with dose, drug potency, duration of treatment, and individual patient response. While sup594

Warnings and contraindications Use corticosteroids with caution in patients with the following conditions: • osteoporosis or any other bone disease • current or past tuberculosis • glaucoma or cataracts

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• sores in the nose or recent nose surgery (if using nasal spray forms of corticosteroids) • underactive or overactive thyroid

who offer cosmetic options can improve the appearance of stained, chipped, and misshapen teeth, and correct uneven gums and replace old fillings with nearly invisible filling materials. Cosmetic dentistry procedures are elective and, therefore, often not covered by insurance.

• liver disease • stomach or intestine problems • diabetes • heart disease • high blood pressure • high cholesterol • kidney disease or kidney stones • myasthenia gravis • systemic lupus erythematosus (SLE) • emotional problems • skin conditions that cause the skin to be thinner and bruise more easily

Interactions Corticosteroids have many drug interactions. Consult specific references. Resources ORGANIZATIONS

American Academy of Allergy, Asthma and Immunology. 611 East Wells Street, Milwaukee, WI 53202. (414) 2726071. . Asthma and Allergy Foundation of America. 1125 15th Street NW, Suite 502, Washington, DC 20005. (800) 727-8462. . National Heart, Lung and Blood Institute. National Institutes of Health, P.O. Box 30105, Bethesda, MD 20824-0105. (301) 251-1222. .

Samuel Uretsky, PharmD

Cortisol tests see Adrenocortical hormone tests

Description The most popular option in cosmetic dentistry is tooth bleaching, an area that is experiencing a 15 to 20% growth a year. Most dental practices offer tooth bleaching, which involves the use of at-home and in-office supervised whitening systems that brighten stained, discolored, or dull-looking teeth. Veneers are the second most popular cosmetic dentistry option. Used to correct chipped, cracked or worn teeth, veneers are ultra thin tooth coverings, sometimes made of porcelain or composite materials. Bonding is another process also used to correct chipped, cracked, or worn teeth. Crowns, dental bridges, and dental implants can be used to replace missing teeth or correct bite dysfunction. Today’s newer technology includes porcelain and ceramic tooth replacements that look real and blend with existing teeth. Cosmetic dentists can correct excessive or uneven gums with cosmetic surgery. Many patients with old or unsightly fillings also can opt to have them replaced by a dentist, who can use resin and porcelain filling materials or crowns to eliminate the look of the previous fillings.

Causes and symptoms Anyone who is unhappy with his or her smile is a candidate for cosmetic dentistry. The reason might be a general displeasure with the look of one’s teeth or a specific aesthetic dental concern. While the reasons for improvement vary, the most common causes are staining due to aging, tobacco use, coffee intake, fluorosis, and tetracycline use. Patients also often want to improve the shape and position of their teeth. Diastemas (spaces between teeth), slight rotations, and malformation of the teeth (e.g., peg laterals, barrel shape teeth) are common reasons for correcting the shape and the position of the teeth.

Diagnosis

Cosmetic dentistry Definition Cosmetic, or aesthetic, dentistry focuses on improving appearance and facial self-image by correcting the alignment, shape, and color of teeth. Dental professionals

The diagnosis of an aesthetic problem involves looking at the entire face; the color of the eyes, skin, and lips often influence the appearance of teeth. The face evaluation is usually divided into imaginary thirds: the first section goes from the hairline to eyebrows, the second from eyebrows to the base of the nose, and the third from the

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• infections of any type (virus, bacteria, fungus, amoeba)

Cosmetic dentistry

KEY TERMS Bleaching—Tooth whitening using a chemical such as carbamide peroxide or hydrogen peroxide. Bridge—A fixed or removable dental appliance used to replace missing teeth and to restore the mouth to function. Caries—Demineralization or calcified tooth tissue, which, if left untreated, results in soft, discolored areas, pain, and eventual loss of the tooth. Crown—A gold, porcelain, or stainless steel cover used to replace a tooth structure that has been lost to decay, accident, or injury. Dental implant—A fixed dental appliance that replaces missing teeth. Diastema—An abnormally large space between two teeth. Periodontitis—Inflammation and infection of gingival tissue, ligaments, and alveolar bone that support teeth. Veneers—Porcelain or composite laminates that are bonded to the surface teeth to improve aesthetics and function.

base of the nose to the lower border of chin. Aesthetic smiles are diagnosed by the dentist, who looks for asymmetry and mobility of the upper and lower lips; midline in relation to the front teeth; gumline; tooth and gum contours; tooth color; tooth to length proportion and relationships; and, finally, restorations. Several factors must be taken into account when assessing these variables, including age, gender, race, and personality. When examining the tooth shade, specifically, certain factors should be considered, such as the light source and surrounding colors. Bleaching of teeth will change the shade of the tooth structure only, which can pose a problem if the patient has several tooth-colored restorations.

Treatment Minor corrections in shape and positions can be done with direct resin bonding and ceramic veneers. If the problem is related to position and is considered to be moderate to severe, it is possible to correct it through the placement of veneers, full crowns, or by orthodontic treatment. Bonding involves applying an enamel-like material to the tooth’s surface and sculpting it to an aesthetically 596

pleasing shape. Once it hardens, the dentist polishes and refines the new tooth. One of the advantages of direct resin bonding over ceramic veneers is that bonding can be done in one session without laboratory involvement, which helps to control cost. The major advantage of direct composite resin restorations is conservation of the tooth structure because, in some cases, little or no enamel removal is required. Longevity, the main advantage of ceramic veneers, is superior to resin bonding. Discoloration caused by extrinsic staining, such as coffee, tea, red wine, tobacco, aging, and some types of medications, are usually yellow or brown in color and can be improved by vital bleaching, using a 10% carbamide peroxide solution. The concentration may be slightly higher or lower, depending on the stains. Discoloration caused by intrinsic staining, such as after root canal treatment, pulp bleeding, tetracycline medication, fluorosis, and some types of inherited disease, are usually blue, gray, or brown and often requires a nonvital bleaching treatment. Non-vital bleaching treatment is done internally to the tooth structure, meaning the bleaching agent is placed inside the tooth crown.

Prognosis The term aesthetics takes into consideration the psychological interpretation of beauty. Because of this subjectivity, it is extremely important to establish a common goal and line of communication between the dentist and the patient. Communication is particularly important when the patient’s expectations exceed the reality of what is possible to achieve. Studies support significant differences among the preferences of dentists and patients for cosmetic dentistry. The results of aesthetic dentistry vary according to the different procedures. It should be noted that the results of the bleaching treatment are not predictable, since it varies according to each case. For the most part, it is possible to lighten the tooth shade on the first few days of treatment. The success of any restoration depends on patient compliance. It is important that the patient be informed about maintenance of his or her treatments, and understand that the results of bleaching are not permanent. Explanations of the etiology of oral diseases, risk factors, and preventive measures are also warranted; these may help to motivate patients keep their new smiles healthy.

Health care team roles Identification of imperfections in patients’ smiles might be done by dental hygienists during care. They may refer patients to the dentist for cosmetic dentistry.

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Creatine kinase test see Cardiac marker tests Creatinine test see Kidney function tests

Creutzfeldt-Jakob disease

Prevention

Definition

Patients can help to keep their teeth healthy and white with good nutritional and lifestyle habits. Preventive measures to reduce or eliminate dental disease, including caries, periodontitis, and oral cancer, are essential to obtaining and maintaining an optimal dental health and aesthetic appearance.

Creutzfeldt-Jakob disease (CJD) is a transmissible, rapidly progressing, fatal neurodegenerative disorder related to “mad cow disease.”

Description

Maintenance remains important after cosmetic dentistry. The proper maintenance of tooth color restorations is important to improve and increase the lifetime of the restorations. This includes cessation or decrease in tobacco use, and cessation or decrease in the intake of caffeine products and stain-producing foods and beverages. Acidic products can also cause erosion of the tooth structure. The use of soft toothbrushes and non-abrasive toothpaste will avoid unnecessary tooth abrasion. Some types of whitening toothpaste can have large particle size, which can act as an abrasive on the restoration surface.

Before 1995, Creutzfeldt-Jakob disease was little known outside the medical profession. Indeed, most physicians did not know much about the disease, and few had ever seen a patient with the disease. But with the discovery of a “new variant” form, the possibility that those with the disease became infected simply by eating beef, and the radical theory that the infectious agent is a rogue protein, CJD has become one of the most talked about diseases in the world, and has taken on a significance far beyond the small number of deaths it currently causes each year.

Resources

First described in the 1920s, CJD is a neurodegenerative disease causing a rapidly progressing dementia which ends in death, usually within eight months of the onset of symptoms. It is also a very rare disease, affecting only about one in every million people in the population worldwide. In the United States, CJD is thought to affect about 250 people each year. CJD affects adults of all ages, but is rare in young adults and most common between ages 50 and 75.

ORGANIZATIONS

Academy of General Dentistry, 211 East Chicago Ave., Chicago, IL 60611. (312) 440-4800. . American Academy of Cosmetic Dentistry. 2810 Walton Commons West, Suite 200, Madison, Wisconsin 53718. 800-543-9220. . American Dental Assistants Association. 203 North LaSalle Street, Suite 1320, Chicago, IL 60601-1225. (312)5411550. . American Dental Association. 211 East Chicago Avenue, Chicago, IL 60611 (312) 440-2500. OTHER

Gordan, Valeria V., DDS, MS. Assistant Professor. University of Florida, College of Dentistry, Operative Dentistry Department, Gainesville, FL. Interview with Lisette Hilton.

Lisette Hilton

CPAP see Ventilation assistance CPR see Cardiopulmonary resuscitation (CPR)

Spongiform encephalopathies The most obvious pathologic feature of CJD is the formation of numerous, fluid-filled spaces in the brain (vacuoles), giving the brain a sponge-like appearance. CJD is one of several human spongiform encephalopathies, diseases that produce this characteristic change in brain tissue. Others include kuru; Gerstmann-Straussler-Scheinker disease, predominantly characterized by cerebellar ataxia; and fatal familial insomnia, associated with progressive insomnia, autonomic system dysfunction, and weakness caused by motor system dysfunction. Kuru was prevalent among the Fore people in Papua New Guinea,. The disease was spread from infected individuals after their deaths through the practice of ritual

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Trained dental hygienists can coordinate patients’ bleaching procedures. Dental assistants help explain what is involved in the cosmetic dental solutions and inform the patient that, in most cases, insurance does not reimburse for cosmetic dentistry. Dental assistants also work with dentists during cosmetic dental procedures and can assist patients and dentists in selecting tooth shades.

Creutzfeldt-Jakob disease

cannibalism, in which the relatives of the dead person honored him by consuming his organs, including the brain. Discovery of the infectious nature of kuru won the Nobel Prize for Carleton Gadjusek in 1976 and also alerted the medical world to the possibility of slow-acting infectious agents, collectively termed slow-virus diseases. The incubation period for kuru was four to 30 years or more. While kuru has virtually disappeared following the cessation of cannibalistic practices, several new cases continue to arise each year. Cases of CJD have been grouped into three types: familial, iatrogenic, and sporadic. • Familial CJD, representing 5–15% of cases, is inherited in an autosomal dominant manner, meaning that either parent may pass along the disease to a child, who may then develop CJD later in life. • Iatrogenic CJD occurs when a person is infected during a medical procedure, such as organ donation and transplantation, blood transfusion, or brain surgery. The rise in organ donation has increased this route of transmission. Grafts of infected corneas and dura mater (the tissue covering the brain) have been linked with the transmission of CJD. Another source is hormones concentrated from the pituitary glands of cadavers, some of whom carried CJD, for use in people with growth hormone deficiencies. Iatrogenic infection represents a small fraction of all cases. The incubation period between exposure to the infectious agent is very long and is estimated to be from less than 10 to more than 30 years. • Sporadic CJD represents at least 85% of all cases. Sporadic cases have no identifiable source of infection. Death usually follows the appearance of the first symptoms within eight months. Animal forms and “mad cow disease” Six different forms of spongiform encephalopathy are known to occur in other mammals: scrapie in sheep, recognized for more than 200 years; chronic wasting disease in elk and mule deer in Wyoming and Colorado; transmissible mink encephalopathy; exotic ungulate encephalopathy in some types of zoo animals; feline spongiform encephalopathy in domestic cats; and bovine spongiform encephalopathy (BSE) in cows. All of these are classified as slow-virus diseases. BSE was first recognized in Britain in 1986. Besides the spongiform changes in the brain, BSE causes dementia-like behavioral changes. This is the origin of the name “mad cow disease.” BSE is thought to be an altered form of scrapie that was transmitted to cows when sheep offal (slaughterhouse waste) was included in their feed. 598

The use of slaughterhouse offal in animal feed has been common in many countries and has been practiced for at least 50 years. The trigger for the BSE epidemic in Britain seems to have come in the early 1980s, when the use of organic solvents for preparation of offal was halted there. It seems likely that these solvents had destroyed the scrapie agent, thereby preventing infection. The change in preparation procedure opened the way for the agent to “jump species” and cause BSE in cows that consumed scrapie-infected meal. The slaughter of infected (but not yet visibly sick) cows at the end of their useful farm lives, and the use of their carcasses for feed, spread the infection rapidly and widely. For at least the first year after BSE was initially recognized in British herds, infected bovine remains continued to be incorporated into feed, spreading the disease still further. It is thought that most cows with BSE became infected as a result of eating meal containing offal from other cows, not sheep. Although milk from infected cows has never been shown to contain or pass the infectious agent, passage from infected mother to calf has occurred through unknown means. Beginning in 1988, the British government took steps to stop the spread of BSE, banned the use of bovine offal in feed and other products, and ordered the slaughter of infected cows. By then, the slow-acting agent had become epidemic in British herds. In 1992, it was diagnosed in over 25,000 animals (1% of the British herd). By mid-1997, the cumulative number of BSE cases in the United Kingdom had risen to more than 170,000. The feeding ban apparently did slow the spread of the epidemic. The number of new cases each week fell from a peak of 1,000 in 1993 to fewer than 300 two years later. The export of British feed and beef to member countries was banned by the European Union, but cases of BSE had developed in Europe by then. About 1,000 cases were identified in Europe by 1997. In 1989, the United States banned the import of British beef and began monitoring U.S. herds in 1990. As of 2001, the U.S. Department of Agriculture reports that BSE has not been detected in the United States. One case has been reported in Canada in a cow imported from Britain. New-variant CJD: the jump to humans From the beginning of the BSE epidemic, scientists and others in Britain feared that BSE might jump species again to infect humans who had consumed infected beef. In 1995, this fear seemed to be realized with the first cases of a new variant of Creutzfeldt-Jacob disease, termed nvCJD. Its victims, 81 as of the beginning of 2001, tend to be much younger than the 60–65 average for CJD, and the time from symptom onset to death has

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Evidence is growing stronger that nvCJD is in fact caused by BSE. • The majority of cases have occurred in Britain, the location of the original BSE epidemic • BSE injected into monkeys produces a disease very similar to nvCJD • BSE and nvCJD produce the same brain lesions after the same incubation period when injected into laboratory mice • Brain proteins isolated from nvCJD victims, but not from the other forms of CJD, share similar molecular characteristics with brain proteins of animals that died from BSE. While definitive proof is still lacking as of 2001, many researchers feel that the connection between BSE and nvCJD has been strongly established. Assuming that BSE is the source, the question that has loomed from the beginning is the number of people that will eventually be affected. Epidemiological models of infectious disease produce estimates ranging from less than 100 to tens of thousands, depending on the assumptions used by those creating the mathematical models. The incubation period of nvCJD in humans is not known, nor are the genetic and environmental risk factors that influence susceptibility. The quantity of infectious agent needed to cause the disease is not known with precision. It is estimated that humans have eaten between one and two million infected cattle, most in the earliest stages of the epidemic. Estimates cannot be based on the very few cases that have developed to date. These cases could represent the very few people with the right combination of exposure and susceptibility to a relatively fast-developing infection, or they could be the first few victims of a slower-acting, more highly infectious agent. Only time will tell.

Causes and symptoms Causes It is clear that Creutzfeldt-Jakob disease is caused by an infectious agent, but it is not yet clear what type of agent that is. Originally assumed to be a virus, evidence is accumulating that, instead, CJD is caused by a protein called a “prion,” (proteinaceous infectious particle) that is transmitted between persons who have CJD. The other spongiform encephalopathies are also hypothesized to be due to prion infection. If this hypothesis is proved true, it would represent one of the most radical new ideas in biology since the discovery of DNA. All infectious diseases, in fact, all

life, use nucleic acids—DNA or RNA—to code the instructions needed for reproduction. Inactivation of nucleic acids destroys the capacity to reproduce. However, when these same measures are applied to infected tissue from spongiform encephalopathy victims, infectivity is not destroyed. Furthermore, purification of infected tissue to concentrate the infectious fraction yields protein, not nucleic acid. While it remains possible that some highly stable nucleic acid remains hidden within the purified protein, this appears less and less likely as further experiments are done. The “prion hypothesis,” as it is called, is now widely accepted, at least provisionally, by most researchers in the field. The most vocal proponent of the hypothesis, Stanley Prusiner, was awarded the Nobel Prize in 1997 for his work on prion diseases. A prion is an altered form of a normal brain protein. The normal protein has a helical shape along part of its length. In the prion form, a sheet structure replaces the helix. According to the hypothesis, when the normal form interacts with the prion form, its helical part is converted to a sheet, thus creating a new prion capable of transforming other normal forms. In this way, the disease process resembles crystallization more than typical viral infection, in which the virus commands the host’s cellular machinery to reproduce more of the virus. Build up of the sheet form causes accumulation of abnormal protein clumps and degeneration of brain cells, causing dementia and ultimately death. The brain protein affected by the prion, called PrP, is part of the membrane of brain cells, but its exact function is unknown. It is composed of about 250 subunits, called amino acids, coded for by a gene on chromosome 20. Slight genetic differences, called polymorphisms, give rise to two slightly different normal protein forms: subunit 129 is a “methionine” in one form, but is “valine” in the other. A person may have all of one, all of the other, or a mixture of the two, depending on the individual’s genetic inheritance. Both forms have the normal helical structure, and function normally. However, susceptibility to prion conversion is influenced by subunit 129: a person with a mixture of forms is more resistant to conversion, and a person with all valine appears to be somewhat more susceptible than one with all methionine. Exposure to the infectious agent is, of course, still required for disease development. Prion diseases are not contagious in the usual sense, and transmission from an infected person to another person requires direct inoculation of infectious material. Familial CJD, on the other hand, does not require exposure but develops through the inheritance of other, more disruptive mutations in the gene for the normal PrP protein. Researchers believe these mutations increase the likelihood that the protein will spontaneously “flip” to the sheet form; once created, these abnormal proteins can

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averaged 12 months instead of eight. EEG abnormalities characteristic of CJD are not typically seen in nvCJD.

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then convert other normal-form molecules. The other two inherited human prion diseases, GerstmannStraussler-Scheinker disease and fatal familial insomnia, involve different mutations in the same gene. The large majority of CJD cases are sporadic, meaning they have no known route of infection or genetic link. Causes of sporadic CJD are likely to be diverse and may include spontaneous genetic mutation, spontaneous protein changes, or unrecognized exposure to infectious agents. It is highly likely that future research will identify more risk factors associated with sporadic CJD. Symptoms About one in four people with CJD begin their illness with weakness, changes in sleep patterns, weight loss, or loss of appetite or sexual drive. A person with CJD may first complain of visual disturbances, including double vision, blurry vision, or partial loss of vision. Some visual symptoms are secondary to cortical blindness related to death of nerve cells in the occipital lobe of the brain responsible for vision. This form of visual loss is unusual in that patients may be unaware that they are unable to see. These symptoms may appear weeks or months before the onset of dementia. The most characteristic symptom of CJD is rapidly progressing dementia, or loss of mental function. Dementia is marked by: • memory losses • impaired abstraction and planning

other forms of dementia. CJD typically shows atrophy or loss of brain tissue. Lumbar puncture, or spinal tap, may be done to rule out other causes of dementia and to identify elevated levels of marker proteins known as 14-3-3. Cell count, chemical analysis, and other routine tests are normal in CJD. Another marker, neuron-specific enolase, may also be increased in CJD. A conclusive diagnosis of CJD can only be accomplished after death using material obtained from a brain autopsy.

Treatment There is no cure for CJD. There is no treatment that slows the progression of the disease. Drug therapy and nursing care are intended to minimize psychiatric symptoms and increase comfort for affected persons. However, the rapid progression of CJD frustrates most attempts at treatment, since ever-worsening cognitive deficits and more prominent behavioral symptoms develop so quickly. Despite the generally grim prognosis, a few individuals with CJD progress more slowly and live longer than the average. For these persons, treatment will be more satisfactory.

Prognosis Creutzfeldt-Jakob disease is invariably fatal, with death following symptom onset by an average of eight months. About 5% of patients live longer than two years. Death from nvCJD has averaged approximately 12 months after onset.

• language and comprehension disturbances

Health care team roles

• poor judgment

Physicians are usually involved in initial identification of CJD. Nurses may provide supportive care. Radiologists obtain CT and MRI scans. Surgeons or physicians obtain spinal fluid. Pathologists and laboratory technicians process samples of bodily fluids and tissues.

• disorientation • decreased attention and increased restlessness • personality changes and psychosis • hallucinations Muscle spasms and jerking movements, called myoclonus, are also a prominent symptom of CJD. Balance and coordination disturbance (ataxia) is common in CJD and is more pronounced in nvCJD. Stiffness, difficulty moving, and other features characteristic of Parkinson’s disease may develop and can progress to akinetic mutism, or a state of being unable to speak or move.

Diagnosis CJD is diagnosed by a clinical neurological exam and electroencephalography (EEG), which shows characteristic spikes called triphasic sharp waves. Magnetic resonance imaging (MRI) or computed tomography scans (CT) should be performed to exclude 600

Prevention There is no known way to prevent sporadic CJD, by far the most common type. Not everyone who inherits the gene mutation for familial CJD will develop the disease, but at present, there is no known way to predict who will and who won’t succumb. The incidence of iatrogenic CJD has fallen with recognition of its sources, the development of better screening techniques for infected tissue, and the use of sterilization techniques for surgical instruments, which inactivate prion proteins. Strategies for preventing nvCJD are a controversial matter, as they involve a significant sector of the agricultural industry and a central dietary element in many

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KEY TERMS Autosomal dominant inheritance—A pattern of inheritance in which a trait is expressed if the gene is inherited from either parent. Encephalopathy—A brain disorder characterized by memory impairment and other symptoms. Iatrogenic—Caused by a medical procedure. Nucleic acids—The cellular molecules DNA and RNA, which act as coded instructions for the production of proteins and which are copied for transmission of inherited traits.

BOOKS

Adams, Raymond D., Maurice Victor, and Allan H. Ropper. Adam’s & Victor’s Principles of Neurology, 6th ed. New York: McGraw Hill, 1997. Chen, Irvin, and Rafi Ahmed. Persistent Viral Infections. New York: John Wiley & Sons, 1999. Donnelley, Christl, and Neil M. Ferguson. Statistical Aspects of BSE and VCJD: Models for Epidemics. Boca Raton, FL: CRC Press, 1999. Rampton, Sheldon, and John C. Stauber. Mad Cow USA: Could the Nightmare Happen Here? Monroe, ME: Common Courage Press, 1997. Ratzan, Scott C. Mad Cow Crisis: Health and the Public Good. New York: New York University Press, 1998. PERIODICALS

Bosch, X. “European Concern Over BSE Transmission.” Journal of the American Medical Association 285(2001): 397-398. Deslyse, J.P., et al. “Screening Slaughtered Cattle for BSE.” Nature, vol. 409, no. 6819(2001): 476-478. Lemonick, M.D. “Can It Happen Here? Panic Over Mad Cow Has Already Infected Europe. Now It’s Our Turn.” Time, vol. 157, no. 4(2001): 58-59. Steelman, V.M. “Creutzfeld-Jakob Disease: Recommendations for Infection Control.” American Journal of Infection Control 22(2001): 312-318. Stockdale, T. “Contaminated Material Caused CreutzfeldtJakob Disease (CJD) in Some Undersized Children Who Were Treated With Growth Hormone (GH).” Nutrition and Health 14(2000): 141-142. Thompson, C. “In Search of a Cure for CJD.” Nature, vol. 409, no. 6821(2001): 660-661. Whitelaw, K. “Sacre Boeuf, It’s Mad Cow. A Beef Scare in France.” U.S. News and World Report, vol. 129, no. 21(2000): 53. ORGANIZATIONS

American Academy of Neurology, 1080 Montreal Avenue, St. Paul, MN 55116. (651) 695-1940. Fax: (651) 695-2791. . [email protected].

Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30333. (404) 639-3534 or (800) 3113435. . . Creutzfeldt-Jakob Disease Foundation, P.O. Box 611625, Miami, FL 33261-1625. (305) 891-7579. Fax: (954) 4367591. . [email protected]. Creutzfeldt-Jakob Disease Support Network, Birchwood, Heath Top, Ashley Heath, Market Drayton, Shropshire, England. (011) 0163-067-3993. . E-mail: Gill Turner, [email protected]. National Creutzfeldt-Jakob Disease Surveillance Unit, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU, UK. 011-0131-537-2128. Fax: 011-0131-343-1404. . [email protected]. OTHER

British Medical Journal. . Human BSE Foundation. . Information Concerning BSE for the Scientific World. . National Institute of Neurological Diseases and Stroke. . Tufts University. . University of Minnesota. . University of Nottingham. .

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countries. The infectious potential of contaminated meat is unknown, because the ability to detect prions within meat is limited. Surveillance of North American herds strongly suggests that no cases of BSE have been confirmed as of 2001. Strict regulations on imports of European livestock make future outbreaks highly unlikely. Therefore, avoidance of all meat originating in North America simply on grounds of BSE risk is a personal choice unsupported by current data. The ban on the export of British beef continues in countries of the European Union, although some herds in these countries have developed low levels of infection as well.

Crohn’s disease

Crohn’s disease is a chronic disorder. Though symptoms can be effectively controlled, patients are not completely cured of the underlying disease.

Crohn’s disease Definition Crohn’s disease is a type of inflammatory bowel disease (IBD) caused by inflammation along any portion of the alimentary canal (the mouth to the anus).

Description Although Crohn’s disease may involve any part of the alimentary canal, it most commonly affects the small intestine. There is evidence that the inflammation is an autoimmune response—when products of the immune system attack the body itself instead of attacking a foreign substance such as a virus or bacteria. The part of the small intestine most commonly affected is the last part of the ileum, also known as the terminal ileum. The colon (large intestine) is less commonly involved. Inflammation may also occur in other areas of the alimentary canal, less frequently affecting the mouth, esophagus, or stomach. Crohn’s disease differs from ulcerative colitis, the other major type of IBD, in the following ways: • The inflammation of Crohn’s disease may be discontinuous, meaning that areas of involvement in the intestine may be separated by normal, unaffected segments of intestine. The affected areas are called “regional enteritis,” while the normal areas are called “skip areas.” • The inflammation of Crohn’s disease is transmural; this means it affects all the layers of the intestinal wall, while ulcerative colitis affects only the lining of the intestine. • Ulcerative colitis does not usually involve the small intestine; in rare cases it involves the terminal ileum (so-called “backwash” ileitis). In addition to inflammation, Crohn’s disease causes ulceration. These ulcers occur because the inflammation has caused areas of tissue destruction. Crohn’s disease may be diagnosed at any age, although most diagnoses are made between the ages 1535. About 0.02-0.04% of the population suffers from this disorder. It affects equal numbers of males and females. Whites are more frequently affected than other racial groups, and people of Jewish origin are between three and six times more likely to suffer from IBD. IBD runs in families; an IBD patient has a 20% chance of having other relatives who are fellow sufferers. 602

Causes and symptoms The cause of Crohn’s disease is unknown. No infectious agent has been positively identified as the cause of Crohn’s disease. Some researchers have theorized that a certain bacterium may have originally been responsible for triggering the immune system, resulting in the abnormal activation of the immune system in the intestines that occurs in Crohn’s disease. Symptoms of Crohn’s disease depend on which section of the alimentary canal is affected. Symptoms may include diarrhea, fever, abdominal pain, loss of appetite, weight loss, and fatigue. Some patients experience severe pain that mimics appendicitis. Unlike patients with ulcerative colitis, it is rare for patients with Crohn’s disease to notice blood in their bowel movements. Because Crohn’s disease severely limits the ability of the affected intestine to absorb the nutrients from food, a patient may have signs of malnutrition, depending on the amount of intestine affected and the duration of the disease. The combination of severe inflammation, ulceration, and scarring that occurs in Crohn’s disease can result in serious complications, including intestinal obstruction, intra-abdominal abscess formation, and fistula formation. An obstruction is a mechanical blockage in the intestine. This obstruction, called a stricture, prevents the intestinal contents from passing beyond the point of the blockage. The intestinal contents “back up,” resulting in constipation, vomiting, and intense pain. Although rare in Crohn’s disease (because of the increased thickness of the intestinal wall due to swelling and scarring), severe bowel obstruction can result in an intestinal wall perforation (a hole in the intestine). A hole in the intestinal wall would allow the intestinal contents, containing bacteria, to enter the abdominal cavity, causing a severe, lifethreatening infection known as peritonitis. Abscess formation is the development of a walledoff pocket of pus. A patient with an abscess in the abdomen will have fever, abdominal pain, and may have a lump or mass that can be palpated (felt) through the wall of the abdomen. Fistula formation is the formation of abnormal channels. These channels may connect one loop of the intestine to a neighboring section of intestine. Fistulas may connect an area of the intestine to the vagina or urinary bladder, or may drain an area of the intestine through the skin. Abscesses and fistulas commonly affect the area

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Patients suffering from Crohn’s disease are at increased risk of other disorders. Some of these may relate specifically to the intestinal disease, and others appear to have some relationship to the compromised immune system. The faulty absorption of the bowel can result in gallstones and kidney stones. Inflamed areas in the abdomen may compress and block the ureter (the tube that drains urine from the kidney to the bladder) causing failure of the kidney on the affected side. Patients with Crohn’s disease also frequently suffer from extraintestinal manifestations such as: • arthritis (inflammation of the joints) • spondylitis (inflammation of the vertebrae, the bones of the spine) • ulcers of the mouth and skin • erythema nodosum (painful, red bumps on the skin) • inflammation of several eye areas • inflammation of the liver, gallbladder, and/or the ducts that carry bile between and within the liver, gallbladder, and intestine The risk of developing cancer of the intestine is greater than average among patients with Crohn’s disease, although the cancer risk is not as high as it is for patients with ulcerative colitis.

Diagnosis Diagnosis is first suspected based on a patient’s symptoms. Blood tests may reveal an increase in white blood cells, an indication that some type of inflammation is occurring in the body. The blood tests may also reveal anemia and other signs of malnutrition due to malabsorption, such as low blood protein; low calcium, potassium, and magnesium present in the blood; and indications of liver inflammation. Stool samples may be examined to rule out various infectious agents, and to see if the stool contains blood. During a colonoscopic exam, a physician passes a flexible tube with a tiny, fiber-optic camera (called an endoscope) through the rectum and into the colon. The physician carefully examines the lining of the intestine for signs of inflammation and ulceration that might suggest Crohn’s disease. A biopsy of the intestine can also be taken through the colonoscope, and the tissue will be examined under a microscope for evidence of Crohn’s disease.

X rays can be helpful for diagnosis, and to determine how much of the intestine is involved in the disease. For these x rays, the patient must either drink a chalky solution containing barium, or receive a barium enema. Barium helps to “light up” the intestine, allowing more detail to be seen on the resulting x rays. Crohn’s disease and ulcerative colitis are similar, but they are distinct conditions. Although it may be difficult to determine whether a patient has Crohn’s disease or ulcerative colitis, it is important to make every effort to distinguish between these two diseases because the longterm complications of the diseases are different, as is the treatment.

Treatment Treatment for Crohn’s disease aims to reduce the underlying inflammation, the resulting malabsorption/ malnutrition, and relieve symptoms of abdominal pain and diarrhea. Treatment is also intended to prevent potential complications such as obstructions, abscesses, and fistulas. Inflammation can be treated with a drug called sulfasalazine. Sulfasalazine is in part related to the sulfa antibiotics; its other component is a form of the antiinflammatory chemical, salicylic acid (related to aspirin). Sulfasalazine is not well absorbed from the intestine, so it remains largely within the intestine, where it is broken down into its components. It is believed that the salicylic acid component actively treats Crohn’s disease by fighting inflammation. Some patients do not respond to sulfasalazine and require corticosteroids such as prednisone. Corticosteroids, however, must be used carefully to avoid the various complications of these drugs, including an increased risk of infection and osteoporosis (weakening of the bones). Patients with intra-abdominal abscesses or those with disease in the large bowel or ileum may be given antibiotics such as metronidazole or ciprofloxacin. Potent immunosuppressive drugs, such as 6-mercaptopurine, azathioprine, cyclosporine, and infliximab, which block the immune system and thereby reduce inflammation, may be prescribed for patients who do not respond to corticosteroids. Serious cases of malabsorption/malnutrition may require treatment with nutritional supplements. These supplements must be in a form that can be absorbed from the damaged, inflamed intestine. Some patients find that certain foods are hard to digest, including milk, large quantities of fiber, and spicy foods. When patients are suffering from an obstruction, or during periods of time when symptoms of the disease are at their worst, they

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around the anus and rectum. These abnormal connections allow the bacteria normally present in the intestine to enter other areas of the body, causing potentially serious infections.

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KEY TERMS Abscess—A walled-off pocket of pus caused by infection. Endoscope—An instrument that can be passed into an area of the body (the bladder or intestine, for example) to allow examination of that area. The endoscope usually has a fiber-optic camera, which allows a greatly magnified image to be shown on a television screen viewed by the operator. Many endoscopes also allow the operator to retrieve a biopsy of the area examined. Fistula—An abnormal channel that creates an open passageway between two structures that do not normally connect. Gastrointestinal tract—The entire length of the digestive system, running from the mouth to the stomach, through the small intestine, large intestine, rectum, and anus. Immune system—The body system responsible for combating infection by viruses, bacteria, fungi, and other foreign invaders. In autoimmune disease, these cells and chemicals turn against the body itself. Inflammation—The result of the body’s attempts to fight off and wall off an area that is infected. Inflammation results in the classic signs of redness, heat, swelling, and loss of function. Obstruction—A blockage. Ulceration—A pitted area or break in the continuity of a surface such as skin or mucous membrane.

may need to drink specially formulated, high-calorie liquid supplements. Those patients who are severely ill may need total parenteral nutrition (TPN). TPN patients receive their nutrition intravenously, or through a catheter inserted directly into a major vein in the chest. A number of medications are available to help decrease the cramping and pain associated with Crohn’s disease. These include loperamide, tincture of opium, and codeine. Fiber preparations (methylcellulose or psyllium) are helpful for some patients; others do not tolerate them well. The first step in treating an obstruction involves general efforts to decrease inflammation with sulfasalazine, steroids, or immunosuppressive drugs. A patient with a severe obstruction is given no food or 604

drink by mouth, allowing the bowel to “rest.” Abscesses and other infections require antibiotics. Surgery may be required to repair an obstruction that does not resolve on its own, to drain an abscess, or to repair a fistula. Such surgery may involve the resection (removal) of the diseased length of the intestine. In extremely severe cases of Crohn’s disease that do not respond to treatment, patients may require a colostomy. In this procedure, a piece of the remaining small intestine is pulled through an opening in the abdomen. This segment of intestine is fashioned surgically to allow a special bag to be placed over it. This bag collects the stool, which can no longer pass through the large intestine and out of the anus.

Prognosis Crohn’s disease is a chronic, lifelong illness. The severity of the disease may vary, and patients may experience periods of time when the disease is not active and they are symptom free. Still, the complications and risks of Crohn’s disease tend to increase over time. More than 60% of all patients with Crohn’s disease will require surgery, and about half of these will require more than one operation over time. Approximately 5-10% of all Crohn’s patients die of their disease, primarily due to massive infection.

Health care team roles Crohn’s disease is often diagnosed by primary care practitioners or gastroenterologists. In many instances, patients require surgical intervention. Imaging studies to assist in diagnosis are performed by x-ray technologists, and laboratory technologists may be involved in obtaining blood and stool samples for analysis. Nurses, dieticians, and nutritional counselors have important roles in teaching patients about dietary changes to manage symptoms. Nurses, social workers, and ostomy specialists may also be involved in educating patients pre- and postoperatively about ostomy care.

Prevention Presently, there is no way to prevent the development of Crohn’s disease. Resources BOOKS

Glickman, Robert. “Inflammatory Bowel Disease: Ulcerative Colitis and Crohn’s Disease.” In Harrison’s Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998.

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ORGANIZATIONS

Crohn’s & Colitis Foundation of America, Inc. 386 Park Avenue South, 17th Floor, New York, NY 10016-8804. (800) 932-2423.

Barbara Wexler

Cross infection Definition Cross infection is the physical movement or transfer of harmful bacteria from one person, object, or place to another, or from one part of the body to another (such as touching a staph-infected hand to the eye). When this cross infection occurs in a hospital or long-term care facility it is called a nosocomial infection. Communityacquired infections are those contracted anywhere except a hospital or long-term care facility.

Description Cross infection accounts for half of all major complications of hospitalization; the rest are medication errors, patient falls, and other noninfectious events. In American hospitals, cross infection affects between 5–10% of patients at a cost in excess of $4.5 billion. Further, with the advent of HMOs and incentives for outpatient care, hospitals now have a concentrated population of seriously ill patients, and an even greater risk of cross infection. On one hand, trends toward same-day surgery, shorter hospital stays, and less-invasive surgical techniques will limit patients’ exposure to hospital pathogens and invasive devices. On the other, long-term inpatients are likely to be older and sicker, requiring the use of invasive devices in treatment or management of their illness. This places them at increased risk of cross infection, a risk that is higher for public and larger hospitals and teaching institutions. Statistics show that about 35 million patients are admitted to 7,000 acute-care institutions in the United States each year. This means that 1.75 million to 3.5 million patients are infected yearly in the United States. If 10% of all cross infections involve the bloodstream, then

175,000 to 350,000 patients acquire these life-threatening septicemic infections each year.

Causes and symptoms Cross infections are caused by bacteria, viruses, fungi, or parasites that may already be present in the patient’s body, or they may come from the environment, contaminated hospital equipment, health care workers, visitors, or other patients. A localized infection is limited to a specific part of the body and has local symptoms. An infected surgical site, for example, would exhibit an area that is red, hot, and painful. A generalized infection that enters the bloodstream causes general systemic symptoms such as fever, chills, low blood pressure, boils all over the body, or mental confusion. Cross infections can occur from surgical procedures, catheters placed in the urinary tract, intravenous fluid sites, or when moisture droplets from the nose or mouth are inhaled into the lungs. The most common cause of cross infection is the failure of health care workers to wash their hands after taking off latex gloves or before donning a new pair. The most frequent types of cross infections occurring in facilities are urinary tract infections (UTIs), pneumonia, surgical site infections (SSIs), and blood stream infections (BSIs). While all patients within a health care facility are vulnerable to cross infection, some patients are at greater risk than others because certain risk factors alter their susceptibility to infection. Intrinsic risk factors are those present in the patient and include age (the very young or the elderly), presence of chronic disease, or a compromised immune system. Extrinsic risk factors are types of interventions performed within the health care facility and the mix of patients present. Fever is often the first sign of infection; other symptoms include rapid breathing, mental confusion, low blood pressure, reduced urine output, painful joints and muscles, and a high white blood cell count. If there is a skin break it may be red and swollen. Patients with a UTI may have pain when urinating along with cloudy or bloody urine. Symptoms of pneumonia include difficulty breathing, chronic deep coughing, and reluctance to lie flat because it makes breathing difficult. A localized infection causes swelling, redness, and tenderness at the site of infection. Common cross infections URINARY TRACT INFECTIONS. Urinary tract infections (UTIs), the most common type of cross infections, usually occur after catheterization, the placement of a catheter through the urethra into the bladder. This proce-

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Long, James W. The Essential Guide to Chronic Illness. New York: Harper Perennial, 1997. Saibil, Fred. Crohn’s Disease and Ulcerative Colitis. Buffalo, NY: Firefly Books, 1997.

Cross infection

dure is done to empty urine from the bladder, relieve pressure in the bladder, measure urine in the bladder, put medicine into the bladder, or for other medical reasons. While there can be bacteria in or around the urethra, a healthy urinary bladder is sterile: it does not normally have any bacteria or other microorganisms in it. When a catheter is inserted, bacteria can be picked up from the urethra and carried into the bladder unless both the area and equipment are properly prepared; once in the bladder, bacteria can multiply. Infections can also arise if health care personnel fail to follow proper sterile technique when emptying the collection bag. Bacteria from the intestinal tract are the most common cause of UTIs, although fungi called Candida albicans are often implicated. Although UTIs are common, they are generally the least severe and least costly type of cross infection. PNEUMONIA. Nosocomial pneumonia is the second

most common type of cross infection; it is defined as an infection of the lungs that develops 48 or more hours after admittance. (Any infection that occurs within the first two days after admission is presumed to have come in with the patient.) Patients requiring invasive respiratory therapy may have infection rates seven to 21 times higher than those who don’t need artificial ventilation. These infections occur because bacteria and other microorganisms are easily introduced into the throat by procedures such as respiratory intubation, suctioning of material from the throat and mouth, tracheostomy, and mechanical ventilation. The microorganisms can come from contaminated equipment, the hands of health care workers, or, depending on the physical health of the patient, from the patient’s own bacteria. The introduced microorganisms quickly colonize the throat area, but do not yet cause an infection. Once the throat is colonized, it is easy for a patient to inhale the microorganisms into the lungs; most nosocomial pneumonia develops within two days of the infecting procedure. This is especially true for patients who cannot cough or gag very well. The occurrence of pneumonia can prolong a hospital stay by at least three or four days at considerable cost. SURGICAL SITE INFECTIONS. Since surgery is a direct invasion of the patient’s body, the natural barrier of the skin is broken, giving bacteria entrance into the normally sterile interior of the body. Surgical site infections (SSIs) can be acquired from contaminated surgical equipment, health care workers who use improper technique to change bandages postoperatively, intubations, and a depressed immune system that permits the body’s natural bacteria to colonize. Other wounds from trauma, burns, and ulcers can also become infected for similar reasons. BLOOD STREAM INFECTIONS. Many patients in health care facilities need an intravenous (IV) catheter

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placed in a vein for the infusion of fluids for hydration, medications, and/or nutrients. This can cause blood stream infections (BSIs) by transmission from the surroundings, contaminated equipment, or health care workers’ hands via the site of catheter insertion. A local infection can develop in the skin around the catheter, or more seriously, bacteria can enter the bloodstream through the vein and cause a generalized infection. The longer a catheter is in place, the greater the risk of infection. BSIs are the most severe of the cross infections, resulting in the most deaths, greatest prolongation of stay, and highest cost. Other procedures that put patients at risk for cross infections are gastrointestinal procedures, obstetric procedures, and kidney or peritoneal dialysis.

Diagnosis An infection is suspected any time a hospitalized or home health care patient develops a fever that cannot be explained by a known illness. Some patients, however, especially the elderly, may not develop a fever. In these patients, the first signs of infection may be rapid breathing, pale clammy skin, or mental confusion. Diagnosis of a cross infection is based on: • signs and symptoms of the infection • examination of wounds and catheter entry sites • review of procedures that might have led to infection • laboratory test results, including blood studies, urinalysis, and culture of any suspicious wound sites A complete physical examination is conducted by the physician, nurse practitioner, or registered nurse caring for the individual in order to determine if an infection is present. Wounds and catheter insertion sites are examined for redness, swelling, the presence of pus, an abscess, or any area of exaggerated tenderness that might indicate an abcess. The registered nurse reports findings to the physician or nurse practitioner who reviews the patient’s record of procedures performed to determine if any posed a risk for infection. Medical technicians perform laboratory tests ordered by the physician or nurse practitioner to look for signs of infection. A complete blood count reveals the white blood cell count, a measure of macrophages whose increasing numbers indicate infection. White blood cells, blood, or “casts” (mineral crystals) may be present in the urine with a UTI as well. Cultures of blood, urine, sputum, other body fluids, or tissue are examined for infectious microorganisms, which must be identified to provide proper treatment. These cultures are obtained by taking a swab of an area or a sample of fluid, blood, or tissue and placing it in a special sterile medium that promotes bacte-

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Treatment Upon identification of the infection, the patient is treated with antibiotics or other medications that destroy the responsible organism. Although many different antibiotics are available, bacteria strains resistant to specific antibiotics have become increasingly prevalent. In one 1998 U.S. report, only 56% of pneumococcal strains of bacteria were still sensitive to penicillin while 16% were highly resistant. At the present time, resistance is highest to penicillin, but resistance to other antibiotics such as cephalosporins, tetracyclines, and erythromycin is also rapidly increasing. Fortunately, most pneumococci are still sensitive to vancomycin, but an increasing number of vancomycin-resistant bacteria have been reported. Newer groups, called fluoroquinolones, are being used to treat resistant bacteria, as are imipenem/ cilastatin (Primaxin), a carbapenem combination, and sanfetrinem, a tricyclic beta-lactam antibiotic. These are powerful new antibiotics that can combat a wide spectrum of bacteria that have become resistant to standard drugs. Unfortunately, some newer studies show that patients with infections resistant to cephalosporins may also have a cross-resistance to the fluoroquinolones. Repeated exposure even to these antibiotics, however, will eventually result in bacterial resistance. It is essential, therefore, that patients who require antibiotics be rigorous about completing their regimen and that those caring for them adhere to aseptic technique rigidly. At highest risk for antibiotic-resistant pneumococci are children under two who live in areas of high antibiotic use and who have used antibiotics in the previous year. Efforts to reduce the number of resistant bacteria include teaching both the public and health care workers that a conservative approach is best when it comes to antibiotics use: not every infection needs medication. A program in Finland, for example, has nearly halved the incidence of erythromycin-resistant bacteria by limiting the use of penicillin and similar antibiotics to only serious infections. Many infections, in fact, are viral, and do not respond to antibiotic therapy. Fungal infections are treated with antifungal medications, such as amphotericin B, nystatin, ketoconazole, itraconazole, and fluconazole, but many of these drugs have negative interactions with other medications that the patient may be using. A number of antiviral drugs

have been developed that slow the growth or reproduction of viruses, and these include acyclovir, ganciclovir, foscarnet, and amantadine.

Prognosis Cross infections are serious illnesses that can cause death in about 1% of all cases. Blood stream infections in intensive care unit (ICU) patients have a mortality rate of almost 35%. Rapid diagnosis and identification of the responsible microorganism are necessary so that specific antimicrobial therapy can be started as quickly as possible.

Health care team roles In all cases, medication for cross infection is administered by a registered nurse in a health care facility, by an intravenous infusion nurse who does home health care, or by a licensed practical nurse in a nursing home. These nurses must be extremely careful that the medication is given exactly as ordered and that they use sterile technique to prevent any additional cross infection. The nurse must also remain alert to additional complications or symptoms that may be significant and report these to the physician or nurse practitioner. Laboratory personnel must be very careful in utilizing sterile technique when drawing blood, as should respiratory therapists who may provide breathing treatments or suction for patients with pneumonia. Patient education If possible, the registered nurse can use the time during treatments to teach the patient how cross infection occurs. This is especially important when the patient is immunocompromised and, therefore, more susceptible to further infection. The nurse could explain the importance of taking medications exactly as ordered and why antibiotics are sometimes not given for illnesses. All health care personnel should explain procedures as they are performed and include the reasons for the particular treatment. The patient’s family may be included in the session to further enforce the necessity of the treatment as well as the appropriate way to perform it.

Prevention Hospitals and other health care facilities have developed extensive infection-control programs to identify all possible sources of infection, including medical procedures, that put patients at risk. The first infection-control committees and policies were developed in the late 1950s and early 1960s when a pandemic of highly virulent antibiotic-resistant Staphylococcus aureus swept through American hospitals. In response, the Centers for Disease

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rial growth. Other tests can be done on blood and body fluids to find and identify bacteria, fungi, viruses, or other microorganisms responsible for the infection. If a patient has symptoms suggestive of pneumonia, a chest x ray is done to look for infiltrates—white blood cells and other inflammatory substances in the lung tissue.

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noted that programs were most successful when data were communicated effectively to hospital staff.

KEY TERMS Abscess—A localized pocket of pus at a site of infection. Candida albicans—A yeast-like fungal organism. Catheter—A thin, hollow tube inserted into the body at specific points in order to inject or withdraw fluids. Culture—The reproduction of microorganisms or of living tissue cells in special media that encourages their growth. Generalized infection—An infection that has entered the bloodstream and has general systemic symptoms such as fever, chills, and low blood pressure. Incubating—The development of an infectious disease from time of the entrance of the pathogen to the appearance of clinical symptoms. Intubation—Placement of a tube inside the body to keep a lumen open, especially the trachea. Localized infection—An infection that is limited to a specific part of the body. Nosocomial infection—An infection acquired during or after hospitalization and that was not present or incubating at the time of the patient’s admission. It includes any infection acquired in a facility that appears after discharge and any newborn infection that is the result of passage through the birth canal. Peritoneal dialysis—A procedure for cleaning the blood when a patient’s kidneys have failed. A catheter implanted in the patient’s abdomen is used to add and remove cleansing fluid that removes waste and impurities from the bloodstream. Unlike hemodialysis, peritoneal dialysis can usually be done at home.

Further recommendations that resulted from these initiatives included analyzing procedures with high risk of contamination, such as urinary catheterization. To minimize cross infection, it was recommended that these procedures be performed only when necessary, and that catheters or other medical devices be left in for as little time as possible. Medical instruments and equipment should be properly sterilized, with appropriate documentation and check devices, to ensure they were not contaminated. Frequent hand washing by health care workers and visitors is absolutely essential to prevent transferring infectious microorganisms to patients, and was cited as the procedure most important for prevention. Patients should be encouraged to ask their health care provider if they washed their hands before allowing them to proceed with an examination. Antibiotics should only be used when necessary because their use not only creates favorable conditions for infection with the fungal organism Candida albicans but their overuse has helped develop antibiotic-resistant bacteria. Resources BOOKS

Braunwald, E., A. Fauci, D. Kasper, S. Hauser, D. Longo, and J. Jameson. Harrison’s Principles of Internal Medicine. New York: McGraw-Hill, 2001. Cecil, R., and L. Goldman. Cecil Textbook of Medicine. Philadelphia: W.B. Saunders, 1999. Rhinehart, E., M. Friedman. Infection Control in Home Care. Aspen Publishers, Inc., 1999. Tortora, G.J., B.R. Funke, C.L. Case. Microbiology: An Introduction San Francisco: Addison Wesley Longman, Inc., 2001. PERIODICALS

Wenzel, R.P., M.B. Edmond. “The Impact of HospitalAcquired Bloodstream Infections.” Emerging Infectious Diseases 7, no. 2 (March/April 2001).

Systemic—Affecting the whole body.

OTHER

Tracheostomy—The creation of an opening into the trachea (windpipe) through the neck, with insertion of an indwelling tube to facilitate passage of air or evacuation of secretions.

Centers for Disease Control and Prevention. . “Hospital-Acquired Infection: General Information.” (Abstracts of Articles from Scientific Journals). . Hospital-Acquired Infections and Resistant Bacteria. .

Control and Prevention (CDC; then the Communicable Disease Center) in Atlanta recommended that hospitals determine the sources of infection in hospital patients, so they could develop and apply preventive measures. One result of this was a CDC-sanctioned maximum of 250 beds for each infection control nurse. They further 608

Linda K. Bennington, CNS

Crowns see Dental crowns, inlays, and bridges

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Definition Crutches are orthopedic devices created to assist in weight bearing when a patient has a leg injury or weakness in the lower extremities.

Purpose Wooden or aluminum axillary (under the arm) crutches are used to assist in weight bearing when a patient has sustained an injury to the leg, knee, ankle, or foot, such as a fracture or severe sprain. Crutches are also used following surgery on the leg, knee, ankle, or foot. Forearm crutches are used to provide stability and moderate support when a patient has generalized weakness in the lower extremities, such as for a patient with cerebral palsy.

Description Axillary crutches can be either wooden or aluminum. Each crutch is comprised of two pieces of wood or aluminum that are connected at the top and middle by a crossbar and join to a third piece that extends to the floor. The top cross bar is slightly concave in shape and fits just 1-2 inches (2.54–5 cm) below the axilla. It is covered with a soft rubber pad and is used to brace the crutches against the body. The middle cross bar is round and covered with a rubber grip. It is adjusted to hand level for gripping the crutches with the hands. The third piece connects the two upper pieces, extends to the floor, and is covered by a rubber tip on the end that meets the floor. Crutches are used in pairs to provide balance and support. Aluminum crutches are lighter and easier to use. Wooden crutches are generally less expensive than aluminum crutches. Forearm crutches are comprised of two pieces of aluminum tubing that are telescoped one within the other to adjust to the correct height of the client. They are fitted with attached, swivel-action arm cuffs that fit partially around the forearm, and with handgrips that are covered with a rubber grip. There is a rubber tip at the end of each crutch where it meets the floor.

Operation Wooden or aluminum axillary crutches come in several sizes. The appropriate size crutches should be selected based on the patient’s height. With the patient standing straight upright, one crutch is held against the patient’s side. The nut bolt which attaches to the bottom piece is loosened and removed. The crutch is then adjust-

ed until it is l-2 inches (2.54–5 cm) below the patient’s axilla. The bolt is placed in the appropriate hole, and the nut wing is tightened securely to hold it in place. The patient then holds his hand down with the elbow slightly bent. The bolt and nut wing for the handgrip are loosened and moved to the correct position for the patient. The hand should be resting at the hip line with the elbow slightly bent. The bolt is placed in the appropriate hole, and the nut wing is tightened securely. The rubber tip, rubber axillary padding, and rubber handgrip are checked to ensure placement and security. The client sits back down, and the other crutch is adjusted at the base and the hand grip to exactly match the measured crutch. Aluminum forearm crutches come in several sizes. The appropriate size crutches should be selected based upon the patient’s height. With the patient standing, one crutch is adjusted by pushing in the locking mechanism and moving the height up until the forearm portion of the crutches can slip comfortably onto the patient’s arm. The crutches are locked by moving the mechanism until the lock clicks securely. The arm cuff is adjusted if necessary. The crutch is checked for stability by pushing down on it. The vinyl padding on the arm cuff, the rubber handgrip, and the rubber tip at the end of the crutch are examined to be sure they are in place and secure. The client then sits back down, and the other crutch is adjusted to exactly match the measured crutch. The patient should not attempt to use the crutches until they are fitted and all of the nut wings or locking mechanisms are secure. The hands and arms bear the patient’s weight, not the axilla. The patient is instructed not to lean on the axillary pads because this can pinch the axillary nerve and cause numbness of the hands and arms. The patient is instructed on crutch safety, how to walk with crutches, how to go up and down stairs with crutches, how to sit, and how to stand up using the crutches. The patient demonstrates competency with the crutches before discharge. The patient is given written instructions about crutch walking and safety to review later after discharge.

Maintenance The screw bolts and nut wings that hold the base of the crutches and the handgrip of the crutches should be checked daily to be sure they are securely tightened. Rubber tips that become worn or tear should be replaced at once to prevent slipping. Rubber handgrips that are torn or worn should be replaced promptly to prevent blisters on the hands or slipping of the hands. Worn or torn rubber padding at the top of axillary crutches should be replaced to prevent pressure injuries. New rubber tips or handgrips can be purchased at most drug stores. Crutches

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are moved forward about 12 inches (30 cm). With the crutches braced against the body, the strength of the hands and forearms are used to push down on the handgrips as the good leg swings through and about 12 inches (30 cm) ahead of the crutches. The patient’s weight is placed on the uninjured leg and the process is repeated. A slow steady rhythm is used when walking. The patient is instructed not to go too fast or swing his leg too far forward because this can cause a loss of balance. The body and head are kept upright. The patient is instructed not to lean forward or put his weight on the axillary pads. The patient is told to look ahead to where he is going and not to look at his feet. The patient practices walking forward, turning, and walking back until he has developed a rhythm and balance with the crutches.

A patient is measured for crutches. (Delmar Publishers, Inc. Reproduced by permission.)

that are kept in good repair can be reused if well maintained but should be re-measured and adjusted for each client. Forearm crutches should be checked daily before use to be sure that the height adjustment pegs are secure, the swivel-action arm cuffs fit correctly, the rubber tips are intact, and the handgrips are secure.

Health care team roles It is most often the responsibility of a licensed nurse or physical therapist to fit crutches and teach crutch walking/safety to the patient in the health care setting. Non-professionals such as orthopedic technicians or ER staff can receive special training to fit crutches and teach crutch walking/safety in some medical settings. Patients must always be instructed on the proper use and safety factors involved in crutch walking prior to discharge with crutches.

Training Instructing a patient about the safe use of crutches should include the following information: • Crutch walking: The crutches are placed under both arms close to the body. The hands are placed firmly upon the handgrips. Both crutches and the injured limb 610

• Sitting: The patient is instructed to back up against the chair until he feels the chair on the back of his legs. The patient’s weight is placed on the uninjured leg, and the injured leg is advanced slightly forward. Both crutches are placed side by side on the uninjured side, beside the patient’s body but not under the arm. The patient holds both handgrips together and reaches back for the armrest of the chair with his other hand. Using the armrest of the chair and the crutch handgrips as support, the patient slowly moves his injured leg forward and lowers himself into the chair. The crutches are placed nearby. Standing them on the axillary pads, when possible, makes it less likely that they will tip over and fall away from the patient. • Standing: When in bed, the patient moves first to a sitting position to get his balance. The patient then inches forward to the edge of the bed or the chair. Both crutches are then placed upright and side-by-side on the uninjured side. The patient grips both handgrips firmly in his hand and rises up on his uninjured leg. The crutches are placed on either side of the body and the patient holds the handgrips. Instruct the patient to take a few minutes to get his balance. Be sure that the patient’s body is upright, the crutches are positioned correctly, and his head is looking forward before beginning to walk. • Climbing up stairs: Climbing stairs with crutches requires strength and flexibility. If the patient is unsure of his strength, he should be instructed to turn around and sit on the stairs and scoot himself up one stair at a time using his uninjured leg to propel him. The patient should be instructed to keep his crutches in one hand and bring them up with him. When climbing stairs with crutches, the patient leads with his uninjured leg and brings the injured leg and crutches up behind him. If the stairway has a handrail, the patient should place both crutches under the arm opposite the handrail and grip the handgrips together in one hand. The patient places his weight on the handrail and the handgrips, leans

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• Going down stairs: Going down stairs with crutches requires strength and flexibility. If the patient is unsure of his strength, he should sit down and scoot down the stairs one at a time, bracing himself with his good leg. The patient should keep his crutches in one hand and bring them down with him. When going down stairs with crutches, the patient should lead with his injured leg and crutches then bring his uninjured leg down behind him. If the stairway has a handrail, the patient should place both crutches under the arm opposite the handrail and grip the handgrips together in one hand. With his weight on his uninjured leg, the patient moves the crutches and the injured leg down one step. Then the patient places his weight on the handrail and the handgrips and brings his uninjured leg down the step. The patient should take time to regain his balance and repeat the process. The patient should be instructed to take his time and rest halfway down the stairs if necessary. To go down stairs with no handrail, the patient puts his weight on his uninjured leg and moves the crutches and injured leg down one step. The patient shifts his weight onto the handgrips of the crutches and brings the uninjured leg down the step. The patient keeps his foot and the crutch tips in the middle of the step, away from the edge to avoid slipping. The patient should be instructed to take his time, rest as needed, and ask for help if necessary. Having someone walk in front of the patient as he walks down the steps can add a sense of security, and the person can assist the patient into a sitting position if he becomes fatigued. • Daily maintenance: The nut wings or locking mechanisms should be checked daily to be sure they are tightened securely. The rubber tip at the bottom of the crutches should also be checked to be sure it is secure. The tip should be replaced if it shows signs of wearing

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slightly forward, and brings his uninjured leg up one step. He then brings the crutches and the injured leg up the step and advances his hand up the handrail. Once the patient has regained his balance, the process is repeated. The patient should be instructed to take his time and rest halfway up the stairs if necessary. To climb stairs with no handrail, the patient leans slightly forward and puts his weight on the handgrips of the crutches. The patient moves the uninjured leg up the step. He then shifts his weight to the uninjured leg and brings the crutches and injured leg up the step. His foot and crutch tips are kept in the middle of the step, away from the edge to avoid slipping. The patient is instructed to take his time, rest as needed, and ask for help if necessary. Having someone walk behind the patient up the stairs can add a sense of security, and the person can assist the patient into a sitting position if he becomes fatigued.

This woman walks with aluminum crutches after her left calf and foot were removed. (Stock Boston, Inc. Reproduced by permission.)

or tearing. The rubber handgrips or vinyl arm cuffs should also be examined to be sure they are intact. They should be replaced if they show signs of wearing or tearing. The rubber axillary padding should be examined and replaced if it shows signs of wearing or tearing. New rubber tips or handgrips can be purchased at most drug stores. • General tips: Items that may cause the patient to trip and fall, such as scatter rugs or extension cords, should be removed. Spilled liquids should be wiped up to avoid slipping. Items the patient needs with him can be carried in a fanny pack, apron with pockets, or knapsack to keep his hands free to grip the crutches. A nonskid bath mat should be used in the shower or tub. A tennis shoe or other flat, rubber-soled shoe should be worn on the patient’s uninjured foot to avoid slipping. The patient should be careful when going through doorways to be sure that the door does not shut on his crutches. The patient should seek help to hold the door

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CT imaging equipment

reconstruct acquired image data for display on a viewing monitor or printed on film. Also referred to as computerized axial tomography (CAT) scanning equipment.

KEY TERMS Axillary—A term used to refer to the area in or around the axilla or armpit.

if necessary. The patient should avoid walking through water or on icy surfaces with crutches. Resources OTHER

“About Crutches.” MediTrade Online, 2001. . “How to Use Crutches, Canes and Walkers.” About Orthopaedics. American Academy of Orthopaedic Surgeons Online. July 2000. . “How to Use Crutches on Stairs.” Physical Therapy. About.com. 2001. . “How to Use Crutches to Walk Safely.” Physical Therapy. About.com. 2001. . “Using Crutches.” McKinley Health Center. University of Illinois Online. November 2000. . “Walking with Crutches.” Rutgers Health Online. 2001. .

Mary Elizabeth Martelli, R.N., B.S.

Cryoglobulin test see Autoimmune disease tests Cryotherapy see Cooling treatments CSF analysis see Cerebrospinal fluid (CSF) analysis CT-myelogram see Myelography

Purpose Computed tomography is an x-ray imaging modality used for a variety of clinical applications. CT imaging equipment is used for spine and head imaging, gastrointestinal imaging, vascular imaging (e.g., signs of stroke, detection of blood clots), cancer staging and radiotherapy treatment planning, screening for cancers and heart disease, rapid imaging of trauma and pediatric patients, measuring bone mineral density for diagnosing osteoporosis, imaging of musculoskeletal disorders, detection of signs of infectious disease, and guidance of certain interventional procedures (e.g., biopsies). CT is the preferred imaging exam for diagnosing several types of cancers. CT scanners are also used to perform noninvasive angiographic imaging to assess the large blood vessels. Three-dimensional (3-D) image reconstruction, a feature available on many CT scanners, allows surgical procedure simulation and planning, postoperative evaluation, 3-D angiography, and virtual colonoscopy. Because computed tomography can clearly image soft tissue, bones, the lungs, and blood vessels, and can be used to diagnose so many diseases and conditions, CT scanners are often considered the backbone of a radiology department, and large hospitals may have multiple scanners to meet imaging demand. Because CT scanners are valuable in aiding in the evaluation of trauma and other emergency medical conditions, hospitals with large emergency volumes and major trauma centers may have a CT scanner located in and dedicated to the emergency department. Some types of CT scanners (electron-beam and multislice, see below) have begun to be used for wholebody scanning for preventive screening purposes; that is, asymptomatic individuals can have a full-body scan to see if heart disease, cancer, or other conditions are present. This application is primarily offered by independent imaging centers and is not reimbursed by insurance companies.

Description

CT imaging equipment Definition CT imaging equipment includes conventional, spiral, multi-slice, and electron-beam computed tomography full-body scanners, which use x rays to acquire cross-sectional images and computer workstations to 612

In general, a computed tomography scanner consists of a gantry, an x-ray system, a patient table, and a computer workstation. The gantry is a large square unit with an opening in the center through which the patient is moved during the scan. The gantry contains the x-ray system, which includes an x-ray tube, detectors, x-ray beam collimators, circuitry, and an x-ray generator. In some older CT scanners, the x-ray generator may be separate from the gantry. The patient table is designed for

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During a CT scan, the x-ray generator supplies power to the x-ray tube. X rays are produced by the x-ray tube and emitted as it is rotated around the patient. The x rays pass through the patient’s body to the detectors, which, depending on the CT scanner type and model, may consist of xenon gas ionization chambers or solidstate crystals (such as cesium-iodide or cadmiumtungstate). During each rotation, the detector produces electrical signals, which are generated after exposure to the x rays. These electrical signals are transferred to the computer, processed, and reconstructed into images using preprogrammed algorithms. Each rotation of the xray tube and detectors is reconstructed into an image that is referred to as a slice. The slice represents a cross-section of anatomical detail, and allows the inside of anatomical structures to be visualized, which is not possible with general radiography. Collimators are located near the x-ray tube and at each detector to minimize scatter radiation and to properly define the x-ray beam for the scan. The height of the collimators determines the slice thickness. There are several types of CT scanners currently in use that differ in configuration and scanning features. Conventional CT scanners, which were introduced in the 1970s, have cables attached to a detector array, and therefore, at the end of one x-ray tube rotation, the assembly must reverse to avoid tangling the cables. Conventional scanners, then, have the slowest scanning speed. Spiral CT scanners, also called helical or volumetric scanners, have a slip-ring configuration that allows continuous one-way rotation. In spiral scanning, the patient table is moved through the gantry while the x-ray tube and detector rotate in a spiral around the patient. Scanning speed is faster, thinner slices are acquired, and shorter patient breathholds are required than for conventional CT. Spiral CT scanners were introduced in 1989, and have since been considered a revolutionary advance in CT imaging due to the improvements in scanning speed and image quality that were possible compared to conventional CT scanners. Multislice scanners, which were introduced in 1998 and are considered the next revolution in CT imaging, have multiple rows of detectors that allow acquisition of multiple image slices during one x-ray tube rotation. Depending on the model and manufacturer, a multislice scanner may be up to eight times faster than a single-slice spiral scanner, and slices half as thin as those acquired on a spiral scanner are attainable. Multislice technology was still under development as of 2001.

Electron-beam CT scanners, also called ultrafast CT scanners, use a different scanning technology than other CT scanners, where x-ray tube rotation is mechanical. Electron-beam CT scanners have no moving parts, which makes such a fast scanning speed possible. An electron gun produces a focused electron beam that generates a rotating x-ray fan beam after being steered along tungsten target rings. Scan times are approximately ten times faster than multislice scanners because only the electron beam moves during scanning. Electron beam CT scanners were introduced in the mid-1980s and were designed for cardiac imaging and imaging of other moving structures (e.g., lungs, colon) due to their fast scanning speed. CT imaging equipment is often supplied with image archiving devices (e.g., compact disk jukebox, tape drive), image hard copy devices (e.g., x-ray film processor, laser imager), and networking capabilities, depending on the needs of the facility. Because CT is a digital modality, CT scanners are frequently networked with other digital equipment, such as ultrasound and magnetic resonance imaging (MRI) systems, to facilitate comparison of images on viewing monitors. In small hospitals or hospitals in rural areas, a CT scanner may not be installed; rather, a mobile CT scanning service may be contracted. A spiral CT scanner is installed in a specially designed trailer, which is driven to the hospital contracting the service. Prescheduled CT scans are then performed for the day or days the scanner is available at the hospital. Obviously, mobile CT only accommodates imaging in cases where the exam is not urgent.

Operation After the technologist properly preps and positions the patient on the scanning table, the technologist goes to the adjacent control room and begins the scan using the control computer workstation. Usually, the computer has preprogrammed scanning protocols for common types of scans (e.g., abdomen and pelvis, chest, head) and some computers allow customized scan protocols to be entered. During scanning, the technologist instructs the patient via an intercom system regarding breathholds and positioning. The controlling computer automatically moves the patient table according to the scanning parameters selected. The scan itself may only take five to 15 minutes, but total examination time may be up to 30 minutes, since the patient must be prepped and positioned. When the examination is completed, the technologist processes the image data using the computer workstation. Depending on the facility, images may be sent to an x-ray film processor or laser imager to be printed as hard copy and taken to a reading room, or they may be put on a

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both vertical and horizontal motion to accommodate various types of patient positions during the scan.

CT imaging equipment Computed tomography (CT) equipment uses x rays to obtain cross-sectional images of soft tissues of the body. (Pete Salutos/Custom Medical Stock Photo. Reproduced by permission.)

computer diskette or transferred via a digital image management system (picture archiving and communication system) for interpretation on a viewing monitor. Before the patient is moved off the table, the radiologic technologist should review the acquired images to be sure they are of sufficient diagnostic quality. Motion artifacts, which are streaks, blurs, or other inconsistencies in the image, may occur if the patient moves during the scan or when imaging moving structures (e.g., heart, lungs). Decreasing the acquired image slice thickness, changing the timing of the contrast material injection, and shortening the patient’s breathhold time can help reduce the occurrence of motion artifacts. The radiologic technologist should choose the scanning protocol that will provide optimal image quality with minimal radiation dose. Typical radiation doses for a CT scan are approximately equal to the amount of natural background radiation the average person is exposed to over a year. The patient radiation dose from a CT scan is slightly higher than that of a typical x-ray procedure. Newer multislice scanners may deliver a significantly higher radiation dose than single-slice spiral scanners; this higher dose is of special concern for pediatric 614

patients. The American Society of Radiologic Technologists (ASRT) has issued a statement regarding scanning protocols for pediatric scanning and recommends that specific scanning protocols be developed for pediatric patients and that CT equipment manufacturers develop a range of suggested parameters for pediatric patients based on weight. In addition, ASRT encourages technologists to be aware of radiation doses for their pediatric cases by using radiation shielding when necessary, adjusting patient positioning, using special dose filters, and increasing the pitch ratio (the table speed per gantry rotation) on spiral scans.

Maintenance Due to its high cost ($500,000 to over $1,000,000) and technical sophistication, CT imaging equipment is usually purchased with a service contract from the manufacturer or third party service provider that covers x-ray tube and other parts replacement and emergency service repair. The facility’s biomedical engineering department and medical physicist may also conduct annual preventive maintenance checks, as well as monthly calibration, image quality testing, and radiation dose moni-

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A technologist stays at computer controls while the patient is scanned with CT equipment. (Custom Medical Stock Photo. Reproduced by permission.)

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KEY TERMS Angiography—Imaging of the blood vessels of the body conventionally performed using an x-ray system and invasive catheterization, but that is performed on some CT scanners as a noninvasive alternative, since only an intravenous injection of contrast material is required. Contrast material—A chemical mixture injected intravenously, swallowed, or administered by enema before and/or during a CT scan to enhance imaging of the area of interest. Digital image management system; picture archiving and communication system—Systems of computer networking that allow exchange of images over the network or Internet, archiving of images for on-line access, and viewing of patient images and other data on a display monitor. These may encompass just the radiology department or an entire facility. CT scanners are frequently networked as part of these larger systems. Gantry—The large square unit that houses the xray system and related components and has an opening in the center through which the patient table is moved. Laser imager—A device that uses laser technology to produce hard copies of CT images; used instead of an x-ray film processor.

toring. A comprehensive quality control program that includes evaluation of image resolution, patient radiation dose, accuracy, image processing, patient table movement, and other overall system performance and image quality features should be followed. The radiologic technologist may be required to assist engineering staff with maintenance checks and service repairs. Most CT manufacturers offer remote diagnostic features on their equipment that facilitate repair of system problems. Communication via modem and telephone with service personnel and diagnostic software allows, for example, ordering of replacement parts, downloading of software to fix a problem, or immediate notification of an operational problem to repair personnel.

Health care team roles A radiologic technologist trained in computed tomography positions the patient on the table, administers any contrast material (intravenously, oral, or by 616

enema), and operates the CT scanner and computer workstation. Before administering any contrast material, the technologist will screen the patient for any allergies to medications or iodine and take a medical history to determine whether the patient has any medical condition (e.g., diabetes, asthma, heart disease, kidney or thyroid problems) that may interfere with CT imaging or indicate a higher risk of reaction to the contrast material. In addition, the technologist will ask female patients whether there is a possibility of pregnancy. The technologist will position lead aprons on appropriate areas of the patient to minimize unnecessary radiation exposure and provide lead aprons and other shielding for any individuals who must remain in the scan room (e.g., parents with children, staff monitoring a critical patient). During the CT scan, the technologist controls the imaging scan parameters using the computer workstation, and communicates instructions to the patient via an intercom system. The technologist is responsible for acquiring the requested images and ensuring that they are of diagnostic quality. A radiologist will interpret the CT images and compile a report that is sent to the requesting physician. Depending on the condition of the patient, other clinical staff may be present during the CT scan. Because CT is frequently used for trauma imaging, emergency medicine staff (nurses, emergency medical technicians) may be required to transport and monitor the patient.

Training Radiologic technologist education programs include specialized training on CT principles of operation, radiation dose, patient positioning and anatomy, and CT imaging techniques. Specific training for a particular CT scanner is provided by the manufacturer upon installation and/or a workshop at the manufacturer facility. Usually, training for technologists and physicians is included in the cost of the CT system and consists of three to four days of technical and clinical instruction. The manufacturer often provides follow-up on-site visits after installation. Resources BOOKS

Robb, Richard A. Biomedical Imaging, Visualization, and Analysis. New York: J. Wiley & Sons, 1999. PERIODICALS

Gunderman, R.B. “Physics of Spiral CT.” Applied Radiology (March 1996, Supplement): 13–16. Harvey, Dan. “Preventive CT Screening: Health Boon or Bane?” Radiology Today 2, no. 6 (March 12, 2001): 8-11. Napel, Sandy. “Design: Primer on Multislice CT Scanner Technology.” Diagnostic Imaging, November 1999

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ORGANIZATIONS

American College of Radiology. 1891 Preston White Drive, Reston, VA 20191-4397. (800)227-5463. . American Registry of Radiologic Technologists. 1255 Northland Drive. St. Paul, MN 55120-1155 (651) 6870048. . American Society of Radiologic Technologists (ASRT). 15000 Central Avenue SE, Albuquerque, NM 87123-2778. (800) 444-2778. . Radiological Society of North America. . OTHER

Computed Tomography (CT) Scanning of the Body. . CT Technology, Expanded Applications Blossom. .

Jennifer E. Sisk, M.A.

CT scans Definition Computed tomography (CT) scans are completed with the use of a 360-degree x-ray beam and computer production of images. These scans allow for crosssectional views of body organs and tissues.

Purpose CT scans are used to image a wide variety of body structures and internal organs. Since the 1990s, CT equipment has become more affordable and available. In some diagnoses, CT scans have become the first imaging exam of choice. Because the computerized image is so sharp, focused, and three-dimensional, many tissues can be better differentiated than on standard x rays. Common CT indications include: • Sinus studies. The CT scan can show details of sinusitis, and bone fractures. Physicians may order CT of the sinuses to provide an accurate map for surgery. • Brain studies. Brain scans can detect hematomas, tumors, and strokes. The introduction of CT scanning, especially spiral CT, has helped reduce the need for more invasive procedures such as cerebral angiography.

• Body scans. CT scans of the body will often be used to observe abdominal organs, such as the liver, kidneys, adrenal glands, spleen, and lymph nodes, and extremities. • Aorta scans. CT scans can focus on the thoracic or abdominal aorta to locate aneurysms and other possible aortic diseases. • Chest scans. CT scans of the chest are useful in distinguishing tumors and in detailing accumulation of fluid in chest infections.

Precautions Pregnant women or those who could possibly be pregnant should not have a CT scan unless the diagnostic benefits outweigh the risks. Pregnant patients should particularly avoid full body or abdominal scans. If the exam is necessary for obstetric purposes, technologists are instructed not to repeat films if there are errors. Pregnant patients receiving CT or any x-ray exam away from the abdominal area may be protected by a lead apron; most radiation, known as scatter, travels through the body and is not blocked by the apron. Contrast agents are often used in CT exams and the use of these agents should be discussed with the medical professional prior to the procedure. Patients should be asked to sign a consent form concerning the administration of contrast media. One common ingredient in contrast agents, iodine, can cause allergic reactions. Patients who are known to be allergic to iodine (or shellfish) should inform the physician prior to the CT scan.

Description Computed tomography, also called CT scan, CAT scan, or computerized axial tomography, is a combination of focused x-ray beams, a detector array, and computerized production of an image. Introduced in the early 1970s, this radiologic procedure has advanced rapidly and is now widely used, sometimes in the place of standard x rays. CT equipment A CT scan may be performed in a hospital or outpatient imaging center. Although the equipment looks large and intimidating, it is very sophisticated and fairly comfortable. The patient is asked to lie on a narrow table that slides into the center of the scanner, called the gantry. The scanner looks like a square doughnut with a round opening in the middle, which allows the x-ray beam to rotate around the patient. The scanner’s gantry section

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Supplement. .

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may also be tilted slightly to allow for certain crosssectional angles. CT procedure The patient will feel the table move very slightly as the precise adjustments for each sectional image are made. A technologist watches the procedure from a window and views the images on a monitor. It is essential that the patient lie very still during the procedure to prevent motion blurring. In some studies, such as chest CTs, the patient will be asked to hold his or her breath during image capture. Following the procedure, films of the images are usually printed for the radiologist and referring physician to review. A radiologist can also interpret CT exams on a special viewing console. The procedure time will vary in length depending on the area being imaged. Average study times are from 30 to 60 minutes. Some patients may be concerned about claustrophobia but the width of the gantry portion of the scanner is narrow enough to preclude problems with claustrophobia, in most instances. The CT image While traditional x rays image organs in two dimensions, with the possibility that organs in the front of the body are superimposed over those in the back, CT scans allow for a more three-dimensional effect. Some have compared CT images to slices in a loaf of bread. Precise sections of the body can be located and imaged as crosssectional views. The technologist’s console displays a computerized image of each section captured by the xray beam and detector array. Thus, various densities of tissue can be easily distinguished. Contrast agents Contrast agents are often used in CT exams and in other radiology procedures to demonstrate certain anatomic details which, otherwise, may not be easily seen. Some contrast agents are natural, such as air or water. Other times, a water-based contrast agent is administered for specific diagnostic purposes. Barium sulfate is commonly used in gastrointestinal procedures. The patient may drink this contrast medium, or receive it in an enema. Oral and rectal contrast are usually given when examining the abdomen or gastrointestinal tract, and not used when scanning the brain or chest. Iodine based contrast media are the most widely used intravenous contrast agents and are usually administered through an antecubital (in front of the elbow) vein. 618

If contrast agents are used in the CT exam, these will be administered several minutes before the study begins. Abdominal CT patients may be asked to drink a contrast medium. Some patients may experience a salty taste, flushing of the face, warmth or slight nausea, or hives from an intravenous contrast injection. Technologists and radiologists have equipment and training to help patients through these minor reactions and to handle more severe reactions. Severe reactions to contrast are rare, but do occur. Spiral CT Spiral CT, also called helical CT, is a newer version of CT scanning which is continuous in motion and allows for three-dimensional recreation of images. For example, traditional CT allows the technologist to take slices at very small and precise intervals one after the other. Spiral CT allows for a continuous flow of images, without stopping the scanner to move to the next image slice. A major advantage of spiral CT is the ability to reconstruct images anywhere along the length of the study area. The procedure also speeds up the imaging process, meaning less time for the patient to lie still. The ability to image contrast more rapidly after it is injected, when it is at its highest level, is another advantage of spiral CT’s high speed. Some facilities will have both spiral and conventional CT available. Although spiral is more advantageous for many applications, conventional CT is still a superior and precise method for imaging many tissues and structures. The physician will evaluate which type of CT works best for the specific exam purpose.

Preparation If a contrast medium must be administered, the patient may be asked to fast from about four to six hours prior to the procedure. Patients will usually be given a gown (like a typical hospital gown) to be worn during the procedure. All metal and jewelry should be removed to avoid artifacts on the film.

Aftercare No aftercare is generally required following a CT scan. Immediately following the exam, the technologist will continue to watch the patient for possible adverse contrast reactions. Patients are instructed to advise the technologist of any symptoms, particularly respiratory difficulty. The site of contrast injection will be bandaged and may feel tender following the exam. Hives may develop later and usually do not require treatment.

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Complications Radiation exposure from a CT scan is similar to, though higher than, that of a conventional x ray. Although this is a risk to pregnant women, the exposure to other adults is minimal and should produce no effects. Although severe contrast reactions are rare, they are a risk of many CT procedures. There is also a small risk of renal failure in high-risk patients.

Results Normal findings on a CT exam show bone, the most dense tissue, as white areas. Tissues and fat will show as various shades of gray, and fluids will be gray or black. Air will also look black and darker than fat tissue. Intravenous, oral, and rectal contrast appear as white areas. The radiologist can determine if tissues and organs appear normal by the different gradations of the gray shadows. In CT, the images which can cut through a section of tissue or organ provide three-dimensional viewing for the radiologist and referring physician. Abnormal results may show different characteristics of tissues within organs. Accumulations of blood or other fluids where they do not belong may be detected. Radiologists can differentiate among types of tumors throughout the body by viewing details of their makeup. Sinus studies The increasing availability and lowered cost of CT scanning has lead to its increased use in sinus studies, either as a replacement for a sinus x ray or as a follow-up to an abnormal sinus radiograph. The sensitivity of CT allows for location of areas of sinus infection, particularly chronic infection, and is useful for planning prior to functional endoscopic sinus surgery. CT scans can show the extent and location of tiny fractures of the sinus and nasal bones. Foreign bodies in the sinus and nasal area are also easily detected by CT. CT imaging of the sinuses is important in evaluating trauma or disease of the sphenoid bone (the wedge-shaped bone at the base of the skull). Sinus tumors will show as shades of gray indicating the difference in their density from that of normal tissues in the area. Brain studies The precise differences in density allowed by CT scanning can clearly show tumors, strokes, or other lesions in the brain area as altered densities. These lighter or darker areas on the image may indicate a tumor or hemorrhage within the brain and skull area.

A computerized axial tomography (CAT) scan of the human brain. (Custom Medical Stock Photo. Reproduced by permission.)

Different types of tumors can be identified by the presence of edema, by the tissue’s density, or by studying blood vessel location and activity. Congenital abnormalities in children, such as hydrocephalus, may also be confirmed with CT. Hydrocephalus is suggested by enlargement of the fluid structures called ventricles of the brain. Body scans The body scan can identify abnormal body structures and organs. Throughout the body, a CT scan may indicate tumors or cysts, enlarged lymph nodes, abnormal collections of fluid, blood, or fat, and metastasis of cancer. Fractures or damage to soft tissues can be more easily seen on the sensitive images produced by CT scanning, though CT is not usually done for these types of examinations because of cost. Liver conditions, such as cirrhosis, abscess, and fatty liver, may be observed with a CT body scan.

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KEY TERMS Aneurysm—The bulging of the blood vessel wall. Aortic aneurysms are the most dangerous. Aneurysms can break and cause bleeding. Contrast (agent, medium)—A substance injected into the body that illuminates certain structures that would otherwise be hard or impossible to see on the radiograph (film). Gantry—A name for the portion of a CT scanner which houses the x-ray tube and detector array used to capture image information and send it to the computer. Hematoma—A collection of blood that has escaped from the vessels. It may clot and harden, causing pain to the patient. Hydrocephalus—A collection of fluid on or around the brain. The pressure from the spinal fluid causes the ventricles to widen.

also assign numerical values to the various densities. Mass lesions in the lungs may be indicative of tuberculosis or tumors. CT will help distinguish between the two. Enlarged lymph nodes in the chest area may indicate lymphoma. Spiral CT is particularly effective at identifying pulmonary emboli (clots in the lung’s blood vessels). Resources BOOKS

Springhouse Corporation. Illustrated Guide to Diagnostic Tests. Springhouse, PA: Springhouse Corporation, 1998. PERIODICALS

Papatheofanis, Frank J. “Helical CT and Pulmonary Disease.” Decisions in Imaging Economics (January/February 1997): 61-63. ORGANIZATIONS

American College of Radiology. 1891 Preston White Drive, Reston, VA 20191-4397. (800)ACR-LINE. .

Stephen John Hage, AAAS, RT(R), FAHRA

Metastasis—Secondary cancer, or cancer that has spread from one body organ or tissue to another. Radiologist—A medical doctor specially trained in radiology (x-ray) interpretation and its use in the diagnosis of disease and injury. Spiral CT—Also referred to as helical CT, this method allows for continuous 360-degree x-ray image capture. Thoracic—Refers to the chest area. The thorax runs between the abdomen and neck and is encased in the ribs.

CT of the aorta CT provides the ability to see and measure the thickness of the aortal wall, which is very helpful in diagnosing aortic aneurysms. The use of contrast will help define details within the aorta. In addition, increased areas of density can identify calcification, which helps differentiate between acute and chronic problems. An abnormal CT scan may indicate signs of aortic clots. Aortic rupture is suggested by signs such as a hematoma around the aorta or the escape of blood from its cavity. Chest scans

Definition Cultural sensitivity begins with a recognition that there are differences between cultures. These differences are reflected in the ways that different groups communicate and relate to one another, and they carry over into interactions with health care providers. Cultural sensitivity does not mean, however, that a person need only be aware of the differences to interact effectively with people from other cultures. If health care providers and their patients are to interact effectively, they must move beyond both cultural sensitivity and cultural biases that create barriers. Developing this kind of culturally competent attitude is an ongoing process. A culturally competent clinician views all patients as unique individuals and realizes that their experiences, beliefs, values, and language affect their perceptions of clinical service delivery, acceptance of a diagnosis, and compliance.

Description

In addition to those findings which may indicate aortic aneurysms, chest CT studies can show other problems in the heart and lungs. The computer will not only show differences between air, water, tissues, and bone, but will 620

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Cultural competence is an important component of nursing care. This is especially true given America’s increasingly diverse patient population and the disparities in the health status of people from different racial, ethnic,

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• Speak in short sentences or phrases, to make translating easier for the interpreter. Make sure the patient understands what he or she has been told by asking for him/her to repeat the message in his/her own words.

Recognizing differences among cultures is important, but the clinician should also be aware that differences also exist within cultures. The assumption that a common culture is shared by all members of a racial, linguistic, or religious group is erroneous. The larger group may share common historic and geographic experiences, but individuals within the group may share nothing beyond that.

• Be sensitive to cultural differences when using nonverbal communication. For example, a touch has many cultural meanings. Clinicians must be aware that personal space has different boundaries in different cultures.

Culture greatly influences how people view their health and the health care services they receive. Clinicians should be aware of these differences, respect them, and work within the parameters set by the patient’s values. Clinicians must also recognize their own cultural values and draw parallels where possible; they should also identify any prejudices and stereotypes that prevent them from communicating effectively with patients from different cultures. The language barrier Language differences between the clinician and the patient are a further barrier to optimum health care. Where possible, hospital or local school translators should be used, since it’s not always in the client’s best interest to have a family member act as an interpreter. The client may feel uncomfortable discussing personal matters in front of a relative. In addition the interpreter may lack a medical vocabulary, or may reinterpret what the patient says in an effort to “help.” Role conflicts may further hinder translation. For example, a child or a person of the opposite sex may be embarrassed by the information or feel it improper to convey the message intended. When using an interpreter the clinician should: • Try to find an unrelated interpreter of the same sex as the patient, who is able to translate medical information clearly. • Schedule more time for the appointment, if possible. Discuss the focus of the session with the interpreter before the patient arrives; be clear about what the interpreter should convey to the patient. • Have the interpreter meet with the patient before the session to assess his or her educational level. This will determine how complex the discussion can become. If the patient has already met the clinician, the interpreter should be presented as a member of the healthcare team.

• Remember who the patient is—keep the focus on the patient, not the interpreter.

Viewpoints One of the biggest debates about cultural competence is whether the health care provider should be of the same culture or speak the same language as the patient. Many clinicians from racial, ethnic, or cultural minorities believe very strongly that providers should be of the same culture as the patient. Others believe this is unnecessary and wrongly maligns people who aren’t members of that specific group. Another area of disagreement is whether training programs, such as diversity workshops, affect cultural competence. The argument against them is that cognitive information does not necessarily change attitudes or behavior.

Professional implications In order to be culturally competent clinicians need not possess full knowledge of every cultural practice and belief. Instead they should be sensitive to others’ preferences and values, and should not assume that one person’s preferences and values apply to everyone in that same group. Patients are often willing to share their customs with those who seek to understand them. Genuine concern about what is important to the client is the best way to insure that culturally competent care will be provided. Resources BOOKS

Chrisman, Noel J., and Phyllis Arn Zimmer. “Cultural Competence in Primary Care.” In Adult Primary Care. Edited by P. V. Meredith and N. M. Horan. Philadelphia: W. B. Saunders, 2000. Chrisman, Noel J., and Phyllis Arn Zimmer. “Transforming Health Care through Cultural Competence Training.” In Cultural Diversity in Nursing: Issues, Strategies and Outcomes. Washington, DC: American Academy of Nursing, 1997.

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socioeconomic, religious, and cultural backgrounds. To value this diversity a clinician must respect the differences seen in other people, including customs, thoughts, behaviors, communication styles, values, traditions, and institutions.

Cultural sensitivity

Cultural Assessment Interview Guide Name: Nickname or other names or special meaning attributed to your name: Primary language: When speaking When writing Date of birth: Place of birth: Educational level or specialized training: To which ethnic group do you belong? To what extent do you identify with your cultural group? Who is the spokesperson for your family? Describe some of the customs or beliefs that you have about the following: Health Life Illness Death How do you learn information best? Reading Having someone explain verbally Having someone demonstrate Describe some of your family's dietary habits and your personal food preferences.

Are there any foods forbidden from your diet for religious or cultural reasons?

Describe your religious affiliation. What role do your religious beliefs and practices play in your life during times of good health and bad health?

Who do you rely on for health care services or healing and what type of cultural health practices have you been exposed to?

Are there any sanctions or restrictions in your culture that the person taking care of you should know?

Describe your current living arrangements.

Cultural assessment interview guide. (Delmar Publishers, Inc. Reproduced by permission.)

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PERIODICALS

Uffen, Ellen. “Becoming a Culturally Competent Clinician.” American Speech-Language Hearing Association Leader (April 2001). OTHER

Blue, Amy V. “Provision of Culturally Competent Health Care.” Medical University of South Carolina, Deans’ Rural Primary Care Clerkship. . Chrisman, Noel J., Ph.D., M.P.H. Professor, Community Health Nursing, School of Nursing, University of Washington. Interview by author. Cohen, Elena, and Tawara D.,Goode. “Why Is There a Compelling Need for Cultural Competence?” National Center for Cultural Competence. . “How Does Cultural Competency Differ from Cultural Sensitivity?” Center for Effective Collaboration and Practice. . King, Mark A., Anthony Sims, and David Osher. “How Is Cultural Competence Intergrated into Education?” Center for Effective Collaboration and Practice. . Palinkas, Lawrence A., Ph.D. Professor, Department of Family and Preventive Medicine, University of California, San Diego. Interview by author. “Why Is Cultural Competence Important for Health Professionals?” Diversity Rx. .

Barb Chandler

Cultures for sexually transmitted diseases see Sexually transmitted diseases cultures Cuts see Wounds CVA see Cerebrovascular accident CVS see Chorionic villus sampling Cyanocobalamin see Vitamin B12

Cyanosis Definition Cyanosis is a physical state characterized by bluish discoloration of the skin and mucus membranes.

This elderly woman’s lips turned purple due to central cyanosis, a condition most commonly due to slow blood circulation, leading to a bluish skin coloration. (Photo Researchers, Inc. Reproduced by permission.)

Description Cyanosis is a physical sign, rather than a diagnosis. The abnormal coloring of a cyanotic patient is due to a low oxygen content of the circulating red blood cells. Typically the abnormal bluish coloring is most noticeable in the nailbeds, lips, ears, and cheeks.

Causes and symptoms One of the many important functions of blood is to pick up oxygen from the air sacs of the lungs and deliver it to sites around the body in need of oxygen. To carry oxygen, red blood cells (RBCs) contain a pigment called hemoglobin. When hemoglobin is carrying its full capacity of oxygen, it will cause the RBC to appear bright red. After the oxygen has been delivered, the RBC has a darker, bluish cast. If the darker-colored RBCs predominate, this gives the skin and mucus membranes the characteristic blue appearance of cyanosis. There are two basic types of cyanosis: central and peripheral. Central cyanosis means that the arterial blood simply does not contain normal levels of oxygen (hypoxemia). This can happen because of lung disease, heart defects, and certain problems with the hemoglobin itself. Peripheral cyanosis means that venous blood (or blood that has unloaded its oxygen) is contributing to skin color more than arterial (or oxygen-rich) blood. A patient may have normal oxygen levels in arterial blood, but still have the bluish color of cyanosis expressed in some part(s) of his body. With peripheral cyanosis the underlying condition may be exposure to the cold, or decreased output from the heart, or local disruptions in the flow of arterial or venous blood.

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opment in a given patient. Prompt recognition and treatment could be very important to clinical outcome.

KEY TERMS Hemoglobin—A colored substance (pigment) in the red blood cell that carries oxygen to tissues and gives blood its red color. Pulse oximeter—A painless device which uses a beam of light directed through the patient’s finger, toe or earlobe to assess oxygen saturation of the blood.

Resources BOOKS

Braunwald, Eugene, et al. Harrison’s Principles of Internal Medicine. New York: McGraw-Hill, 2001. Carolson, Karen J., Stephanie A. Eisenstat, and Terra Ziporyn. The Harvard Guide to Women’s Health. Cambridge, MA: Harvard University Press, 1996.

Erika J. Norris Patients may or may not have symptoms with cyanosis, depending on its cause. With central cyanosis patients are often short of breath, dizzy, or even unconscious. With a peripheral cause of cyanosis, patients may have complaints localized to the affected parts of the body.

Definition

Diagnosis Cyanosis is a subjective observation, so there is no test to confirm it. A patient’s skin pigmentation and the presence or absence of anemia can make cyanosis more or less obvious. But there are objective tests to verify the presence or absence of hypoxemia (or low oxygen content of the blood). A non-invasive pulse oximeter can be used by a nurse or respiratory therapist to give a fairly accurate approximation of arterial oxygenation, and arterial blood gases can be drawn by a physician or respiratory therapist if detailed information is needed. If the arterial oxygen level is low, the cyanosis is central; if the oxygen level is normal, the cyanosis is peripheral in nature. If the affected body parts regain normal color with massage and warming, the cause was peripheral. Occasionally cyanosis has both central and peripheral elements.

Treatment Treatment of cyanosis is based on identifying and treating its cause, and restoring normal flow of oxygenated blood.

Prognosis Prognosis is dependent on the disease process underlying the cyanosis. If the underlying condition (such as heart or lung disease) can be properly treated, the skin will return to its normal coloring.

Health care team roles Health care team members should be alert to cyanosis as a warning sign, particularly as a new devel624

Cybermedicine Cybermedicine, also known as e-health, involves the provision of health care services using the Internet for communication.

Description The growth of the Internet since the early 1990s, from a small network used in academia and government to a global infrastructure, has radically affected the delivery of health care. The health care industry has begun the complex process of linking previously disparate computer databases and patient-management applications together via the Internet. It is also adopting Internet-ready technologies, such as hand-held computers, Web cameras, decision-support and voice-recognition software, and wireless-transmission technology. The loftiest hope for cybermedicine is that it will create a fertile ground for patient-clinician partnerships as well as allow for more efficient management of health-related information. However, many issues of concern remain before the benefits of cybermedicine can be maximized while closely protecting the privacy and confidentiality rights of patient and clinician. The strongest advocates of cybermedicine currently are consumers who use the Internet as a health-research tool. As of 2001, nearly one-third of the 250 million annual searches on the Medline Web site managed by the National Library of Medicine were conducted by patients and the general public. Thousands of public- and privatesector health Web sites exist; some target specific diseases such as prostate cancer, while others provide general health information. Some of these sites allow individuals to conduct disease screenings, or lifestyle and

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The Internet is also increasingly used for telemedicine, which is cybermedicine involving the provision of care over the Internet. Patients with access to computers and the Internet may consult with their physicians online, receiving a diagnosis, treatment plan, and drug prescriptions for relatively simple disorders without faceto-face meetings. Computer-based decision-support software and videoconferencing technology are also used to provide telemedicine to chronically ill patients at home, and to help people with chronic diseases to self-monitor their conditions. People with diabetes, for example, may download data from a blood-glucose meter, record information about their medications, diet, and symptoms, and transmit these data to their health care providers. Teleradiology has been in operation for years but has vastly improved with the ability to transfer large amounts of data quickly. Genetics specialists are using telemedicine for genetic evaluations and services in rural areas. The future of telemedicine is projected to include longdistance robotic surgeries and quick tests of patients’ DNA. Remote surgery is an application of interest. Using a Web camera, a live transmission is sent from the operating room, where the patient is, to the office of a specialist, in another location. The specialist guides the on-site surgeon through the procedure. One of the fastest growing applications of cybermedicine is in health business-support services. For example, WebMD, Medscape, and the American Medical Association’s Medem are gradually moving traditional, office-based medical practices to the Web by offering online services for physicians, including the electronic transmission and storage of patient information, claims processing, billing procedures, and access to medical databases.

Viewpoints Since e-mail and other tools of cybermedicine are more impersonal than face-to-face communication, critics observe that cybermedicine may challenge the ability of patients and clinicians to make emotional connections, such as to foster trust; physicians may find it too easy to dehumanize patients, thereby lessening patients’ involvement in decision making. As regards remote surgery, critics question what happens if the Internet service fails during a crucial transmission. Perhaps the major issue of

concern is how to protect patient privacy/confidentiality over the Internet. Proponents of cybermedicine point out that the ability to improve the flow of information between patients and clinicians gives significant potential to improve patient health. E-mail allows patients and clinicians to transmit detailed medical information and may increase opportunities for clinicians to provide social support to patients. Cybermedicine offers the potential to empower patients because patients may access the same on-line medical information as clinicians, thereby making the clinician-patient relationship potentially more democratic. Patients armed with accurate medical information may not be able to treat themselves, but they will be better informed and better able to assist in treatment decision making. Another concern about cybermedicine is the difficulty of ensuring that Internet health content is both accurate and unbiased toward any product brands, thus maintaining the integrity of the line between e-health and e-commerce. To address this issue, many health-information Web sites are establishing ethical guidelines addressing issues such as commercial advertising, privacy, and accuracy of information. The American Telemedicine Association and the American Medical Informatics Association have established ethical and clinical guidelines for health care Web sites, health-related e-mail, and home-based telemedicine.

Professional implications All indications suggest that cybermedicine practices will only increase. Health care practitioners should learn how to take advantage of this technology while recognizing its potential drawbacks, including concerns about individual patients’ ability to assess symptoms and relate status effectively and clearly via the Internet. There is research suggesting that patients with chronic diseases such as diabetes or asthma and other chronic obstructive pulmonary disease (COPD) tend to underestimate the severity of their symptoms and to overestimate the degree of control that exists. Patients with breathing difficulties, for instance, cannot be adequately or accurately assessed without physical evaluation of the lungs and trachea and without in-office pulmonary-function tests. People with diabetes may find ways to modify results or underplay symptom reports via e-mail, so medications will not be changed. Practitioners will also need to stay abreast of legal developments in cybermedicine. One legislative development expected to play a role in cybermedicine is the Health Insurance Portability and Accountability Act of 1996 (HIPAA). This act calls for protection of patient

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quality-of-life assessments. Government health organizations, such as the Centers for Disease Control and Prevention, take advantage of the Internet’s large audience by using the Internet as a public-health information bulletin board. Similarly, the World Health Organization reports communicable-disease outbreaks on the Internet.

Cystic fibrosis

health information, and it allows patients to access their medical records, which in the context of cybermedicine will probably be done electronically. In December of 2000, the HIPAA Privacy Rule was issued. It gives patients greater access to their own medical records and allows them to control how personal health information is used. Resources

Cystic fibrosis Definition Cystic fibrosis (CF) is an inherited disease that affects the lungs, digestive system, and sweat glands, and causes infertility in males. Its name derives from the fibrous scar tissue that develops in the pancreas, one of the principal organs affected by the disease.

PERIODICALS

Bauer, K. “Using the Internet to Empower Patients and to Develop Partnerships with Clinicians?” The American Journal of Bioethics Online: In Focus 2001: 1, 2. . Eysenbach, G., T. Diepgen, et al. “Shopping Around the Internet Today and Tomorrow: Towards the Millennium of Cybermedicine.” British Medical Journal 319, no. 1 (1999): 294. Furguson, T. “Online Patient-helpers and Physicians Working Together.” British Medical Journal 321 (2000): 1129-32. Winker, M. A., et al. “Guidelines for Medical and Health Information on the Internet: Principles Governing AMA Web Sites.” Journal of the American Medical Association 283 no. 12 (2000): 1600-6. ORGANIZATIONS

The American Health Information Management Association. 233 North Michigan Avenue, Suite 2150, Chicago, IL 60601. (312) 233-1100. . American Medical Association. The Council on Ethical and Judicial Affairs. 515 North State Street, Chicago, IL 60610. (312) 464-4823. . American Medical Informatics Association. 4915 St. Elmo Avenue, Suite 401, Bethesda, MD 20814 (301) 6571291. . American Telemedicine Association. 910 Seventeenth Street NW, Suite 314, Washington, DC 20006. (202) 223-3333. . ANA, American Nurses Association, 600 Maryland Avenue SW, Suite 100 West, Washington, DC 20024. (800) 2744ANA. . Center for Bioethics at the University of Pennsylvania, Suite 320, 3401 Market Street, Philadelphia, PA 19104-3308. (215) 898-7136. . NSNA, National Student Nurses Association, 555 West 57th Street, New York, NY 10019. (212) 581-2211. . OTHER

Health Care Financing Administration. The Health Insurance Portability and Accountability Act of 1996 (HIPAA) Page. .

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Description Cystic fibrosis affects the body’s ability to move salt and water in and out of cells. This defect causes the lungs and pancreas to secrete thick mucus, an inflammatory response that blocks passageways—particularly airway passages—and therefore prevents proper functioning of the affected areas. CF affects approximately 30,000 children and young adults in the United States, where approximately 3,000 babies are born with CF every year. CF primarily affects people of white northern-European descent. Rates of CF are much lower in nonwhite populations. Many of the symptoms of CF can be treated with drugs or nutritional supplements. Close attention to and prompt treatment of respiratory and digestive complications have dramatically increased the expected life span of a person with CF. Several decades ago, most children with CF died by the age of two years. By the end of the twentieth century, about one-half of all people with CF lived past 31 years of age. That median age is expected to grow as new treatments are developed. It is estimated that a person born in 2001 with CF has a median expected life span of about 40 years.

Genetic profiles Cystic fibrosis is a genetic disease, meaning it is caused by a defect passed on through the genes. Genes, found in the nucleus of all body cells, control cell function by serving as the blueprint for the production of proteins. Proteins carry out a wide variety of functions within cells. The cystic fibrosis transmembrane conductance regulator (CFTR) gene, when defective, causes CF. A simple defect in this gene leads to all the consequences of CF. There are more than 500 known defects in the CFTR gene that can cause CF. However, mutation delta F508 in exon 10 is present in about 70% of CF chromosomes worldwide. Genes can be thought of as long strings of chemical words, each made of chemical letters called nucleotides. Just as rearranging its letters can change a word and changing a word can change a sentence, genes can be

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The CFTR protein helps to produce mucus. Mucus is a complex mixture of salts, water, sugars, and proteins that cleanses, lubricates, and protects many passageways in the body, including those in the lungs and pancreas. The role of the CFTR protein is to allow chloride ions to exit from mucus-producing cells. When the chloride ions leave these cells, water follows, thinning the mucus. In this way, the CFTR protein helps to keep mucus from becoming thick and sluggish, thus allowing the mucus to be moved steadily along the passageways to aid in cleansing. In CF the CFTR protein does not allow chloride ions out of the mucus-producing cells. With less chloride leaving, less water leaves, and the mucus becomes thick and sticky. It can no longer move freely through the passageways, so they become clogged. In the pancreas, clogged passageways prevent secretion of digestive enzymes (including insulin) into the intestine, causing serious impairment of digestion, especially of fats, which may lead to malnutrition. Mucus in the lungs may plug the airways, preventing good air exchange and, ultimately, leading to emphysema or COPD. The mucus is also a rich source of nutrients for bacteria, leading to frequent infections such as sinusitis, bronchitis, and gastritis. Inheritance factor To understand the inheritance pattern of CF, it is important to realize that genes actually have two functions. First, they serve as the blueprint for the production of proteins. Second, they are the material of inheritance: parents pass on characteristics to their children by combining the genes in egg and sperm to make a new individual. Each person actually has two copies of each gene, including the CFTR gene, in each of their body cells. During sperm and egg production, however, these two copies separate, so that each sperm or egg contains only one copy of each gene. When sperm and egg unite, the newly created cell once again has two copies of each gene. The two gene copies may be the same or they may be slightly different. For the CFTR gene, for instance, a person may have two normal copies, or one normal and one mutated copy, or two mutated copies. A person with two mutated copies will develop cystic fibrosis. A person

with one mutated copy is said to be a carrier. A carrier will not have symptoms of CF but can pass on the mutated CFTR gene to children. When two carriers have children, they have a one-infour chance of having a child with CF each time they conceive, a two-in-four chance of having a child who is a carrier, and a one-in-four chance of having a child with two normal CFTR genes. There are large differences in the frequency of mutated CF genes among different ethnic populations. For example, the frequency is highest in populations of northern-European descent—approximately one in every 25 Americans of northern-European descent is a carrier of the mutated CF gene, while only one in 17,000 African Americans and one in 30,000 Asian Americans are carriers. Since carriers are symptom-free, very few people know whether or not they are carriers unless there is a family history of the disease. Two white Americans with no family history of CF have a one-in-2,500 chance of having a child with CF. It may seem puzzling that a mutated gene with such harmful consequences would remain so common. One might expect that the high mortality rate for CF patients before reaching childbearing age would quickly lead to the loss of the mutated gene from the population. It appears, however, that carriers may be protected from the intense diarrhea and eventual death by dehydration caused by cholera and typhoid fever. (This so-called “heterozygote advantage” is seen in some other genetic disorders, including sickle-cell anemia.) Some researchers believe that when these epidemics spread through early European populations, which were then much smaller, they would wipe out vast numbers in that population. However, people who carried one copy of the CF gene would have a greater chance of survival and so, therefore, would the defective gene. The incidence of the gene, then, would increase to a high level within that population. In hot climates, where dehydration from chronic excessive salt loss (perspiring) caused more deaths than occasional bouts of life-threatening diarrhea, the CF gene never gained the foothold it did in the colder European countries. Also, some researchers propose that CF heterozygotes are more resistant to asthma.

Causes and symptoms The most severe effects of cystic fibrosis are seen in two body systems: the gastrointestinal (digestive) system, and the respiratory tract from the nose to the lungs. CF also affects the sweat glands and male fertility. Symptoms develop gradually; gastrointestinal symptoms are often the first to appear.

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mutated, or changed, by changes in the sequence of their nucleotide letters. The gene defects in CF are called point mutations, meaning that the gene is mutated only at one small spot along its length. In other words, the deltaF508 mutation is a loss of one “letter” out of thousands within the CFTR gene. As a result, the CFTR protein made from its blueprint is made incorrectly and cannot properly perform its function.

Cystic fibrosis

may eventually become barrel-shaped as the patient struggles with breathing and with the formation of emphysema-like symptoms. Diabetes becomes increasingly likely as a person with CF ages. Scarring of the pancreas slowly destroys those pancreatic cells that produce insulin, producing type I, or insulin-dependent, diabetes mellitus. Gall stones affect approximately 10% of adults with CF. Liver problems are less common, but can be caused by the buildup of fat within the liver. Complications of liver enlargement may include internal hemorrhaging, abdominal fluid (ascites), spleen enlargement, and liver failure. Lung tissue from a patient with cystic fibrosis. (Custom Medical Stock Photo. Reproduced by permission.)

Gastrointestinal system Ten to fifteen percent of babies who inherit CF have meconium ileus at birth. Meconium is the first dark stool that a baby passes after birth. Ileus is an obstruction of the digestive tract. The meconium of a newborn with meconium ileus is thickened and sticky due to the presence of thickened mucus from the intestinal mucus glands. Meconium ileus causes abdominal swelling and vomiting, and often requires surgery immediately after birth. Presence of meconium ileus is considered highly indicative of CF. Borderline cases may be misdiagnosed, however, and attributed instead to a “milk allergy.” Other abdominal symptoms are caused by the inability of the pancreas to supply digestive enzymes to the intestine. During normal digestion, as food passes from the stomach into the small intestine, it is mixed with pancreatic secretions (including insulin) that help break down the nutrients for absorption. While the intestines themselves also provide some digestive enzymes, the pancreas is the major source of enzymes for the digestion of all types of foods, especially fats and proteins. In CF, thick mucus blocks the already inflamed pancreatic duct. Eventually, the duct becomes completely closed off by subsequent scar tissue formation, leading to a condition known as pancreatic insufficiency. Without pancreatic enzymes large amounts of undigested food pass into the large intestine. Bacterial action on this rich food source can cause gas and abdominal swelling. The large amount of fat remaining in the feces makes it bulky, oily, and foul-smelling. Because nutrients are poorly digested and absorbed, a person with CF is often ravenously hungry, underweight, and shorter than expected for a given age. When CF is not treated for a longer period, a child may develop symptoms of malnutrition, including anemia, bloating, and—paradoxically—appetite loss. The rib cage 628

Other gastrointestinal symptoms can include a prolapsed rectum, in which part of the rectal lining protrudes through the anus; intestinal obstruction; and rarely, intussusception (telescoping), in which part of the intestinal tube slips over an adjoining part, cutting off blood supply. Somewhat less than 10% of people with CF do not have gastrointestinal symptoms. Most of these people do not have the delta-F508 mutation, but rather a different one, which presumably allows at least some CFTRinduced proteins to function normally in the pancreas. Respiratory tract The respiratory tract includes the nose, throat, trachea (or windpipe), main bronchus, bronchi (that branch off from the main stem bronchus within each lung), the smaller bronchioles, and the blind sacs called alveoli in which gas exchange takes place between air and blood through the capillaries feeding the alveoli. Swelling of the sinus mucus membrane lining is common in people with CF. This usually shows up on x ray and may aid the diagnosis of CF. However, this swelling, called pansinusitis, rarely causes problems unless there is blockage and infection. Children with CF have a high rate of infection of the sinuses, requiring antibiotic therapy to prevent the infection from proceeding to the lungs. Nasal polyps, or growths, affect about one in five people with CF. These growths are not cancerous and do not require removal unless they block nasal drainage enough to cause chronic sinus infections. However, they are usually treated medically before surgery is considered. While nasal polyps appear in older people without CF, especially those with allergies, they are rare in children without CF. The lungs are the site of the most life-threatening effects of CF. The hyperinflammatory state of the membranes causes production of a thick, sticky mucus (that is actually the body’s attempt to soothe the affected area).

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The bronchioles and bronchi normally produce a thin, clear mucus that traps foreign particles, including bacteria and viruses. Tiny hair-like projections, called cilia, on the surface of these passageways slowly move mucus out of the lungs and up the bronchus to the trachea and the back of the throat, where it may be swallowed or coughed up. This “mucociliary escalator” is one of the principal defenses against lung infection. The thickened mucus of CF prevents ciliary movement of debris out of the lungs and increases the irritation and existing inflammation of airways and lung tissue. This inflammation swells the passageways, partially closing them down, further hampering the movement of mucus. A person with CF is likely to cough more frequently and more vigorously as their lungs attempt to clean themselves out. At the same time, infection becomes more likely, since the mucus is a rich source of nutrients. Bronchitis, bronchiolitis, and pneumonia are frequent in CF. The most common infecting organisms are the bacteria Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas aeruginosa. A small percentage of people with CF have infections caused by Burkholderia cepacia, a bacterium that is resistant to most current antibiotics (Burkholderia cepacia was formerly known as Pseudomonas cepacia). The fungus Aspergillus fumigatus may infect older children and adults. The body’s response to inflammation and infection is to increase mucus production; white blood cells fighting the infection thicken the mucus even further as they break down and release their cell contents. These white blood cell constituents serve as messengers to enhance the production of both inflammatory and antiinflammatory cells and mediators. As mucus accumulates it can plug up the smaller passageways in the lungs, decreasing functional lung volume. Inhaling enough air (oxygen) can become difficult; fatigue, shortness of breath, and intolerance of exercise become more common. Because air passes obstructions more easily during inhalation than during exhalation, over time, air becomes trapped in the smallest chambers of the lungs, the alveoli. As millions of

alveoli gradually expand, the chest takes on the enlarged, barrel-shaped appearance typical of emphysema. For unknown reasons recurrent respiratory infections or impairment lead to “digital clubbing,” in which the last joint of the fingers and toes becomes slightly enlarged and the distal fingernail edges curl around and over the enlarged fingertip. Sweat glands The CFTR protein helps to regulate the amount of salt in perspiration. People with CF have perspiration with a higher salt content than normal, and measuring the saltiness of a person’s sweat is a key diagnostic test for CF. Parents may notice that their infants taste salty when they kiss them. Excess salt loss is not usually a problem, except during prolonged exercise or heat. While most older children and adults with CF compensate for this extra salt loss by eating more salty foods, infants and young children are in danger of suffering its effects (such as heat prostration), especially during summer, and require electrolyte supplementation. Heat prostration is marked by lethargy, weakness, and loss of appetite, and should be treated as an emergency condition, especially in children and the elderly. Fertility Ninety-eight percent of men with CF are sterile due to complete obstruction or absence of the vas deferens, the tube carrying sperm out of the testes. While boys and men with CF form normal sperm and have normal levels of sex hormones, sperm are unable to leave the testes, and fertilization is not possible. Most women with CF are fertile, though they often have more difficulty conceiving than women without CF. In both boys and girls, puberty is often delayed, most likely due to the effects of poor nutrition or chronic lung infection. Women with CF who have good lung health usually have no problems with pregnancy, while those with ongoing lung infection often do poorly. The potential for digestive disruption from intestinal displacement may also pose problems, regardless of lung function.

Diagnosis The decision to test a child for cystic fibrosis may be triggered by concerns about recurring gastrointestinal or respiratory symptoms, or salty sweat. A child born with meconium ileus will be tested before leaving the hospital. Families with a history of CF may wish to have all children tested, especially if one child has already manifested the disease. Some hospitals now require routine screening of newborns for CF.

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However, this mucus increases the likelihood of infection, decreases the ability to protect against infection, and causes further blockage of normal functioning in the airways. This blockage, in turn, exacerbates the inflammation and swelling. The functional capacity of the lungs is therefore severely compromised and may ultimately lead to emphysema. People with CF will live with chronic obstructive pulmonary disease (COPD) or bacterial residence in their lungs. Lung infection is the major cause of death for those with CF.

Cystic fibrosis

Treatment

Sweat test The sweat test is both the easiest and most accurate test for CF. In this test, a small amount of the drug pilocarpine is placed on the skin. A very small electrical current is then applied to the area, which drives the pilocarpine into the skin. The drug stimulates sweating in the treated area. The sweat is absorbed onto a piece of filter paper and analyzed for its salt content. A person with CF will have salt concentrations that are one and one-half to two times greater than normal. The test can be done on persons of any age, including newborns, and its results can be determined within an hour. Virtually every person who has CF will test positively on it, and virtually everyone who does not have the disease will test negatively. Genetic testing The discovery of the CFTR gene mutation in 1989 allowed the development of an accurate genetic test for CF. Genes from a small blood or tissue sample are analyzed for specific mutations; presence of two copies of the mutated gene confirms the diagnosis of CF in all but a very few cases. However, since there are so many different possible mutations, and since testing for all of them would be too expensive and time consuming, it is important to remember that a negative gene test cannot rule out the possibility of CF. Couples planning a family may decide to have themselves tested if one or both have a family history of CF. Prenatal genetic testing is possible through amniocentesis. Many couples who already have one child with CF decide to undergo prenatal screening in subsequent pregnancies and use the results to determine whether to terminate the pregnancy. Siblings in these families are also usually tested, both to determine if they will develop CF and if they are carriers. This aids in their own family planning. If the sibling has no symptoms, determining carrier status is often delayed until the teen years or later, when persons are closer to needing the information to make decisions. Newborn screening Some states now require screening of all newborns for CF using a test known as the IRT test—a blood test that measures the level of immunoreactive trypsinogen. Babies with CF generally have higher levers of IRT; however, this test is not an accurate predictor as it gives many false positive results immediately after birth. A second test is therefore required several weeks later for validation. A second positive result indicates the need to conduct a sweat test. 630

There is no cure for cystic fibrosis. Treatment has advanced considerably since the mid-1900s, increasing both the life span and the quality of life for most people affected by CF. Early diagnosis is important to prevent malnutrition and infection from weakening a young child. With proper management, many people with CF may participate in the full range of school and sports activities. Nutrition People with CF usually require high-calorie diets and vitamin supplements. Height, weight, and growth of a person with CF are regularly monitored. Most people with CF need to take pancreatic enzymes to supplement or replace the inadequate secretions of the pancreas. Tablets containing pancreatic enzymes are taken with every meal; depending on the size of the tablet and the meal, as many as 20 tablets may be needed at a time. Because of incomplete absorption even with pancreatic enzymes, a person with CF needs to take in about 30% more food than a person without CF. Low-fat diets are not recommended, except in special circumstances, since fat is a source of both essential fatty acids and abundant calories, but the high calorie diet does not include increased fat intake (above normal). Some people with CF cannot absorb enough nutrients from the foods they eat, even with specialized diets and enzymes. For these people, tube feeding is an option. Nutrients can be introduced directly into the stomach through a tube inserted either through the nose (a nasogastric tube) or through the abdominal wall (a gastrostomy tube). A jejunostomy tube, inserted into the small intestine, is also an option. Tube feeding can provide nutrition at any time, including at night while a person is sleeping, allowing constant intake of high-quality nutrients. The feeding tube may be removed or temporarily occluded during the day, allowing the patient to take food by mouth. Respiratory health The key to maintaining respiratory health in a person with CF is regular monitoring and early treatment. Pulmonary function tests are done frequently to track changes in functional lung volume and respiratory effort. Sputum samples are analyzed to determine the types of bacteria present in the lungs. Chest x rays are usually taken at least once a year. Lung scans are performed with the patient inhaling radioactive contrast gas that helps define areas on the lungs not visible with x rays. Pulmonary circulation may be monitored by injection of a radioactive substance into the bloodstream.

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Clearing mucus from the lungs also helps prevent infection, and mucus control is an important aspect of CF management. Bronchial drainage (postural drainage) allows gravity to aid the mucociliary escalator. For this technique the patient lies on a tilted surface with head downward (Trendelenburg); alternately on the stomach, back, or side, depending on the section of lung to be drained. An assistant performs respiratory percussion techniques with varying strokes, rhythms, and hand positions, moving systematically over the patient’s chest, rib cage, and upper back to help loosen secretions. A device called a “flutter” offers another way to loosen secretions: it consists of a stainless steel ball in a tube. When a person exhales through it, the ball vibrates, sending vibrations back through the air in the lungs. Some special breathing techniques, such as diaphragmatic breathing, and rib cage expansion and locking that allows the diaphragm freedom of movement, may also help clear the lungs. Several drugs are available to prevent the airways from becoming clogged with mucus. Bronchodilators can help open up the airways, steroids reduce inflammation, and mucolytics loosen secretions. Surfactants are used to reduce the surface tension of the mucus, like a detergent breaks the surface tension of water and oils. Acetylcysteine (Mucomyst) has been used as a mucolytic for many years but now is less frequently prescribed, while DNase (Pulmozyme) is a newer product gaining in popularity. DNase is an enzyme that helps break down the DNA from dead white blood cells and bacteria found in thick mucus. People with CF may contract cross-infected bacteria from other persons with CF. This is especially true of Burkholderia cepacia, which is not usually found in people without CF. While the ideal recommendation from a health standpoint might be to avoid contact with others who have CF, this is not always practical (since CF is a familial disease and CF clinics are a major site of care), nor does it meet the psychological and social needs of patients. At a minimum, CF centers recommend avoiding prolonged close contact between people with CF, and the use of scrupulous hygiene techniques, including frequent hand washing. Some CF clinics schedule appointments

on different days for those with and without B. cepacia colonies. Some doctors choose to prescribe antibiotics for patients with CF only during an infection, while others prefer long-term prophylactic antibiotic treatment against S. aureus. The choice of antibiotic depends on the particular organism or organisms found. Some antibiotics are given as aerosols directly into the lungs. Antibiotic treatment for patients with CF, by necessity, may be prolonged and aggressive. Supplemental oxygen may be needed as lung disease in CF progresses. In some cases, respiratory failure episodes require the temporary use of a ventilator to perform the work of breathing until the patient can begin to regain control and be weaned from the machine. Lung transplantation is another option for people with CF, although the number of people who receive them is still much lower than those who need them. Transplantation is not a cure, however, and has been likened to trading one disease for another because longterm immunosuppression is required, increasing the likelihood of contracting opportunistic infections. About 50% of adults and more than 80% of children with CF who receive lung transplants live longer than two years posttransplant. Liver transplants may also be required for people with CF whose livers have been damaged by fibrosis. Long-term use of ibuprofen as an antiinflammatory agent has been shown to help some people with CF. Close medical supervision is necessary, however, since the effective dose for patients with CF is high and not everyone benefits. Ibuprofen at these higher doses interferes with kidney function and, if taken together with aminoglycoside antibiotics, may cause kidney failure. A number of experimental treatments are under research. Some evidence indicates that aminoglycoside antibiotics may help overcome the genetic defect in some CF mutations, allowing the protein to be made normally. While promising, these results would apply to only about 5% of those with CF. Gene therapy has become the most ambitious approach to curing CF. In this set of techniques, copies of the healthy CFTR gene are delivered to affected cells, where they are accepted and used to create the CFTR protein. While elegant and simple in theory, gene therapy has met with a large number of difficulties in trials so far, including immune resistance, very short life-cycle duration of the introduced gene, and inadequately widespread distribution.

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People with CF live with chronic bacterial colonization. This means that their lungs are constantly host to several species of bacteria. Good general health, especially good nutrition, may keep the immune system functioning well, decreasing the frequency with which the resistant bacterial colonies multiply and cause infection or attack lung tissue. Exercise is also important to promote pulmonary health, and people with CF are encouraged to maintain a regular exercise program.

Cystic fibrosis

Alternative treatment

KEY TERMS Carrier—In CF, a person with one copy of a defective gene who does not have the disease it causes but can pass along the defective gene to offspring.

In homeopathic medicine the primary goal is to address the symptoms of CF in order to enhance quality of life. It is not yet possible to treat the cause, owing to the genetic basis of the disease. Homeopathic medicine seeks to treat the whole person, however, and in cystic fibrosis, this approach may include:

Chronic obstruction pulmonary disease (COPD)—A progressive disease process that commonly stems from smoking. COPD is characterized by difficulty breathing, wheezing, and a chronic cough.

• mucolytics to help thin the mucous

Cystic fibrosis transmembrane conductance regulator (CFTR)—The protein responsible for regulating chloride movement across cells in some tissues. When a person has two defective copies of the CFTR gene, cystic fibrosis is the result.

• hydrotherapy techniques (such as nighttime mist tents) to help ease respiratory symptoms and help the body eliminate mucus from the lungs

Emphysema—A pathologic accumulation of residual air in organs or tissues. This term is especially applied to the condition when in the lungs. Gastrostomy tube—A tube that is inserted through a small incision in the abdominal wall and that extends through the stomach wall into the stomach for the purpose of introducing parenteral feedings. Jejunostomy tube—A tube inserted through the abdominal wall and into the small intestine for the purpose of introducing parenteral feeding. Lung surfactant—A surface active agent that renders the alveolar surfaces hydrophobic and prevents the lung filling with water by capillary action. Meconium ileus—Obstructed bowel due to impacted, tenacious, meconium (infant’s first stool). Mucociliary escalator—The coordinated action of tiny projections on the surfaces of cells lining the respiratory tract that moves mucus up and out of the lungs. Mucolytic—An agent that dissolves or destroys mucin, the chief component of mucus. Nasogastric tube—A tube inserted through the nose, extending through the pharynx and esophagus, and into the stomach for the purpose of introducing parenteral feeding. Pancreatic insufficiency—Reduction or absence of pancreatic secretions into the digestive system due to scarring and blockage of the pancreatic duct.

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• supplementation of pancreatic enzymes to assist in digestion • addressing respiratory symptoms to open lung passages

• immune enhancements (such as vitamin supplementation) to help prevent development of secondary infections • dietary enhancements and adjustments to treat digestive and nutritional problems

Prognosis Approximately half of all people with CF live past the age of 30 years; however, because of earlier intervention and enhanced treatment, a person born in 2001 with CF may be expected, on average, to live to 40 years of age. People with CF may lead relatively normal lives. Careful consideration of the effects pregnancy may have on a woman with CF is essential before beginning a family. Issues of parental longevity and the potential for the child to be a carrier are also concerns. Although most men with CF are functionally sterile, new procedures for removing sperm from the testes are being attempted that may offer more men suffering from CF the chance to become fathers.

Health care team roles A pediatrician usually makes the initial diagnosis of CF. Family physicians, internists, and pulmonologists can manage persons with CF. Radiologists take images to document the extent of CF. Nurses, respiratory therapists, physical therapists, and nutritionists provide symptomatic treatments and supportive services. Surgeons are needed if transplantation is required.

Prevention As of 2001 there was no way to prevent the development of CF in a person with two defective copies of

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Resources BOOKS

Boat, Thomas F. “Cystic Fibrosis.” In Nelson Textbook of Pediatrics, 16th ed., Eds. Richard E. Behrman, et al. Philadelphia: Saunders, 2000, 1315-1327. Boucher, Richard C. “Cystic Fibrosis.” In Harrison’s Principles of Internal Medicine, 14th ed. Eds. Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 1488-1451. Gold, Susan D. Cystic Fibrosis. Berkeley Heights: Enslow Publishers, Inc., 2000. Orenstein, David M, and Robert C. Stern, eds. Treatment of the Hospitalized Cystic Fibrosis Patient. New York: Marcel Dekker, 1998. Orenstein, David M, Robert C. Stern, and Beryl J. Rosenstein. Cystic Fibrosis: Medical Care. Philadelphia: Lippincott Williams & Wilkins, 2000. Welsh, Michael J. “Cystic Fibrosis.” In Pocket Companion to Cecil Textbook of Medicine. 21st ed. Eds. Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, 401-405. Yankaskas, James R., and Michael R. Knowles. Cystic Fibrosis in Adults. Philadelphia: Lippincott Williams & Wilkins, 1999. PERIODICALS

Abbott, J., M. Dodd, L. Gee, and K. Webb. “Ways of Coping with Cystic Fibrosis: Implications for Treatment Adherence.” Disability and Rehabilitation 23, no. 8 (2001): 315-324. Braekeleer, M.D., G. Bellis, G. Rault, C. Allard, M. Milot, and F. Simard. “Disease Knowledge in a High-Risk Population for Cystic Fibrosis.” Patient Education and Counseling 43, no. 3 (2001): 265-270. Dakin, C., R.L. Henry, P. Field, and J. Morton. “Defining an Exacerbation of Pulmonary Disease in Cystic Fibrosis.” Pediatric Pulmonology 31, no. 6 (2001): 436-442. Kurland, G., and D.M. Orenstein. “Lung Transplantation and Cystic Fibrosis: The Psychosocial Toll.” Pediatrics 107, no. 6 (2001): 1419-1420. Truby, H., and A.S. Paxton. “Body Image and Dieting Behavior in Cystic Fibrosis.” Pediatrics 107, no. 6 (2001): E92. Wilson, D.C., M. Rashid, P.R. Durie, A. Tsang, D. Kalnins, M. Andrew, M. Corey, J. Shin, E. Tullis, and P.B. Pencharz. “Treatment of Vitamin K Deficiency in Cystic Fibrosis: Effectiveness of a Daily Fat-Soluble Vitamin Combination.” Journal of Pediatrics 138, no. 6 (2001): 851-855.

ORGANIZATIONS

American Lung Association, 1740 Broadway, New York, NY 10019. (212) 315-8700. . American Thoracic Society. 1740 Broadway, New York, NY 10019. (212) 315-8700. . Canadian Cystic Fibrosis Foundation. 2221 Yonge Street, Suite 601, Toronto, Ontario, M4S 2B4. (416) 485-9149. . Cystic Fibrosis Foundation. 6931 Arlington Road, Bethesda, Maryland 20814. (301) 951-4422 or (800) 344-4823. . International Association of Cystic Fibrosis Adults. . OTHER

American Association for Respiratory Care. . CF Web. . Cystic-L. . Merck Manual. . Michigan State University (testing). . National Institute of Diabetes and Digestive and Kidney Diseases. . National Library of Medicine. and .

L. Fleming Fallon, Jr., M.D, Dr.P.H.

Cystometry Definition Cystometry is a test of bladder function in which pressure and volume of fluid in the bladder is measured during filling, storage, and voiding.

Purpose A cystometry study is performed to diagnose problems with urination, including incontinence, urinary retention, and recurrent urinary tract infections. The urinary bladder stores urine produced by the kidneys. The main muscle of the bladder wall, the detrusor, relaxes to allow expansion of the bladder during filling. The ure-

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the relevant gene from both parents. Adults with a family history of CF may obtain a genetic test of their carrier status for purposes of family planning. Prenatal testing is also available to determine the genetic status of the infant with regard to CF.

Cystometry

rectal probe to account for the contribution of the abdominal muscles to the pressure recording.

KEY TERMS Anticholinergics—Drugs that prevent the action of acetylcholine, a compound released by nerve endings. Cholinergics—Drugs that mimic the action of acetylcholine, a compound released by nerve endings. Detrusor—Muscle of the bladder wall. Residual urine volume—Amount of urine remaining after voiding. Sphincter—Ring of muscle between the bladder and the urethra that functions to close off the urethra. Urethra—Tube which empties urine from the bladder to the exterior of the body.

thra, the tube through which urine exits, is held closed by a ring of muscle known as the urethral sphincter. As volume increases, stretching of the detrusor and pressure on the sphincter sends signals to the brain, indicating the need for urination, or voiding. Voluntary relaxation of the sphincter and automatic contractions of the detrusor allow successful and virtually complete voiding. Urinary difficulties may occur because of weak or hyperactive sphincter or detrusor, or non-coordination of their two activities. Infection of the bladder or urethra may cause incontinence, as can obstruction of the urethra from scar tissue, prostate enlargement, or other benign or cancerous growths. Loss of sensation due to nerve damage can lead to chronic overfilling.

Precautions The mild irritation of the urinary tract necessary for insertion of the catheter may occasionally cause flushing, sweating, and nausea. Cystometry is contraindicated in patients with urinary tract infection because of the potential for false results and the possibility of exacerbating the infection.

The bladder is then gradually filled with either warm water, room temperature water, saline solution, carbon dioxide gas, or a contrast solution for x-ray analysis, depending on the type of study being done. The patient is asked to describe sensations during filling, including temperature sensations and when the first feeling of bladder fullness occurs. Once the bladder has completely filled, the patient is asked to begin voiding, and pressure and volume measurements are again taken, as well as flow rate. It is important to instruct the patient not to strain while voiding during the test. Straining can alter the test results.

Preparation There are no special food or fluid restrictions needed to prepare for this test. The patient may be asked to stop taking certain medications in advance of the test, including sedatives, cholinergics, and anticholinergics.

Aftercare Cystometry may be somewhat uncomfortable. Urinary frequency or urgency and some hematuria (reddish urine), may last for a day. Increasing fluid intake helps to flush out the bladder. Caffeinated, carbonated, or alcoholic beverages are discouraged, because they may irritate the bladder lining. A warm bath or sitz bath may be recommended to soothe the patient.

Risks There is a risk of upper or lower urinary infection due to tearing of the urethral lining. Although extremely rare, in some male patients, infection of the epididymis (tubules at the back of the testis) can occur and lead to infertility. Damage to the urethra or bladder sometimes occurs but usually heals without treatment. Rarely an allergic reaction may occur due to the contrast dye or medications. Patients should notify their health care provider if they develop any of these symptoms: • blood in the urine beyond several voidings • fever or chills

Description

• lower back pain

The patient begins by emptying the bladder as much as possible. A thin plastic catheter is then gently inserted into the urethra until it reaches the bladder. Measurements are taken of the residual urine volume and bladder pressure. Pressure measurements may require a 634

Results The normal bladder should not begin contractions during filling and should initially expand without resistance. A feeling of fullness occurs with a volume of 100-

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Inability of the bladder to relax during filling, or low bladder volume, may indicate interstitial cystitis, prostate enlargement, or bladder cancer. Contraction of the bladder during filling may be due to irritation from infection or cysts, obstruction of the bladder outlet, or neurological disease such as stroke, multiple sclerosis, or spinal cord injury. Diminished sensation may occur with nerve lesions, peripheral neuropathy, or chronic overfilling.

Health care team roles A cystometry may be performed in the hospital, doctor’s office, or outpatient facility by a physician or nurse. Resources BOOKS

Lamm D. L., A. S. Paola, and F. A. Paola. Campbell’s Urology: Review and Assessment. Philadelphia: W.B. Saunders, 1995.

Purpose Cystoscopy is performed by urologists to examine the entire bladder lining and take biopsies of any questionable areas. Cystoscopy may be prescribed for patients who display the following: • blood in the urine (hematuria) • inability to control urination (incontinence) • urinary tract infection • signs of congenital abnormalities in the urinary tract • suspected tumors in the bladder • bladder or kidney stones • signs or symptoms of an enlarged prostate • pain or difficulty urinating (dysuria) • disorders of or injuries to the urinary tract • symptoms of interstitial cystitis Blood and urine studies, in addition to x rays of the kidneys, ureters, and bladder, may be performed before a cystoscopy to obtain as much diagnostic information as possible. During the cystoscopy, a retrograde pyelogram may also be performed to examine the kidneys and ureters.

Precautions

ORGANIZATIONS

American Nephrology Nurses Association. ANNA National Office, East Holly Avenue Box 56 Pitman NJ 080710056. (888) 600-2662. . Society of Urologic Nurses and Associates. National Headquarters, East Holly Avenue, Box 56, Pitman, NJ 08071-0056. (888) TAP-SUNA. .

Cystoscopy is a commonly performed procedure, but it is an invasive technique that involves small yet significant risk. If anesthesia is required, there is additional risk, particularly for people who are obese, smoke, or are in poor health. Those undergoing anesthesia must inform the doctor of any medications they are taking.

OTHER

Kidney Information Clearing House. .

Maggie Boleyn, R.N., B.S.N.

Cystoscopy Definition Cystoscopy (cystourethroscopy) is a diagnostic procedure that uses an endoscope especially designed for urological use to examine the bladder, lower urinary tract, and prostate gland. It can also be used to collect urine samples, perform biopsies, and remove small stones.

Description A cystoscopy typically lasts from 10 to 40 minutes. The patient is asked to urinate before surgery. A welllubricated flexible or rigid cystoscope (urethroscope) is inserted through the urethra into the bladder where a urine sample is taken. Fluid is then injected to inflate the bladder and allow the urologist to examine the entire bladder wall. The cystoscope uses a lighted tip for guidance and enables biopsies to be taken or small stones to be removed through a hollow channel in the cystoscope. During a cystoscopy, the urologist may remove bladder stones or kidney stones, gather tissue samples, and perform x-ray studies. To remove stones, an instrument that resembles a tiny basket or grasper is inserted through the cystoscope so that small stones can be extracted through the scope’s channel. For a biopsy, specially designed forceps are inserted through the cystoscope to

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200 ml. Adult bladder capacity varies dependent on gender. Normal adult female bladder capacity ranges between 250 to 550 ml, and normal adult male capacity ranges from 350 to 750 ml. The sphincter should relax and open when the patient wills it, accompanied by detrusor contractions. During voiding, detrusor contraction should be smooth and lead to a steady urine stream.

Cystoscopy

Light cord Cystoscope (a type of endoscope)

Urinary bladder

Water cord Light Prostate gland

Rectum

Illustration of cytoscopy procedure. (Delmar Publishers, Inc. Reproduced by permission.)

pinch off a tissue sample. Alternatively, a small brushlike instrument may be inserted to scrape off some tissue. To perform x-ray studies such as a retrograde pyelogram, a dye is injected into the ureters by way of a catheter passed through the cystoscope. After completion of all needed tests, the cystoscope is removed.

Preparation Cystoscopy can be performed in a hospital, doctor’s office, or outpatient surgical facility. Spinal or general anesthesia may be used for the procedure. Distension of the bladder with fluid is particularly painful, and if it needs to be done, as in the case of evaluating interstitial cystitis, general anesthesia is required. Cystoscopy is typically performed on an outpatient basis, but up to three days of recovery in the hospital is sometimes required. 636

Aftercare Patients who have undergone a cystoscopy are instructed to: • take warm baths to relieve pain • rest and refrain from driving for several days, especially if general anesthesia was needed • expect any blood in the urine to clear up in one to two days • avoid strenuous exercise during recovery • postpone sexual relations until the urologist determines that healing is complete Patients may be prescribed pain relievers and antibiotics following surgery. Minor pain may also be treated with over-the-counter, non-prescription drugs such as acetaminophen.

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As with any surgical procedure, there are some risks involved with a cystoscopy. Complications may include profuse bleeding, a damaged urethra, a perforated bladder, a urinary tract infection, or an injured penis. Patients should contact their physician if they experience any of the following symptoms following the procedure: pain, redness, swelling, drainage or bleeding from the surgical site; signs of generalized infection, which may include headache, muscle aches, dizziness or an overall ill feeling and fever; nausea or vomiting; or difficult or painful urination.

Results A successful cystoscopy includes a thorough examination of the bladder and collection of urine samples for cultures. If no abnormalities are seen, the results are indicated as normal. Cystoscopy allows the urologist to detect inflammation of the bladder lining, prostatic enlargement, or tumors. If these are seen, further evaluation or biopsies may be needed. Cystoscopy with bladder distention can also evaluate interstitial cystitis. Bladder stones, urethral strictures, diverticula, or congenital abnormalities can also be detected.

Health care team roles Cystoscopy is performed in a hospital operating room, cystoscopy suite, or urologist’s office, depending on the condition of the patient and the anesthesia required. If general anesthesia is required, an anesthesiologist is necessary to administer the anesthesia and monitor the patient. The cystoscopy procedure is performed by a urologist, urologic surgeon, or urogynecologist, with assistance from nurses experienced in urologic procedures. If x rays are taken during the procedure, a uroradiologist or radiologic technologist is required to operate the x-ray equipment. Biopsy tissue samples are sent to the clinical laboratory for examination by a pathologist.

KEY TERMS Diverticula—A pouch or sac occurring normally or from a herniation or defect in a membrane. Cystoscopy can detect diverticula in the urinary tract. Endoscopy—A minimally invasive procedure that involves examination of body organs or cavities using an endoscope (a lighted optical instrument used to see inside body cavities). A cystoscope is a type of endoscope. Interstitial cystitis—A chronic inflammatory condition of the bladder involving symptoms of bladder pain, frequent urination, and burning during urination. Diagnosis is confirmed by cystoscopy with the bladder distended by fluid. Retrograde pyelogram—A pyelography or x-ray technique in which radiopaque dye is injected into the kidneys through the ureters. Ureter—The tube that carries urine from the kidneys to the bladder. Urethra—The tube that carries urine from the bladder to outside the body. In females, the urethral opening is between the vagina and clitoris; in males the urethra travels through the penis, opening at the tip. Urogynecologist—A physician that specializes in female medical conditions concerning the urinary and reproductive systems. Uroradiologist—A radiologist who specializes in diagnostic imaging of the urinary tract and kidneys.

Tierney, Lawrence M. Jr., Stephen J. McPhee, and Maxine A. Papadakis, eds. “Urology.” In Current Medical Diagnosis and Treatment. Stamford, CT: Appleton & Lange, 1996. PERIODICALS

Sant, Grannum R., and Philip M. Hanno. “Interstitial Cystitis: Current Issues and Controversies in Diagnosis.” Urology 57, Supplement 6A (June 2001): 82-88.

Resources

ORGANIZATIONS

BOOKS

American Urological Association. 1120 North Charles Street, Baltimore, MD 21201. (410) 727-1100. . Interstitial Cystitis Association. 51 Monroe Street, Suite 1402, Rockville, MD 20850. (301) 610-5300. . Society of Urologic Nurses and Associates. East Holly Avenue, Box 56, Pitman, NJ 08071-0056. (609) 256-2335. .

Buckman, Robert. “Bladder.” In What You Really Need to Know about Cancer: A Comprehensive Guide for Patients and Their Families. Baltimore, MD: The Johns Hopkins University Press, 1997. Segen, Joseph C., and Joseph Stauffer. “Cystoscopy.” In The Patient’s Guide to Medical Tests: Everything You Need to Know about the Tests Your Doctor Prescribes. New York: Facts On File, 1998.

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Complications

Cytomegalovirus antibody screening test

OTHER

“What is IC? Interstitial Cystitis Fact Sheet.” Interstitial Cystitis Association. .

Jennifer E. Sisk

Cytogenetic tests see Genetic testing

Blood is usually screened for CMV antibodies before being transfused into a person with a weakened immune system. CMV infection can be very similar to illness due to Epstein-Barr virus. If there is a need to know the specific source of a patient’s symptoms, antibody screening distinguishes between these two infections.

Cytomegalovirus antibody screening test Definition

Precautions

Cytomegalovirus (CMV) is a common human virus. When first exposed to CMV, a healthy person’s immune system is triggered and quickly makes antibodies to fight the virus. Specialized screening tests can be done to document the presence or absence of antibodies specific to the cytomegalovirus. Antibodies to CMV can be evidence of a current or a past infection.

Purpose Up to 85% of people have antibodies to CMV by the time they are 40 years old. In a healthy, nonpregnant person, CMV infection is almost never serious. Symptoms, if present, are mild, often resembling infectious mononucleosis caused by the Epstein-Barr virus. However, consequences of CMV infection can be devastating to the fetus, transplant patients, patients with human immunodeficiency virus (HIV) and other patients with suppressed immune systems. People with weakened immune systems are vulnerable to infection from several routes, including from another person, from a donated organ or transfused blood, or from reactivation of a past infection. CMV is related to the herpes simplex and varicella (chickenpox) viruses in that it remains dormant in the body but can resurface with or without symptoms. Antibody screening helps control the infection risk for high risk groups. For instance, before a transplant, both the recipient and donor are usually tested for antibodies. A recipient who has never had CMV (negative for antibodies) should not receive an organ from a donor who has had CMV (positive for antibodies) because active infection could be acquired by the recipient. CVM infection in this context can be associated with organ rejection, or can cause illness such as pneumonia, hepatitis, or death. In some transplant patients, particularly after bone marrow transplantation, testing may be done as often as every week to screen for new or recurrent infection. 638

Women who do not have evidence of previous CMV infection (i.e. antibody screen negative) should try to avoid exposure to CMV in pregnancy. CMV infection is the most common congenital infection (existing at birth). The infection, passed from mother to baby, can cause permanent mental or physical damage, or death. However, CMV antibody screening is not routinely ordered as part of prenatal care.

Tests for CMV are performed on serum or biopsied tissue. Blood is collected by venipuncture by a nurse or phlebotomist. When collecting blood or handling tissue the health care provider should observe universal precautions for the prevention of transmission of bloodborne pathogens. Tests for immunoglobulin M (IgM) antibodies to CMV may be falsely positive in persons with rheumatoid arthritis. It is important to remember that an antibody screening test may not be useful in a person without an intact immune system. People with weak immune systems may not generate antibodies against CMV. A suspected infection in a transplant patient or a person with AIDS is confirmed with other tests, such as a viral culture, examination of biopsied material for cytopathic effects, or a viral DNA assay such as the polymerase chain reaction.

Description The most frequently used antibody test for CMV is an enzyme linked immunosorbent assay (ELISA). In this test, CMV antigens are attached to the bottom of the wells of a microtiter plate. An initial dilution of the patient’s serum is added to a well of the plate and incubated. If antibodies to the CMV virus are present they attach to the CMV antigens in the well. The plate is washed and antihuman immunoglobulin G (IgG) or IgM conjugated to alkaline phosphatase is added. This antibody will attach to any antigen-antibody complexes in the wells. The plate is washed again, and substrate (e.g., p-nitrophenylphosphate) is added. The plate is incubated to allow the enzyme to split the phosphate from the substrate, which results in production of a yellow color. After incubating, a reagent (strong alkali) is added to stop the enzyme reaction and the optical density of the wells is measured. The test is interpreted as positive if the optical density of the patient’s sample is equal to or high-

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Preparation This test requires 5 mL of blood. Collection of the sample takes only a few minutes.

Aftercare Discomfort or bruising may occur at the puncture site, or the person may feel dizzy or faint. Pressure to the puncture site until the bleeding stops reduces bruising. Applying warm packs to the puncture site relieves discomfort.

Complications The most common complication is a bruise at the site of the puncture or excessive bleeding. The patient can apply moist warm compresses if there is any discomfort.

Results A person without previous exposure to CMV will test negative. A positive test for CMV antibodies means the person is infected or has been infected previously with the virus. An antibody titre that is significantly higher at the end of the illness than at the beginning, or the presence of IgM antibodies, indicates a recent or current first-time infection. A positive antibody test does not mean that the person has lifetime immunity. After an infection, this virus, like all members of the herpesvirus group, can stay dormant inside a person and cause infection if the person’s immune system later weakens and antibody protection decreases. In fact, reactivation of such latent infection is not uncommon and usually occurs without symptoms.

KEY TERMS Antibodies—Proteins made by the body to attach to foreign molecules called antigens and aid in their destruction. Antigen—A marker on the surface of a molecule which stimulates an immune response and can be identified using the specific antibody formed against it. Titre—A term denoting the concentration of an antibody. The titre is defined as the reciprocal of the highest dilution of the sample that gives a positive reaction.

Health care team roles CMV antibody tests are ordered and interpreted by a physician. The sample is usually collected by a nurse or phlebotomist. Testing is performed by clinical laboratory scientists/medical technologists. Nurses, nurse practitioners, and physician assistants will educate patient about the purpose of the test, the nature of the CMV infection, and the consequences specific to the individual’s situation. Resources BOOKS

Fischbach, Frances Talaska. A Manual of Laboratory and Diagnostic Tests. 5th ed. Philadelphia: Lippincott, 2000, p. 607-608. Tierney, Lawrence M., Stephen J. McPhee, and Maxine A. Papadakis. Current Medical Diagnosis and Treatment 2001. New York: Lange Medical Books/McGraw-Hill, 2001, p. 1316-1317. OTHER

“CMV Screening.” Centers for Disease Control. 2001. . MedLine Plus. 2001. .

Erika J. Norris

Cytomegalovirus test see TORCH test

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er than the low-level standard. Multiple calibrators can be used to quantify the amount of anti-CMV in the patient’s sample. Tests that measure a specific type of antibody help differentiate between a current and a past infection. IgM antibodies appear at the beginning of an infection and last only weeks. IgG antibodies appear 1014 days later and can last a lifetime. A person suspected of having a current infection should be tested at the beginning of the infection and again 10-14 days later. The CMV antibody screening test is also called the transplant reaction screening test.

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D D-dimer test see Fibrin degradation products test D-Xylose tolerance test see Malabsorption tests

Dance therapy Definition Dance therapy is a type of psychotherapy that uses movement to further the social, cognitive, emotional, and physical development of the individual. Dance therapists work with people who have many kinds of emotional problems, intellectual deficits, and life-threatening illnesses. They are employed in psychiatric hospitals, day care centers, mental health centers, prisons, special schools, and private practice. They work with people of all ages in both group and individual therapy. Some also engage in research. Dance therapists try to help people develop communication skills, a positive self-image, and emotional stability.

Origins Dance therapy began as a profession in the 1940s with the work of Marian Chace. A modern dancer, she began teaching dance after ending her career with the Denishawn Dance Company in 1930. In her classes, she noticed that some of her students were more interested in the emotions they expressed while dancing (loneliness, shyness, fear, etc.) than the mechanics of the moves. She began encouraging them by emphasizing more freedom of movement rather than technique. In time, doctors in the community started sending her patients. They included antisocial children, people

with movement problems, and those with psychiatric illnesses. Eventually, Chace became part of the staff of the Red Cross at St. Elizabeth’s Hospital. She was the first dance therapist employed in a formal position by the federal government. Chace worked with the emotionally troubled patients at St. Elizabeth’s and tried to get them to reach out to others through dance. Some of them were schizophrenics and others were former servicemen suffering from post-traumatic stress disorder. Success for these patients meant being able to participate with their class in moving to rhythmic music. “This rhythmic action in unison with others results in a feeling of well-being, relaxation, and good fellowship,” Chace said once. Chace eventually studied at the Washington School of Psychiatry and began making treatment decisions about her patients along with other members of the St. Elizabeth’s medical team. Her work attracted many followers, and the first dance therapy interns began learning and teaching dance therapy at St. Elizabeth’s in the 1950s. Other dancers also began using dance therapy in the 1940s to help people feel more comfortable with themselves and their bodies. These dancers included Trudi Schoop and Mary Whitehouse. Whitehouse later became a Jungian analyst and an influential member of the dance therapy community. She developed a process called “movement in-depth,” an extension of her understanding of dance, movement, and depth psychology. She helped found the contemporary movement practice called “authentic movement.” In this type of movement, founded on the principles of Jungian analysis, patients dance out their feelings about an internal image, often one that can help them understand their past or their current life struggles. One of Whitehead’s students, Jane Adler, furthered Whitehead’s work in authentic movement by establishing the Mary Starks Whitehouse Institute in 1981. In 1966, dance therapy became formally organized and recognized when the American Dance Therapy Association (ADTA) was formed.

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Benefits Dance therapy can be helpful to a wide range of patients—from psychiatric patients to those with cancer to lonely elderly people. Dance therapy is often an easy way for a person to express emotions, even when his or her experience is so traumatic he or she can’t talk about it. It is frequently used with rape victims and survivors of sexual abuse and incest. It can also help people with physical deficits improve their self-esteem and learn balance and coordination. Dance therapists also work with people who have chronic illnesses and life-threatening diseases to help them deal with pain, fear of death, and changes in their body image. Many people with such illnesses find dance therapy classes to be a way to relax, get away from their pain and emotional difficulties for a while, and express feelings about taboo subjects (such as impending death). Dance therapy is suitable even for people who are not accomplished dancers, and may even be good for those who are clumsy on the dance floor. The emphasis in dance therapy is on free movement, not restrictive steps, and expressing one’s true emotions. Children who cannot master difficult dances or can’t sit still for traditional psychotherapy often benefit from free-flowing dance therapy. Even older people who cannot move well or are confined to wheelchairs can participate in dance therapy. All they need to do is move in some way to the rhythm of the music. Dance therapy can be useful in a one-on-one situation, where the therapist works with only one patient to provide a safe place to express emotions. Group classes can help provide emotional support, enhanced communication skills, and appropriate physical boundaries (a skill that is vital for sexual abuse victims).

Description There are currently more than 1,200 dance therapists in 46 states in the United Sates and in 29 foreign countries. Like other mental health professionals, they use a wide range of techniques to help their patients. Some of the major “schools of thought” in dance therapy include the Freudian approach, Jungian technique, and object relations orientation. Many therapists, however, do not ascribe to just one school, but use techniques from various types of dance therapy. The authentic movement technique is derived from the Jungian method of analysis in which people work with recurring images in their thoughts or dreams to derive meaning in their life. Instead of asking the patient to dance out certain emotions, the therapist instructs the patient to move when he or she feels “the inner impulse.” 642

The moves are directed by the patient and the therapist is a noncritical witness to the movement. The moves are supposed to emerge from a deep level within the patient. In Freudian technique, dance therapists work with patients to uncover feelings hidden deep in the subconscious by expressing those feelings through dance. In object relations technique, the therapist often helps the patient examine problems in his or her life by considering the primary initial relationship with the parents. Emotions are expressed in a concrete, physical way. For instance, a patient would work out his fears of abandonment by repeatedly coming close to and dancing at a distance from the therapist. Dance therapists sometimes use other types of therapy along with dance, such as art or drama. Therapists also discuss what happens during a dancing session by spending time in “talk therapy.” Dance therapists use visualizations during sessions, too. For example, the therapist might instruct patients to imagine they are on a beautiful, peaceful beach as they dance. In one frequently used technique, the therapist mirrors the movements of the patient as he or she expresses important emotions. This is especially powerful in private one-on-one therapy. It is thought that this device provides a sense of safety and validates the patient’s emotions. The underlying premise of dance therapy is that when people dance, they are expressing highly significant emotions. A fist thrust out in anger into the air or a head bent in shame has deep significance to a dance therapist. Through dance therapy, the theory goes, patients are able to more easily express painful, frightening emotions, and can progress from there. After experiencing dance therapy, they can talk about their feelings more freely and tear down the barriers they have erected between themselves and other people. The hope is that eventually they can go on to live more psychologically healthy lives.

Preparations People who want to use dance therapy should find a qualified therapist. The ADTA provides lists of qualified therapists. The person should begin dance therapy with an open mind and a willingness to participate so he or she can get the most benefit.

Precautions A qualified dance therapist should have completed a graduate program in dance therapy approved by the ADTA and should be registered with the ADTA. He or

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Side effects No known side effects.

Research and general acceptance Dance therapy was once dismissed as simply an ineffective, “feel good” treatment, but it is now more respected. Many research studies have proven that dance therapy can be an effective tool to help people overcome psychological problems. In a 1993 study, older people with cognitive deficits showed that dance therapy could significantly increase their functional abilities. Patients improved their balance, rhythmic discrimination, mood, and social interaction. In 1999, a pilot study of 21 university students showed that those who took a series of four to five group dance therapy sessions in a period of two weeks significantly reduced their test anxiety as measured by a wellknown exam called the Test Anxiety Inventory. Afterwards, the subjects reported that their dance movement experience was positive and provided them with psychological insight. The researchers concluded that dance therapy could be a viable method of treatment for students who suffer from overwhelming test anxiety, and should be researched further. In another 1999 study presented at the ADTA national conference in November 1999, dance therapist Donna Newman-Bluestein reported success in using techniques of dance therapy with cardiac patients. In a stress reduction class, health professionals used dance therapy methods to teach body awareness, relaxation, self-expression, creativity, and empathy. According to NewmanBluestein, the dance therapy techniques helped the patients deal with such stressful emotions as anger, increased their self-awareness, made them more relaxed, and helped them adjust emotionally to having heart disease.

Training and certification Dance therapists should have dance experience and a liberal arts background with coursework in psychology for their undergraduate degree. Professional dance therapy training takes place on the graduate level. A qualified dance therapist has received a graduate degree from a school approved by the ADTA, or has a master’s degree in dance or psychology and has taken additional dance therapy credits.

KEY TERMS Authentic movement—A type of movement that is influenced heavily by Jungian analysis, and works by analyzing the internal images of the patient. Patients are also urged to dance only when they feel the “impulse” to move. Freudian analysis—A type of psychological treatment where the therapist seeks to help the patient resolve conflicts and traumas buried in the subconscious. Jungian analysis—A method of psychological treatment where the patient strives to understand the internal, often mythic images in his or her thoughts and dreams. Psychotherapy—A medical treatment that seeks to resolve psychological traumas and conflicts, often by discussing them and emotionally reliving difficult events in the past. Test anxiety—A name for the stress and anxiousness that commonly occur in students before they take exams.

After graduation, dance therapists can become registered with the ADTA, meaning that they are qualified to practice. After two years they may receive an additional recognition when they become an Academy of Dance Therapist Registered. They can then teach dance therapy and can supervise interns. Dance therapists can also obtain psychological credentials by taking a test and becoming registered by the National Board for Certified Counselors, Inc. Resources BOOKS

Halprin, Anna. Dance as a Healing Art: Returning to Health Through Movement and Imagery. Mendocino, CA: LifeRhythm, 2000. Levy, Fran J., ed. Dance and Other Expressive Art Therapies: When Words Are Not Enough. New York: Routledge, 1995. Pallaro, Patrizia, ed. Authentic Movement: Essays by Mary Starks Whitehouse, Jane Adler and Joan Chodorow. London: Jessica Kingsley Publishers, 1999. PERIODICALS

Brody, Jane. “Dancing Shoes Replace the Therapist’s Couch.” New York Times (10 October 1995): C13.

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she should not just be a dancer, but should also have extensive training in psychology.

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“Dance/Movement Therapy Opens Communication Pathways.” Brown University Long-Term Quality Advisor (July 15, 1996). Erwin-Grabner, et al. “Effectiveness of Dance/Movement Therapy on Reducing Test Anxiety.” American Journal of Dance Therapy 21, no. 1 (Spring/Summer 1999). ORGANIZATIONS

American Dance Therapy Association. (410) 997-4040. [email protected]. . OTHER

Newman-Bluestein, Donna. “You Gotta Have Heart: Integrating Dance Therapy into Cardiac Rehabilitation Stress Management.” Presented at the ADTA National Conference. (November 1999).

Barbara Boughton

Deafness see Hearing loss

Death and dying Definition Death is the end of life, a permanent cessation of all vital functions. Dying refers to the body’s preparation for death, which may be very short in the case of accidental death, or can last weeks or months in some cancer patients.

Description Quality and method of death differs between cultures, circumstances and degrees of preparation. For many years, the terminally ill did not have choices in their manner of death, often enduring excruciating pain before the inevitable end of life. In recent years changes have been made to allow for a better quality for end of life, such as hospice care and preparatory actions by the patient. It is important to recognize the differences in the ways people grieve. Each culture socializes a person in a certain way to deal with death. Death affects a person cognitively, behaviorally and socially. The death and grieving attitudes of a person affect the subjects of death, dying, bereavement, suicide and euthanasia. While a person may be able to verbalize feelings about death, internal contradictory feelings of anxiousness are common. Each person handles the subject individually, and seeking appropriate assistance will help the person to come to terms with the event in his or her own time and way. 644

Hospice care A diagnosis of terminal illness is a sad and traumatic circumstance. Hospice care provides quality, caring services for both the patient and his or her loved ones. Most communities have a variety of hospice providers. A physician or hospital patient services can assist with provider names. The yellow pages of the phone book, or referral services from United Way, the local council on aging, Visiting Nurse Association or the American Cancer Society are other information sources. While the patient should be the one to choose hospice care, it is always appropriate to discuss all care options. Hospice staff are sensitive to concerns of both patient and family members and assist in the planning process as requested. Most physicians are aware of the services provided by hospice and will cooperate fully. The hospice program will work closely with the physician to optimize the patient’s care. The patient will sign consent and insurance forms, which are similar to those signed for hospital admission. There is also a form that states the patient’s understanding that hospice care is aimed at pain relief and symptom control (palliative), rather than curative. Should a patient’s condition improve and hospice services are no longer necessary, or the patient is in remission, services can be discontinued and the patient may return to regular care options. There is no obligation to remain with hospice care if it is not necessary. Should the patient need readmission to the program, medical insurance and Medicare may allow additional funding for this purpose. Once hospice services are approved, the provider will perform a needs assessment, then assist in locating the equipment necessary for the patient’s care. Quite often, the earlier needs are minimal, increasing as the illness becomes more serious. The purpose of hospice care is to make the home environment a comfortable haven for the patient. The hospice team prepares a plan of care that is tailored to the patient. This will address the amount of care necessary to maintain the patient’s comfort and wellbeing. The staff visits the home regularly and provides instruction on patient care, as well as answers medical questions and supports the caregivers. As the illness progresses, care becomes more difficult. Hospice plans provide staff around the clock to consult by phone or to make visits if deemed appropriate. Respite care is also available for exhausted caregivers, so that the home can remain functional. Hospice patients are cared for by a team of doctors, nurses, counselors, social workers, clergy, and volunteers, among others. Each provides assistance based on

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The management of pain is very often an issue in terminal illness. The mission of hospice is to address all types of pain, not only the physical. Support is available to assist the patient in achieving the highest quality of life possible under individual circumstance. This may include physical and occupational therapists to keep the patient as self-sufficient and mobile as possible. Music therapy, art therapy, massage and diet counseling are available. The latest medications and devices for relief from pain and other symptoms is available. Also, counselors, some of whom are clergy members, assist both the patient and the family as needed/requested. However, hospice programs are not affiliated with religious groups and do not expect participants to adhere to any particular belief system. The goal of the hospice program is to keep the patient both as pain free and alert as possible. Constant communication with the patient and caregivers assist in the high success rate of the hospice program. After the loved one’s death, hospice programs provide both individual and group support for caregivers for at least one year, longer if necessary. Preparing for death legally An advance directive is a way to allow caregivers to know a patient’s wishes, should the patient become unable to make a medical decision. People who are admitted to hospitals must be told about advance directives at the time of admission. Description of the type of care for different levels of illness should be in an advance directive. For instance, a patient may wish to have or not to have a certain type of care in the case of terminal or critical illness or unconsciousness. An advance directive will protect the patient’s wishes in these matters. A living will is one type of advance directive and may take effect when a patient has been deemed terminally ill. Terminal illness in general assumes a life span of six months or less. A living will allows a patient to outline treatment options without interference from an outside party. A durable power of attorney for health care (DPA) is similar to a living will; however, it takes effect any time unconsciousness or inability to make informed medical decisions is present. A family member or friend is stipulated in the DPA to make medical decisions on behalf of the patient.

Whie both living wills and DPAs are legal in most states, there are some that do not officially recognize these documents. However, they may still be used to guide families and doctors in treatment wishes. Do-not-resuscitate (DNR) orders can be incorporated into an advance directive or by informing hospital staff. Unless instructions for a DNR are in effect, hospital staff will make every effort to help patients whose hearts have stopped or who have stopped breathing. DNR orders are recognized in all states and will be incorporated into a patient’s medical chart if requested. Patients who benefit from a DNR order are those who have terminal or other debilitating illnesses. It is recommended that this be discussed with a physician by a patient who has not already been considered unable to make sound medical decisions. None of the above documents are complicated. They may be simple statements of desires for medical care options. If they are not completed by an attorney, they should be notarized and a copy should be given to the doctor, as well as a trusted family member.

Viewpoints In the Hague, Netherlands, euthanasia was legalized in April 2001, and the country became the first in the world to allow doctors to end the lives of patients with painful, terminal illnesses. The Dutch Senate voted 46-28 in favor of the law, which took effect in the summer of 2001. Prior to the vote, Health Minister Els Borst assured the legislators that euthanasia would not be abused by doctors because of the strict supervision that would accompany the measure. The practice has been discreetly practiced in the Netherland for decades, and preliminary guidelines were established by the country’s Parliament in 1993. In the United States, Oregon has permitted doctors to perform assisted suicides since 1996. Mourning and grieving among cultures The death of a loved one is a severe trauma, and the grief that follows is a natural and important part of life. No two people grieve exactly the same way, and cultural differences play a significant part in the grieving process. For many, however, the most immediate response is shock, numbness and disbelief. Physical reactions may include shortness of breath, heart palpitations, sweating and dizziness. At other times, there may be reactions such as loss of energy, sleeplessness or increase in sleep, changes in appetite, or stomach aches. Susceptibility to

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area of expertise. Additionally, hospices provide supplies, equipment, medications and other services related to the terminal illness. Hospice does not hasten nor does it delay the death process. However, hospices do provide specialized care that eases some of the anxiety and worry that accompany oncoming death.

Death and dying

common illnesses, nightmares, and dreams about the deceased are not unusual during the grieving period. Emotional reactions are as individual as physical reactions. A preoccupation with the image of the deceased, feelings of fear, hostility, apathy and emptiness, even fear of one’s own death may occur. Depression, diminished sex drive and anger at the deceased, as well as extreme sadness may occur. Bereavement may cause short- or long-term changes in the family unit and other relationships of the bereaved. It is important for the bereaved to work through their feelings and not avoid emotions. If this does not occur through family, friends, or primary support group methods, then a therapist should be consulted to assist with the process. Various cultures and religions view death in different manners and conduct mourning rituals according to their own traditions. In the Christian faith, bodies of deceased are normally on view at a funeral parlor for one or more days before the actual funeral service. Specific hours are given for visitation or viewing. Visitors come to express their condolences to the family and to bid farewell to the deceased. At times, funeral services are private. Various ethnic groups host a gathering after the funeral for those who attended. If it is held at the family’s home, very often relatives and others will bring food and drink. Others choose to hold this event at a restaurant or some other public venue. It is common for these events to become a celebration of the life of the deceased, which also helps the bereaved to begin the mourning process positively. Memories are often exchanged and toasts made in memory of the deceased. Knowing how much a loved one is cherished and remembered by friends and family is a comfort to those who suffer the loss. Other methods of condolences include sending flowers to the home or the funeral parlor; sending a mass card (for Catholics); sending a donation to a charity that the family has chosen; bringing a meal to the family during the weeks after the death. In the Jewish culture, bodies are buried as soon after death as possible, even as early as sundown of the day after death. For the Jewish population, this marks a sign of respect to the deceased. A seven-day period of morning follows, which is called Shiva or sitting Shiva. Friends and community visit the family and often bring food, so that the family does not have to worry about meals. Normal activities are suspended for the family of the deceased at this time, so that the bereaved can focus fully on their grief, thus enabling them to re-enter life a bit easier after the period of mourning. The first meal that is served after return from the cemetery is called seudat havrach, prepared by friends and neighbors. Eggs and 646

other round objects are traditionally served. These are objects that are symbolic of life, hope and the full circle of life, which ends in death. Flowers are not traditional; however, donations to charities chosen by the family are acceptable in memory of the deceased. In the Muslim faith, everyone accompanies the funeral procession to the gravesite. The permitted mourning period for a deceased Muslim is three days, except for a widow, who is permitted to mourn her spouse for four months and 10 days. Traditionally, people leave the gravesite after offering condolences and offering assistance. However, some families do hold gatherings at home. Friends and neighbors bring food and drink to alleviate the family from the worry of providing refreshments. Flowers are often sent after the funeral to the family’s home. Buddhists normally hold a funeral within a week after the death. Flowers or a donation to a charity in the deceased’s name are appropriate signs of respect. Caskets are often open, and guests are expected to view the deceased and bow slightly toward it. Friends are invited to call at the deceased’s home after the funeral service but not before. The funeral service itself is usually held within 24 hours after the death. Then the body is kept at home until the traditional cremation ceremony. Flowers are acceptable from visitors and are placed at the feet of the deceased. Fruit is also a customary gift to bring to the family.

Professional implications The primary concern of health care workers in most cases is preserving the life and health of an individual. Severely ill patients may be given nutrition and fluids intravenously or have their breathing supported by a ventilator. In cases in which the heart stops, CPR (cardiopulmonary resuscitation) is performed. In the case of terminally ill, dying patients, the role of health care professionals is to provide palliative care, to ensure that proper arrangements are made for the person after death, and to address the concerns of family members. Physical signs The causes of death vary greatly. Injuries, illness and more violent deaths occur routinely. However, as the time of death grows near for the dying, certain signs are common as their bodies begin to shut down. The time variable is as much as a few days and as little as a few hours. There is no particular order of events and not everyone experiences all of them. Support and caring by those surrounding the dying person are essential to make the passing as comfortable and with as little stress as possible.

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As circulation slows down, the patient may lose the ability to realize his or her body temperature. The arms will become cool and begin to turn a bluish color. The underside of the body may darken. The caretaker should provide additional blankets or remove them as necessary. The patient should be kept as comfortable as possible.

There will be less interest in eating and drinking. Refusal of food indicates a readiness to die. Fluid intake may be reduced to only as much as will keep the mouth from feeling dry. At this time it is important for caretakers to offer food, drink, and medications, but they should not be forced. Pain may not be an issue when the end is near, so the patient may not feel the need for the medication.

Loss of control of the bladder and bowel may occur at the time of death. Breathing and heartbeat will stop. The jaw may sag open slightly as it relaxes. The eyelids may close partially, but the eyes will be fixed.

The patient will begin to sleep more and begin to detach from his or her surroundings. The caregiver should not interfere, except to make the patient as comfortable as possible. The caregiver’s presence is the most important factor.

Resources

Mental confusion may occur as less oxygen reaches the brain. Loss of hearing and vision may occur. The patient may complain of strange dreams. The caregiver should gently remind the patient of the day and time, who is present, and where the patient is at the moment. This should be done in a conversational manner. The caregiver should speak louder than normal if that is necessary, but not draw attention to the patient’s loss of senses. The room should be kept at the light and temperature that the patient requests. All conversations should be carried on as if the patient were aware. Hearing is the last of the senses to leave entirely, even in the case of stroke victims who sometimes appear completely unaware. However, many patients are able to speak even just a few minutes before death and are reassured by loving words. Secretions may collect at the back of the throat. This may cause a gurgling sound as the patient breathes and possibly tries to cough up mucus. A cool mist humidifier in the room may help. If not, it may be advisable to turn the patient on his or her side, propped up with pillows, so that secretions can drain out of the mouth. The caregiver can cleanse the mouth with glycerin-dipped swabs, mineral oil, or cool water. Near the end, there may be periods of non-breathing or irregular breathing. As death comes nearer, breathing may resume regularity but become shallow and mechanical. The patient may become agitated, try to get out of bed, hallucinate or pull at the bed linens. The caregiver should calmly reassure the patient and try to prevent the patient from falling if an attempt is made to get out of bed. A massage or soothing music may help.

After a patient dies, health care staff allow family members time to grieve with the body before starting post-mortem procedures.

BOOKS

Aminoff, Michael J. “Nervous System.” In Current Medical Diagnosis and Treatment. Edited by Lawrence M. Tierney, Jr., et. al. Stamford, CT: Appleton and Lange, 1996, p. 954. Bennett, J. Claude, and Fred Plum, eds. Cecil Textbook of Medicine. Philadelphia: W.B. Saunders, 1996. OTHER

American College of Physicians. “How to help during the final weeks of life.” ACP Home Care Guide for Advanced Cancer. 2001. . American College of Physicians. “What to do before and after the moment of death.” ACP Home Care Guide. 2001. . Partnership for Caring. “Talking about your choices.” 2001. .

Jacqueline N. Martin, M.S.

Decompression sickness Definition Decompression sickness (DCS) is a dangerous and occasionally lethal condition caused by nitrogen bubbles that form in the blood and other tissues of scuba divers who surface too quickly. It also occurs in the blood of tunnelers or miners who work in conditions of increased pressure and return to normal atmospheric pressure too quickly.

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The health care professional should keep the patient comfortable. Eggshell mattresses or foam cushions can prevent bedsores, as can changing the patient’s position in bed. Sheets should be changed at least twice a week. Helping the patient with mouth care often makes him or her feel better.

Decompression sickness A hyperbolic chamber is used to treat patients for decompression sickness, or “the bends.” (AP/Wide World Photos. Reproduced by permission.)

Description According to the Divers Alert Network (DAN), a worldwide organization devoted to safe-diving research and promotion, fewer than 1% of divers fall victim to DCS or the rarer bubble problem called gas embolism, air embolism, or arterial gas embolism (AGE). A study of the U.S. military community in Okinawa, where tens of thousands of sport and military dives are made each year, identified 84 cases of decompression sickness and 10 instances of arterial gas embolism between 1989 and 1995. These numbers included 9 deaths. Translated, this provides an estimated incidence of one case of decompression sickness in every 7,400 dives and one death in every 76,900 dives. Since symptoms of decompression sickness can be quite mild, many cases go unnoticed by divers; thus this estimate is probably understated. Different terminology is used in discussing decompression sickness and it can be confusing. Sometimes the term illness is used instead of sickness. Others treat decompression illness as a term that encompasses both decompression sickness and arterial gas embolism. An older term for decompression sickness is caisson disease. 648

This term was coined in the nineteenth century, when bridge construction crews working at the bottom of lakes and rivers in large pressurized enclosures (caissons) were found to experience joint pain (a typical symptom of decompression sickness on returning to the surface).

Causes and symptoms The air we breathe is mostly a mixture of two gases, nitrogen (78%) and oxygen (21%). Unlike oxygen, nitrogen is a biologically inert gas, meaning that it is not metabolized (converted into other substances) by the body. For this reason, most of the nitrogen we inhale is expelled when we exhale, but some is dissolved into the blood and other tissues. During a dive, however, the lungs take in more nitrogen than usual. This happens because the surrounding water pressure is greater than the air pressure at sea level (twice as great at 33 ft [10 m], for instance). As the water pressure increases, so does the pressure of the nitrogen in the compressed air inhaled by the diver. Because increased pressure causes an increase in gas density, the diver takes in more nitrogen with each breath than would occur at sea level. But instead of being exhaled, the extra nitrogen safely dissolves into the tis-

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tus), skin rashes, and skin mottling (cutis marmorata) are other relatively common symptoms. All of these are sometimes classified as manifestations of Type 1 or “mild” decompression sickness. Type 2 or “serious” decompression sickness can result in paralysis, brain damage, heart attack, and death. Many persons with decompression sickness experience both Type 1 and Type 2 symptoms.

How much extra nitrogen enters the tissues varies with the dive’s depth and the duration of the dive. Dive tables prepared by the U.S. Navy and other organizations specify how long most divers can safely remain at a particular depth. If the dive table limits are exceeded, the diver must pause on the way up, to allow the nitrogen to diffuse out of tissues and into the bloodstream without forming bubbles. These pauses are called decompression stops and are carefully calibrated. Decompression sickness can occur, however, even when a diver obeys safediving rules. In such cases, the predisposing factors include fatigue, obesity, dehydration, hypothermia, and recent alcohol use. People who fly or travel to high-altitude locations without letting 12–24 hours pass after their last dive are at risk for DCS, because their bodies undergo further decompression. This is true even when flying in commercial aircraft, since the cabin pressure in commercial aircraft is set much lower than the pressure at sea level. At 30,000 ft (9,144 m), for instance, cabin pressure is usually equivalent to the pressure at 7,000–8,000 ft (2,133–2,438 m) above sea level, a safe level for everyone except people who have recently been diving. Exactly how long a diver should wait before flying or traveling to a high-altitude location depends on how much time has been spent diving. If there is uncertainty about the appropriate waiting period, the sensible course of action is to let a full 24 hours pass.

Decompression sickness is treated by giving the affected person oxygen and placement in a hyperbaric chamber. A hyperbaric chamber is an enclosure in which the air pressure is first gradually increased and then gradually decreased. This shrinks the bubbles and allows the nitrogen to safely diffuse out of the tissues. Hyperbaric chamber facilities exist throughout the United States. No matter how mild symptoms may appear, immediate transportation to a facility with a hyperbaric chamber is essential. Treatment is necessary even if the symptoms clear up before the facility is reached, because bubbles may still be in the bloodstream and still pose a threat. The Divers Alert Network maintains a list of facilities and a 24-hour hotline that can provide advice on handling decompression sickness and other diving emergencies.

Since the nitrogen bubbles that cause decompression sickness can affect all body tissues, many different symptoms are possible. Symptoms can appear minutes after a diver returns to the surface. The appearance of symptoms occurs within eight hours in about 80% of cases. Pain is often the only symptom. This is sometimes called “the bends,” although many people incorrectly use that term as a synonym for decompression sickness. Pain, which ranges from mild to severe, is usually limited to the joints, but can be felt anywhere. Severe itching (pruri-

Diagnosis Diagnosis is determined by taking a thorough medical history and conducting a physical examination.

Treatment

Prognosis People suffering from decompression sickness who undergo chamber treatment within a few hours of symptom onset usually enjoy a full recovery. If treatment is delayed, the consequences are less predictable, although many people have been helped even after several days have passed. A 1992 report on diving accidents indicated that full recovery following chamber treatment was immediate in about 50% of divers. Some people, however, suffer numbness, tingling, or other symptoms that last for weeks, months, or even a lifetime. In another study, 6 out of 94 (6.4%) persons experienced long-lasting symptoms even after repeated chamber treatments.

Health care team roles Paramedics often make the initial diagnosis of decompression sickness. Physicians supervise treatment in a hyperbaric chamber, while RNs provide support and monitor the patient during the period of decompression.

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sues, where it remains until the diver begins the return to the surface. Under some circumstances, the extra dissolved nitrogen can cause nitrogen narcosis, although this condition is different from decompression sickness. On the way up, decompression occurs; in other words, the water pressure drops. With the decrease in pressure, the extra nitrogen gradually diffuses out of the tissues and is delivered by the bloodstream to the lungs, which expel it from the body. If the diver surfaces too quickly, potentially dangerous nitrogen bubbles can form in the tissues and cause decompression sickness. These bubbles can compress nerves, obstruct arteries, veins, and lymphatic vessels, and trigger harmful chemical reactions in the blood. The precise reasons for bubble formation remain unclear.

Defibrillators, portable

KEY TERMS Cutis marmorata—Skin that has a marbled appearance due to conspicuous veining of small vessels. Gas embolism—The presence of a gas bubble in the bloodstream that obstructs circulation. Hyperbaric chamber—A sealed compartment in which air pressure is gradually increased and then gradually decreased, allowing nitrogen bubbles to shrink and the nitrogen to safely diffuse out of body tissue. Lymphatic vessels—Vessels that carry a plasmalike fluid called lymph from tissues to the bloodstream. Nitrogen narcosis—Also called “rapture of the deep,” the condition is caused by increased nitrogen pressure at depth and is characterized by symptoms similar to alcohol intoxication. Pruritus—The symptom of itching or an uncontrollable sensation leading to the urge to scratch.

Prevention The obvious way to minimize the risk of decompression sickness is to follow the rules of safe diving and air travel after a dive. People who are obese, suffer from lung or heart problems, or are otherwise in poor health should not dive. Because the effect of nitrogen diffusion on the fetus remains unknown, diving while pregnant is not recommended.

Decompression Sickness in Human Research Subjects.” Aviation, Space and Environmental Medicine 71(2000): 115-118. Moon, R.E. “Treatment of Diving Emergencies.” Critical Care Clinician 15(1999): 429-456. ORGANIZATIONS

American College of Hyperbaric Medicine, P.O. Box 25914130, Houston, TX 77265. (713) 528-0657. . [email protected]. Divers Alert Network, The Peter B. Bennett Center, 6 West Colony Place, Durham, NC 27705. (919) 684-8111. Fax: (919) 490-6630. . [email protected]. International Congress on Hyperbaric Medicine, 1592 Union Street, San Francisco, CA 94123. . [email protected]. Undersea and Hyperbaric Medical Society, 10531 Metropolitan Ave, Kensington, MD 20895. (301) 9422980. Fax: (301) 942-7804. . [email protected]. OTHER

Diving Medicine Online. . Federal Aviation Administration website. . Mt. Sinai Hospital website. . Virtual Naval Hospital. .

L. Fleming Fallon, Jr., MD, PhD, DrPH

Decubitus ulcer see Pressure ulcer Defibrillator, automatic see Implantable cardioverter-defibrillator

Resources BOOKS

Bookspan, Jolie. Diving Physiology in Plain English. 2nd ed. San Francisco: Undersea & Hyperbaric Medical Society, 1997. Jackson, Jack. Scuba Diving. Mechanicsburg, PA: Stackpole Books, 2000. Jain, K.K. Textbook of Hyperbaric Medicine. 3rd ed. Seattle, WA: Hogrefe & Huber, 1999. PERIODICALS

Branger, A.B., C.J. Lambertsen, and D.M. Eckmann. “Cerebral Gas Embolism Absorption During Hyperbaric Therapy: Theory.” Journal of Applied Physiology 90 (2001): 593600. Cheshire, W.P., and M.C. Ott. “Headache in Divers.” Headache 41(2001): 235-247. Krause, K.M., and A.A. Pilmanis. “The Effectiveness of Ground Level Oxygen Treatment for Altitude 650

Defibrillators, portable Definition A portable defibrillator is a device, often automated and generally weighing less than 5 lbs (2.2 kilograms), that is commonly used in non-hospital settings to administer a shock and re-establish a regular heartbeat to treat sudden cardiac arrest.

Purpose Rapid defibrillation is the most significant factor in the survival of the abrupt disruption of the heart function known as sudden cardiac arrest (SCA). In non-hospital

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settings, the most common method of administering such a shock is by using a portable defibrillator, also known as an automated external defibrillator (AED). AEDs are now common equipment in airports, malls, casinos, golf courses, businesses, hotels, schools, on airplanes, and through various emergency response groups such as the police, fire departments, and paramedic squads. Contrary to the perception portrayed by television and movies, defibrillation is not effective in treating hearts showing a flat-line electrocardiogram (ECG). Instead, defibrillation is most effective in reversing arrhythmias (abnormal rhythms of the heart) such as those that can cause SCA. This condition is often characterized by ventricular fibrillation, a rapid, nonproductive contraction of the ventricles. To treat this problem, the shock stops the chaotic electrical activity and allows the natural pacemaker of the heart, the sinoatrial node, to regain control of the beat. SCA is the cause of death of more than 350,000 Americans per year, striking persons of all ages and in both sexes equally. Unlike a heart attack, SCA often occurs without warning symptoms. The American Heart Association estimates that nearly 300 persons per day would be saved if everyone who suffered from SCA had access to treatment with an AED within 10 minutes. AED models are now available for treatment of adults, children, and infants. Because many AEDs include an ECG display, the device can also be used during cardiac emergencies to monitor and record the heart’s electrical signals before, during, and after any given treatment. This is true even when the person suffers from a heart condition that does not warrant administering a shock, as determined by the device’s automatic analysis of the heart problem.

Description AED devices include an ECG to monitor the heartbeat of the patient, software and voice prompting to guide the operator, other software to analyze the advisability of administering a shock, and a shock generator to administer a shock of set duration and power. The device itself is enclosed in a case that includes a display, a speaker, leads running to two pad-shaped electrodes, and two buttons (power and shock). More sophisticated versions of this device can include manual over-rides (for control by trained medical personnel of the power and duration of the shock) and pacing abilities. Generally, defibrillators are available that produce two types of shocks, monophasic and biphasic. Monophasic shocks move from one electrode to the other, while biphasic shocks move from one electrode to the other, and then reverse direction. Biphasic shocking

A portable defibrillator is used in an attempt to revive a man who suffered a heart attack before he is transported to an emergency room. (Photograph by Adam Hart-Davis. Science Source/Photo Researchers. Reproduced by permission.)

is usually more effective than monophasic in taking a heart out of fibrillation and is associated with less posttreatment heart or brain dysfunction. Biphasic shocking, combined with pre-shock impedance measurements, is a method particularly successful in treating obese patients, a situation that can be a challenge to other types of defibrillation therapies. The analysis of the heartbeat is done using an algorithm (a sequence of mathematical steps) that compares the electrical output of the patient’s heart to known heartbeats to determine if a shock should be administered. The four characteristics of the output examined are rate, conduction, stability, and amplitude. Rate is measured in beats per minute (bpm), with normal being between 60 and 100. Increased rate is characteristic of many common arrhythmias. Conduction is evaluated by looking at the characteristics of the R wave of the ECG, which is the portion of the electrical signal of the heart where there is a tall, narrow spike. Rounded wide R waves can indicate problems with conduction. Stability of the heartbeat is evaluated by comparing one heartbeat signal to the next. In healthy hearts, the beats repeat themselves with a regular pattern. Unhealthy hearts have varied beat signals, an indication of instability. Finally, the algorithm looks at the amplitude (height) of the electrical signal put out by the heart. Lowered amplitude is a characteristic of an unhealthy heart.

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KEY TERMS Algorithm—A sequence of mathematical steps used by an automated external defibrillator to evaluate whether a shock is appropriate treatment for the patient attached to the machine’s electrodes. Biphasic—A term to describe a defibrillation shock that travels from one electrode to another and back again. Monophasic—A term to describe a defibrillation shock that travels from one electrode to the other.

Additionally, many AEDs have systems to filter out artifacts, electrical signals that do not come from the heart of the patient being evaluated and that may interfere with the evaluation process.

Operation The operation of an AED is as straightforward as possible so a person can use the machine correctly even without training. When in automatic mode, the machine provides voice and display prompts to guide the operator through its use. Many models have only two buttons, a green power button and an orange or other brightly-colored shock button. The use of a defibrillator to treat SCA is one part of a four-step program known as the chain of survival. The four critical steps include early access to emergency care (by calling 911 or another emergency number), early cardiopulmonary resuscitation (CPR), early defibrillation, and early advanced cardiac support. Thus, before using an AED, the operator should have someone call 911 and then begin CPR, if possible. AEDs should only be used on individuals who are unresponsive, not breathing, and have no pulse. On activation, the machine asks the operator to confirm that these conditions are present. Next, the operator is directed to place the electrode pads on the collapsed person. The two pads are placed on the chest, one on the patient’s upper right chest area, and the other below the ribs on the patient’s left side. Often, there is a diagram on the machine to aid in electrode placement. At this point, the machine directs the operator to plug in the electrodes, guided by a light. Some machines skip this step, as the electrodes are permanently attached. The machine then directs everyone to stand clear of the patient so that the heartbeat can be evaluated. If the 652

condition can be treated with a shock, the operator is directed to both visually and verbally clear the area around the patient and then push the shock button. After the shock is delivered, the machine automatically checks the heartbeat for change and, if further shocks are needed, the machine directs their delivery.

Maintenance Older AEDs require periodic maintenance and calibration by using external devices, sending the machine to the factory, or service contracts with outsource providers of maintenance. However, newer machines have internal maintenance programs that carry out the required routine performance checks and function adjustments. Many will check the ability of the machine’s shock function on a daily basis. The internal maintenance functions, combined with heavy-duty, easy-to-carry external casings, facilitate the use of AEDs as emergency equipment in non-health care settings. Wall mountings such as those that are used for fire extinguishers are available to keep the equipment in sight but protected.

Health care team roles AEDs are specifically designed to be used by people who have no medical training. Indeed, a study using AEDs showed that sixth grade students, without the benefit of training or ability to ask questions, took only 30 seconds longer to administer a shock than trained emergency technicians. In a hospital setting, portable defibrillators are often available for use by hospital personnel in order to assure quick access to defibrillation equipment in intensive care units and other areas of the hospital where SCA might occur. The manual settings found on more sophisticated units can be used by health care providers such as doctors, nurses, paramedics, and emergency medical technicians who have training in advanced life support techniques. Their training allows them to identify specific abnormal rhythms that may require different energy settings for the most effective correction.

Training When an AED program is implemented, for example, by a business, training for the employees is often accomplished using a four-hour course, with refreshers suggested every three months. Training programs are available from the company that manufactures the AED or from organizations such as the American Red Cross.

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BOOKS

Every, Nathan R., and W. Douglas Weaver. “AEDs: Automatic and Advisory Transchest Defibrillation.” In Defibrillation of the Heart, ed. W.A. Tacker, Jr. St. Louis: Mosby, 1994.

50%, infants have an estimated 77%, and the elderly have 46% to 52%. An increase in body fat causes a decrease in the percent fluid content because fat does not contain significant amounts of water.

Causes and symptoms

PERIODICALS

Gundry, J.W., et al. “Comparison of Naive Sixth-Grade Children with Trained Professionals in the Use of an Automated External Defibrillator.” Circulation 100 (October 19, 1999): 1703-07. Page, Richard L., et al. “Use of Automated External Defibrillators by a U.S. Airline.” The New England Journal of Medicine 343 (October 26, 2000): 1210-16. Valenzuela, Terence D., et al. “Outcomes of Rapid Defibrillation by Security Officers after Cardiac Arrest in Casinos.” The New England Journal of Medicine 343 (October 26, 2000): 1206-09. ORGANIZATIONS

National Center for Early Defibrillation. University of Pittsburgh, 230 McKee Place, 4th Floor, Suite 911, Pittsburgh, PA 15213-4910. (866) AED-INFO. (412) 647-2694. .

Michelle L. Johnson, M.S., J.D.

Degenerative arthritis see Osteoarthritis

Dehydration Definition Dehydration is the excessive loss of water from body tissues accompanied by an imbalance in essential electrolytes, such as sodium, potassium, and chloride.

Description Dehydration occurs when the body loses more fluid than it takes in. Dehydration can be caused by illness, injury, infection, prolonged exposure to sun or high temperatures, inadequate water intake, or overuse of diuretics or other medications that increase urination. Water is distributed throughout three compartments in the body: inside the cells (intracellular), in the tissue (interstitial), and in the bloodstream (intravascular). Each compartment contains differing amounts of electrolytes that must remain in balance in order for body organs and systems to function correctly. Dehydration upsets this delicate balance. Total body water also varies in relation to age, gender, and amount of body fat. Adult males have approximately 60% water content, adult females have

Different types of dehydration have different causes. When managing patients with dehydration, the type of water loss must be determined to ensure appropriate treatment. In addition, water and sodium levels in the body are closely related; if one is abnormal, the other often is too. Isotonic dehydration is an equal loss of water and sodium. Isotonic means that the number of particles contained on one side of a permeable membrane is the same as on the other side, thus there is no fluid shift in either direction. The amount of intracellular and extracellular water remains in balance. This can be caused by a complete fast, vomiting, and diarrhea. Hypertonic dehydration occurs when water loss is greater than sodium loss. Blood sodium levels may be >145 mmol/l (normal range=135 to 145 mmol/l). Higher blood sodium levels combined with decreased water in the intravascular space increases the osmotic pressure in the bloodstream, which, in turn, pulls more fluid out of the cells. This type of dehydration is usually caused by extended fever with limited oral rehydration. Mortality is more likely to occur from hypertonic than from isotonic dehydration. Hypotonic dehydration occurs when sodium loss is greater than water loss. Blood sodium levels may be less than 135 mmol/l; and the osmotic pressure is greater inside the cells, which pulls more fluid out of the intravascular space into the intracellular space. This type of dehydration occurs with overuse of diuretics, which causes excessive sodium and potassium loss. Potassium depletion affects respiration, increases nausea, and, if severe enough, may cause respiratory arrest or central nervous system (CNS) seizures. Potassium depletion may also cause arrhythmias (an alteration in the heartbeat). As a result, patients are told to take diuretics with orange juice or to eat a banana, both of which are high in potassium. Strenuous activity, excessive sweating, prolonged time in the sun, and extended vomiting or diarrhea cause fluid loss. Elderly people who move to warm, dry climates frequently become dehydrated because of the climate change combined with a tendency to not drink enough water. Large amounts of fluid can also be lost from prolonged fever. Healthy people require about 1 milliliter of water for each calorie their body metabo-

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Resources

Dehydration

lizes; but during a fever the metabolic rate increases by seven percent for each 1°F rise in body temperature. Fever also increases the respiratory rate, resulting in additional water loss from the lungs. Further causes of fluid loss that may be overlooked include caffeine and alcohol consumption, which increase urination and fluid excretion. Decreased oral intake of fluids is a common cause of dehydration and often occurs during times of appetite loss from illness or after oral surgery or injury. The elderly are at high risk for decreased intake because their thirst mechanism may no longer function or they may be physically unable to get a drink. Infants, another highrisk group, are more likely to develop dehydration than adults because they have a higher metabolic rate and their immature kidneys have difficulty concentrating urine. Children who do not wet their diapers for three hours or more are dehydrated. Dehydration is also associated with disorders of the adrenal glands, which regulate water-electrolyte balance; diabetes mellitus; eating disorders; renal disease; and chronic lung disease. Symptoms of dehydration at any age may include some or all of the following: cracked lips, dry or sticky mucous membranes, sunken eyes, lethargy, and/or confusion. Urine output is minimal and the skin loses its elasticity (turgor) and is slow to return to its normal position after being raised off the back of the hand (tenting). The heart rate and respiratory rate may be elevated. A dehydrated infant may not shed tears when crying and may have a depressed fontanel (soft spot on their head), although recent studies have shown that a depressed fontanel is not an accurate indicator of dehydration.

Diagnosis The general diagnosis of dehydration can be made based on the patient’s symptoms and medical history. Physical examination may reveal any of the symptoms mentioned above, along with shock, rapid heart rate, and low blood pressure. Blood tests are required to determine what deficiency exists (or what is elevated) so that therapy for electrolyte replacement can be planned. Blood tests to check electrolyte levels and urine tests such as urine specific gravity are used to evaluate the severity of the fluid loss. Other laboratory tests may be ordered to determine if an underlying condition (e.g., diabetes or an adrenal gland disorder) is the cause.

Treatment Increased fluid intake and replacement of lost electrolytes are usually sufficient to restore fluid balance in patients who are mildly or moderately dehydrated. For 654

individuals who are mildly dehydrated, just drinking plain water may be all the treatment that is needed. Adults may replace lost electrolytes by drinking sports beverages, such as Gatorade or Recharge. Parents should follow label instructions when giving children Pedialyte or other commercial products recommended for the treatment of dehydration in children. Children who are dehydrated should be given only clear fluids for the first 24 hours. A child who is vomiting should sip one or two teaspoons of liquid every 10 minutes. A child who is less than a year old and who is not vomiting should be given one tablespoon of liquid every 20 minutes. A child who is more than one year old and who is not vomiting should take two tablespoons of liquid every 30 minutes. A baby who is being breast-fed should be given clear liquids for two consecutive feedings before breastfeeding is resumed. A bottle-fed baby should be given formula diluted with water to half the formula strength for the first 24 hours after symptoms of dehydration are identified. To calculate fluid loss accurately, weight changes should be charted every day and a record kept of how many times a patient vomits or has diarrhea. A record of fluid output (including sputum or vomit) and of fluid intake or replacement should be kept for at least 24 to 48 hours to see if balance is being accomplished. Parents should note how many times a baby’s diaper must be changed. If dehydration continues, emergency department treatment or hospitalization to receive intravenous fluids and electrolytes may be necessary. Children and adults can gradually return to their normal diet after they have stopped vomiting and no longer have diarrhea. Gelatin is often a welcomed substitute for additional water and does count as fluid replacement. Bland foods should be reintroduced first, with other foods added as the digestive system is able to tolerate them. Milk, ice cream, cheese, and butter should not be eaten until 72 hours after symptoms have disappeared. When treating dehydration, the underlying cause must be addressed. For example, if dehydration is caused by vomiting or diarrhea, medications should be prescribed to resolve these symptoms. Patients who are dehydrated due to diabetes, kidney disease, or adrenal gland disorders must receive treatment for these conditions as well as for the resulting dehydration. If dehydration is being caused by diuretics. a dose adjustment made by the physician or a change to a different diuretic may be necessary.

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Mild dehydration rarely results in complications. If the cause is eliminated and lost fluid is replaced, mild dehydration can usually be resolved in 24 to 48 hours. Vomiting and diarrhea that continue for several days without adequate fluid replacement can be fatal since more is lost than water and sodium. Severe potassium loss may lead to cardiac arrhythmias, respiratory distress or arrest, or convulsions (seizures). The risk of lifethreatening complications is greater for young children and the elderly. However, dehydration that is rapidly recognized and treated has a good outcome.

Health care team roles The nurse and the physician have the greatest responsibility in recognizing and treating dehydration. For hospitalized patients, the physician should order appropriate fluid and electrolyte replacement and the nurse should ensure that the correct fluids are given to the patient. The nurse should monitor the patient for signs that the dehydration (e.g., decrease in fever, increase in blood pressure, reduced heart rate) is resolving and should notify the physician if it is not. Blood tests used to diagnose dehydration are collected by specially trained nursing assistants or by laboratory technicians. Outpatient samples in a physician’s office may be taken by the nurse or a technician. In some institutions, the nurse collects the blood sample. Usually, urine samples are collected by the nurse, and results calculated by the laboratory technician.

Dementia

Prognosis

KEY TERMS Extracellular—Outside the cells. Hypertonic—One solution having a greater amount of solute (dissolved substance in a solution) than another solution, thus it exerts more osmotic pressure than the second solution and the body will attempt to equalize pressure by passing fluid through the cell membranes. Hypotonic—One solution having a lesser amount of solute than another solution, thus it exerts less osmotic pressure than the second solution. Intracellular—Inside the cells. Isotonic—Two solutions exerting the same amount of osmotic pressure on a cell membrane. Osmotic pressure—The pressure exerted on a semipermeable membrane that separates two solutions and the particles they contain.

Resources BOOKS

Andreoli, Thomas E., et al., eds. Cecil Essentials of Medicine, 5th ed. Philadelphia, PA: W.B. Saunders Company, 2001. Porth, C. Pathophysiology: Concepts of Altered Health States. Philadelphia, PA: Lippincott, 1998. Rakel, Robert E., ed. Conn’s Current Therapy 2000. Philadelphia, PA: W.B. Saunders Company, 1999. Thelan, Lynne, et al. Critical Care Nursing: Diagnosis and Management. St. Louis, MO: Mosby, 1998. PERIODICALS

Prevention Patients who are vomiting or who have diarrhea can prevent dehydration by drinking enough fluid to keep their urine the color of pale straw. Infants and young children with diarrhea and vomiting can be given electrolyte solutions such as Pedialyte to help prevent dehydration, as well as suppository medication to stop the vomiting. People who are not ill can maintain proper fluid balance by drinking several glasses of water before going outside on a hot day. It is also a good idea to avoid coffee and tea, which increase body temperature and water loss. Patients should ask a pharmacist whether or not any medications they are taking may cause dehydration and what to do to prevent it other than adequate fluid intake. Prompt medical attention should be sought to correct any underlying condition that increases the risk of dehydration.

Pace, B. “Preventing Dehydration from Diarrhea.” JAMA 285, no. 3 (2001): 362. Sullivan, A. “Hydration for Adults.” Nursing Standard 14, no. 8 (1999): 44-46.

Abby Wojahn, R.N.,B.S.N.,C.C.R.N.

Dementia Definition Dementia is a condition characterized by a progressive, irreversible decline in mental ability, accompanied by changes in behavior and personality. There is commonly a loss of memory and skills that are required to carry out activities of daily living.

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Description Dementia is a group of symptoms caused by the gradual death of brain cells. The loss of cognitive abilities that occurs with dementia leads to impairments in memory, reasoning, planning, and personality. Dementia can occur at any age and may affect younger people as the result of disease such as AIDS, hypoxia (a deficiency of oxygen reaching the tissues of the body), or injury. However, it is primarily a disease of the elderly, affecting more than 15% of those over 65 years of age, and as many as 40% of those over the age of 80. The condition is somewhat more common among women than men. Some studies suggest that the risk for dementia is higher for African Americans and Hispanic Americans than it is for Caucasians. More than half of all nursing home admissions occur because of dementia. While the overwhelming majority of people with dementia are elderly, it is not an inevitable part of aging. One of the challenges for health care professionals is to differentiate the early-stage cognitive deficits of dementia from normal age-related memory impairment. Persons with age-related memory impairment may tend to learn new information more slowly; but, if they are given additional time, their cognitive performance is usually adequate. Other problems that may be mistakenly labeled dementia include delirium, psychosis, depression, and the side effects of various medications. Dementia presents a major health problem for the United States because of its huge impact on individuals and their families, the health care system, and society overall. The costs of dementia are considerable. While most people with the disease are retired and do not suffer income losses, the cost of care is often enormous. Financial burdens include lost wages for family caregivers, medical supplies and drugs, and home modifications to ensure safety. Nursing home care may cost several thousand dollars a month or more. As of 1998, the cost of caring for Alzheimer’s dementia patients alone was estimated to be slightly over $50 billion. The psychological costs are not as easily quantifiable, but can be even more profound. The person with dementia loses control of many of the essential features of life and personality, and loved ones lose a family member even as they continue to cope with the burdens of increasing dependence and unpredictability.

Causes and symptoms Causes Dementia is usually caused by degeneration in the cerebral cortex, the part of the brain responsible for thoughts, memories, actions, and personality. Death of 656

brain cells in this region leads to the cognitive impairment that characterizes dementia. Dementia may be caused by a variety of illnesses. The most common cause of dementia is Alzheimer’s disease (AD), accounting for half to three-quarters of all cases. Vascular dementia accounts for 5–30% of all dementias in the United States. It occurs from a decrease in blood flow to the brain, most commonly due to a series of small strokes (multi-infarct dementia). Other cerebrovascular causes include vasculitis from syphilis, Lyme disease, or systemic lupus erythematosus; subdural hematoma; and subarachnoid hemorrhage. Because of the usually sudden nature of its cause, the symptoms of vascular dementia tend to appear more abruptly than those of Alzheimer’s dementia. Symptoms may progress with the occurrence of new strokes. Unlike AD, the incidence of vascular dementia decreases after the age of 75. Other conditions that may cause dementia include: • AIDS • Parkinson’s disease • Lewy body disease • Pick’s disease • Huntington’s disease • Creutzfeldt-Jakob disease • brain tumors • hydrocephalus • head trauma • prolonged abuse of alcohol or other drugs • vitamin B12 deficiency • hypothyroidism • hypercalcemia Symptoms Dementia is marked by a gradual decline of thought and other mental activities. The onset may be slow, occurring over months or years. The slow progression of dementia is in contrast with delirium, which involves some of the same symptoms, but has a very rapid onset and fluctuating course with alteration in the level of consciousness. However, delirium may occur along with dementia, especially since the person with dementia is more susceptible to the delirium-inducing effects of many types of drugs. Symptoms of dementia may include: • Memory losses: Memory loss is usually the first symptom noticed. It may begin with misplacing valuables

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• Impaired abstraction and planning: The person with dementia may lose the ability to perform familiar tasks, to plan activities, and to draw simple conclusions from facts. • Language and comprehension disturbances: The person may be unable to understand instructions, or follow the logic of moderately complex sentences. Later, the individual may not be able to understand his or her own sentences, and have difficulty forming thoughts into words. • Poor judgment: The person may not recognize the consequences of his or her actions or be able to evaluate the appropriateness of behavior. Behavior may become ribald, overly friendly, or aggressive. Personal hygiene may be ignored. • Impaired orientation: The person may not be able to identify the time of day, even from obvious visual clues; or may not recognize a location, even if familiar. This disability may stem partly from losses of memory and partly from impaired abstraction. • Decreased attention and increased restlessness: These symptoms may cause the person with dementia to begin an activity and quickly lose interest, and to wander frequently. Wandering may cause significant safety problems, when combined with disorientation and memory losses. The person may begin to cook something on the stove, then become distracted and wander away while it is cooking. • Personality changes and psychosis: The person may lose interest in once pleasurable activities, and become more passive, depressed, or anxious. Delusions, suspicion, paranoia, and hallucinations may occur later in the disease. Sleep disturbances may occur, including insomnia and sleep interruptions.

Diagnosis Since dementia usually progresses slowly, diagnosing it in the early stages can prove difficult. However, as the elderly population grows and the prevalence of dementia increases, the importance of recognizing the early symptoms has become imperative. Dementia may be suspected by the health care professional if memory deficits are exhibited during an examination or assessment. Information from the family members, friends, and caregivers may point to dementia as well. Diagnosis begins with a thorough physical exam

and complete medical history. A family history of either Alzheimer’s disease or cerebrovascular disease may provide clues to the cause of symptoms. Simple tests of mental function, including word recall, object naming, and number-symbol matching, are used to track changes in the person’s cognitive ability. If dementia is suspected, a complete review of medications and an assessment for chronic disease processes are indicated. If the patient shows no improvement after eliminating unnecessary medications and treating the chronic disease, then other tests are warranted. Physical examination and a variety of laboratory tests may rule out potentially treatable causes of dementia. These may include hearing or visual deficits, hypothyroidism, vitamin B12 deficiency, and depression. Some of the laboratory tests that might be performed include a complete blood cell count and urinalysis (to rule out infection), serum electrolytes, glucose and calcium levels, and kidney and liver function tests. The use of computed tomography (CT) or magnetic resonance imaging (MRI) to rule out vascular disease is somewhat controversial, since even if a cause is discovered, less than 11% of patients with cognitive decline have partially or fully reversible disease.

Treatment Treatment of dementia starts with treatment of the underlying disease, where possible. The underlying causes of nutritional, hormonal, tumor-caused, and drugrelated dementias may be reversible to some extent. Treatment for stroke-related dementia begins by minimizing the risk of further strokes, including smoking cessation, aspirin therapy, and treatment of hypertension. There are no known therapies that can reverse the progression of Alzheimer’s disease. Early intervention may allow the patient to compensate for the alterations in functioning, help to minimize complications, and have an improved quality of life. It may also allow the patient and family to plan for the future and to identify resources. Periodically, new drugs are studied for the treatment of dementia. The only drugs currently approved for the symptomatic treatment of AD are tacrine (Cognex) and donepazil (Aricept). These drugs act by slowing down the degradation of neurotransmitters. They may provide temporary improvement in cognitive functioning for about 40% of patients with mild-to-moderate AD. However, drug therapy can be complicated by forgetfulness, especially if the drug must be taken several times a day. Psychotic symptoms, including paranoia, delusions, and hallucinations, may be treated with antipsychotic

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such as a wallet or car keys, then progress to situations such as forgetting appointments, where the car was left, or the route home. More profound losses follow, such as forgetting the names and faces of family members.

Dementia

KEY TERMS Amyloid plaques—Abnormal structures composed of parts of nerve cells surrounding protein deposits, found in the brains of persons with Alzheimer’s disease. Neurofibrillary tangles—Abnormal structures composed of twisted masses of protein fibers within nerve cells, found in the brains of persons with Alzheimer’s disease.

drugs such as haloperidol, chlorpromazine, risperidone, and clozapine. Side effects of these drugs can be significant. Anti-anxiety drugs such as Valium may improve behavioral symptoms, especially agitation and anxiety, although BuSpar has fewer side effects. The anticonvulsant carbamazepine is also sometimes prescribed for agitation. Depression is treated with antidepressants, usually beginning with selective serotonin reuptake inhibitors (SSRIs) such as Prozac or Paxil. In general, medications should be administered very cautiously to demented patients, in the lowest possible effective doses, to minimize side effects. Supervision of taking medications is generally required. The primary goals of treatment for progressive dementia are to preserve as much functioning and independence as possible, and to maintain quality of life as long as possible. It is important that the patient and caregivers are aware that caring for a person with dementia can be difficult and complex. The patient must learn to cope with functional and cognitive limitations, while family members or other caregivers may need to assume increasing responsibility for the person’s physical needs. The patient and family should be educated early on in the disease progression to help them anticipate and plan for inevitable changes. Behavioral approaches may be used to reduce the frequency or severity of problem behaviors such as aggression or socially inappropriate conduct. Problem behavior may be a reaction to frustration or over-stimulation. Understanding and modifying the situations that trigger it can be effective; strategies may include breaking down complex tasks such as dressing or feeding into simpler steps, or reducing the amount of activity in the environment to avoid confusion and agitation. Pleasurable activities such as crafts, games, and music can provide therapeutic stimulation and improve mood. Modifying the environment can increase safety and comfort while decreasing agitation. Home modifications 658

for safety include removal or lock-up of hazards such as sharp knives, dangerous chemicals, and tools. Childproof latches may be used to limit access as well. Bed rails and bathroom safety rails can be important safety measures. Confusion may be reduced with the use of simpler decorative schemes and the presence of familiar objects. Covering or disguising doors may reduce the tendency to wander. Positioning the bed in view of the bathroom can decrease incontinence. Long-term institutional care may be required for the person with dementia, as profound cognitive losses often precede death by a number of years. Early planning for the financial burden of nursing home care is critical. Useful information about financial planning for longterm care is available through the Alzheimer’s Association. Family members or others caring for a person with dementia are often subject to extreme stress, and may develop feelings of anger, resentment, guilt, and hopelessness, in addition to the sorrow they feel for their loved one and for themselves. Depression is an extremely common consequence of being a full-time caregiver for a person with dementia. Support groups can be an important way to deal with the stress of caregiving. Contact numbers are available from the Alzheimer’s Association; they may also be available through a local social service agency.

Prognosis The prognosis for dementia depends on the underlying disease. On average, people with Alzheimer’s disease live eight years past their diagnosis, with a range from one to 20 years. Vascular dementia is usually progressive, with death resulting from stroke, infection, or heart disease.

Health care team roles Any member of the health care team may work with patients with dementia. The physician normally makes the diagnosis. Laboratory technicians may obtain laboratory tests, and radiology technicians may perform imaging studies, if ordered. Nurses assess patients and how dementia affects their functioning. Patient education is very important in managing dementia and is a nursing responsibility.

Prevention There is no known way to prevent AD, although several drugs under investigation may reduce its risk or slow its progression. The risk of developing multi-infarct

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Resources BOOKS

Beers, Mark H., and Robert Berkow. The Merck Manual of Diagnosis and Therapy, 17th ed. Whitehouse Station, NJ: Merck and Company, Inc., 1999. PERIODICALS

The swollen area can rupture, allowing the pus to drain, but it will return if the cause of infection is not removed. As an abscess develops, the bacteria and host cells cause rapid destruction of connective tissues around the tooth and into the jawbone. Abscesses can be acute or chronic, with the acute abscess being the most painful. A chronic abscess may produce a dull pain with intermittent swelling, but can develop into an acute abscess at any time. The most common types of dental abscesses are:

“Progress Report on Alzheimer’s Disease.” National Institute on Aging, National Institutes of Health (1999). Santacruz, Karen S., and Daniel Swagerty. “Early Diagnosis of Dementia.” American Family Physician (February 15, 2001): 703. ORGANIZATIONS

Alzheimer’s Association. 919 North Michigan Ave., Suite 1000, Chicago, IL 60611. (800) 272-3900. . Alzheimer’s Disease Education and Referral Center (ADEAR). P.O. Box 8250, Silver Spring, MD 209078250. (800) 438-4380. .

• Periapical abscess: located at the apex of an infected tooth surrounding the roots. • Periodontal abscess: located in the periodontal ligament (PDL) surrounding the tooth. Studies by the American Academy of Periodontology (AAP) find that periapical abscesses can occur on any tooth that has severe decay or is broken or chipped, but periodontal abscesses commonly involve the mandibular and maxillary first molars, maxillary incisors, and cuspids, followed by maxillary second molars.

Causes and symptoms Deanna M. Swartout-Corbeil, R.N.

Demyelinating disease see Multiple sclerosis

Dental abscess Definition A dental abscess is a localized collection of pus in a cavity formed by the disintegration of tissues from a bacterial infection.

Description Dental abscesses occur when a small area of tissue becomes infected and the body is able to “wall off” the infection and keep it from spreading. White blood cells, the body’s defense against some types of infection, migrate through the walls of the blood vessels in the area of the infection and collect within the damaged tissue. During this process pus forms, which is an accumulation of fluid, living and dead white blood cells, dead (necrotic) tissue and bacteria, or any other foreign invaders or materials; popcorn hulls, calculus, etc. This pus pocket is the abscess, characterized by swelling, redness, and pain.

Periapical abscesses usually result from dental caries that allow bacteria to infect the center area of the tooth (pulp). But they can also occur after a traumatic injury to the tooth resulting in necrosis (death) of the pulp. This infection may spread out from the root of the tooth to the bones supporting the tooth, causing an abscess. This type of abscess is extremely painful and very sensitive to cold and hot, and to the touch. Acute inflammation of the apex commonly occurs with the tooth seeming to be slightly extruded from its socket. The patient may also have a fever and redness of the cheeks and gum tissue. The abscess itself may feel hot and hard to the touch. The bigger the abscess gets, the more painful it becomes. A periodontal abscess occurs where pre-existing periodontitis is present. This infection occurs in the walls of the periodontal pocket as a result of bacterial invasion into the periodontal tissue. While abscesses usually spontaneously occur in patients with untreated periodontitis, they are more common in periodontitis patients with a systemic disease, in which there is a reduced ability to combat infections, such as individuals with diabetes or HIV, or patients on chemotherapy. Periodontal abscesses are generally not sensitive to heat, and the pain is not as severe as with a periapical abscess, but the discomfort level is constant. They appear red, edematous (swollen), shiny, and very sensitive to the touch.

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dementia may be avoided by reducing the overall risk for strokes.

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Other symptoms of a dental abcess include:

During this process the patient is given a local anesthetic to minimize the pain. Often with a periapical abscess, the infection is severe and pain is so intense that the anesthetic is injected into the tooth or infected area for immediate relief. Extraction of the tooth is sometimes required, especially if an injury to the tooth has fractured through the bifurcation area and saving the tooth is not possible.

• earache • general ill feeling • bad breath or foul taste in mouth • fever • continuous or throbbing pain

Diagnosis When a patient has swelling and pain it is necessary to locate the exact region causing the pain. X rays greatly aid in locating the tooth or teeth in question. Hot and cold tests may be performed by touching the teeth with ice or heated instruments. This helps to pinpoint the exact location of the pain and to determine the type of abscess. Percussion tests may also be done by tapping the teeth in question lightly with the small end of an explorer. After diagnosis, the general dentist may choose to treat the abscess, but may also refer the patient to an endodontist or periodontist. The entire treatment may take a number of visits to complete depending on the severity of the abscess. The cost for treatment of a periapical abscess is normally covered under dental insurance at 80%. The cost is usually a few hundred dollars or more if the patient is referred to an endodontist because of the specialty field. The insurance then only covers a certain amount of the usual and customary charge (UCR), commonly about 50%. A patient has to consider whether to have a general dentist treat the abscess, or whether to pay the extra cost to have a specialist perform the treatment. Usually having a specialist treatment the abscess is worth the extra cost in the long run. For a periodontal abscess, a dental hygienist may perform the necessary scaling and root planing required to treat this condition. The cost for periodontal abscess treatment is commonly covered by dental insurance at 80%. Even when treated by a periodontist, insurance normally covers the treatment at 80% because a periodontal abscess is considered part of the periodontal disease for which the patient is already being seen by the specialist.

The principle treatment for a periodontal abscess is to establish drainage of the inflammation and to eliminate the infective agent. Anesthetics are required because of the pain involved and the discomfort caused by scaling and root planing. Careful insertion of a dull probe into the pus pocket along the tooth will usually produce the drainage needed and the symptoms normally dissipate. Scaling and root planing through the periodontal pocket to rid the area of the cause of the infection is necessary. If necessary, surgical procedures may be undertaken. Surgery aims at pocket reduction if not elimination. An incision into the gum tissue and the laying open of a flap of tissue may be necessary in order to reach the infection more easily. Surgery must be gentle and efforts are made to avoid damage to the remaining periodontal attachment. As soon as the etiologic factors have been eliminated the swelling is reduced. The healing process is usually uneventful and regeneration frequently occurs. The abscess will recur unless the cause of the infection is removed and the depth of the pocket is reduced. Extraction of the tooth is indicated after the acute symptoms have subsided, but in some cases, normal tissue contours cannot be developed and maintained. In cases where the periodontal destruction approaches the periapical region of the tooth (the apex) the patient may develop pulpitis. Treatment may cause the patient to experience pain and discomfort following the root planing treatment and treatment for pulpitis will need to be completed, usually with root canal therapy. Antibiotics are vital in ridding the system of any infection for both periapical and periodontal abscesses. If the infection is not eliminated the abscesses will recur with a stronger infection and more severe symptoms. The types of antibiotics prescribed for acute abscesses include:

Treatment The goal of treating a dental abscess is to eliminate the infection while preserving the teeth and to prevent any complications. Releasing the direct pressure of the infection build up is the first step in the treatment.

• Penicillin VK: an initial dose of 1000 mg followed by 500 mg four times daily for seven days.

With a periapical abscess, the pus is drained through an incision in the gum tissue, or by enlarging the hole in the tooth. This alleviates the pain and the tissue swelling.

• Erythromycin: 1000 mg first followed by 500 mg four times daily for seven days (for patients allergic to penicillin).

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• Amoxicillin (Augmentin): 250 mg three times daily for ten days.

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Warm salt-water rinses can soothe the gum tissue and help with the healing process. Over-the-counter medication can be taken for pain along with the antibiotics. Medications such as acetaminophen (Tylenol) reduce fever (if any) and pain. Anti-inflammatory medicines such as ibuprofen (Motrin and Advil) aid in reducing fever and also help reduce swelling and inflammation in the tissue.

Prognosis While the loss of periodontal attachment is commonly rapid during an acute periodontal abscess, the potential for repair and healing is very high if the abscess is treated quickly and appropriately. The prognosis for a periapical abscess is similar, if it is treated quickly and appropriately with the elimination of the infection that is causing the abscess.

Health care team roles The role of the dentist is vital in combating the infection of a dental abscess. The patient needs to be educated that abscesses and infections of the mouth do not subside on their own without recurrence. An endodontist should be consulted if a periapical abscess needs to be treated. A periodontist should be consulted if an existing condition of periodontitis is being treated. Each type of dentist needs to have a good working relationship with the patient. The dental hygienist can complete the scaling and root planing of the abscessed area in the dental office or the periodontist’s office. Dental assistants can aid in taking x rays of the area needing treatment and in sterilization of the instruments. The front desk is the first to greet a patient and the last to see a patient leave. Having a warm and courteous front office is vital to any dental office where treating disease, emergencies, and healing of patients is accomplished. All roles are important to the successful functioning of the health care team and good patient care.

Prevention Dental abscesses can be prevented with regular dental care, including daily brushing and flossing, and regular dental check ups and cleaning. Wearing mouth guards during sports is one of the best ways to prevent an injury and trauma to the mouth.

KEY TERMS Acute—Extremely sharp or severe, reaching a crisis rapidly. Apex—The point at the end of the root of a tooth in the gum tissue. Bifurcation—The area where the roots of the teeth separate into individual roots. Calculus—Calcium deposits on teeth from the build up of plaque. Chronic—Of long duration or frequent recurrence. Cuspids—The teeth that are considered the cornerstone teeth of the mouth on the upper and lower jaws. More commonly known as the “eye” teeth. Dental caries—Dental decay. Edematous (edema)—An abnormal accumulation of serous fluid in the tissue. Endodontist—A dentist who specializes in the diagnosis and treatment of disorders affecting the inside structures of the tooth. Extraction—Surgical removal of a tooth. Incisors—The teeth on the upper jaw right and left sides that sit next to the central front teeth. Mandibular—Relating to the lower jaw region. Maxillary—Relating to the upper jaw region. Necrotic, necrosis—Pathologic death of tissue. Periodontal—Tissue and structures that surround and support the teeth. Periodontist—A dentist with specialized training for periodontal treatment and care. Pulpitis—Inflammation of the pulp of a tooth involving the blood vessels and nerves. Root canal—The space within a tooth that runs from the pulp chamber to the tip of the root. Root canal therapy—The process of removing diseased or damaged pulp from a tooth, then filling and sealing the pulp chamber and root canals. Root planing—Making the tooth smooth by removing built up calculus and tartar from below the gum tissue. Scaling—The removal of food and debris from the portion of the tooth above the gum line. Prosthodontist—A dentist with specialized training in crown and bridge treatment.

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For chronic infections or infections with an inadequate response to penicillin, clindamycin is often prescribed (300 mg daily for seven days).

Dental anatomy

Resources

Teeth

BOOKS

Physicians Desk Reference. Montvale, NJ: Medical Economics, 2000. PERIODICALS

Meng, Huan X. “Periodontal Abscess.” Journal for Periodontology 4 (December 1999): 79-82. ORGANIZATIONS

American Academy of Periodontology, 4157 Mountain Road, PBN 249, Pasadena, MD 21122. (410) 437-3749. . American Dental Association (ADA), 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-2500. . American Institute for Preventive Medicine, 1431 Saratoga Ave. Suite C-9, Morgantown, VW 26505. (304) 5996981. <www.peiapathways.com>. UCLA School of Dentistry, 10833 Le Conte Ave. Box 951668, Los Angeles, CA 90095-1608. (310) 825-2337. <www.dent.ucla.edu>. OTHER

Marais, J.T. “What Is a Dental Abscess?” Electronic Doctor, December 1999. <www.edoc.co.za/dhw/faq/ abscess.html>. “Oral Health Topic: Abscess.” ADA.org, January 2, 2001. <www.ada.org/public/topics/abscess.html>. “Periodontal Abscess.” UCLA Dental School, 2001. <www.dent.ucla.edu.81/pic/courses/antibiotics/abscess/>.

Cindy F. Ovard, RDA

The teeth are derived from the ectoderm and the mesoderm in the embryonic stages of development. Each tooth arises from either the maxilla (the bone that makes up the upper jaw) or the mandible (the bone that makes up the lower jaw). Teeth originating from the maxilla are considered to be in the superior dental arch, or the maxillary dental arch. Teeth arising from the mandible are considered to be in the inferior dental arch, also known as the mandibular dental arch. Each tooth consists of: • Crown: The visible portion of a tooth. • Root: The portion of the tooth embedded in the gum. • Pulp: Located in the center of the tooth, it contains the arteries, veins, nerves and lymphatic tissue. • Blood vessels: They carry nutrients to the pulp. • Root canal: The canal in the root of the tooth is where the nerve and blood vessels travel with nutrients to the tooth from the mandible or the maxilla. • Ligament: The connective tissue that surrounds the root of a tooth and connects it to the maxilla or mandible. • Bone: Alveolar bone forms tooth socket and part of the teeth. • Cementum: The layer of tissue covering the dentin on the root of the tooth. Serves the same role as enamel. • Dentin: The calcified tissue underlying the enamel (on the crown) and cementum (on the root), making up the main bulk of the tooth. • Enamel: The calcified outer layer of the crown of the tooth.

Dental anatomy Definition Dental anatomy is the study of the classification and morphology of teeth, as well as the study of the principles of occlusion.

Description Dental anatomy may be considered the study of teeth at three different levels. First, teeth may be studied in terms of the elements of each individual tooth (for example, dentin and enamel). Second, teeth may be studied in terms of classification and numbering systems. Third, teeth may be studied in the larger context of the oral cavity, along with the principles of occlusion and structures that may display pathology such as the gingiva and the temporomandibular joint. 662

Although each tooth has the same basic structure, some variation exists. Different types of teeth have variation in their roots. Incisors and cuspids have only one root. Maxillary (upper) premolar teeth commonly have two roots, whereas the mandibular premolars commonly have one. The premolars may also have two roots fused to look as one. The molars on the maxillary arch have three roots, while, on the other hand, the molars on the mandibular arch have two roots. Tooth types Permanent teeth are divided into four groups based on their function and placement in the jaw. Teeth are given the same name whether they are in the upper or lower jaw. From medial (middle of the mouth) to lateral, the four types of teeth are listed below: • Incisors cut the food. They are divided into central and lateral. They are the two most medial teeth on either

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Dental anatomy

Upper lip

Central incisor

Gingiva

Lateral incisor Canine First premolar Second premolar

Hard palate

First molar Second molar

Soft palate Uvula

Tonsil Pharynx Third molar Tongue

Second molar First molar Second premolar First premolar Canine

Gingiva Lateral incisor Central incisor Lower lip

Major structures of the oral cavity. The maxillary third molars are missing in this adult dentition. (Delmar Publishers, Inc. Reproduced by permission.)

side (left and right) in the upper and lower jaw, for a total of eight. • Cuspids also known as canines, cut and tear the food. They are the third teeth from the center, and there are a total of four (two upper, two lower). • Pre-molars seize and shear the food. They are also known as bicuspids because they have two cusps, or projections on the surface of the teeth. There are eight total (four upper, four lower) between the cuspids and the molars. • Molars grind the food. They are the most lateral teeth. There are a total of twelve, including the four “third molars” also known as wisdom teeth. Children who still have their temporary teeth (also known as primary, deciduous, or “baby” teeth) have incisors (four upper, four lower), cuspids (two upper, two

lower), and molars (four upper and four lower), but lack pre-molars. There are 20 total primary teeth. Tooth classification and numbering systems Universal tooth numbering and classification allows health care professionals to discuss and identify teeth with a measure of certainty. Permanent dentition has a universal numbering system that begins by splitting the mouth into four quadrants; the upper right quadrant, the upper left quadrant, the lower right quadrant, and the lower left quadrant. Each quadrant contains eight teeth. The upper right quadrant consists of the eight teeth on the upper right side of the mouth from the third molar (wisdom tooth) to the right central incisor. The upper left quadrant is the same except on the left portion of the mouth from the third molar (wisdom tooth) to the left central incisor. The lower right quadrant consists of the

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• Masseter: The main muscle for the movement of the mandible for chewing.

KEY TERMS Gingiva—The gum tissue surrounding the teeth. Mandible—The bone that helps make up the lower jaw of the mouth. Mastication—Chewing and biting of the food in the mouth. Maxilla—The bone that helps make up the upper jaw of the mouth. Occlusal—Biting surface of the teeth.

teeth from the third molar on the lower left to the lower right central incisor. The same with the lower left quadrant from the third molar on the lower left to the lower left central incisor. Each quadrant can be named using acronyms; upper right (UR), upper left (UL), lower right (LR), lower left (LL). General dentists generally number the teeth, beginning with the third molar in the upper right quadrant (number one), crossing to the upper left quadrant (the third molar is number 16), proceeding to the lower left quadrant (the third molar is number 17), and ending in the lower right quadrant with the third molar number 32 (third molars are known more commonly as the wisdom teeth). In contrast, orthodontists and oral surgeons use the acronyms of quadrants to help identify teeth, and number the teeth from medial to lateral (one to eight). Thus the upper right first (or central) incisor is also known as UR1, whereas the upper left third molar is known as UL8. LL5 would be the lower left second premolar and LR6 is the lower right first molar. Primary, or temporary, teeth are systematically lettered in an alphabetical order beginning with A on the upper right quadrant, ending with J for the second molar in the upper right quadrant, proceeding with K for the second molar in the lower left quadrant, and ending with T for the second molar in the lower right quadrant. Primary teeth consist of twenty teeth total; ten on the maxilla and ten on the mandible

• Lateral pterygoid: This muscle has a horizontal position and is the prime mover of the mandible into a protrusive position. • Medial pterygoid: Works with the masseter muscle to aid in the elevation of the mandible. It is almost a mirror image of the masseter muscle—it gives extra aid in chewing. TEMPOROMANDIBULAR JOINT. Also known as the TMJ, this is the connecting hinge between the lower jaw (the mandible) and the bone at the (lateral) base of the skull (the temporal bone). This joint is very fragile. A meniscus (piece of cartilege) separates the lower jawbone from the socket where it rests. Tendons, ligaments and muscles hold the TMJ in position. TMJ disorders can arise from pain because of muscle dysfunction (myofascial pain), pain because of degenerative bone disease (like arthritis), pain because of a broken bone, pain arising from dislocation of the meniscus, or pain arising from the dislocated joint. These dysfunctions can result in headaches, jaw soreness, neckaches and pain when chewing (often accompanied with a noise). Bite splints may be used to treat TMJ disorders caused by dislocation. Other therapies, ranging from isometric muscle exercises to oral surgery, may be required, based on the nature and severity of the TMJ disorder.

Gingiva Normal, healthy gingiva may appear smooth or stippled. Known also as the gum tissue of the mouth, the gingiva shows the first signs of periodontal disease. Daily brushing and flossing help keep the gingiva healthy.

Function Dental anatomy serves the important function of mechanical disruption and processing of food.

Role in human health

Occlusion When discussing occlusion, one is essentially discussing the operation and conjunction of the teeth at rest and in the process of mastication (chewing). Two important elements in mastication are the muscles involved, and the temporomandibular joint. MUSCLES. The four main mandibular muscles for dental anatomy are the:

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• Temporalis: Maintains the position of the mandible at rest when a person is upright. During chewing it pulls the mandible back into the rest position.

Properly functioning dental anatomy is essential for one of the first stages of food digestion—chewing. Chewing is essential for human health because (most) food is not prepared in a readily digestable form. Chewing increases the total surface area of the food by breaking it into smaller pieces, which allows more food to be digested. Chewing also breaks down any lessdigestable barriers which may hinder absorption of food

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Common diseases and disorders The most common childhood disease of the dentition is tooth decay. The bacteria demineralizes the enamel and dentin of the teeth, causing pain and swelling of the surrounding tissue if left untreated. Periodontal disease is a common disease among older adults associated with infectious bacteria affecting the tissues that support the teeth. Temporomandibular joint (TMJ) disorders cause pain to patients upon talking or chewing. TMJ disorders are commonly found in patients with physical, emotional, and social problems, as well as in individuals who experience work-related stress. Many types of TMJ have an excellent prognosis if treated. Resources BOOKS

Karst, N.S., and S.K. Smith. Dental Anatomy: A SelfInstructional Program. 10th ed. Stamford, CT: Appleton and Lange, 1998. ORGANIZATIONS

Adam.com Health and Medical Association Online. adam.com; 90 Tehama Street, SF, CA 94105. (415) 5419164. . American Dental Association. 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-2500. . National Institute of Dental & Craniofacial Research. Building 45, Room 4AN-24, 45 Center Drive, MSC 6402, Bethesda, MD 20892-6402. (301) 594-9898. . Oregon Health & Science University. 3181 SW Sam Jackson Park Rd., Portland, Oregon 97201. (503) 494-3462. . OTHER

Ladd Dental. Dental Anatomy of a Tooth. 2333 W Lincoln Rd., Kokomo, IN, 46902. (765) 455.0085. . Mediplus Online Medical Resources. Adam.com. . Nangle, Simon J. Dental Wisdom. . National Institute of Dental and Craniofacial Research. National Institutes of Health. Pamphlet, brochure for TMJ anatomy. .

The National Women’s Health Information Center. TMD/TMJ (Jaw disorders). . Nirog.com. Online Magazine for Medical and Dental Professionals. . Project Micro Images. . Wyche, Haywood E., DDS. Dental Anatomy. 1145 19th Street, N.W. Suite 316, Washington, DC 20036. .

Cindy F. Ovard, RDA

Dental and periodontal charting Definition Dental and periodontal charting provide a graphic description of the conditions in a patient’s mouth, including caries (i.e., decay), restorations, missing or malposed teeth, clinical attachment levels, furcation (root) involvement, mobility, pocket depths, bleeding sites, and other deviations from normal. Other conditions that may be charted include erosion, abrasion, developmental anomalies and use of prostheses.

Purpose Thorough charting of both visual and radiographic findings allows dental practitioners to collate information needed to assess the patient’s level of dental and periodontal health or disease. Charting should be updated with each visit to follow the patient’s progress with home care, monitor disease progression, and to track completed dental procedures.

Description Dental charting is part of both initial and periodic dental examinations, and is included in the cost of care. Exams are normally covered by dental insurance. Charting begins with tooth naming and numbering. The maxillary, or upper arch, and the mandibular, or lower arch, each contain 16 teeth in a full adult dentition. Teeth are paired right and left by size, shape, and function. Beginning at the midline, each arch includes two central incisors side by side. Continuing outward to right and left are pairs of lateral incisors, canines (cuspids), first premolars (first bicuspids), second premolars (sec-

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in the gastrointestinal tract, For example, even after an orange is peeled, thin membranous tissue still surrounds the juicy, fruity portion of the orange. Chewing breaks down that barrier, making the nutrients inside much more accessible.

Dental and periodontal charting

ond cuspids), first molars, second molars, and third molars (wisdom teeth).

face of a tooth); and distal (i.e., proximal surface of a tooth farthest from the midline).

In a primary, or deciduous, dentition there are no premolars or third molars. From the midline, pairs are central incisors, lateral incisors, canines, first molars, and second molars. As the adult dentition erupts, first and second primary molars are replaced by adult premolars. Adult molars erupt behind the primary molars in space created by the lengthening maxilla and mandible.

For the purposes of communication, tooth surfaces are referred to by their first initial. For instance, a restoration on the mandibular left first molar that covers the mesial and occlusal surfaces would be called an MO on 19. A carious lesion that extends from mesial to facial to incisal surface of the maxillary right lateral incisor would be an MFI on 7.

The widely used universal system, adopted in 1974, assigns the permanent teeth numbers from 1 to 32. Primary teeth are assigned letters from a to t, regardless of their position in the mouth. In the permanent dentition, 1 is the third molar of the maxillary (upper jaw) right quadrant. Numbering continues sequentially around the upper arch to 16, the third molar of the maxillary left quadrant. Number 17 is the third molar of the mandibular (lower jaw) left quadrant, and numbering again continues sequentially around the lower arch to 32, the third molar of the mandibular right quadrant. Teeth may drift due to factors including other missing teeth, malocclusion, malpositioning, or congenital abnormalities.

Both restorations and lesions can also be classified according to location. The G.V. Black system of classification is as follows:

Lettering of primary teeth is similar. An a is assigned to the second molar of the maxillary right quadrant, and lettering continues sequentially around the upper arch to j, the second molar of the maxillary left quadrant. The letter k is the second molar of the mandibular left quadrant, and lettering continues sequentially around the lower arch to t, the second molar of the mandibular right quadrant. An older system, sometimes used by orthodontists, is Palmer’s Notation. In that system, teeth are numbered 1 through 8 or lettered a through e by quadrant, beginning at the midline. Permanent maxillary canines, for instance, would be referred to as “upper right 3” and “upper left 3” instead of 6 and 11. Primary mandibular first molars would be referred to as “lower right d” and “lower left d” instead of s and l. When written down, the numbers or letters are enclosed in half boxes to denote upper or lower, left or right. A dental chart can be anatomically correct, showing several views of each tooth, or it can be stylized, showing two rows of 16 circles each. Small boxes are usually placed above and below the rows to allow coded notations for each tooth. Each circle represents a tooth, and is divided to show a smaller round center and four outside surfaces. The round center represents the occlusal (i.e., biting surface) of posterior teeth, or the incisal (i.e., biting edge) of anterior teeth. The four surfaces surrounding the center, noted clockwise from the top, are buccal (i.e., outside surfaces of posterior teeth) or facial (i.e., outside surfaces of anterior teeth; mesial (i.e., proximal surface of a tooth closest to the midline); lingual (i.e., inside sur666

• Class I: Pits and fissures of the occlusal surfaces of posterior teeth, and lingual surfaces of anterior teeth. • Class II: Proximal surfaces of posterior teeth. • Class III: Proximal surfaces of anterior teeth. • Class IV: Proximal surfaces of anterior teeth that involve an incisal edge. • Class V: Gingival third (i.e., closest to the gumline) of the facial, buccal, or lingual surfaces of anterior and posterior teeth. • Class VI: Cusp tips. A carious lesion on the proximal surface of the maxillary left canine could therefore be referred to as a Class III lesion on 11. Missing teeth are normally charted first, marked out with an X or a single vertical line. Unerupted teeth may be completely circled, with the circle altered if necessary to show partial eruption. Both carious lesions and restorations are marked by coloring the portion of the tooth affected, usually in different colors. For more precise charting, shadings, colors or coded letters may be used to differentiate between types of restorations. Amalgam (i.e., silver) restorations might be colored blue, for instance, while composite (i.e., white) restorations might be outlined in blue. Gold crowns might be marked with a “G” (or designated with a blue outline and oblique lines), and porcelain crowns with a “P.” Additionally, full-coverage crowns are usually marked by circling just the crown of the tooth on the chart in blue. Areas of decay or defective restorations are marked in red. Endodontic (i.e., root canal) restorations can be marked with a black line extending up the length of the tooth root. A periapical abscess (i.e., infection of the tooth nerve) is marked with a small circle at the apex of the root. Conditions such as erosion, abrasion, and congenital abnormalities can be identified with boxed notes. The directions of malpositioned, drifted, and super-erupted teeth can be indicated with arrows.

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When a single clinician writes and draws findings on a dental chart, there are concerns about time, accuracy, and cross-contamination. Charting by hand is most efficient with two people, one performing the exam and the other recording the findings on the chart. If a computer is available in the treatment area, a clinician can use a headset microphone and voice-activated charting software for ease and convenience. Once the teeth themselves have been charted, periodontal charting is indicated. The periodontium, or support structure for teeth, includes gingiva (i.e., gums), periodontal ligaments and membranes, and bone. Baseline data, recorded as part of the initial examination, is a resource for treatment planning. During treatment, the chart offers direction for instrumentation, alerting the clinician to complex pocketing, mobility, and root furcation involvement. Later, periodically updated charts evaluate the success of home care and professional treatment. Further uses for periodontal charting are as legal evidence, to support a diagnosis and justify treatment, and as forensic evidence. The best defense in a malpractice suit is complete and accurate documentation. For a periodontal chart, the clinician measures and records pocket depths surrounding the teeth. In a healthy mouth, each tooth is surrounded by a free collar of marginal gingiva. At a depth of 0–3 millimeters, the gingiva is attached to the cementum, the surface of the tooth root. The surrounding 0–3 mm. space within the free collar is referred to as the sulcus. In an unhealthy condition, sulcus depths can be much greater because of loss of attachment and are referred to as periodontal pockets. Measurement is accomplished with a calibrated periodontal probe, inserted into the sulcus parallel to the long axis of the tooth. Depending on design, the probe may be marked at each millimeter up to 10. A more common design has the markings at four and six deleted for easier reading. Color-coded probes may be marked in blocks, with a green block up to 3 mm (i.e., indicating a healthy condition), and a red block up to 6 mm (i.e., indicating and unhealthy condition and the presence of periodontal disease). Probes are designed with blunt or ball-tipped ends to avoid puncturing the junctional epithelium at the base of the sulcus during probing. Electronic probes are also available that record pocket depths automatically on a computerized chart. For a full periodontal chart, six readings are taken on each tooth and recorded in six boxes above and below teeth on the chart. Beginning with tooth number 1, a

measurement is taken at the mesio-buccal line angle, the midbuccal, the distobuccal line angle, the distolingual line angle, the mid-lingual, and the mesio-lingual line angle. The probe can be “walked” around the circumference of the tooth for complete exploration. As the sulcus is probed, other conditions can be noted. Inflamed gingiva can bleed spontaneously from finger pressure or from probing, even though the probe does not puncture tissue. A bleeding index can be determined by dividing the number of sites bleeding by the number of sites examined. If 24 sites are probed, for example, resulting in 12 of those sites exhibiting bleeding, the patient has a bleeding index of 50%. Bleeding sites can be noted on the chart by a red dot or by the letter B. A plaque index can be determined by the same method. A clinician counts the number of teeth where plaque, a biofilm, is present, and divides that by the number of teeth examined. A plaque index is a useful motivational tool for patients when measured at periodic intervals. Other conditions that might be noted on a periodontal chart include the presence of exudate, tooth mobility, color and contour of the gingiva, recession, and the amount of plaque and calculus. All these conditions, when added together, provide the clinician a comprehensive picture of the patient’s periodontal status. Planning and treatment can only begin when these conditions have been fully documented. Some clinicians prefer to assign standardized classifications to the patient’s degree of periodontal health. The five recognized classifications are: • Case Type I: Gingivitis is present when inflammation is apparent and the gingiva is characterized by changes in color, form, position and appearance. Bleeding and/or exudate may be present. • Case Type II: Slight periodontitis is present when inflammation has progressed from the gingiva to deeper periodontal structures and bone, with slight bone loss. Probing depths are 3–4 mm, and there is some loss of connective tissue attachment. • Case Type III: Moderate periodontitis is a more advanced stage of Slight Periodontitis, with increased destruction and tooth mobility. There may be furcation involvement in multirooted teeth. • Case Type IV: Advanced periodontitis involves major loss of bone support and increased tooth mobility and furcation involvement. • Case Type V: Refractory progressive periodontitis is diagnosed when there is rapid bone and attachment loss

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Implants can be drawn on the chart in their relative positions, with fixed bridgework noted by connected lines. Partial and complete dentures can be marked with brackets.

Dental and periodontal charting

KEY TERMS Calculus—Calcified mass of bacteria, fungi, dequamated epithelial cells and food debris that forms on the surface of a tooth. Caries—Tooth decay. Cusp—Pointed projection on the crown of the tooth. Deciduous teeth—Primary, or “baby” teeth. Distal—Proximal surface of tooth farthest from the midline. Facial—Outside surface of anterior tooth, adjacent to the face. The term includes buccal (cheek) and labial (lips) areas. Gingiva—Gum tissue. Incisal—Biting edge of anterior tooth. Lingual—Inside surface of tooth, adjacent to the tongue. Mesial—Proximal surface of tooth closest to the midline. Occlusal—Biting surface of posterior tooth. Periodontics—Study of the support structures of teeth, including gingiva, ligaments and alveolar bone. Plaque—Collection of bacteria growing in a soft mass on surface of tooth or gingiva. Also called biofilm. Sulcus—Normal 0–3mm space between the tooth and the junctional epithelium and the gingival margin.

or slow, but continuous, loss. Normal therapy is resisted, and there is gingival inflammation and continued pocket formation. A simplified method of charting periodontal conditions was adapted in 1992 from a system in use in Europe called the Community Periodontal Index of Treatment Needs (CPITN). The CPITN is endorsed by both the World Health Organization and the Federation Dentaire Internationale for periodontal screening. The 1992 adaptation, called Periodontal Screening and Recording (PSR) TM, is endorsed by the American Dental Association (ADA) and the American Academy of Periodontology (AAP). It is best described as an early detection system for periodontal disease. PSR TM is not intended to replace full periodontal charting, but to serve as a simple and con668

venient screening tool. PSR TM can indicate to the clinician when a more comprehensive examination is needed. The ADA and AAP recommend using PSR TM at regular intervals as an integral part of oral examinations. Pocket depths are scored in sections by codes, rather than individually by millimeters. For this system, the mouth is divided into sextants: maxillary right, anterior and left; and mandibular right, anterior and left. The PSR TM probe is ball-tipped and coded with a single colored marking from 3.5 mm to 5.5 mm. The clinician records a single sextant code according to the deepest probing depth found in that sextant. Where there are no teeth present in a sextant, an X is recorded. Code 0 is used when the colored area of the probe remains visible in all the pockets of the sextant. The clinician detects no calculus and no defective margins on restorations. No bleeding is evident on probing. Code 1 indicates nearly the same conditions as Code 0, but bleeding is detected on probing. Code 2 is used when calculus, either above or below the gumline, is detected. It may also be used to indicate defective restorative margins. The colored area of the probe is still completely visible. Code 3 is necessary when the colored area of the probe is only partly visible in at least one pocket of the sextant. Code 4 is used when the colored area of the probe is not visible in at least one pocket of the sextant, indicating a program depth more than 5.5 mm. An asterisk is added to a sextant score to indicate problems such as mobility, root furcation involvement, mucogingival abnormalities, or gingival recession greater than 3.5 mm. The sextant scores are recorded in a set of six attached boxes that can be drawn on the chart. Printed stickers are also available and can be added to the chart on the appropriate date.

Results After dental and periodontal charting, a patient is found to be in good dental health if there is no decay, no restorations or replacements are needed, and the patient’s periodontal pockets are between 0–3 mm with no bleeding or abnormal conditions. A prophylaxis (i.e., cleaning) is usually the only treatment prescribed. The patient is placed on recall at 3- to 12-month continued care intervals for routine, preventive, and oral health maintenance care. Any decay found, however, calls for treatment by elimination of active disease, restoration, or extraction. Endodontics may be necessary to preserve a tooth. Crowns, bridgework, implants or dentures may also be

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Health care team roles Any member of the dental team is equipped to perform dental charting, including the dentist, hygienist, expanded function dental auxiliary, or assistant. If no computer is available, charting is easier with two people. One performs the examination and calls out the findings while the other enters them in the chart. Dental hygienists normally handle periodontal charting as part of the initial or periodic exam. Again, if no computer is available, charting is easier with two people. Periodontal screenings provide an excellent opportunity for patient education. While working, the dental hygienist can explain the meaning of any findings to the patient, and discuss their implications. During periodic exams, the patient can be told if scores have improved since the last visit. Resources BOOKS

Woodall, Irene R. R.D.H., M.A., Ph.D. Comprehensive Dental Hygiene Care. C.V. Mosby Co., 1993. Darby, Michele Leonardi, R.D.H., M.S., and Eleanor J. Bushee, B.S., D.D.S., F.A.C.D. Comprehensive Review of Dental Hygiene, 4th ed. C.V. Mosby Co., 1998. ORGANIZATIONS

American Dental Association, 211 E. Chicago Ave., Chicago, IL 60611. (312) 440-2500. . American Academy of Periodontics, 737 N. Michigan Ave., Suite 800, Chicago, IL 60611-2690. . OTHER

Periodontal Screening and Recording. Workbook. American Dental Association and American Academy of Periodontics, September 1992.

Cathy Hester Seckman, R.D.H.

Dental anomalies Definition Dental anomalies are craniofacial abnormalities of form, function, or position of the teeth, bones, and tissues of the jaw and mouth.

Description Dental anomalies can range from missing or stained teeth to cleft palates. Many are expressions of other, more complex disorders. The National Institute of Dental and Craniofacial Research (NIDCR) estimates that in the United States a baby is born every hour with a craniofacial defect.

Causes and symptoms Many dental anomalies are caused by inherited genetic defects or result from spontaneous genetic mutations. The Center for Biotechnology Information recognizes 1,250 gene loci for craniofacial diseases and disorders. Dental deformities may also have environmental, traumatic, or nutritional causes; these may develop or become clinically apparent at any time during an individual’s life. Genetic defects The most common genetic craniofacial deformity is clefting of the lip and/or palate, a defect estimated by the NIDCR to occur once in every 500 births. A family history of clefting increases the chances of inheriting the disorder. Seen more often in boys than in girls, cleft lip is usually unilateral, appearing three times more frequently on the left side than on the right. Less common is a bilateral cleft, a condition formerly known as “harelip.” An incomplete cleft stops short of the nostril; a complete cleft extends into the nostril. Both types frequently involve the palate as well. The typical patient with cleft palate and cleft ridge exhibits large defects in the roof of the palate with a direct opening into the nasal cavity. Dentinogenesis imperfecta type II (DGI-II), another genetic defect, causes severely discolored teeth that break easily. Amelogenesis imperfecta produces only a soft, thin layer of tooth enamel. This lets the dentin show through, making teeth look yellow, and leaves them weak, easily damaged, and susceptible to decay. Other genetic anomalies are less debilitating. Malocclusion, meaning bad or misaligned bite, is caused by crowding teeth, extra teeth, missing teeth, or jaws that are out of alignment. Most malocclusions are inherited genetically, although some can be caused by accidents, early or late loss of baby teeth, or prolonged thumb sucking. Orthodontia usually corrects this problem. Relative microdontia is an inherited condition that produces smaller-than-normal teeth, usually in the upper jaw. To correct this condition crowns or veneers are applied to make the teeth the same size as the others. Microdontia is neither painful nor harmful; treatment is intended to improve the patient’s bite and appearance.

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indicated. If periodontal pockets deeper than 3 mm are found, they indicate the presence of periodontal disease, which must then be evaluated and treated appropriately.

Dental anomalies

Partial anodontia, or congenitally missing teeth, is a condition in which one or more permanent teeth fail to appear, although primary (baby) teeth usually erupt. Third molars are absent in as many as 35 percent of all subjects examined. Maxillary lateral incisors and maxillary and mandibular second premolars (bicuspids) also frequently fail to appear. When this happens, many dentists choose to leave the primary tooth in place to prevent the malocclusion that might otherwise occur. If this is not feasible, a dentist may extract the tooth and close the space with braces or cover it with a bridge. Idiopathic anomalies Stafne’s bone cavity, also called static bone cyst or lingual mandibular bone concavity, is an anomaly of unknown etiology. A painless condition, it is an indentation of the jawbone that may contain muscle or salivary tissue. The skin covering this area is soft to the touch and feels concave. No treatment is required, although biopsies are often performed to rule out the presence of a malignant tumor. Condylar hyperplasia, another idiopathic anomaly, affects the temporomandibular joint and surrounding tissues. The condition is characterized by unrestrained growth of the condyle, which deforms the face, jaw, and bite. Surgery is usually required to restore order, although once growth has stopped orthodontics are often helpful. Condylar hypoplasia occurs when one condyle is markedly shorter than the other, a condition that also causes facial and dental deformities. Surgery can restore balance, and orthodontics are indicated as well. Environmental causes Environmental anomalies are caused by external agents, including diet, that affect the teeth and gums. Extended use of the antibiotic tetracycline in young children, for example, can cause dark brown discoloration of the teeth. Fluorosis, an overabundance of fluorine in the diet, can create white or mottled spots on the teeth. This is most commonly seen in children who ingest greaterthan-recommended amounts of fluoride by swallowing large quantities of fluoridated toothpaste. Teeth naturally darken with age, as the enamel thins and the dentin shows through. Coffee, tea, and red wine can also stain the teeth. Even children who swim an average of six hours or more a week in a pool may develop brown stains on their teeth. Bulimia can cause severe decalcification of the teeth. Acid from constant regurgitation eats away at the enamel, especially in the molar region. This weakens the teeth, making them both susceptible to decay and highly sensitive. Unless the bulimia is arrested, sensitivity 670

increases until the nerve is exposed and root canal therapy is needed or extraction is required. Poor nutrition can also cause dental anomalies. Scurvy, a disease caused by a lack of vitamin C, affects periodontal and other connective tissue, causing purple, swollen, bleeding gums and, if untreated, tooth loss. Anemia, caused by a lack of iron in the diet, causes fiery red gum tissues. Both of these anomalies can be corrected with proper nutrition and routine care. Other anomalies Concrescence is the fusion of teeth above and below the gum line, although each tooth has separate roots. The teeth are united by cementum only. It may be caused by crowding or injury. Most commonly it occurs with the second premolars (bicuspids). This is a painless anomaly and treatment is required only for cosmetic reasons. Supernumerary teeth are extra permanent teeth that may or may not erupt and can be found anywhere in the mouth. The most common is the mesiodens, a small tooth with a cone-shaped crown and a short root situated between the maxillary central incisors. Heredity may play a role in the development of supernumerary teeth, but other factors are thought to contribute as well. Supernumerary teeth can be extracted with no harm to the patient.

Diagnosis Dental anomalies can be evidence of systemic disease and may have more than one cause. After weighing the patient’s symptoms, pain (if any), health risks, family history, aesthetic considerations, treatment costs, and insurance coverage, the dentist will decide whether to treat or simply monitor the condition.

Treatment Treatment is intended to eliminate or diminish the defect, manage pain, and alleviate the patient’s concerns. Treatment may progress in multiple phases, including a program of continuing care that allows the dentist or doctor to evaluate the treatment’s effectiveness. In most cases, surgery can correct the deformity. Cleft lips are usually repaired before the infant is a month or two old, with excellent cosmetic and functional results. Surgical repair of a cleft palate, however, is not usually performed until the patient is approximately eighteen months old, to minimize the risk of damaging important growth centers. Psychological services are often included as part of the treatment along with speech and hearing services.

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Prognosis Although many orofacial anomalies are currently managed, rather than treated, the rapid advance of science—such as the ability to identify mutated genes— promise future cures and treatments that will eliminate or reduce the number of defects currently seen. Gene therapy may also someday be applied to the treatment of many craniofacial anomalies, both to repair congenital defects and to accelerate healing after trauma. Gene mapping may also help doctors know which patients are susceptible to what type of anomalies. The NIDCR is the primary sponsor of craniofacial research and training in the United States. The institute supports a variety of projects, including basic studies of cell migration and differentiation, cell signaling, patterns of gene expression, growth factor effects, tooth formation and eruption, and bone formation. These studies explore the genetic and molecular mechanisms behind craniofacial abnormalities and are intended to prevent or correct the anomaly or improve the patient’s ability to function with it.

Health care team roles No one specialist can provide the range of treatment that is frequently needed for many dental anomalies. The most effective management is accomplished with a team of professionals who can render a comprehensive diagnosis, determine treatment needs and priorities, and supervise long-term planning. A list of physicians and specialists required to treat a craniofacial deformity might include: plastic surgeon, otolaryngologist (ear, nose, and throat specialist), audiologist, speech-language pathologist, oral/maxillofacial surgeon, orthodontist, pediatric/family dentist, dental hygienist, prosthodontist, geneticist/genetic counselor.

Prevention The ADA advises dentists to discourage patients from using tobacco and illicit drugs, and to emphasize sound nutrition to maintain oral health and prevent nutritional anomalies. The NIDCR encourages clinical studies to diagnose genetic anomalies, decrease environmental risks, and improve treatment. Genetic counseling, map-

KEY TERMS Anomaly—A deformity or abnormality. Bridge—A dental prosthesis covering an open space in the mouth. Cementum—A bony substance that covers the root of the tooth. Condyle—The uppermost end of the mandible that sits in the zygomatic arch and allows the jaw to move. Congenital—Present at birth; a nonhereditary condition acquired in utero. Crown—1. The natural part of the tooth covered by enamel. 2. A restorative, protective shell that fits over a diseased or malformed tooth. Decalcification—The wearing away of the enamel on the teeth. Etiology—Cause or origin. Extraction—Removal of the tooth. Genetic—Inherited from the parents. Mandible—Jaw, especially the lower jawbone. Maxillary—Relating to the upper jaw region. Maxillary central incisors—The front teeth on the upper jaw. Maxillary lateral incisors—The teeth on the right and left quadrants of the upper jaw next to the front centrals. Root canal therapy—Removal of the pulp of a tooth. Veneer—A thin porcelain overlay that covers only the anterior surface of a tooth.

ping, and testing can help prevent dental anomalies in the next generation of children. Resources PERIODICALS

Tai, Chi-Chia E., I. Scott Sutherland, and Leland McFadden. “Prospective Analysis of Secondary Alveolar Bone Grafting Using Computed Tomography.” Journal of Oral and Maxillofacial Surgery (November 2000): vol. 58, no. 11, 1241–1249. ORGANIZATIONS

American Dental Association. 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-2500. .

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Depending on the severity of the anomaly, treatment can be expensive, but medical and dental insurance can help limit out-of-pocket expenses for the patient. Sometimes treatment will be covered by medical insurance if procedures are performed by an oral surgeon or medical doctor instead of a dentist.

Dental assisting

National Institute of Dental & Craniofacial Research. Building 45, Room 4AN-24 45 Center Drive, MSC 6402 Bethesda, MD 20892-6402. (301) 594-9898 . University of Minnesota School of Dentistry. Professor Karlind Moller, Preventive Sciences, 15-209 Moos Tower, 515 Delaware St. SE, Minneapolis, MN 55455. (612) 625-5945. . OTHER

Howell, Dr. Maria Lopez. “Dental Discoloration: Causes and Cures.” ADA Dental Minutes video. . Howell, Dr. Maria Lopez. “ Genetics and Dentistry.” ADA Dental Minutes video. . Howell, Dr. Maria Lopez. “Swimming Stains Teeth.” ADA Dental Minutes video. .

Cindy F. Ovard, RDA

Dental assisting Definition Dental assistants are part of the dental health care team. They assist dentists in delivering oral health care to patients.

A dental assistant uses a suction tube while a dentist drills a patient’s tooth. (Photograph by Francoise Sauze. Science Source/Photo Researchers. Reproduced by permission.)

Description The dental assistant uses interpersonal, administrative, and technical skills to perform a variety of tasks in the dental office. Dental assistants work with dentists when they perform dental treatments. Some of the tasks they perform before and during dental treatment include preparing patients for the treatment, passing dentists instruments and other materials, and keeping patients’ mouths dry and clear using suction and other devices. They expose and develop x rays, or radiographs, as well as take impressions of teeth. Sometimes, dental assistants take patients’ blood pressure, pulse, and medical histories. Dental assistants help comfort patients before, during, and after treatment. They also teach patients how to prevent oral disease and maintain their overall dental health. Administratively, a dental assistant may oversee an office’s infection control practices, schedule patient appointments, answer phones, coordinate billing, and order supplies. 672

The career offers variety of work, flexibility in scheduling, and direct contact with people. As of 1998, more than three in 10 dental assistants worked part-time. The median hourly wages in the profession was $10.88 in 1998.

Work settings Dental assistants work in general dental offices and all dental specialty settings, including orthodontics, pediatric dentistry, periodontics, endodontics, and oral surgery. They also work in solo practices or in public health dentistry, assisting in settings such as schools and community clinics. Dental assistants also work in hospitals to help treat bedridden patients and in dental school clinics, assisting dental students. Other opportunities for dental assistants exist in the insurance industry, as dental insurance claims processors; in vocational and other schools as instructors; and in dental product sales.

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Oral and maxillofacial surgery—The dental specialty that focuses on the correction of orofacial deformities and removal of teeth. Orthodontics—The dental specialty concerned with treating malocclusions, or bad bites. Pediatric dentistry—The dental specialty concerned with the dental treatment of children and adolescents. Periodontics—The dental specialty focused on treating diseases of the soft and hard tissues that surround and support the teeth.

BOOKS

Occupational Outlook Handbook, Dental Assistants section. U.S. Department of Labor. Bureau of Labor Statistics. Division of Information Services. 2 Massachusetts Ave., NE, Room 2860. Washington, D.C. 20212. (202) 6915200. . ORGANIZATIONS

American Dental Assistants’ Association. 203 North LaSalle Street, Suite 1320, Chicago, IL 60601-1225. (312) 5411550. . American Dental Association. 211 E. Chicago Ave., Chicago, IL 60611. (312) 440-2806. .

Lisette Hilton

Radiographs—X rays.

Education and training While, in some states, dental assistants can work in the field without a college degree, dental assistants are usually trained at community colleges, vocational schools, technical institutes, universities, or dental schools. The Commission on Dental Accreditation of the American Dental Association is the agency that accredits dental assisting programs, of which there are over 200 in the United States. After completing a program that takes about nine to 11 months, plus an exam, dental assistants receive a certificate in dental assisting. To become a Certified Dental Assistant, or CDA, dental assistants must take the CDA examination after they have completed an accredited dental assisting program, or have at least two years of full-time on-the-job training as a dental assistant.

Advanced education and training Associate or baccalaureate degrees are often required for dental assistants who want to go into teaching at colleges, technical institutes, vocational schools, or universities.

Future outlook Job prospects in the field of dental assisting are expected to grow much faster than average, compared to other occupations. The job turnover is expected to be high, creating even more opportunity. Also, as the population ages and people keep their teeth, dental assistants will continue to be in demand.

Dental caries Definition Dental caries, also known as tooth decay, is the destruction of the outer surface (enamel) of a tooth. Decay results from the action of bacteria that live in plaque, which is a sticky, whitish film formed by a protein in saliva (mucin) and sugary substances in the mouth. The plaque bacteria sticking to tooth enamel use the sugar and starch from food particles in the mouth to produce acid. Tooth decay can result in tooth loss.

Description Thanks to the benefits of fluoride and fluoridated water, dental caries, also called dental cavities, are not as prevalent as in the years before and including the 1980s. While the majority of senior citizens a generation ago lost all their teeth, the vast majority of the elderly today have some or all of their natural teeth. Although anyone can have a problem with tooth decay, children and senior citizens are the two high-risk groups. While both groups experience a diminishing caries rate, senior citizens are getting more cavities than children. Since older adults are keeping their teeth longer, they have become more prone to root caries, or root decay. Other high-risk groups include people who eat a lot of starchy and sugary foods, people living in areas without a fluoridated water supply, and people who already have numerous dental restorations (fillings and crowns).

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Resources

KEY TERMS

Dental caries

other sweetened liquids also contribute to bottle-mouth syndrome. The first signs of damage are chalky white spots or lines across the teeth. As decay progresses, the damage to the child’s teeth becomes obvious.

Dental caries charting: classification of cavities Classification and location Class I Cavities in pits or fissures Occlusal surfaces of premolars and molars Facial and lingual surfaces of molars Lingual surfaces of maxillary incisors Class II Cavities in proximal surfaces of premolars and molars

Class III Cavities in proximal surfaces of incisors and canines that do not involve the incisal angle

Class IV Cavities in proximal surfaces of incisors or canines that involve the incisal angle Class V Cavities in the cervical 1/3 of facial or lingual surfaces (not pit or fissure)

Class VI Cavities on incisal edges of anterior teeth and cusp tips of posterior teeth

Method of examination

Causes and symptoms

Direct or indirect visual Exploration Radiographs are not useful

Early caries: by radiographs only Moderate caries not broken through from proximal to occlusal: Visual by color changes in tooth and loss of translucency Exploration from proximal Extensive caries involving occlusal: direct visual Early caries: by radiographs or transillumination Moderate caries not broken through to lingual or facial: Visual by tooth color change Exploration Radiograph Extensive caries: direct visual Visual Transillumination

Direct visual: dry surface for vision Exploration to distinguish demineralization: whether rough or hard and unbroken Areas may be sensitive to touch

The elderly are more prone to dental caries because more than 95% of senior citizens have lost some of the gum tissue that protects the tooth roots, exposing the roots to plaque and decay. It also is common to see decay around filling margins. Over time, fillings tend to weaken, fracture, and leak around the edges, which fosters the accumulation of bacteria. Another reason that the elderly get more cavities is that many take medications that reduce saliva, which naturally protects the teeth from caries. Chewing tobacco is another culprit that increases the risk of tooth decay. A study showed that men who use chewing tobacco are four times more likely to have one or more decayed or filled root surfaces, compared to those who had never chewed tobacco.

Direct visual May be discolored

SOURCE: Alvarez, K.H. Williams & Wilkins’ Dental Hygiene Handbook. Baltimore: Williams & Wilkins, 1998.

Diagnosis

Baby bottle tooth decay Baby bottle tooth decay is a dental problem that frequently develops in infants who are put to bed with a bottle containing a sweet liquid. Baby bottle tooth decay is also called nursing-bottle caries and bottle-mouth syndrome. Bottles containing liquids such as milk, formula, fruit juices, sweetened drink mixes, and sugar water continuously bathe an infant’s mouth with sugar during naps or at night. The bacteria in the mouth use this sugar to produce acid that destroys the child’s teeth. The upper front teeth are typically the ones most severely damaged, the lower front teeth receiving some protection from the tongue. Pacifiers dipped in sugar, honey, corn syrup, or 674

Tooth decay requires the simultaneous presence of three factors: plaque bacteria, sugar, and a vulnerable tooth surface. Although several microorganisms found in the mouth can cause tooth decay, the primary disease agent appears to be Streptococcus mutans. The sugars used by the bacteria are simple sugars such as glucose, sucrose, and lactose. They are converted primarily into lactic acid. When this acid builds up on an unprotected tooth surface, it dissolves the minerals in the enamel, creating holes and weak spots (cavities). As the decay spreads inward into the middle layer (the dentin), the tooth becomes more sensitive to temperature and touch. When the decay reaches the center of the tooth (the pulp), the resulting inflammation (pulpitis) produces a toothache.

Tooth decay develops at varying rates. It may be found during a routine six-month dental checkup before the patient is even aware of a problem. In other cases, the patient may experience common early symptoms, such as sensitivity to hot and cold liquids or localized discomfort after eating very sweet foods. The dentist or dental hygienist may suspect tooth decay if a dark spot or pit is seen during a visual examination. Front teeth may be inspected for decay by shining a light from behind the tooth. This method is called transillumination. Areas of decay, especially between the teeth, will appear as noticeable shadows when teeth are transilluminated. X rays may be taken to confirm the presence and extent of the

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Development of dental caries. (Photograph by Biophoto Associates. ScienceSource/Photo Researchers, .Inc. Reproduced by permission.)

decay. The dentist then makes the final clinical diagnosis by probing the enamel with a sharp instrument. Tooth decay in pits and fissures may be differentiated from dark shadows in the crevices of the chewing surfaces by a dye that selectively stains parts of the tooth that have lost mineral content. A dentist can also use this dye to tell whether all tooth decay has been removed from a cavity before placing a filling. Diagnosis in children Damage caused by baby bottle tooth decay is often not diagnosed until the child has a severe problem, because parents seldom take their infants and toddlers for dental check-ups. Dentists want to initially examine primary teeth between 12 and 24 months. Children still drinking from a bottle anytime after their first birthday are likely to have tooth decay.

Treatment To treat most cases of tooth decay in adults, the dentist removes all decayed tooth structure, shapes the sides of the cavity, and fills the cavity with an appropriate material, such as silver amalgam or composite resin. The filling is put in to restore and protect the tooth. If decay has attacked the pulp, the dentist or a specialist called an endodontist may perform root canal treatment and cover the tooth with a crown. In cases of baby bottle tooth decay, the dentist must assess the extent of the damage before deciding on the treatment method. If the problem is caught early, the teeth involved can be treated with fluoride, followed by

changes in the infant’s feeding habits and better oral hygiene. Primary teeth with obvious decay in the enamel that has not yet progressed to the pulp need to be protected with stainless steel crowns. Fillings are not usually an option in small children because of the small size of their teeth and the concern of recurrent decay. When the decay has advanced to the pulp, pulling the tooth is often the treatment of choice. Unfortunately, loss of primary teeth at this age may hinder the young child’s ability to eat and speak. It may also have a bad effect on the alignment and spacing of the permanent teeth when they arrive.

Prognosis With timely diagnosis and treatment, the progression of tooth decay can be stopped without extended pain. If the pulp of the tooth is infected, the infection may be treated with antibiotics prior to root canal treatment or extraction. The longer decay goes untreated, however, the more destructive it becomes and the longer and more intensive the necessary treatment will be. In addition, a patient with two or more areas of tooth decay is at increased risk of developing additional cavities in the future. Scientists are working on several advances in the reversal and prevention of tooth decay. The advances under development include: Smart fillings to prevent further tooth decay, toothpaste to strengthen and restore tooth minerals, and mouthwashes and chewing gums that reverse early decay. Scientists are studying the use of calcium phosphate cements (CPC), used to repair cranial defects, for fractures and bone loss from gum

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disease. CPC might provide a successful drug delivery system in Smart fillings to prevent tooth decay from recurring around existing fillings and surrounding teeth. Other calcium phosphate-based technologies used in chewing gum and mouth rinses are being tested to remineralize hard tooth tissues or slow demineralization produced by caries. Scientists are researching controlled-release fluoride systems, placed between the teeth or in tooth pits and fissures, that deliver high fluoride concentrations to localized areas. Research is also being done on the use of filling materials to repair exposures of the tooth pulp, which could eliminate the need for root canal therapy.

Health care team roles Dental assistants can provide patients and their families with education in caries prevention. This often includes instructions for home care and fluoride information. Dental assistants often participate in the treatment of dental caries, performing such tasks as taking x rays, assisting with materials during treatment, and setting up and maintaining treatment rooms. In some dental practices, dental hygienists assist with patient charting and taking x rays. Dental hygienists interpret findings and are often the first to see the decay during routine cleanings.

MOUTH CARE IN CHILDREN. Parents can easily prevent baby bottle tooth decay by not allowing a child to fall asleep with a bottle containing sweetened liquid. Bottles should be filled with plain, unsweetened water. A child should be starting to drink from a cup at around six months of age, and weaned from bottles at 12 months. If an infant seems to need oral comfort between feedings, a pacifier specially designed for the mouth may be used. Pacifiers, however, should never be dipped in honey, corn syrup, or other sweet liquids. After the eruption of the first tooth, parents should begin routinely wiping an infant’s teeth and gums with a moist piece of gauze or soft cloth, especially before bedtime. Parents may begin brushing a child’s teeth with a small, soft toothbrush at about two years of age, when most of the primary teeth have come in. They should apply only a very small amount (the size of a pea) of toothpaste containing fluoride. Too much fluoride may cause spotting (fluorosis) of the tooth enamel. As the child grows, he or she will learn to handle the toothbrush, but parents should control the application of toothpaste and do the follow-up brushing until the child is about seven years old.

Fluoride application

Prevention It is easier and less expensive to prevent tooth decay than to treat it. The four major prevention strategies include: proper oral hygiene, fluoride, sealants, and attention to diet. Oral hygiene GENERAL CARE OF THE MOUTH. The best way to prevent tooth decay is to brush the teeth at least twice a day, preferably after every meal and snack, and to floss daily. Cavities develop most easily in spaces that are hard to clean. These areas include surface grooves, spaces between teeth, and the area below the gum line. Effective brushing cleans each outer tooth surface, inner tooth surface, and the horizontal chewing surfaces of the back teeth, as well as the tongue. Flossing once a day also helps prevent gum disease by removing food particles and plaque at and below the gum line, as well as between teeth. Patients should visit their dentist every six months for an oral examination and professional cleaning. MOUTH CARE IN OLDER ADULTS. Older adults who have lost teeth or had them removed still need to maintain a clean mouth. Bridges and dentures must be kept clean to prevent gum disease. Dentures should be relined

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and adjusted by a dentist whenever necessary to maintain a proper fit. These adjustments help to keep the gums from becoming red, swollen, and tender.

Fluoride is a natural substance that slows the destruction of enamel and helps to repair minor tooth decay damage by remineralizing tooth structure. Toothpaste, mouthwash, fluoridated public drinking water, and vitamin supplements are all possible sources of fluoride. It is important to note that bottled water and water from home purifiers often does not contain fluoride, so people who drink from these sources may have to supplement their fluoride use. Children living in areas without fluoridated water should receive 0.5 mg/day of fluoride (0.25 mg/day if using a toothpaste containing fluoride), from three to five years of age, and 1 mg/day from 6-12 years. While fluoride is important for protecting children’s developing teeth, it is also of benefit to older adults with receding gums. It helps to protect the newly exposed tooth surfaces from decay. Older adults can be treated by a dentist with a fluoride solution that is painted onto selected portions of the teeth or poured into a fitted tray and held against all the teeth. Sealants Because fluoride is most beneficial on the smooth surfaces of teeth, sealants were developed to protect the

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Diet Choosing foods wisely and eating less often can lower the risk of tooth decay. Foods high in sugar and starch, especially when eaten between meals, increase the risk of cavities. The bacteria in the mouth use sugar and starch to produce the acid that destroys the enamel. The damage increases with more frequent and longer periods of eating. For better dental health, people should eat a variety of foods, limit the number of snacks, avoid sticky and overly sweetened foods, and brush often after eating. Drinking water is also beneficial by rinsing food particles from the mouth. Children can be taught to “swish and swallow” if they are unable to brush after lunch at school. Similarly, saliva stimulated during eating makes it more difficult for food and bacteria to stick to tooth surfaces. Saliva also appears to have a buffering effect on the acid produced by the plaque bacteria and to act as a remineralizing agent. Older people should be made aware that some prescription medications may decrease salivary flow. Less saliva tends to increase the activity of plaque bacteria and encourage further tooth decay. Chewing sugarless gum increases salivation and thus helps to lower the risk of tooth decay. Resources BOOKS

“Dental Caries and Its Complications—Tooth Decay.” In The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, Robert Berkow, and Mark Burs. 17th ed. Rahway, NJ: Merck Research Laboratories, 1999.

KEY TERMS Amalgam—A mixture (alloy) of silver and several other metals, used by dentists to make fillings for cavities. Caries—The medical term for tooth decay. Cavity—A hole or weak spot in the tooth surface caused by decay. Dentin—The middle layer of a tooth, which makes up most of the tooth’s mass. Enamel—The hard, outermost surface of a tooth. Fluoride—A chemical compound containing fluorine that is used to treat water or applied directly to teeth to prevent decay. Mucin—A protein in saliva that combines with sugars in the mouth to form plaque. Plaque—A thin, sticky, colorless film that forms on teeth. Plaque is composed of mucin, sugars from food, and bacteria that live in the plaque. Pulp—The soft, innermost layer of a tooth containing blood vessels and nerves. Sealant—A thin plastic substance that is painted over teeth as an anti-cavity measure to seal out food particles and acids produced by bacteria. Transillumination—A technique of checking for tooth decay by shining a light behind the patient’s teeth. Decayed areas show up as spots or shadows.

ORGANIZATIONS

American Dental Association. 211 East Chicago Avenue, Chicago, IL 60611. (312)440-2500. . American Dental Hygienists’ Association. 444 North Michigan Avenue, Chicago, IL 60611. (800)847-6718. Anna Nelson, Certified Dental Assistant, and president of the American Dental Assistants’ Association. 203 N. LaSalle St., Suite 1320, Chicago, IL 60601-1225. (312) 541-1550 or for Anna Nelson direct (415) 239-3479. <www.dentalassistant.org>. National Institute of Dental Research. 31 Center Drive, MSC 2190, Building 31, Room 5B49, Bethesda, MD 208922190. OTHER

Healthtouch Online. .

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irregular surfaces of teeth. A sealant is a thin plastic coating that is painted over the grooves of chewing surfaces to prevent food and plaque from being trapped there. Sealant treatment is painless because none of the tooth is removed, although the tooth surface is etched with acid so that the plastic will adhere to the rough surface. Sealants are usually clear or tooth-colored, making them less noticeable than silver fillings. They cost less than fillings and can last up to 10 years, although they should be checked for wear at every dental visit. Children should get sealants on their first permanent “6-year” molars, which come in between the ages of 5 and 7, and on the second permanent “12-year” molars, which come in between the ages of 11 and 14. Sealants should be applied to the teeth shortly after they erupt, before decay can set in. Although sealants have been used in the United States for about 25 years, one survey by the National Institute of Dental Research reported that fewer than 8% of American children have them.

Dental casts

Dental casts Definition A dental cast is any dental prosthetic or device formed in a mold or used as a mold.

Purpose Dental casts copy a patient’s teeth and mouth structures for diagnostic purposes and are used as models for further casting of dental prosthetics such as bridges, crowns, implants, dentures, and partial dentures. Casts may also be used as education tools for dentists as they explain characteristics of a patient’s bite or particular dental needs. Diagnostic casts can also show how a restoration will look when the work is complete.

Description Dentists are challenged to create solutions for problems that patients present from chipped or missing teeth, a collapsed bite, or teeth that are irregular or misshapen. A clear diagnosis of the condition often is made through the use of plaster-like dental casts of the patient’s teeth and gums. These diagnostic casts allow the dentist to examine how the teeth fit together and what may be hampering the patient from chewing or speaking well. Often, the dentist will recommend replacement prosthetic devices for missing teeth. In the case of severely crooked teeth, the dentist may urge the patient to have the teeth realigned through braces or other orthodontic appliances. From these initial casts, dental prosthetics are made that will fit into a patient’s jaw structure and resemble the other teeth there. A variety of prosthetic devices can be cast from these initial casts: individual teeth for implants, crowns, bridges, dentures, and partial dentures. The dentist first makes an impression of the patient’s teeth and gums. A variety of impression materials are available, some are firm when used (waxes, plasters, puttys, zinc oxide pastes) and some are more pliable (alginates and elastic silicones and polyvinyls). The elastic mediums are more stable and can stand longer before the casts are poured. Some impressions materials require that the cast be poured immediately or within a few hours. Some can wait several days or up to two weeks. The impression produces a negative replica of the patient’s teeth, which can then be cast in a variety of materials. Usually, plaster is used because it is inexpensive and sets up quickly. Other materials used include dental stone or special die stone. Both are very strong, but die stone is more abrasion resistant. 678

Dental casts are made from the impression of a patient’s teeth, and may be used to help diagnose problems with bite, chewing, etc. (O.J. Staats, MD/Custom Medical Stock Photo. Reproduced by permission.)

From these casts, the dental technician can create wax diagnostic models of the proposed restoration. These wax models are finely-detailed sculptures of the mouth, showing how the restoration will look. From these, the prosthetics are cast.

Operation The dental assistant prepares the impression medium and fills an impression tray that fits over the patient’s mouth. The patient’s teeth are dried either with gauze or a chemical product before the impression tray is fitted over the patient’s teeth. The tray is held in place by the dental assistant for a brief time. The tray is removed in one motion, not rocked, in order to have a clean impression. The impression is rinsed and disinfected and left to set. The dental assistant pours in the casting material. Sometimes this is only a few minutes after the impression is made; sometimes it can be several hours or days later. Plaster-type casts are usually made first. These are used in diagnosis, patient education, and the creation of dental restorations. The dental technician makes a single wax model of the prosthetic device to fit the patient’s mouth, using the plaster cast as a guide. An investment mold is poured around the wax model and fired. The wax melts and drains out of the investment mold, leaving behind a durable mold into which the technician can pour a casting material. Restorative casting materials can be metals (gold, silver, amalgam), resins, or ceramics. These are poured into the investment mold to craft individual teeth, crowns, and other dental prosthetics. The mold is broken or opened, depending on whether the mold is reusable.

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Maintenance Alginate impressions are affected by water and can shrink or swell. This material often comes in powder form and should not be inhaled. Casts made directly from impressions from plaster can be damaged through rough handling. Dental stone and dental die stone are more durable. Dental prosthetics made from molds are long lasting and only require regular dental maintenance like tooth brushing and flossing. Dentures and partial dentures need to be rinsed and soaked to remove stains and odor. The dentist and dental assistant should inspect dental prosthetics often for any damage or wear, especially around the wires of partial dentures. It should be noted that the impressions used to make plaster-like casts of the patient’s mouth should be disinfected and dried before the casts are made. This protects dental personnel from any infectious agent attached to the impression when the cast was made and could be transferred to the cast.

Health care team roles Dentists, dental assistants, and dental technicians work as a team to create and maintain dental casts. Dentists diagnose a particular problem in a patient’s mouth and present solutions, depending on the specific nature of the case and the patient’s comfort and budget. Sometimes, the exact solution is not fully determined until impressions of the patient’s mouth are made and the dentist consults with the dental technician. Impressions are crucial to the problem-solving that the dentist and dental technician do. The dental assistant makes an impression of the patient’s teeth and mouth structures and pours a hardened cast. The dentist examines this cast and sends it to the dental technician with recommendations for the creation of dental restorations. Dental technicians make wax diagnostic models from the mouth cast for various restorations (crowns, bridges, partial dentures, implants). These models are used by technicians to create metal frameworks and tooth structures in investment molds.

Training Dental assistants and hygienists usually require some specialized training. Dental hygienists are often licensed. Dental technicians are trained at dental laboratories, though some dental schools offer coursework in dental restorations.

KEY TERMS Bite—How the upper teeth and lower teeth fit together so that a person can chew and speak. Bridge—A device that has at least one prosthetic tooth and two crowns. It is used to replace a missing tooth or teeth. The bridge is held in place when the adjacent crowns on the bridge are cemented over the two teeth on each side of the space left by the missing tooth or teeth. Crown—A dental prosthetic that copies an existing tooth’s shape (or ideal shape) and covers the tooth. It is cemented into place and feels like and is used as a normal tooth. Denture—A dental prosthetic device consisting of a full set of teeth to fill the upper or lower jaw, or both. Also called false teeth. Implant—A prosthetic tooth anchored permanently into the jaw bone by a post. It has the same strength and appearance as natural teeth. Impression—An exact copy of the teeth and mouth using materials that will set sufficiently so that a more durable cast of the mouth can be made from plaster, dental stone, or other casting materials. Investment mold—A plaster-like substance that is created around a wax model of an object that is to be cast in metal. Lost wax casting—A process of casting metal that involves making a mold around a wax object that has been shaped exactly in the likeness of the intended finished object. The mold is then fired and the wax melts. The resultant mold is durable and capable of receiving molten metals which will be cast in the mold in the shape of the desired object. Mold—A form or physical outline of an object used to hold a pliable material in order to copy the same shape or design. Orthodontic appliances—Devices that help straighten the teeth; e.g. invisible braces, retainers, etc. Partial dentures—A dental prosthetic of two or more teeth used to replace missing teeth. Prosthetic device—A re-creation of a tooth or series of teeth to replace or improve the structure or appearance of a tooth or teeth. Restoration—Any prosthetic device or process used to replace or improve the structure or appearance of a tooth or teeth.

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This technique is called lost wax casting and has been used for centuries to cast bronze sculptures or craft fine jewelry.

Dental crowns, inlays, and bridges

Resources ORGANIZATIONS

American Dental Association. 211 East Chicago Ave., Chicago, IL 60611. (800) 947-4746. (312)440-2500. . OTHER

Christensen, Gorden J. Efficient Dental Assisting for Fixed Prosthodontics. [video] Provo, UT: Practical Clinical Courses, 1990. “The Dental Impression.” Quality Dentistry. April 2001. . “Impression Materials.” Dental Materials Science. April 2001. .

Janie F. Franz

Dental cleaning see Nonsurgical periodontal therapy

Dental crowns, inlays, and bridges Definition Dental crowns, inlays, and bridges are prosthetic devices that replace missing teeth or part of a tooth. They are made of metal, porcelain, and resin, or a combination of these materials.

Purpose Bridges, crowns, and inlays are created to restore a tooth’s appearance, structure, or function. Inlays and crowns are intended to repair damage to individual teeth. They replace tooth structure lost by decay or injury, protect the part of the tooth that remains, and restore the tooth’s shape and function. Bridges fill in a space in the jaw left by a missing tooth or teeth. They protect the shape of the mouth and restore function of the teeth and jaw.

Precautions Some patients are allergic to the medications used for local anesthesia in dental restorations. In addition, many people are afraid of dental work. Most dentists in practice today can help patients with this specific fear.

Description Crowns The crown of a tooth is the portion that is covered by enamel. A restorative crown replaces this outer part to 680

protect and strengthen the tooth. This protection becomes necessary when a tooth cracks, has its entire structure weakened by decay, or becomes brittle after a root canal. Crowns can also cover dental implants or abutment (adjacent) teeth when fitting a bridge. Crowns are also used to cover discolored or otherwise aesthetically displeasing teeth. Cosmetic dentistry does not use crowns as much as it once did, since crowns, though aesthetically pleasing, require more radical dental techniques. Dentists are opting for more conservative methods such as bleaching, bonding, or veneers to improve the aesthetic appearance of teeth. The dentist first removes the decayed portion of the tooth. The tooth is then prepared for a crown. It may be tapered on the outside edges to a peg, reinforced with a cast metal core, or rebuilt with both a cast metal core and a post. An impression of the prepared tooth and the teeth next to it is made. A retraction cord is placed around the tooth in order to get the impression medium under the gum where the crown will be fitted. The dental technician will create a new crown, using a cast made from this impression. The technique the technician uses is called lost wax casting. A wax model is made of the crown. Another mold is made around the wax model and both are fired in a kiln. The wax melts, leaving an opening into which a restorative material can be poured. The crown may be made of gold or stainless steel alone, metal with a veneer of tooth-colored porcelain or resin, or of porcelain or resin alone. The finished crown is then placed over the prepared tooth, adjusted, and cemented into place. When a tooth has had a root canal and the root has been filled, the tooth may not be strong. Post crowns are used in these cases. The tooth is leveled at the gum line and a stainless steel or gold post is fitted into the root canal. This post can then receive the new crown and hold it in place. For other patients, it may be necessary to implant the crown. In this case, a steel post is embedded in the patient’s jawbone. It is left in place until the bone adheres to the post. The post is exposed and the crown is made and fitted. New computerized techniques are making the restoration process faster and more comfortable. Chairside Economical Restoration of Esthetic Ceramics (CEREC) uses a computer system to allow the dentist to create ceramic crowns, inlays, and onlays, in one sitting. The tooth is prepared as usual but impressions are made digitally, using a hand-held camera. These photographs are converted to three-dimensional images on the computer screen, thus eliminating the need to take a physical impression of the patient’s teeth. The dentists uses special 3D CAD/CAM software to design the crown. A milling

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system attached to the CEREC machine is able to make a ceramic crown in 10-15 minutes. Crowns can last 5-15 years or more, if they are well taken care of. Bridges Bridges are restorations that fill in a gap caused by missing teeth. They prevent the remaining teeth from shifting and provide a more stable surface for chewing. If the gap is not filled, the other teeth shift, affecting the patient’s bite (occlusion), which sometimes produces pain in the jaw joint. As the teeth move and become crooked, they also become more difficult to keep clean. The risk of tooth decay and gum disease increases, also increasing the likelihood that additional teeth will be lost. A bridge is inserted to prevent this risk. Bridges are appliances consisting of a metal framework and one or more artificial teeth (pontics) anchored to adjacent teeth. The abutment teeth carry the pressure when the patient chews food. Bridges can be removable or fixed (permanent). Removable bridges are attached to the abutment teeth by wires or precision attachments. Fixed bridges are attached to permanent crowns placed on abutment teeth. There are two types of fixed bridges—the crown-and-bridge design and the Maryland Bridge. A Maryland Bridge does not have crowns on it. The backs of the abutment teeth are reduced slightly and small wing- like appendages on the bridge are cemented to the back of the abutment teeth. When the adjacent teeth are not strong enough to support a bridge, a two-implant bridge is required. This type of bridge takes longer for the permanent bridge to be fitted because of the necessity for the gums to heal. Posts are surgically implanted into the patient’s bone and the gum closed. It takes several weeks for the bone to attach to the posts. The posts are re-exposed and the bridge is made to fit. It is then cemented in place. Inlays An inlay resembles a filling in that it fills the space remaining after the decayed portion of a tooth has been removed. The difference is that an inlay is shaped outside the patient’s mouth and then cemented into place. After the decay is removed and the cavity walls are shaped, the dentist makes a wax pattern of the space. A mold is cast from the wax pattern. An inlay is made from this mold and sealed into the tooth with dental cement. Inlays and their counterparts, onlays, are conservative alternatives to crowns. They don’t require as much

A cavity is cut into a tooth in preparation for a dental inlay. An oral camera determines the exact dimensions of the cavity and the data are used to cut a perfectly fitting inlay from a ceramic block. (Photograph by Volker Steger. Science Source/Photo Researchers. Reproduced by permission.)

tooth preparation and often are more durable than amalgam fillings. Inlays cover the grooves on the surface of the molar. Onlays wrap over the tooth, covering more of its surface. Inlays used to be made entirely of gold for its durability. New inlay alloys of palladium, nickel, or chromium are frequently used. Metals have been the dentist’s choice for inlays in molars. When inlays are required for teeth that will be seen when a patient smiles, tooth-colored composites and porcelains are used. Reinforced porcelain and Lucite porcelain are durable but still may not be suitable for patients who grind their teeth. Composites are also used in fillings.

Preparation Before a restoration is placed in the mouth, the dentist removes all traces of decay or damage and shapes the remaining tooth structure for the restoration. When bridges or crowns are necessary, the tooth or teeth that are to receive the crowns are shaped into posts or pegs. Temporary crowns and bridges are installed until the permanent restoration is delivered by the laboratory.

Aftercare Temporary crowns or bridges must stay in place until the permanent restorations have been fitted to the patient’s mouth. Dentists and dental assistants should educate the patient about ways to keep the temporary in place; e.g. avoid hard foods, gum and other sticky or chewy foods. If possible, the dental assistant and dentist

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Complications

KEY TERMS Abutment tooth—A crowned tooth that stabilizes a bridge or partial denture. Bridge—An appliance of one or more artificial teeth anchored by crowns on the adjacent teeth. CAD/CAM—A computer-aided design and manufacturing package. Complete denture—A full set of upper or lower teeth, mounted in a plastic base. Dentures are also called false teeth. Crown—A protective shell that fits over the tooth. Dental caries—A disease of the teeth in which microorganisms convert sugar in the mouth to acid that erodes the tooth. Enamel—The hard outermost surface of a tooth. Inlay—A filling that is made outside of the tooth and then cemented into place. Occlusion—The way upper and lower teeth fit together during biting and chewing. Pontic—An artificial tooth. Pulp—The soft innermost layer of a tooth that contains its blood vessels and nerves.

should encourage the patient to avoid eating foods on the side of the mouth where the temporary is. Also, the patient should be reminded to call immediately if the temporary is loosened so that it can be re-cemented. There can be some gum swelling or discomfort when a crown or bridge is fitted. If a bridge implant was completed, there is naturally some discomfort from the surgery. The dentist can recommend medications or oral rinses to mitigate the discomfort. Patients may also experience sensitivity to cold foods or drinks for a few weeks after a crown, bridge, or inlay is in place. Patients should be urged to maintain normal oral hygiene while they wear a temporary and after the crown or bridge is in place. Specialty brushes and floss threaders may be used to remove plaque and food from around crowns and bridges. The patient should see the dentist for an adjustment if there is any discomfort or irritation resulting from a restoration. Otherwise, the patient should see the dentist at least twice a year for an oral examination. 682

Restoration procedures typically require local anesthesia. Some people may have allergic reactions to the medication. A very small number of people are allergic to one or more of the metals used in a dental restoration. In most cases, the dentist can use another material.

Results A well-made restoration should feel comfortable and last a relatively long time with proper care. Artificial dental restorations only approximate the original tooth, however. It is better, therefore, to prevent the need for restorative dental work than to replace teeth. Restorations are expensive, may require many appointments, and still need careful cleaning and attention.

Health care team roles The dentist is crucial in diagnosing a patient’s particular dental needs and determining the correct remedy. The dentist will prepare a patient’s teeth for restorative work. Often, this requires a great deal of skill and structural knowledge in order to remove enough tooth material for the restoration to fit and yet leave enough architecture within the tooth in order to stabilize the restoration. The dental technician prepares the restoration so that it will fit the prepared tooth and fit in with the rest of the patient’s mouth structure. The technician is part scientist and part artist in order to craft natural looking teeth that match the others in a patient’s mouth. The dental assistant prepares the patient and the patient’s teeth for the dentist to do what is necessary to determine what restoration is best suited for this particular patient. The dental assistant takes impressions of the patient’s teeth and gums and makes plaster-type casts to aid the dentist in diagnosis and the dental technician in creating life-like restorations that fit comfortably in the patient’s mouth. Resources BOOKS

Shillingburg, Herbert T., Jr., Sumiya Hobo, and Lowell D. Whitsett. Fundamentals of Fixed Prosthodontics. Chicago: Quintessence Pub. Co, 1997. PERIODICALS

Doyle, Audrey. “Digital Dentistry.” Computer Graphics World 23 (October 2000): 50. “Technology Triggering Brighter Smiles.” USA Today v. 129, no. 2666 (November 2000): 7.

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Academy of General Dentistry. Suite 1200, 211 East Chicago Avenue, Chicago, IL 60611. (312)440-4300. . American Dental Association. 211 East Chicago Avenue, Chicago, IL 60611. (312)440-2500. . OTHER

“Inlays & Onlays: What’s the Difference?” Dentistry Online. April 9, 2001. .

Janie Franz

Dental emergency see Dental trauma

Dental examination Definition A dental examination is part of an oral examination: the close inspection of the teeth and tissues of the mouth using physical assessment, radiographs, and other diagnostic aids. Dental care begins with this assessment, and is followed by diagnosis, planning, implementation, and evaluation.

Purpose The examination identifies tooth decay and evaluates the health of the gums and other oral tissues. The fit of dentures and bridges (if any) are evaluated. The patient’s bite and oral hygiene are also assessed. The dentist then recommends the best treatment options to the patient.

Precautions Before a dental examination patients with heartvalve disease must take antibiotics to prevent bacteria that may spread into the bloodstream from causing endocarditis. Hypertensive patients may need to have their blood pressure measured. Many dentists prefer not to examine patients who have active herpes sores on or near the mouth. To maintain a sterile environment, dentists and their assistants don gloves and masks.

Description A dental examination is part of a comprehensive oral examination to evaluate the mouth, jaw, and teeth. The American Dental Association (ADA) recommends that

patients seeing a dentist for the first time receive a comprehensive examination, and that established patients be thoroughly evaluated every three years, with professional oral care and periodontal maintenance between examinations. Comprehensive evaluations are usually combined with a dental cleaning, x rays, and other diagnostic tests. If a new patient presents with an emergency, the situation will be evaluated and treated first. Once the emergency is over, an appointment for a complete oral examination will be scheduled. The examination begins with a review of the patient’s complete medical and dental history, which is usually a form or questionnaire completed by the patient. Once the dentist is familiar with any special conditions that may affect the patient during the exam—heart disease, relevant allergies, or the use of medications such as blood thinners—the examination and cleaning can proceed. Teeth The dentist or dental hygienist uses instruments such as a mouth mirror, periodontal probe, and explorer to examine the teeth. Every tooth is checked for cavities; the conditions and positions of the teeth, both erupted and impacted, are noted; previous treatments, such as crowns and other restorations, are evaluated. The dentist’s observations are recorded on a tooth chart. The jaw joint and bite are evaluated, since an irregular bite can lead not only to excessive wear on the teeth but other dental problems as well. The fit of dentures and bridges, if worn, are inspected. Dentists frequently order other diagnostic tests such as x rays, blood tests, and dental casts as well. Gums The dentist or hygienist evaluates the gingiva, or gum tissue, for periodontal disease by checking for loose teeth, bone loss, and bleeding, swollen, or receding gums. A periodontal probe measures the depth of the pocket around each tooth. If the gums are healthy the pocket will be less than three millimeters deep. Pockets of four millimeters or more indicate periodontal disease. The deeper the pocket, the greater the chance for tooth loss unless treatment is begun. Tissues of the mouth An oral cancer screening is part of the dental examination. The dentist feels the lymph nodes on the face and neck, and checks the entire oral cavity—including the hard and soft palates, tongue, cheeks, lips, and floor of the mouth—for irregularities. If caught early, many types of oral cancer can be treated successfully.

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ORGANIZATIONS

Dental examination A dentist and assistant check a woman’s teeth during a dental exam. (Photograph by Carolyn A. McKeone. Science Source/Photo Researchers. Reproduced by permission.)

Patient education

Aftercare

Oral exams often include instructing the patient in flossing and brushing techniques, the use of fluoride toothpastes, and the prevention of tooth damage from contact sports and other activities. Patient concerns can also be discussed during a counseling session.

Complications

Insurance Oral examinations are covered by most dental insurance at 100%. Annual x rays are also covered. Panorex and full-mouth x rays are usually covered every three to five years, except for emergencies or third molar (wisdom tooth) surgery.

Preparation The dental office prepares for an examination by sterilizing all the equipment that will be used during the examination. The patient prepares by having a complete medical and dental history available or alerting the dentist or hygienist to any health changes, and taking pretreatment medication, if necessary. 684

The patient will be advised that the teeth may be tender after a thorough cleaning and examination, and ibuprofen (Advil, Motrin) or acetaminophen (Tylenol) may be recommended to alleviate the discomfort. This tenderness usually subsides within a day or two.

Complications from an oral examination are rare, although the tissues and teeth may be sore for a few days.

Results An oral examination should give the dentist a good idea of the patient’s oral health. Once this is established, a complete treatment program can be scheduled and maintained.

Health care team roles The dental staff work as a team during the examination. The front office confirms the appointment with the patient a day ahead of time, and reminds the patient of

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Resources ORGANIZATIONS

American Academy of Periodontology. 4157 Mountain Road, PBN 249, Pasadena, MD 21122. (410) 437-3749. . American Dental Association. 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-2500. . National Institute of Dental & Craniofacial Research. Building 45, Room 4AN-24, 45 Center Drive, MSC 6402 Bethesda, MD 20892-6402. (301) 594-9898. .

KEY TERMS Full-mouth x rays—A set of x-ray films that show all the teeth, consisting of 14 periapicals and two or four bitewings. Panorex—Trade name for a single panoramic x ray taken by a camera that travels around the head, it shows all the teeth and both jaws in one film. It can reveal impacted teeth, cysts or tumors of the jaw, along with possible sinus infections and temporomandibular joint dysfunction. RDA—Registered dental assistant, a licensed professional trained to assist the dentist at chairside, including preparation and maintenance of dental instruments, preparation of dental materials, taking impressions, etc. RDH—Registered dental hygienist, a licensed professional. RDHs evaluate patient histories, clean teeth by removing deposits such as plaque and tartar, process dental x rays, and educate patients about oral hygiene.

OTHER

American Association of Pediatric Dentistry. “Regular Dental Visits.” Brochure. . American Dental Association. “Baby’s First Dental Visit,” News release. February 2000, updated April 20, 2001; . “Dental Check Ups.” MedlinePlus Dental Health; Reuters; April 9, 2001; . Green, Stuart. “The Complete Dental Examination.” . Houston Chronicle.com. “Exam: Dental; Dr. Allan Bruckhiem,” 2001. Tribune Media Services 435 N. Michigan Ave., Suite 1400, Chicago, IL 60611. . Institutes of Health. National Institute of Dental and Craniofacial Research. “First-Ever Surgeon General’s Report on Oral Health.” NIDCR News. . National Institutes of Health. National Library of Medicine. MedlinePlus “Dental Health.” .

Cindy F. Ovard, RDA

Dental filling materials see Restorative dental materials

Dental fillings Definition Dental fillings are metal amalgams or composite resins used to fill a cavity.

Purpose Dentists use dental fillings to restore teeth damaged by dental caries (tooth decay). Dental caries are caused by microorganisms that convert sugars in food to acids which erode the enamel of a tooth, creating a hole or cavity. The dentist cleans out the decayed part of the tooth and fills the opening with an artificial material (a filling) to protect the tooth’s structure and restore the appearance and utility of the tooth.

Precautions As in any dental procedure, the dentist and dental assistant will need to use sterile techniques. Gloves and masks are essential as well as the sterilization of equipment and tools. This not only helps prevent the spread of infectious diseases like AIDS and hepatitis, but also the common cold. The patient’s reaction to anesthesia is the other main concern of the dentist and dental assistant when perform-

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information that will be needed for medical and dental histories. The registered dental hygienist (RDH) assesses the patient’s health history, takes x rays, and cleans the teeth. Next the registered dental assistant (RDA) and dentist chart the existing conditions of the mouth and teeth, and counsel or educate the patient. This helps the patient feel comfortable and knowledgeable about the treatment required for optimum health.

Dental fillings

ing dental fillings. Nitrous oxide should be avoided with pregnant patients, and local anesthetics should be used with caution, though they are considered safe. Local anesthetics like Novocain and lidocaine have been in practical use for decades with few side effects reported. Some patients, however, are allergic to these drugs.

Description

Gold fillings or inlays are created outside of the mouth by a dental technician and then cemented into place. They are also used to fill the back molars. Gold fillings are very durable. Like amalgam, however, they are not as aesthetically pleasing as tooth-colored fillings. Composite fillings

Though dentists are encountering fewer and smaller cavities in their patients, there is still a need for dentists to fill cavities. Old fillings suffer wear and need to be replaced. Patients are demanding more restorative work on their teeth, sometimes opting for full mouth restorations that involve installing crowns, bleaching teeth or applying veneers, and replacing dark metal fillings with tooth-colored ones that create a monochomatic view in a patient’s mouth. Once the decay is removed and the tooth is prepared (see Preparation), the dentist has a wide choice of dental filling materials to choose from. Amalgam fillings The most common and strongest filling material is amalgam. It is a silver filling that is usually placed on the rear molars, which endure more stress during chewing. Amalgam fillings—used for large, deep cavities—are strong and very resistant to wear. Amalgam has been in use since 1833. Amalgam is a mixture (an amalgam) of several metals, including liquid mercury (35% silver, 15% tin or tin and copper, a trace of zinc, and 50% mercury). When it is prepared, it has a malleable consistency which can easily be shaped to fit the prepared tooth. It hardens to a durable metal. Despite its durability, many dentists and patients avoid amalgam fillings. Dentists have found that amalgam has a tendency to expand with time. As a result, teeth become fractured from the inside, often splitting the tooth. Patients often avoid amalgam for strictly aesthetic reasons. Amalgam fillings darken over time and make teeth look as if they are decayed. The biggest reason amalgam has lost favor is a health concern due to its 50% mercury content. Although the American Dental Association (ADA) has pronounced amalgam safe in the quantity and composition of amalgam, some patients and dentists are disturbed by various reports of illness in relation to the mercury in amalgam fillings. Mercury is a toxic material. Some states are required to dispose of mercury waste as if it were a hazardous product. There is also an added risk of inhaling mercury particles when old fillings are removed. 686

Gold fillings

Composite fillings, often called white fillings, are made of a plastic resin and finely ground glass. They must be applied to the tooth surface in thin layers. Dentists try to match the color of composites with neighboring teeth for a more natural look, making the filling appear invisible. Composite resin fillings often are made smaller than amalgam fillings and require less tooth preparation, thereby saving more natural tooth surface. Composite fillings are bonded to the tooth so that the tooth becomes stronger than it was before. They are also less sensitive to temperature changes in the mouth that can damage the tooth; therefore there is less chance that the tooth will shatter because of the filling. These fillings may not be suitable for large cavities in molars. Though composite durability increased in the 1990s, a porcelain inlay or crown may be the best choice for a durable, natural-looking restoration of a molar. The major drawback of composite resin fillings is cost. They average one-and-a-half to two times more than the price of amalgam fillings. They also can be stained from drinking coffee and tea. Large composite fillings tend to wear out sooner than amalgam fillings. Composite fillings can last seven to ten years, which is similar to the lifespan of amalgam fillings. Resin ionomer Resin ionomers are new, tooth-colored filling materials that contain a resin and fluoride. They are very suitable for children and for older adults who suffer from root decay that occurs as a person ages. These fillings seal the tooth and also protect it from future decay because of the fluoride that they release.

Preparation During a routine checkup, the dentist may find a cavity in a tooth with a metal tooth probe. A new diagnostic tool, the DIAGNOdent, can detect evidence of cavities and pre-cavity conditions on the tooth’s surface. A lowpowered laser, the DIAGNOdent is able to detect decay so early that a dental cavity can be avoided. These precavity areas can be protected with a sealant, thereby preventing further decay.

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There are some dentists who use electronic dental anesthesia (EDA), a device that sends electrical charges to the gum through electrodes. Sometimes this is enough anesthesia for the procedure. At other times, EDA numbs the area where the anesthesia is administered, so that the patient doesn’t feel the needle as it goes into the gum. Some dentists also provide soothing music to calm patients during the procedure. Other dentists will use local anesthesia in combination with nitrous oxideoxygen analgesia to minimize discomfort through the drilling phase of a filling. Dental lasers that generate a low-powered beam of light are being used to cut away decay, but without the whine of the drill and without using anesthesia. Though a bit slower than the conventional drill, lasers are very efficient at preparing a tooth to receive a filling. Unfortunately, lasers cannot yet remove old fillings or prepare a tooth surface to receive a crown. Air abrasion is another way to remove decay without using anesthesia. Air abrasion machines produce a spray of air and powder. There is no vibration or heat. Because it has no vibration, it avoids microfractures in the tooth that sometimes occur with drills. Air abrasion removes only a small amount of the tooth’s structure. Therefore, it is suitable for small cavities and the repair and replacement of old fillings. It also can repair chipped teeth and clean discolored or stained teeth. After the cavity is cleaned of decay, the walls of the tooth are shaped and are ready to receive a filling material. If a composite resin filling is used, the tooth next needs to be etched so that the resin will adhere to the tooth. The tooth then is filled, shaped, and polished. The composite filling then must be hardened by shining a special light on it.

Aftercare The dentist and dental assistant should advise the patient that the teeth, lips, and tongue may be numb for several hours after the procedure, if a local anesthetic was used. Some patients experience sore gums or a sensitivity to hot and cold in the tooth that has just been

filled. Normally, patients are advised to avoid chewing hard foods directly on new amalgam fillings for 24 hours. Composite fillings require no special caution since they set immediately. If patients experience continued pain or an uncomfortable bite, they should call their dentist.

Complications Some patient’s have allergic reactions to local anesthesia.

Results Fillings restore a tooth’s function and appearance. They permit the patient to continue to eat and chew properly and last for several years. Normal fillings will need to be replaced over a patient’s lifetime. Since fewer dental caries have been observed since the last decade of the twentieth century, dentists are initially filling fewer teeth, but are replacing fillings as they fail and sometimes systematically, especially if the patient decides to cosmetically enhance his or her teeth. Since many of the initial cavities are quite small, patients are opting for more aesthetically pleasing filling materials even if they are not as durable.

Health care team roles When the dentist discovers a cavity, filling options are discussed with the patient. The dental assistant prepares the dentist’s workstation and lays out the specific instruments that are needed. The dental assistant prepares the filling material according to the manufacturer’s directions and assists the dentist in preparing the tooth for filling and in the filling procedure itself. The dental assistant cleans the patient’s mouth and returns the procedure room to order. All of the instruments that have been used are sterilized by the dental assistant. Resources PERIODICALS

“Beaming Smile.” Technology Review 103(July 2000): 21. Droste, Therese. “Welcome to the Gilded Age of Dentistry.” The Washington Post (August 1, 2000): Z10. “Electronic Device Allays Needle Injection Discomfort.” USA Today 129, no. 2665 (October 2000): 8. McDaniel, Randall J., et al. “Causes of Failure Among Cuspal-Coverage Amalgam Restorations: A Clinical Survey.” Journal of the American Dental Association 131(February 2000): 173-178. ORGANIZATIONS

American Dental Association. 211 East Chicago Ave., Chicago, IL 60611. (800)947-4746. (312)440-2500. .

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Cavities found since the 1990s are relatively small and not very deep, so there may be no need to anesthesize the area where the dental work will be done. Highspeed drills often are able to clean out the decay quickly and with little discomfort. If the cavity is not very deep, the drill may not reach the sensitive nerves in the teeth which usually cause pain. Children and some adults may need anesthesia in any case. The dentist and the dental assistant need to be aware of the patient’s history and if the patient reacts adversely to local anesthesia. (See Precautions and Complications.)

Dental hygiene

and therapeutic dental services, such as preventive care, dental examinations, and instruction about how patients can better care for their teeth and gums.

KEY TERMS Amalgam—A mixture of metals, primarily mercury used to make large, durable fillings. Also called silver fillings. Anesthesia—A condition created by drugs that produces a numb feeling. General anesthesia produces unconciousness whereas a local anesthesia produces numbness around the site where the drug was introduced. Composite filling—A resin material that is tooth colored and is used to fill a tooth once decay has been removed. It is used most often in front teeth but may be used in any tooth for aesthetic reasons. Crown—An artificial covering prepared by a lab technician to fit over a damaged tooth or one weakened by decay. Dental caries—Tooth decay caused by microorganisms that convert sugars in food to acids which erode the enamel of a tooth. Dental laser—A device that generates a low-powered beam of light that is used in place of a dentist’s drill to cut away decay from a tooth or remove gum tissue. Enamel—The hard outer surface of a tooth.

Dental hygienists are trained to provide dental hygiene care for patients, they work with dentists to deliver oral care to patients, and they use their interpersonal skills to educate and motivate patients about how to prevent dental disease and maintain oral health. In the clinical setting, dental hygienists: • Assess patients’ teeth and gums and review oral histories. • Educate patients about nutrition and self-care to prevent dental disease, teaching them how to clean the mouth using aids such as toothbrushes, interdental devices, and other efficacious products. • Examine head, neck and dental areas for disease. • Perform x rays and other diagnostic tests. • Perform preventive dental services, such as removing calculus, stains and plaque from teeth, to keep the teeth and gums healthy. • Screen for oral cancer and high blood pressure. • Educate patients about oral health and its link to general health. • Place and remove periodontal dressings or temporary fillings.

OTHER

“Composite (White) Fillings.” Quality Dentistry. April 2001. . Invisible Fillings: The Latest Advances in Dental Materials. ADA News Release, October 1999 (accessed April 2001). .

Janie F. Franz

Dental floss see Oral hygiene aids

Dental hygiene Definition Dental hygiene is the profession of cleaning teeth and helping patients maintain oral health. Dental hygienists are licensed professionals—key members of the dental health care team who provide educational, clinical, 688

Description

• Make impressions of teeth to use as models for dentists to evaluate treatment needs. • Apply preventive agents such as sealants and fluorides to keep teeth healthy. • Remove sutures. In administrative roles, dental hygienists consult with dental health or insurance companies, market dental products, and initiate community dental health programs. Dental hygienists also hold positions at colleges and universities, where they teach dental hygiene or conduct clinical research. Another area of opportunity is in public health, where dental hygienists provide health policy, program administration and management; research community-based care methods; focus on oral health promotion and disease prevention; and help assess, develop, evaluate, and initiate oral health care delivery systems. In these capacities they often have little or no direct individual patient contact. Dental hygiene is a profession that requires its practitioners to work closely with patients, earning their trust, maintaining a high level of oral care, and teaching them

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Types of services

Purpose

Individual

Family

Community

Preventive: Primary

To prevent disease occurrence

Sealants

Counsel parents on prevention of baby-bottle tooth decay

Promote water flouridation

Preventive: Secondary

Early treatment to prevent disease progression

Plaque/calculus removal

Counsel on harmful oral habits

Oral screening and referrals

Educational

Guide to good health behaviors

Home care instruction

Nutritional counseling

Oral health units in schools

Therapeutic

Stop or control disease and maintain healthy oral tissues

Scaling/root planing Postoperative care

Smoking cessation, counseling

Sealant programs Fluoridation of water supply

SOURCE:

Alvarez, K.H. Williams & Wilkins’ Dental Hygiene Handbook. Baltimore: Williams & Wilkins, 1998.

the skills they need to stay healthy. Providing these valuable services usually fosters a tremendous sense of personal fulfillment. Dental hygiene is a highly skilled, prestigious discipline with room for advancement. Flexible hours and work environments make the work attractive. Dental hygienists have little problem finding full- or part-time work during daytime, evening and weekend hours in almost every area of the world. Many also enjoy the job security that dental hygiene offers. Rapid advances in preventive dentistry combined with an aging and growing population ensures that dental hygienists will be busy for the foreseeable future.

Work settings Dental hygienists usually work in private dental practices. However, other employment settings include health maintenance organizations, long-term care facilities, schools, military bases, universities, research facilities, governmental agencies, dental supply companies, or in veterinary dental medicine.

Education and training Dental hygienists are licensed oral health care professionals who have either a two-year diploma, certificate, or associate degree in dental hygiene or a four-year baccalaureate degree. They are educated through community college academic programs, technical colleges, dental schools, or universities. Dental hygienists should work well with others and have good manual dexterity and hand-eye coordination to use dental instruments in the small area of a person’s mouth. Students in dental hygiene programs receive laboratory, clinical, and classroom instruction in subjects such as anatomy, physiology, chemistry, microbiology, pharmacology, nutrition, radiography, histology, periodontology, pathology, dental materials, dental hygiene theory and practice, and social and behavioral sciences.

Dental hygienists must be licensed in the jurisdiction in which they practice. To become licensed, dental hygienists must have graduated from an accredited dental hygiene school and passed written and clinical examinations. Accredited dental hygiene programs require an average of 2,000 curriculum hours, including 585 hours of supervised clinical dental hygiene instruction. Two-year associate’s degrees allow dental hygienists to take national, state, or regional license examinations. Usually, an associate’s degree is qualification enough for those who want to practice in a private dental office. High school students considering a career in dental hygiene should consider taking such courses as health, biology, psychology, chemistry, mathematics, and speech. Some baccalaureate degree programs require that applicants first complete two years of college before being accepted into dental hygiene programs. About half of the dental hygiene programs prefer applicants who have completed at least one year of college. Students or school counselors should contact individual programs for their requirements.

Advanced education and training Dental hygienists who go into research, education, or administration usually need a master’s degree in dental hygiene. Those oral hygienists who choose to go into public health dental hygiene usually must pursue graduate public health education at both schools of public health and dentistry.

Future outlook Dental hygiene is projected to be among the 30 fastest growing occupations due to the increasing population and people’s longer retention of their natural teeth.

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Examples of services provided by dental hygienists

Dental indices

KEY TERMS

Proper dental hygiene clinical attire Outer garments (gowns, lab coats, scrub suits, uniforms) should adequately cover arms and street clothing. They should be disposable or laundered commercially (not taken home or worn outside the clinic). The face mask should block out particles as small as microns and have a lining impenetrable to moisture. The mask should cover the nose and mouth and fit comfortably under glasses, if worn. Change the face mask before each patient and wear for no longer than 1 hour. Protective eyewear should be worn by both the patient and client. The eyewear should be shatterproof, lightweight, easily disinfected, and provide wide coverage with side shields. Gloves should be strong and durable, and impermeable to saliva, blood, and bacteria. The gloves should be nonirritating or harmful to skin and fit properly. Jewelry should not be worn on hands and wrists to minimize areas for microorganisms. SOURCE:

Alvarez, K.H. Williams & Wilkins’ Dental Hygiene Handbook. Baltimore: Williams & Wilkins, 1998.

Resources ORGANIZATIONS

American Dental Association. 211 E. Chicago Ave. Chicago, IL 60611. (312) 440-2806. . American Dental Education Association (ADEA). 1625 Massachusetts Avenue, NW, Washington, DC 200362212. 202-667-9433. . American Dental Hygienists’ Association. 444 North Michigan Avenue, Suite 3400, Chicago, IL 60611. (312) 440-8900. . OTHER

Commission on Dental Accreditation. 211 E. Chicago Avenue, Chicago, IL 60611. 312-440-2718. [email protected]. U.S. Department of Labor. Bureau of Labor Statistics. Division of Information Services. “Occupational Outlook Handbook.”

Lisette Hilton

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Histology—Study of tissue structure. Periodontology—Study of gum disease. Plaque—Colorless, sticky film composed of acid and bacteria, which causes tooth decay.

Dental indices Definition

In fact, the career path is expected to grow much faster than average through 2008. Salaries of dental hygienists are based on their responsibilities and specific positions, the geographic location of employment, and their type of work environment. They are similar to those of other health care personnel with similar education and experience. In 1998 dental hygienists earned median hourly wages of $22.06. The middle 50% earned between $17.28 and $29.28 an hour. The lowest 10% earned less than $12.37; the highest 10% earned more than $38.81 an hour.

Dental implants see Dental prostheses

Calculus—A hard mineral deposit formed on teeth; tartar.

Dental indices provide a quantitative method for measuring, scoring, and analyzing dental conditions in individuals and groups. An index describes the status of individuals or groups with respect to the condition being measured.

Description Oral health surveys depend on dental indices, as do researchers and clinicians, to help in understanding trends and patients’ needs. In epidemiological oral health surveys, an index is used to show the prevalence and incidence of a particular condition, to provide baseline data, to assess the needs of a population, and to evaluate the effects and results of a community program. Researchers use indices to determine baseline data and to measure the effectiveness of specific agents, interventions, and mechanical devices. In private practice, index scores are used to educate, motivate, and evaluate the patient. By comparing scores from the initial exam during a follow-up exam, the patient can measure the effects of personal daily care. The first dental index, developed by Schour and Massler, was known as a Papilla, Marginal gingiva and Attached gingiva (PMA) Index. Each of those areas was examined and scored from 0 to 5, depending on the severity of inflammation. The PMA Index, largely of historic interest now, was primarily used in surveys of acute gingivitis. Today, dental indices are used to assess both individual and group oral health and disease status. They can be simple, measuring only the presence or absence of a condition, or they can be cumulative, measuring all evidence of a condition, past and present. Irreversible indices measure conditions that will not change, such as dental caries.

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faces, they are facial (or buccal), mesio-facial, mesio-lingual, lingual, disto-lingual, and disto-facial.

The status of a patient’s periodontal health or disease is commonly measured by an index in private practices. One of the most widely used is the Periodontal Screening and Recording (PSR)TM Index, adapted in 1992 from a system in use in Europe called the Community Periodontal Index of Treatment Needs. The PSRTM is an early detection system for periodontal disease. It is not intended to replace full periodontal charting, but to serve as a simple and convenient screening tool. (The PSRTM is more fully discussed in the entry on dental and periodontal charting.)

To determine an individual’s score, the clinician multiplies the number of surfaces with plaque by 100, and divides that by the number of tooth surfaces examined. For example, if an individual has 26 teeth, that equals 104 surfaces. If eight surfaces are found to have plaque, then 800 is divided by 104, leaving a plaque control index of 7.6%. A score under 10% is considered good.

In addition to measuring a patient’s periodontal status, dental indices can measure the amount of plaque and calculus present or not present in a patient’s mouth, the amount of bleeding present in the gingiva, the amount of tooth mobility present at a given time, the amount of fluorosis present, and the number of decayed, missing, or filled teeth present. Some of the more widely known indices are: Plaque index (PI) The PI as developed by Silness and Loe assesses the thickness of plaque at the cervical margin of the tooth (closest to the gum). Four areas, distal, facial or buccal, mesial, and lingual, are examined. Each tooth is dried and examined visually using a mirror, an explorer, and adequate light. The explorer is passed over the cervical third to test for the presence of plaque. A disclosing agent may be used to assist evaluation. Four different scores are possible. A zero indicates no plaque present; 1 indicates a film of plaque present on the tooth; 2 represents moderate accumulation of soft deposits in the gingival pocket or on the tooth that can be seen by the naked eye; 3 represents an abundance of soft matter within the pocket or on the tooth. Each area of each tooth is assigned a score from 0 to 3. Scores for each tooth are totaled and divided by the four surfaces scored. To determine a total PI for an individual, the scores for each tooth are totaled and divided by the number of teeth examined. Four ratings may then be assigned: 0 = excellent, 0.1-0.9 = good, 1.0-1.9 = fair, 2.0-3.0 = poor. Plaque control record A similar system for measuring plaque is credited to O’Leary, Drake, and Naylor. This system measures plaque present, rather than plaque not present, but no attempt is made to differentiate in the quantity of plaque seen on each surface. The number of surfaces examined may be increased from four to six. When using six sur-

Oral hygiene index (OHI) The OHI, developed by Greene, Vermillion, and Waggener, has two components, the debris index and the calculus index, and is an indication of oral cleanliness. The scores may be used singly or in combination. For scoring, the clinician divides the dentition into sextants and selects the facial (or buccal) and lingual tooth surface in each sextant that is covered with the greatest amount of debris and calculus. Twelve surfaces, therefore, will be evaluated. For this index, a surface includes half the circumference of the tooth. Greene and Vermillion have also developed a simplified OHI in which the clinician measures only one tooth surface in each sextant, equaling only six surfaces. DEBRIS INDEX (DI). For this index, debris is defined as soft, foreign matter consisting of bacterial plaque and food debris. The criteria include 0, no debris or stain present; 1, debris covering not more than one-third of the tooth surface or extrinsic stain without debris; 2, debris covering between one- and two-thirds of the tooth surface; and 3, debris covering more than two-thirds of the tooth surface. CALCULUS INDEX (CI). Calculus, a hard calcified deposit of inorganic salts, is scored for this index with four criteria. They are 0, no calculus present; 1, supragingival calculus present covering not more than one third of the tooth surface; 2, supragingival calculus covering between one- and two-thirds of the tooth surface, or scattered subgingival calculus; and 3, supragingival calculus covering more than two-thirds of the tooth surface, or a continuous heavy band of subgingival calculus around the tooth.

To arrive at an OHI score, one first calculates the DI and CI scores by dividing the total scores for each tooth by the number of sextants. The DI and CI scores are then added to determine an OHI score. A perfect score would be 0, and the worst score possible is 12. In the simplified OHI, the worst score possible is 6. Gingival index (GI) Also attributed to Loe and Silness, the GI assesses the severity of gingivitis based on color, consistency, and

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A reversible index measures conditions that can be changed, such as the amount of bacterial plaque present.

Dental indices

ference with normal function. The tooth is not loose or drifting.

Types of dental indices Type

Purpose

Individual assessment

Evaluation and monitoring the progress and maintenance of oral health Measures effects of personalized disease control programs over time Monitors progress of disease healing Patient education, motivation

Clinical trial

Epidemiologic survey

Determines the effect of an agent or procedure on the prevention, progression, or control of a disease

Scores for each tooth are added, and the total divided by the number of teeth examined. Scores can be interpreted as follows: • 0-0.2: Clinically normal supportive tissues. • 0.3-0.9: Simple gingivitis.

Comparison of an experimental group with a control group

• 0.7-1.9: Beginning destructive periodontal disease.

Survey for the study of disease characteristics of populations

• 1.6-5.0: Established destructive periodontal disease. • 3.8-8.0: Terminal periodontal disease.

Not designed for evaluation of an individual patient

Gingival bleeding index (GBI)

SOURCE: Alvarez, K.H. Williams & Wilkins’ Dental Hygiene Handbook. Baltimore: Williams & Wilkins, 1998.

bleeding on probing. Each tooth is examined at the mesial, lingual, distal, and facial (or buccal) surface. A probe is used to press on the gingiva to determine its degree of firmness, and to run along the soft tissue wall adjacent to the entrance to the gingival sulcus. Four criteria are possible: 0, normal gingiva; 1, mild inflammation but no bleeding on probing; 2, moderate inflammation and bleeding on probing; 3, severe inflammation and ulceration, with a tendency for spontaneous bleeding. Each surface is given a score, then the scores are totaled and divided by four. That number is divided by the number of teeth examined to determine the GI. Ratings are 0, = excellent; 0.1-1.0 = good; 1.1-2.0 = fair; 2.1-3.0 = poor. Periodontal index (PI) Developed by Russell, the PI determines the periodontal disease status of populations in epidemiologic studies. Each tooth is scored according to the condition of the surrounding tissues. On examination, each tooth is assigned a score using the following criteria: • 0: Negative. Neither overt inflammation nor loss of function caused by the destruction of supporting tissue is noted. • 1: Mild Gingivitis. Overt inflammation in the free gingiva is present, but does not circumscribe the tooth. • 2: Gingivitis. Inflammation surrounds the tooth, but there is no apparent break in the epithelial attachment. • 6: Gingivitis with pocket formation. The epithelial attachment of gum to tooth is broken. There is no inter692

• 8: Advanced destruction with loss of function. The tooth may be loose or drifting. It may sound dull on percussion and may be depressible in the socket.

Unwaxed dental floss is used to measure a GBI, developed by Carter and Barnes. A full complement of teeth has 28 proximal areas to be examined. Floss is passed interproximally, first on one side of the dental papilla, then on the other. The clinician curves the floss around each tooth and passes it below the gingival margin, taking care not to lacerate the gingiva. Any bleeding noted indicates the presence of disease. The numbers of bleeding areas versus proximal areas scored is recorded and used for patient motivation. Mobility index The mobility index, developed by Grace and Smales, can be useful to track the amount of mobility in teeth over a period of time. Grade 0 indicates no apparent mobility. Grade 1 is assigned to a tooth in which mobility is perceptible, but less than 1mm buccolingually. Grade 2 mobility is between 1-2 mm, and Grade 3 mobility exceeds 2mm buccolingually or vertically. Dean’s Dental Fluorosis Index Dean’s is used to score the amount of dental fluorosis (discoloration) present on teeth. Fluorosis generally appears as a horizontal striated pattern across a tooth. Molars and bicuspids are most frequently affected, followed by upper incisors. The mandibular incisors are usually least affected. Fluorosis tends to be bilaterally symmetrical. Defects may appear as fine white or frosted lines or patches near the incisal edges or cusp tips. A score is given based on the two teeth most affected. If the teeth are not equal in appearance, the less affected tooth is the one scored. Scores used in Dean’s Index are as follows:

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judged the site of origin is recorded as a 1. These criteria apply to all numbers.

• Questionable (1): There are slight aberrations from the translucency of normal enamel. Lesions may range from a few white flecks to occasional spots.

• 2: Filled teeth, with additional decay, are termed 2. No distinction is made between primary caries which is not associated with a previous filling, and secondary caries, adjacent to an existing restoration.

• Very mild (2): Opaque paper-white areas are visible, involving less than 25% of the facial or buccal tooth surface. • Mild (3): White opacity of the enamel is more apparent than for code 2, but still covers less than 50% of the surface. • Moderate (4): Marked wear and brown stain, frequently disfiguring, is visible. • Severe (5): Hypoplasia is so marked that the general form of the tooth may be altered. Pitted or worn areas and brown stain are widespread. Teeth often have a corroded appearance. • Excluded (8): Used for crowned teeth. • Not recorded (9): Used for missing teeth or teeth that cannot be scored. Decayed, missing and filled teeth (DMFT) index To assess dental caries in a population, a DMFT index is used. During a systematic examination with a mirror and explorer that includes the crown and exposed root of every primary and permanent tooth, each crown and root are assigned a number based on the result of that exam. The numbers are recorded in boxes corresponding to each tooth to provide a DMFT chart. It is recommended that care be taken to record all tooth-colored fillings, which may be difficult to detect. Number are assigned as follows: • 0: A zero indicates a sound crown or root, showing no evidence of either treated or untreated caries. A crown may have defects and still be recorded as 0. Defects that can be disregarded include white or chalky spots; discolored or rough spots that are not soft; stained enamel pits or fissures; dark, shiny, hard, pitted areas of moderate to severe fluorosis; or abraded areas. • 1: One indicates a tooth with caries. A tooth or root with a definite cavity, undermined enamel, or detectably softened or leathery area of enamel or cementum can be designated a 1. A tooth with a temporary filling, and teeth that are sealed but decayed, are also termed 1. A 1 is not assigned to any tooth in which caries is only suspected. In cases where the crown of a tooth is entirely decayed, leaving only the root, a 1 is assigned to both crown and root. Where only the root is decayed, only the root is termed a 1. In cases where both the crown and root are involved with decay, whichever site is

• 3: A 3 indicates a filled tooth with no decay. If a tooth has been crowned because of previous decay, that tooth is judged a 3. When a tooth has been crowned for another reason such as aesthetics or for use as a bridge abutment, a 7 is used. • 4: A 4 indicates a tooth that is missing as a result of caries. Only crowns are given 4 status. Roots of teeth that have been scored as 4 are recorded as 7 or 9. When primary teeth are missing, the score should be used only if the tooth is missing prematurely. Primary teeth missing because of normal exfoliation need no recording. • 5: A permanent tooth missing for any other reason than decay is given a 5. Examples are teeth extracted for orthodontia or because of periodontal disease, teeth that are congenitally missing, or teeth missing because of trauma. The 5 is assigned to the crown, the root is given a 7 or 9. Knowledge of tooth eruption patterns is helpful to determine whether teeth are missing or not yet erupted. Clues to help in the determination include appearance of the alveolar ridge in the area in question, and caries status of other teeth in the mouth. • 6: A 6 is assigned to teeth on which sealants have been placed. Teeth on which the occlusal fissure has been enlarged and a composite material placed should also be termed 6. • 7: A 7 is used to indicate that the tooth is part of a fixed bridge. When a tooth has been crowned for a reason other than decay, this code is also used. Teeth that have veneers or laminates covering the facial surface are also termed 7 when there is no evidence of caries or restoration. A 7 is also used to indicate a root replaced by an implant. Teeth that have been replaced by bridge pontics are scored 4 or 5; their roots are scored 9. • 8: This code is used for a space with an unerupted permanent tooth where no primary tooth is present. The category does not include missing teeth. Code 8 teeth are excluded from calculations of caries. When applied to a root, an 8 indicates the root surface is not visible in the mouth. • 9: Erupted teeth that cannot be examined—because of orthodontic bands, for example—are scored a 9. When applied to a root, a 9 indicates the tooth has been extracted. The crown of that tooth would be scored a 4 or 5.

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• Normal (0): The enamel is smooth, glossy and translucent, usually a pale creamy-white color.

Dental indices

KEY TERMS Buccal—Surface of a posterior tooth closest to the cheek. Caries—Tooth decay. Cementum—Outer surface of the tooth root. Disclosing agent—Tablet or liquid containing a red dye that is used to color and reveal plaque in a patient’s mouth. Distal—Surface of a tooth farthest from the midline. Edentulous—Without teeth. Facial—Surface of an anterior tooth closest to the lips. Fixed bridge—Two or more prosthetic crowns covering teeth on either side of a missing tooth. A pontic, or artificial tooth, is suspended between the crowns to fill the space. Fluorosis—Mottled discoloration of tooth enamel due to excessive systemic ingestion of fluoride during tooth development. Hypoplasia—Incomplete or defective development of the enamel of a tooth. Lingual—Surface of a tooth closest to the tongue. Mandibular—Pertaining to the lower jaw. Maxillary—Pertaining to the upper jaw. Mesial—Surface of a tooth closest to the midline. Papilla—Triangular pad of gum tissue filling the space between the proximal surfaces of two adjacent teeth. Pontic—Artificial tooth suspended between two prosthetic crowns to fill a space left by a missing tooth. Sealant—Composite resin applied to pits and fissures of teeth to prevent decay. Sulcus—Groove between the surface of a tooth and the epithelium lining the free gingiva.

• T: Indicating trauma, a T is used when a crown is fractured, with some of its surface missing but with no evidence of decay. The “D” of DMFT refers to all teeth with codes 1 and 2. The “M” applies to teeth scored 4 in subjects under age 30, and teeth scored 4 or 5 in subjects over age 30. The “F” refers to teeth with code 3. Those teeth coded 6, 7, 8, 9, or T are not included in DMFT calculations. 694

To arrive at a DMFT score for an individual patient’s mouth, three values must be determined: the number of teeth with carious lesions, the number of extracted teeth, and the number of teeth with fillings or crowns. A patient who has two areas of decay, six missing teeth and 11 filled or crowned teeth for example, has a DMFT score of 19. Teeth that include both decay and fillings or crowns, are only given one point, a D. Thirteen teeth (based on a full dentition of 32) remain intact. It is also possible to determine more detailed DMFS (decayed, missing, or filled surface) scores. As anterior teeth have four surfaces and posterior teeth have five, a full dentition of 32 teeth includes 128 surfaces. A patient with seven decayed surfaces, 20 surfaces from which teeth are missing, and 42 surfaces either filled or included in a crown, the DMFS score is 69. Fifty-nine surfaces are intact. For primary dentition, scoring is referred to as “deft” or “defs” (decayed, extracted, or filled). Significant caries index In 2000, the World Health Organization developed the significant caries index (SiC) to be used when studying DMFT scores on a global basis. A single population may include a number of individuals with low DMFT scores, as well as those with high scores. A mean DMFT value would not accurately reflect the status of the population. The SiC Index isolates and highlights those individuals with the highest caries values in a particular population. To calculate a SiC Index, individuals are sorted according to DMFT values. The third of the population with highest caries scores is isolated, and a mean DMFT for this subgroup is calculated. The resulting value is the SiC Index.

Viewpoints Researchers all over the world develop dental indices to suit their particular needs, resulting in some duplication. There are at least six indices that measure the presence or absence of plaque. Indices have become flexible, able to be adapted, modernized, or simplified to fit different needs. They will continue to develop as those needs change again.

Professional implications Dental professionals from the private practice clinician to the researcher use indices to benefit their patients. A dentist or hygienist might use a PI to impress upon a patient the need for better oral hygiene. A World Health Organization researcher might use the same index to assess the home care practices of a population. Indices

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Dental instruments

will continue to be important and necessary tools for dental professionals. Resources BOOKS

Collins, W.J.N., et al. A Handbook for Dental Hygienists. 4th ed. Woburn, MA: John Wright, 1999. Wilkins, Esther M. Clinical Practice of the Dental Hygienist. 7th ed. Philadelphia: Williams and Wilkins, 1994. ORGANIZATIONS

American Dental Association, 211 E. Chicago Ave., Chicago, IL 60611. (312) 440-2500. . OTHER

“Oral Health Methods and Indices.” WHO Oral Health Country/Area Profile Programme, 1997. .

Cathy Hester Seckman, R.D.H.

Dental injuries see Dental trauma

Dental instruments Definition Dental instruments are tools used in the assessment, diagnosis, and treatment of oral diseases.

Purpose Dental instruments are designed to be used by the dentist and staff during dental care. Instruments aid in the assessment and treatment of dental disease. Each is designed for a specific purpose.

Description There are many different dental instruments used by oral health care professionals in their different roles and specialties. Certain types of instruments are unique to various therapeutic procedures. Assessment

Dental drill. (Photograph by Randy Duchaine. The Stock Market. Reproduced by permission.)

• Probes: used to measure the depth of periodontal pockets or sulci. • Explorers: used to detect dental caries in tooth grooves and pits. Restorative procedures During restorative treatment the following types of instruments may be used: • Amalgam carriers: for transferring amalgam from the tray to the patient’s mouth. • Burnishers: for smoothing the amalgam filling. • Composite: for use as an alternate filling material when silver fillings are not appealing. • Excavators: for removal of small amounts of decay close to the nerve.

During an examination by a general dentist the following diagnostic instruments may be used:

• High speed hand piece: for removal of tooth decay. It is commonly known as the drill.

• Cotton pliers: used for placing cotton rolls or plugets to dry up saliva.

• Slow speed hand piece: for removal of deep decay from the teeth. It is commonly known as the slow drill, and is also used in extrinsic stain removal.

• Mouth mirror: used to view hard-to-see areas such as the roof of the mouth, behind the molars, and behind the anterior teeth.

• Spatulas: for mixing compounds, such as alginate, plaster, dycal, and cements.

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• Brush holders: for holding tiny brushes and reaching far in to the mouth.

• Utility plier: used to cut thick wires before placement in the mouth.

• Carvers: for carving the amalgam filling to the shape of the tooth.

• Debonding instruments: used to remove molar bands from the molars.

• Pluggers: for placing amalgam filling deep in the excavated tooth.

• Debanding instruments: used to remove brackets from the teeth.

• Syringes: for washing out excavated teeth with sterile water.

• Ligature forceps: used to place ligature ties around the brackets. • Mosquito forceps: used to place ligature ties around odd angled teeth.

Periodontal procedures During periodontal treatment (concerning tissues surrounding the teeth), the following types of instruments may be used: • Gingival knives: small knives used to cut gum tissue in the area of treatment. • Chisels: surgical instruments that aid in the removal of infected bone. • Surgical burs: used in high speed hand drills to aid in the sectioning of the infected bone or roots.

• Explorers: used to the remove ligature ties around the brackets. Surgical procedures During surgical procedures heavy-duty steel instruments are needed for leverage and lifting. The instruments are used to remove diseased bone or the roots of teeth. The following instruments may be used: • Elevators: used to raise gum tissue or bone.

• Bone files: surgical instruments that aid in the filing of infected bone in order to remove that portion of infected bone.

• Hemostats: used to grasp tissue for removal or retraction.

• Scalers/curets: used for the removal of bacterial toxins and calculus below the gum line.

• Tissue forceps: used to remove or retract tissue.

• Root tip picks: used to remove sectioned-off root tips. • Bone files: used to file down and remove diseased bone.

Endodontic procedures During endodontic treatment (concerning diseases of the pulp), the following instruments may be used:

• Retractors: used to hold the cheeks and tongue out of the way.

• Explorers: used to assess the root canals of the tooth.

• Wire cutters and twisters: used to cut wire during wire surgery for better healing of the bone and tissue.

• Spreaders: used to spread the hot gutta percha into the individual root canals. • Files: used to clean out the nerve of the infected tooth. Files come in different lengths and sizes. • Reamers: used to ream out the nerve. Reamers are bigger than a file.

• Extraction forceps: used to remove teeth. • Periosteal elevators: used to elevate the periosteal (external to bone) tissue for better viewing of the surgical site. • Scissors: used to cut soft tissue and surgical sutures.

• Broach: used to remove hardened nerve tissue (dead nerve tissue) and enlarge the canal.

• Scalpel: used to incise gum tissue.

• Syringes: used to flush the canals with sterile water for cleaning.

• Surgical sutures: made from silk or thread, used to suture tissue together.

Orthodontic procedures

Operation

During orthodontic treatment (concerning alignment of teeth), the following instruments may be used: • Cutting instruments: used to cut the wires already placed in the mouth. • Wire forming: used to curve the wire to the correct spree for the individual patient. 696

• Needle holders: used to hold the needle during suturing.

Dental instruments have a variety of applications. Many of the instruments can be used repeatedly after the sterilization process. The life span of the instruments depends on their usage, care, and the method of sterilization. Sterilization prevents the spread of diseases like hepatitis B. Following guidelines set by the ADA and the

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Non-critical instruments can be treated with disinfectants classified as high, intermediate, or low relative to their effectiveness against bacterial spores and viruses. Non-critical instruments, such as articulators and spatulas, have no contact with mucous membranes. They do not require sterilization. Semi-critical instruments touch mucus membranes but do not break the barrier of the mucosal surface or skin. They require sterilization or high-level disinfection, depending on whether they are affected by heat. Sterilization is usually achieved through methods that use extreme heat. Semi-critical instruments include amalgam condensers, hand pieces, and plastic vacuum tips. Critical instruments require sterilization. These instruments penetrate or touch broken skin or mucus membranes. Critical instruments include needles, scalpels, surgical instruments, dental explorers, dental burs, and endodontic instruments. They must be sterilized. Endodontic instruments need to be checked daily to determine usability. Files, reamers and broaches become brittle after months of sterilization. The CDCP and ADA recommend critical instruments be cleaned, bagged and then fully sterilized after each procedure. Heavy-duty gloves worn by the dental assistants during cleaning, disinfecting and sterilizing of most dental instruments is advised.

Maintenance The ADA recommends that the working parts of all instruments be checked monthly. It is also recommended that a sufficient supply of instruments be maintained in order to allow for proper sterilization.

Health care team roles Ultimately, the dentist is responsible for the ordering of dental instruments, but many offices delegate that task to a supervising dental assistant. The entire office staff is responsible for instrument sterilization. Instrument sterilization prevents disease transmission and maximizes the longevity of the instrument. Training Following the guidelines set forth by the instrument manufacturer is the best procedure for instrument maintenance and recirculation. The ADA recommends purchasing instruments from reputable companies that have the ADA seal of approval.

KEY TERMS Amalgam—The material used in silver fillings. Endodontic—Referring to the nerve and pulp of a tooth. Endodontist—Dentist specializing in the removal of the nerve and pulp of the teeth. Gutta percha—Material used during root canal therapy to fill the canals after the nerve has been removed. Orthodontic—Referring to the movement of the teeth. Orthodontist—Dentist specializing in the field of tooth movement. Periodontal—Gum tissue surrounding the teeth. Periodontist—A dentist who specializes in treating the gum tissue and bones of the mouth. Sulcus—An indentation in an anatomic structure.

Resources ORGANIZATIONS

American Dental Association (ADA). 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-2500. . OTHER

ADA seal of approval board. Standards and Guidelines for Dental Materials, Instruments and Equipment. April 20, 2001. . A Titan Instruments Ordering Catalog, 2001. . Centers for Disease Control and Prevention. Recommended Infection-Control Practices for Dentistry. MWMR 1993; 42(No. RR-8). . Dental Instruments. Denticon Catalog, 2001. . Howell M.L. The Last Hundred Years in Dentistry. ADA Dental Minute TV clip. August 17, 2000. . MICRO-MEGA DENTAL EXPORT. MM endodontic instruments. . Palenik C.J. Dental Instrument Sterilization: A Six-Step Process. .

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Cindy F. Ovard, RDA 697

Dental instruments

manufacturer for proper sterilization of non-critical, semi-critical and critical instruments is advised.

Dental laboratory technology

Dental laboratory technology Definition Dental laboratory technology is the science and craft of creating dental prostheses. It involves artistic talent, aptitude for precision work, good eyesight, and a high degree of manual dexterity. Knowledge of CAD/CAM computer programs, digital cameras, and digital imaging systems is also required.

Description Preventive education has decreased the incidence of dental caries. Better dental health means that the demand for dentures has declined, while the need for dental prostheses and cosmetic procedures has increased. Dental laboratory technicians are sought by dental laboratories, private dental practices, and medical institutions. These skilled craftspeople are part scientist, part artist, and part engineer. They must have manual dexterity, good eyesight, and a penchant for detailed, precision work. Dental laboratory technicians create a variety of dental prostheses including crowns, bridges, artificial teeth, partial dentures, and complete dentures. They also prepare inlays—ceramic or resin structures that are cemented into a prepared tooth. Technicians also create onlays from those same materials which fit over the tooth but do not cover the tooth completely like a crown. In large laboratories, dental technicians may specialize in a single type of restoration, such as crowns or partial dentures. Some laboratories have ceramists who specialize in creating ceramic restorations of every type. In order to design and craft these prostheses, a dental technician prepares wax diagnostic models from patients’ mouth impressions. These wax models are finely detailed sculptures of the mouth, showing how the restoration will look and how it will work. From these, the prostheses are cast in investment molds through an ancient bronze casting and jewelry method, called the lost wax technique. The investment mold is poured around the wax model of the prosthesis and is fired. The wax melts and drains out of the investment mold, leaving behind a durable mold into which the technician can pour a casting material. Restorative casting materials can be metals (gold, silver, amalgam), resins, or ceramics. These are poured into the investment mold to craft individual teeth, crowns, and other dental prostheses. New computer applications are making the restoration process faster, more accurate, and more comfortable. 698

Implant and crown design is often time consuming, requiring several appointments to ensure a proper fit. Duplication technology (e.g. Geomagic Studio from Raindrop Geomagic of Morrisville, NC) uses 3-D scanners to scan a patient’s mouth. This duplicates the shape, thickness, and color of the natural teeth. This information is processed through CAD software and used to generate a digital prosthesis that is virtually inserted into the digital image of the patient’s mouth to check for an accurate fit. The dental prosthesis is then crafted in real materials and fitted into the patient’s mouth.

Work settings Dental laboratory technicians work mainly in dental laboratories. These are usually independent businesses, with one technician out of five owning his or her own laboratory. Some laboratories may also be connected with a dentist or a team of dentists, to create a one-stop service for patients. Some technicians work in hospitals or institutions which provide dental services to in-house patients, e.g. VA hospitals. Laboratory facilities are clean, well lit, and carefully ventilated. Workstations may be equipped with computers, grinding equipment, polishing machines, and a variety of tools for fine detailed work. Most dental laboratory owners keep their facilities equipped with state-of-the-art tools, equipment (including a dental kiln), and materials. They also provide continuing training for their technicians in current procedures, techniques, and material use.

Education and training Though most dental laboratory technicians learn while working on the job in the laboratory, many are now seeking professional training at junior colleges, dental schools, and vocational/technical institutions before seeking employment. Some dental schools offer course work in dental laboratory technology. In any event, technicians will still need to train on the job in order to learn the techniques and styles of a particular dental laboratory. Early tasks on the job may be relatively menial in contrast to the skills the technicians will display later for the laboratory. They may prepare dental impressions or fire already prepared crowns or dentures. After three or four years of training, technicians are then able to design and craft dental prostheses for patients. The ADA Commission on Dental Accreditation has accredited 34 programs in dental laboratory technology. Classroom instruction includes oral anatomy, dental materials science, fabrication procedures, computer software applications, digital imaging, and ethics. Students

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Certification is available in some states through the National Board. This is voluntary and not necessary to work in the profession. Five areas of certification are available; crowns and bridges, ceramics, partial dentures, complete dentures, and orthodontic appliances.

Advanced education and training Most dental schools offer specialization in prosthodontics. A prosthodontist is a dentist who does only dental restorations. Usually, prosthodontists have three or more years of education beyond their DDS (doctor of dental surgery) degree. They may supervise full mouth restorations or single crowns. They are often able to oversee the manufacture and fitting of fixed bridges, dentures, implants, or a combination of these prostheses. Periodontists, specialists in gums and bones, and oral and maxillofacial surgeons may also fit implants into the jaw. They also are required to have three or more years of education beyond their DDS degree.

Future outlook More people in their retirement years have full, (or almost full) sets of teeth and no longer require complete dentures in old age. They are, however, requesting more enhancements to their appearance and more prostheses to improve their ability to chew and enjoy their food. Employment for dental laboratory technicians is favorable and may increase as the demand for prosthetic and cosmetic services increases with the aging of baby boomers. Resources BOOKS

Shillingburg, Herbert T., Jr., Sumiya Hobo, and Lowell D. Whitsett. Fundamentals of Fixed Prosthodontics. Chicago: Quintessence Publishing Co., 1997.

KEY TERMS Bridge—An appliance of one or more artificial teeth anchored by crowns on the adjacent teeth. CAD/CAM—A computer-aided design and manufacturing package for the fabrication of dental prostheses. Complete denture—A full set of upper or lower teeth, mounted in a plastic base. Dentures are also called false teeth. Crown—A protective shell that fits over the tooth. Dental caries—An infectious disease of the teeth in which microorganisms convert sugar in the mouth to acid that erodes the tooth structure. Inlay—A filling that is made outside of the tooth and then cemented into place. Onlay—A restoration that covers the upper surface of a tooth. It is bigger than a filling but smaller than a crown.

National Association of Dental Laboratories, 1530 Metropolitan Blvd., Tallahassee, FL, 32308. (800) 9501150. . OTHER

“The Art & Science of Dental Laboratory Technology.” National Association of Dental Labs. . (Accessed May 1, 2001.) “Dental Laboratory Technology.” ADA Career Brochures. . (Accessed May 1, 2001.) “Dental Laboratory Technicians.” Occupational Outlook Handbook. . (Accessed May 1, 2001.)

PERIODICALS

Janie F. Franz

“Technology Triggering Brighter Smiles.” USA Today 129, no. 2666 (November 2000): 7. Thilmany. Jean. “Dental Implants Done Digitally.” Mechanical Engineering: CIME 122(December 2000): 16.

Dental patient preparation

ORGANIZATIONS

Academy of General Dentistry, Suite 1200, 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-4300. . American Dental Association, 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-2500. .

Definition Dental patient preparation is the process of preparing a patient mentally and physically to receive dental care.

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complete course work in two years and receive an associate’s degree.

Dental patient preparation

Purpose Good preparation helps patients form a positive attitude about dental health care. Ideally, this attitude will continue throughout life, enhancing optimal oral health. An important aspect of patient preparation is education about the risks and benefits of dental procedures. The patient should understand beforehand the reasons for any procedure and what to expect during and afterwards. The patient should have the opportunity to weigh the pros and cons of any procedure and make a knowledgeable decision based on accurate, honest, and timely information.

additional expense to achieve increased patient satisfaction and compliance.

Preparation Using brochures and other written materials is one way to prepare patients. They have the advantages of giving patients time away from the office to consider new information and can answer common concerns without taking up staff time. It is also helpful to take a moment to explain procedures and answer questions when calling patients to confirm appointments.

Precautions Patients must be prepared in a manner that is understandable and appropriate. Groups that might need special preparation include the poor, the elderly, and people from different cultures. In addition, health care providers must give special attention in preparing children and mentally handicapped adults for dental care, and include a parent or caregiver in all decisions as well as information regarding aftercare.

Aftercare A phone call from the dentist is common aftercare, especially following a surgical procedure. The dentist assesses patient comfort, answers questions, and reminds patients of what to expect during recovery. Good aftercare protocol builds the patient/doctor confidence and trust and can help detect medical complications before they become serious.

Description Undergoing dental care can be frightening to children and even to many adults. Stress and anxiety are reduced when a patient understands the reasons for procedures and what to expect. Risks of procedures must also be carefully explained, so that informed consent can be made. Patient education is needed in cases of:

Complications Poor patient preparation can lead to misunderstandings, including unwarranted fear about procedures or confusion about financial obligations. Rushing through explanations or using too much professional jargon, for example, might lead a patient to back out of treatment and neglect oral health care.

• dental benefits, insurance, and financial options • initial examinations

Results

• x rays

Many people avoid visiting the dentist because of fear of discomfort or embarrassment about poor dental hygiene. Care in patient preparation can go a long way in making patients feel more at ease, making them more likely to maintain better oral health and visit their dentist regularly.

• crown preparation • crown delivery • implants treatment • inlay preparation • restorative therapy • root canal therapy

Health care team roles

• periodontal therapy • oral and maxillofacial surgery Time spent by the dental office staff for patient preparation is not billed separately to the patient or to insurance companies. Extra staff time in preparation and follow-up phone calls, as well as the cost of informational brochures, are usually well worth the relatively small 700

The dentist or specialist prepares the patient and answers questions. The dental assistant plays a supportive role in patient education and preparation. The front office staff can provide brochures as recommended by the dentist or dental assistant, and help the patient work out financial arrangements.

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Crown delivery—Placement of a porcelain crown. Normally, the tooth is prepared two weeks prior to this procedure. Crown prep—Preparing a tooth to receive a crown or cap. Implant—A surgical procedure involving permanently placing a false tooth into the gum tissue. Inlay—Preparing a tooth for a partial crown made out of porcelain or gold. This is similar to a crown, but only part of the tooth is involved. Restorative treatment—Any type of dental procedure that restores a tooth’s function. This is usually accomplished with silver (amalgam) fillings. Root canal—Removal of the nerves and pulp of the tooth. Tooth extraction—Surgical removal of a tooth.

Resources PERIODICALS

“Patient Preparation.” Dentistry Online Magazine, Jerry Massimei DDS, APC. August 2000. . “Patient Preparation: Calming the Patient.” American Academy of Pediatric Dentistry (AAPD). . “Patient Preparation: Talk about Anxiousness.” JADA May 2001. . ORGANIZATIONS

American Academy of Pediatric Dentistry (AAPD). 211 East Chicago Avenue, Suite 700, Chicago, IL 60611-2663. . American Dental Association. 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-2500. . Medical University of South Carolina. 171 Ashley Avenue, Charleston, SC 29425. . OTHER

“The Dental Patient.” Michael Maroon, DMD, FAGD, Editor and Publisher. 39 Webster Square Road, Berlin, CT 06037. (800) 770-3933. .

Cindy F. Ovard, RDA

Definition Dental prostheses, artificially made devices resembling natural teeth, are used to replace missing or damaged teeth. These devices include inlays/onlays, crowns, bridges, dentures, partial dentures, and dental implants.

Purpose Crowns and inlays/onlays are intended to repair damage to individual teeth. They replace tooth structure lost by decay or injury, protect the part of the tooth that remains, and restore the tooth’s shape and function. Bridges, dentures, and partial dentures fill in a space in the jaw left by a missing tooth or teeth. They protect the shape of the mouth and restore function of the teeth and jaw.

Precautions Some patients are allergic to the constituents in local or general anesthesic agents. In addition, many people are afraid of dental work and therefore may experience stress-related symptoms, even fainting, while in the dental office. Most dentists can help patients with this specific fear. Also, the dentist and dental assistant will need to be aware of any pre-existing conditions in the patient’s history, e.g. diabetes, high blood pressure, heart disease, hemophilia, or HIV/AIDS.

Description Inlays/onlays An inlay resembles a filling in that it fills the space remaining after the decayed portion of a tooth has been removed. The difference is that an inlay is shaped outside the patient’s mouth and then cemented into place. After the decay is removed and the cavity walls are shaped, the dentist makes a wax pattern of the space. A mold is cast from the wax pattern. An inlay is made from this mold and sealed into the tooth with dental cement. Inlays and their counterparts, onlays, are conservative alternatives to crowns. They don’t require as much tooth preparation and often are more durable than amalgam fillings. Inlays cover the grooves on the surface of the molar. Onlays wrap over the tooth, covering more of its surface. Inlays used to be made entirely of gold for durability. New inlay alloys of palladium, nickel, or chromium are now frequently used. Metals are the dentists’ choice for inlays in molars. When inlays are required for visible anterior teeth, tooth-colored composites and porcelains

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Dental prostheses

KEY TERMS

Dental prostheses

are used. Reinforced porcelain and Lucite porcelain are durable but may not be suitable for patients who grind their teeth. Composites are also used in fillings. Crowns A prosthetic crown replaces the outer portion of the tooth to protect and strengthen it. This protection becomes necessary when a tooth cracks, has its entire structure weakened by decay, or becomes brittle after a root canal. Crowns can also cover dental implants or abutment (adjacent) teeth when fitting a bridge. Crowns can also cover discolored or otherwise aesthetically displeasing teeth. Cosmetic dentistry does not use crowns as much as it once did. Crowns, though aesthetically pleasing, require more radical dental techniques. Dentists are opting for more conservative methods such as bleaching, bonding, or veneers. The dentist first removes the decay, and the tooth is then prepared for a crown. It may be tapered on the outside edges to a peg, reinforced with a cast metal core, or rebuilt with both a cast metal core and a post. An impression of the prepared tooth and the teeth next to it is made. A retraction cord is placed around the tooth in order to get the impression medium under the gum where the crown will be fitted. The dental technician will create a new crown, using a cast made from this impression. The technique the technician uses is called lost wax casting. A wax model is made of the crown. Another mold is made around the wax model and both are fired in a kiln. The wax melts, leaving an opening into which a restorative material can be poured. The crown may be made of gold or stainless steel alone, metal with a veneer of tooth-colored porcelain or resin, or of porcelain or resin alone. The finished crown is then placed over the prepared tooth, adjusted, and cemented into place. When a tooth has had a root canal and the root has been filled, the tooth may not be strong. Post crowns are used in these cases. The tooth is leveled at the gum line and a stainless steel or gold post is fitted into the root canal. This post can then receive the new crown and hold it in place. For other patients, it may be desirable to implant the crown. In this case, a steel post is embedded in the patient’s jawbone. It is left in place until the bone adheres to the post. The post is exposed and the crown is made and fitted. New computerized techniques are making the restoration process faster and more accurate. Chairside Economical Restoration of Esthetic Ceramics (CEREC) uses a computer system that allows the dentist to create 702

ceramic crowns, inlays, and onlays, in one sitting. The tooth is prepared as usual but impressions are made digitally, using a hand-held camera. These photographs are converted to 3-D images on the computer screen, thus eliminating the need to take a physical impression of the patient’s teeth. The dentist uses special 3-D CAD/CAM software to design the crown. A milling system attached to the CEREC machine is able to make a ceramic crown in 10 to 15 minutes. Provided they are well taken care of, crowns can last 5–15 years or more. Bridges Bridges fill in the spaces caused by missing teeth. They prevent the remaining teeth from shifting and provide a more stable surface for chewing. If the gap is not filled, the other teeth shift, affecting the patient’s bite (occlusion), which sometimes produces pain in the jaw joint. As the teeth move and become crooked, they also become more difficult to keep clean. The risk of tooth decay and gum disease rises, increasing the likelihood that additional teeth will be lost. A bridge is inserted to prevent this from happening. Bridges are made of a metal framework and one or more artificial teeth (pontics), which are anchored to adjacent teeth. The abutment teeth carry the pressure when the patient chews food. Bridges can be removable or fixed (permanent). Removable bridges are attached to the abutment teeth by wires or precision attachments. Fixed bridges are attached to permanent crowns placed on abutment teeth. There are two types of fixed bridges, the crown-and-bridge design and the Maryland Bridge. A Maryland Bridge does not have crowns. The backs of the abutment teeth are reduced slightly and small wing-like appendages on the bridge are cemented to the back of the abutment teeth. When the adjacent teeth are not strong enough to support a bridge, a two-implant bridge is required. This type of bridge takes longer for the permanent bridge to be fitted because of the necessity for the gums to heal. Posts are surgically implanted into the patient’s bone and the gum closed. It takes several weeks for the bone to attach to the posts. The posts are re-exposed and the bridge is made to fit. It is then cemented in place. Implants Dental implants are hard plastic or metal fixtures surgically embedded through the soft tissue into the jawbone that will act as artificial roots or anchors for a prosthetic tooth. Over time, bone will grow around these fixtures, firmly anchoring them. The implant posts are then surgically exposed and an artificial tooth is crafted and

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fitted over these anchors. Implants may also serve as stable abutments for bridges, partial dentures, or over-dentures. Dental implants may be the best choice for patients who have denture intolerance or who cannot chew food properly with other prostheses. Partial dentures A partial denture is similar to a bridge in that it fills a gap left by missing teeth. It is a removable dental appliance consisting of artificial teeth fitted onto a metal frame, which attaches to an abutment tooth or teeth, with a metal clasp or precision attachment. A partial denture is often used at the end of a row of natural teeth, where there is only one abutment tooth. The pressure exerted by chewing is shared by the abutment tooth and the soft tissues of the gum ridge beneath the appliance. Complete dentures Complete dentures may be worn when all of the top or bottom teeth have been lost. A complete denture consists of artificial teeth mounted in a plastic base molded to fit the remaining oral anatomy. It may or may not be held in place with a denture adhesive. Removable implant supported over-denture Some people cannot wear dentures because they cannot tolerate having a foreign substance in their mouths. Others simply can no longer wear dentures because of serious bone loss. In response to this denture intolerance, a removal implant supported over-denture may be the best solution. Implant anchors may be installed in either the upper or lower dental arch or both. Five or six implants are anchored into the bone of the upper arch and four or five are placed in the lower arch. Each group of jaw implants is connected by a stabilizing bar. A custom-made over-denture is placed over the bar by means of a silicone gasket, which holds the denture in place and provides a cushion between the denture and the implants. For patients with Parkinson’s disease, telescopic attachments are added to the over-denture that have the ability to adjust to varying pressures within the mouth, allowing these patients to chew better.

Preparation Before a restoration is placed in the mouth, the dentist removes all traces of decay or damage and shapes the remaining tooth structure to receive the restoration. Impressions are taken of the mouth and models are created from which the dental prostheses are made. When bridges or crowns are necessary, the tooth or teeth that are to receive the crowns are shaped into posts or pegs.

False teeth. (AP/Wide World Photos. Reproduced by permission.)

Prostheses are made up in a laboratory using a model of the tooth structure. Temporary crowns and bridges are installed until the permanent restoration is delivered by the laboratory.

Aftercare Temporary crowns or bridges must stay in place until the permanent restorations have been fitted to the patient’s mouth. Dentists and dental assistants educate the patient about ways to keep the temporary in place, e.g. avoiding hard foods, gum, and other sticky or chewy foods. If possible, the dental assistant and dentist encourage the patient to avoid eating food on the side of the mouth where the temporary has been placed. Also, the patient is reminded to call immediately if the temporary is loosened so that it can be re-cemented. There may be some gum swelling or discomfort when prostheses are fitted, or if surgery is performed. The dentist can recommend medications or oral rinses to reduce the discomfort. Patients may also experience sensitivity to cold foods or drinks for a few weeks after a crown, bridge, or inlay is placed. Patients are urged to maintain normal oral hygiene while they wear a temporary, and after the actual the crown or bridgeis in place. Dental prostheses, especially partial and full dentures, may take several weeks to adjust to. Inserting and removing dentures and other removable appliances takes practice. Speaking clearly may be difficult at first, but this usually passes with continued usage. Eating may also feel awkward. The patient should begin by eating small pieces of soft foods. Very hard or sticky foods should be avoided. Care should also be taken when eating hot food

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or food with bones, since artificial prostheses may make the mouth less sensitive to hard objects and hot food. Also, patients may experience a reduced sense of taste, since teeth act as taste sensors. Many patients will eat a lot of very spicy, salty, or sweet foods because they can taste them better. Since it is important to include a variety of foods in the diet so that proper nutritional needs are met, it may be necessary to adjust seasonings to counter the blandness patients may be experiencing. Permanent prostheses should be cleaned as regularly as real teeth. Specialty brushes and floss threaders may be used to remove plaque and food from around crowns and bridges. Full or partial dentures should be removed and brushed daily with a specially designed brush and a denture cleaner or other mild soap. Optimally, full and partial dentures should be removed at night and soaked in a cleaning solution. This allows the soft tissues in the mouth to recover from the pressures of the prostheses. The solution will preserve the denture material, since it may shrink or warp if it dries out. At this time, patients should also clean their gums to increase blood circulation and maintain healthy bones and gums. The patient should see the dentist for an adjustment if there is any discomfort or irritation resulting from a prosthesis. Otherwise, the patient should see the dentist at least twice a year for an oral examination. If the patient has had several teeth extracted before dentures were installed, these prostheses should be adjusted within the first six months after the dentures have been fitted. Patients should also expect to have their full dentures adjusted if they lose or gain ten pounds or more. Also, dentures may need to be relined or replaced every five to ten years.

Complications Restoration procedures typically require local anesthesia. In some cases, the patient may require general anesthesia because the procedures involve gum surgery or the extraction of several teeth. Some people may have allergic reactions to either kind of anesthesia. A very small number of people are allergic to one or more of the metals or acrylics used in dental restorations. In most cases, the dentist can use another material. Surgery is an invasive procedure. The risk of trauma or infection is always present, though it is often a minor risk. The patient may commonly experience swelling, nausea, pain, or bleeding. When these symptoms are prolonged or fever is present, there may be infection. Rarely, nerve disturbances or bone fractures may occur. Some patients experience speech difficulties when they have dental prostheses, especially with full dentures 704

or several implants. Usually, this occurs during the first weeks after they have been fitted with prostheses for the maxillary or upper jaw bone. Once patients adapt to the prostheses, this problem disappears.

Results A well-made dental prosthesis should feel comfortable and last a relatively long time with proper care. Artificial dental restorations only approximate the original tooth, however. They will never feel as comfortable or function as well as natural teeth. It is better, therefore, to prevent the need for dental prostheses to replace teeth. They are expensive, may require many appointments, and still need careful cleaning and attention.

Health care team roles The dentist is crucial in diagnosing a patient’s particular dental needs and determining the correct remedy. The dentist will prepare a patient’s teeth for dental prostheses. Often, this requires a great deal of skill and structural knowledge in order to remove enough tooth material for the prosthesis to fit, yet leave enough architecture within the tooth in order to stabilize the restoration. The dental technician prepares the dental prosthesis so that it will fit the prepared tooth and be compatible with the rest of the patient’s mouth structure. The technician is part scientist and part artist and is able to craft natural-looking teeth that match the patient’s mouth and facial features. The dental assistant prepares the patient and the patient’s teeth for the dentist. The dental assistant takes impressions of the patient’s teeth and gums and prepares study models to aid the dentist in diagnosis and the dental technician in creating life-like prostheses that function comfortably in the patient’s mouth. Resources BOOKS

“Dentistry in Medicine: Dental Restorations and Appliances.” In The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, Robert Berkow, and Mark Burs. 17th ed. Rahway, NJ: Merck Research Laboratories, 1999. Shillingburg, Herbert T., Jr., Sumiya Hobo, and Lowell D. Whitsett. Fundamentals of Fixed Prosthodontics. Chicago: Quintessence Pub. Co, 1997. PERIODICALS

Carter, Ann. “Denture Care.” Clinical Reference Systems (Annual 2000): 467. “Custom-Made Dentures Can Improve Chewing Ability.” Health & Medicine Week (January 15, 2001): 23.

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Abutment tooth—A healthy tooth or a crowned one that stabilizes a bridge or partial denture. Anesthesia—A condition created by drugs that produces a loss of sensation, particularly pain. General anesthesia produces unconsciousness, a local anesthesic only results in localized numbness. Bridge—An appliance of one or more artificial teeth anchored by crowns onto the adjacent teeth. Complete denture—A full set of upper or lower teeth, mounted in a plastic base. Dentures are also called false teeth. Crown—A protective shell that fits over a prepared tooth in order to restore its function. Inlay—A filling that is made outside the tooth and then cemented into place. Occlusion—The way upper and lower teeth fit together during biting and chewing. Onlay—A restoration that covers the upper surface of a tooth. It is bigger than a filling but smaller than a crown. Pontic—An artificial tooth suspended between two prosthetic crowns to fill a space left by a missing tooth.

“Denture Wearers at Risk for Poor Nutrition.” Tufts University Health & Nutrition Letter 18(July 2000): 3. Doyle, Audrey. “Digital Dentistry.” Computer Graphics World 23(October 2000): 50. “Technology Triggering Brighter Smiles.” USA Today, v. 129, no. 2666 (November 2000): 7. ORGANIZATIONS

Academy of General Dentistry, Suite 1200, 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-4300. . American Dental Association, 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-2500. . OTHER

“Upper Jaw Implants.” Dentistry Online. . (May 1, 2001)

Janie F. Franz

Dental radiographs see Dental x rays

Definition There are nine dental specialties approved by the Council on Dental Education and Licensure of the American Dental Association (ADA). These are: • Dental public health: Dental public health is the dental specialty devoted to promoting public dental health and preventing and controlling dental diseases through community and public education. • Endodontics: Endodontics is the dental specialty focused on the morphology, physiology, and pathology of the periradicular (tooth root) tissues and human dental pulp. • Oral and maxillofacial pathology: Oral and maxillofacial pathology deals with the nature, identification, and management of diseases affecting the regions of the mouth, jaw and adjacent parts of the face. • Oral and maxillofacial surgery: Oral and maxillofacial surgery is the dental specialty that focuses on the diagnosis, surgical, and related treatment of diseases, injuries and deficiencies of the hard and soft tissues of the oral and maxillofacial regions. These specialists address functional and esthetic aspects of the areas treated. • Orthodontics and dentofacial orthopedics: Orthodontics and dentofacial orthopedics is the specialty concerned with guiding and correcting children’s and adults dentofacial structures. • Pediatric dentistry: Pediatric dentistry is the dental specialty that is devoted to providing primary and comprehensive preventive and therapeutic dental health care from infancy through adolescence. Pediatric dentists also provide dental care to children with special health care needs. • Periodontics: Periodontics involves the prevention, diagnosis, and treatment of diseases affecting the tissues supporting and surrounding the teeth. The specialty also focuses on the maintenance of healthy gums and supporting dental tissues. • Prosthodontics: Prosthodontics is the specialty concerned with the restoration of natural and replacement teeth, as well as contiguous oral and maxillofacial tissues. • Oral and maxillofacial radiology: No definition has yet been approved by the ADA House of Delegates for this newly granted dental specialty. However, these specialists use imaging techniques to assist general dentists and other oral health specialists in the diagnostic assessment of diseases of the head and neck.

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Dental specialties

KEY TERMS

Dental specialties

While there are overlapping responsibilities among the specialties, each focuses on an aspect of the oral cavity, maxillofacial area, or adjacent associated structures.

Description According to the ADA, about 20% of all dentists practice a dental specialty, while the rest remain general dentists. Orthodontics and dentofacial orthopedics and oral and maxillofacial surgery make up nearly half of all specialties. Dental public health specialists view the community, rather than the individual, as their patient. Their roles are to educate the public, using applied dental research, and initiate community-wide dental care and preventive programs. Endodontics encompasses basic and clinical sciences of normal pulp biology and the causes, diagnosis, prevention, and treatment of diseases and injuries to the pulp and associated periradicular conditions. Endodontists specialize in root canal treatments to remove damaged tissue from inside tooth root canals. Root canal treatment, a nonsurgical endodontic treatment, treats the soft inner tissue of the tooth, called the pulp, when it becomes inflamed or infected. During a root canal, endodontists remove the damaged pulp, clean the area and fill and seal it to preserve the tooth. Surgical procedures performed by endodontists include apicoectomy, which removes infection or inflammation of the bony area surrounding the tooth’s end. Oral and maxillofacial pathologists research the causes, processes, and effects of diseases that affect the oral and maxillofacial regions, which include the head, face, mouth, teeth, gums, jaws, and neck. These specialists use clinical, radiographic, microscopic, biochemical, and other examinations to research and diagnose disease. The practice of oral and maxillofacial pathology includes research; clinical, radiographic, microscopic, biochemical or other disease diagnosis; and patient management. Oral and maxillofacial surgeons treat patients who have problems with wisdom teeth, facial pain and misaligned jaws. They treat accident victims with facial injuries, perform reconstructive and dental implant surgery, offer treatments for tumors and cysts of the jaws, and specialize in functional and cosmetic conditions of the head, face, mouth, teeth, gums, jaws, and neck. Oral and maxillofacial surgeons also offer preventive care of the teeth, mouth, jaws, and facial structures. These specialists offer a wide variety of surgical procedures performed in the office and hospital, including dentoalveolar surgery to treat impacted teeth and reconstructive surgery to address inadequate bone structure of 706

the upper or lower jaws, which can result from injury, some types of surgery, and dentures. They place dental implants, which are an option for replacing missing teeth, and treat facial infections, which can develop into lifethreatening conditions if not addressed. Oral and maxillofacial surgeons are often called in to treat trauma of the face, jaws, mouth, and teeth, often from injuries such as falls, as well as facial pain from such things as temporomandibular joint (TMJ) disorders. Other conditions treated by oral and maxillofacial surgeons include deformities in skeletal growth between the upper and lower jaws, which can affect chewing and swallowing, and snoring or obstructive sleep apnea, a condition that can lead to excessive daytime sleepiness. Not all procedures performed by oral and maxillofacial surgeons are covered by dental or health insurance because they also offer some cosmetic procedures of the face, mouth, and neck. Orthodontists and dentofacial orthopedic specialists specialize in diagnosing, preventing, and treating dental and facial irregularities, known as malocclusions. Orthodontists represent about 6% of all dentists. Orthodontists treat children and adults. The American Association of Orthodontists recommend that all children have an orthodontic screening no later than age seven. Malocclusions are often inherited but can be caused by trauma, pacifier sucking, airway obstruction, dental disease, or premature loss of primary or permanent teeth. Orthodontists most commonly treat crowding of the teeth, overbites, open bites (when upper and lower incisor teeth do not touch when biting down), spacing problems, crossbite and underbites, or lower jaw protrusion. Orthodontic treatment, often involving the placement of braces, helps not only cosmetically, but also functionally. Pediatric dentists provide primary and specialty oral care for healthy, normal children, as well as those with special needs. Much of what the pediatric dentist does involves educating parents and children. The pediatric dentist will advise parents about thumb sucking and pacifier habits, dental decay in the early years, proper brushing habits, bottle and breast-feeding, and more. In a child’s later years, they’ll advise children and their parents about protecting teeth during sports and other preventive dental issues. Pediatric dentists offer techniques that can protect children’s teeth, such as dental sealants, which fill the crevices on the surfaces of the teeth to protect teeth from decay. Periodontists specialize in preventing, diagnosing, and treating periodontal disease. Periodontal diseases are bacterial infections of the tissues around the tooth, which, if untreated, can result in tooth loss. Periodontists place dental implants, which replace missing teeth and look

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Prosthodontists understand dental laboratory procedures and work closely with dental technicians to create comfortable and attractive custom-made prostheses for patients. Prosthodontists offer patients options for replacing missing teeth. Sometimes this involves the placement of dentures or fixed bridges, while other patients prefer dental implants. Prosthodontists receive training in diverse dental conditions, including complex care management involving many specialties, post-oral cancer reconstruction, some children’s dental problems, jaw joint conditions, traumatic injuries, and snoring and sleep disorders. Prosthodontists are also trained in some types of cosmetic dentistry, including bleaching techniques, tooth bonding, and veneers. Oral and maxillofacial radiologists are dentists who specialize in the use of imaging and other technologies to diagnose and manage dental and associated diseases. They also advise state agencies and dental professionals about regulatory compliance in the use of and advances in radiologic technology.

Work settings Dentists work in private practice offices, public hospitals and clinics, for the Federal Government, and in dental research.

Education and training Most dentists go through three years or more of undergraduate school with an additional four years of dental school to become a general dentist. All dentists graduate from dental school with a degree in general dentistry, receiving either the DMD (Doctor of Dental Medicine) or DDS (Doctor of Dental Surgery) designation. While most schools today award DDSs, there is no difference in these degrees for general dentistry. Dental specialists must then undergo additional postgraduate training to become a dental specialist. About 17 states require dentists to achieve specialty licenses before practicing as specialists. Dental public health specialists must successfully complete two years of academic study in a program

accredited by the Commission on Dental Accreditation leading to a graduate degree in public health, or complete two or more years of dental public health advanced education by a non-U.S. institution followed by completion of an accredited U.S. residency dental public health program. Endodontists possess advanced surgical and nonsurgical skills that allow them to treat routine and complex cases. Endodontists attend two- or three-year advanced dental school endodontic programs. Orthodontists and dentofacial orthopedic specialists must successfully complete a two- to three-year residency program of advanced education in orthodontics after graduating from a general dentistry program accredited by the Commission on Dental Accreditation of the ADA. Through their advanced training, orthodontists acquire the skills necessary to manage tooth movements and guide facial development. Oral and maxillofacial surgeons undergo four years or more of postdoctoral, hospital-based surgical residency training after graduating from a four-year dental school program. Their education intensity is similar to that of internal medicine physicians and general surgeons. Pediatric dentists need two to three years of specialty training following dental school to learn about children’s dental problems and how to educate parents and children about avoiding these problems. They also learn about the care of special needs children, including hospitalized, handicapped, and chronically ill children. Periodontists receive three years of periodontal training after graduating from dental school. Prosthodontists receive three years of specialized training in an American Dental Association (ADA) accredited graduate education program after completing dental school. Oral and maxillofacial radiology programs are between two and three years long.

Advanced education and training All dental specialists can attend continuing education courses to keep up with research, clinical procedures, and technology. They can also apply to become board certified in their dental specialties.

Future outlook While, the dental profession is expected to experience slower than average growth through 2008 because more people are avoiding problems associated with tooth decay, the demand for specialists could rise. Babyboomers coming into middle age will require complicated work, including bridges. The elderly will be more

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and feel like natural teeth, and they perform periodontal surgery used to treat severe cases of periodontal disease. While simple procedures might suffice to remove the plaque and calculus below the gum line and remove bacteria, surgical procedures are often necessary if periodontal disease has caused deep pockets in the gums and loss of supporting bone structure. Cosmetic periodontal procedures include treatments to improve a gummy smile, as well as treatment to correct long teeth, or receding gums.

Dental trauma

American Association of Endodontists. 211 E. Chicago Ave., Suite 1100. Chicago, IL 60611-2691. (800) 872-3636. <www.aae.org>.

KEY TERMS Calculus—Calcified deposits that have formed around teeth. Dentition—The natural teeth. Dentofacial—Relating to the dentition, or natural teeth. Etiology—The science of disease origins and cycles. Human dental pulp—The soft, moist, coherent solid tissue within the pulp cavity of the tooth. Malocclusion—Bad bite. Maxillofacial—The area of the jaws and face. Morphology—The study of the configuration or structure. Pathology—The study of the nature and cause of diseases and the changes produced by them.

American Association of Oral and Maxillofacial Surgeons. 9700 W. Bryn Mawr Avenue, Rosemont, Illinois 600185701. (847) 673-6200. <www.aaoms.org>. American Association of Orthodontists. 401 N. Lindbergh Blvd., St. Louis, MO 63141-7816. 314-993-1700. <www.aaortho.org>. American Association of Public Health Dentistry. 1321 N.W. 47th Terrace, Gainesville, FL 32605. . American College of Prosthodontists. 211 East Chicago Ave., Suite 1000, Chicago, IL 60611. (312) 573-1260. <www.prosthodontics.org>. American Dental Association. 211 E. Chicago Ave., Chicago, IL 60611. (312) 440-2500. <www.ada.org>. OTHER

American Dental Association. Dentistry Definitions. <www.ada.org> (page updated October 5, 2000).

Periradicular tissues—The tissue around the top of a tooth root.

Lisette Hilton

Physiology—The science that looks at normal life processes (functions and activities) of organisms. Temporomandibular joint (TMJ)—The joint of the lower jaw.

Dental trauma likely to keep their teeth into old age and also will need complex procedures. Future general dental care will focus more on prevention and education. Resources BOOKS

Occupational Outlook Handbook. Washington, DC: U.S. Department of Labor, Bureau of Labor Statistics, 2000. . ORGANIZATIONS

American Academy of Oral and Maxillofacial Pathology. 710 E. Ogden Ave., Suite 600, Naperville, IL 60563-8614. (888) 552-2667. <www.aaomp.org>. American Academy of Oral and Maxillofacial Radiology. PO Box 55722, Jackson, MS 39296. (601) 934-6060. <www.aaomr.org>. American Academy of Pediatric Dentistry. 211 East Chicago Ave., Suite 700, Chicago, IL 60611-2663. (312) 3372169. <www.aapd.org>. American Academy of Periodontology. 737 N. Michigan Ave., Suite 800, Chicago, IL 60611. (312) 573-3256. <www.perio.org>.

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Definition Dental trauma is an injury to the mouth and teeth, including oral structures such as the lips, tongue and cheeks.

Description Dental trauma can occur during contact sports, motor vehicle accidents, falling and hitting the face, fighting and/or from untreated tooth decay. It can be caused by physical abuse or domestic violence.

Causes and symptoms Injuries to a broken or knocked out (evulsed) tooth can cause severe pain. If the lower jawbone is cracked or broken, the patient will be unable to move the jawbone without pain and discomfort. Broken fillings or old crowns are susceptible to decay. They can weaken and undermine the tooth structure, causing the tooth to break. This could result in sharp edges and corners that may damage the tongue tissue.

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X rays (taken to reveal the extent of dental trauma to hard tissue) together with a thorough examination, aid in finding the source of the trauma.

Treatment Tooth movement If the entire tooth is knocked out of the socket (evulsion), the tooth must be found and repositioned back in the socket. If this is done in the first 20 minutes, there is a 90% chance of tooth survival. Thirty to 60 minutes cuts the tooth survival rate to 75%. • The tooth should be picked up gently and held by the crown, not the root. • The tooth should be carefully rinsed with water; it should not be scrubbed. • The tooth should be kept moist; it should not be dried. • If possible, the tooth should be placed in the socket; if this is not possible, it should be placed in a cup of milk. If a tooth is bumped and still in the socket, but in the wrong position (luxation), dental help should be sought immediately. The following steps should be followed, depending on the position of the tooth. • An upper tooth hanging down or lower tooth raised up (extrusion) should be repositioned in the socket using firm pressure. The tooth should then be stabilized by having the patient bite down firmly, or bite on a piece of cloth or a handkerchief. • A tooth pushed back toward the tongue or pulled forward toward the face (lateral displacement) requires repositioning by using firm pressure. This may cause severe pain and biting down on a piece of cloth or handkerchief will help alleviate some of this pain and help to stabilize the tooth. • Teeth pushed into the gum tissue or teeth that look short (intrusion) require no intervention. Repositioning may damage both tooth nerve and tissue. Broken and fractured teeth The fractured area should be cleaned, and a cold compress outside the cheek area should be applied. Dental help should be sought promptly. If a piece of the outer tooth has chipped off, but the inner soft tissue core (pulp) is undisturbed, the rough edges may be smoothed by the dentist and a simple filling placed. If most of the tooth is missing, but the pulp is not damaged, the tooth will require a protective covering with a crown. If the pulp has been damaged, the tooth will require root canal

treatment and a crown. A tooth fractured below the gumline will require root canal treatment and protective restoration. A tooth with little remaining structure to retain a crown may have to be removed (extraction). Cuts, abscesses, and pain Cut lips, gums, or tongue require mild rinsing with cold water to remove debris. A cold compress should be applied to the injured area. Most cuts and abrasions are minor; a dental visit is not required. Dental care, however, should be sought if bleeding does not stop and the cut is deep. Pain and swelling can be controlled by ibuprofen (e.g., Advil, Motrin), which is an anti-inflammatory and a painkiller. Abscesses and swollen gums are due to infection in the gum tissue or bone; ice should be placed on the swollen cheek to alleviate discomfort. Antibiotics and painkillers are generally needed to fight infection. If left untreated, the local infection can enter the bloodstream, causing serious illness. It could become life threatening in some cases. Treatment for the cause of an abscess should also be addressed. A periodontal abscess requires therapeutic sealing and root planing. An endodontic abscess requires a root canal and sometimes an apicoectomy (surgical removal of the tooth root). Severe pain is caused mainly by trauma, but can be caused also by gum abscesses, tooth infection, bone infection, and some dental procedures. Prompt dental care can alleviate worries and aid in pain control. With jawbone injuries, the jaw should not be moved. A handkerchief or towel should be tied around the jaw and over the head to secure the jaw in place. Immediate dental care should be sought. Severe pain may stem from temporomandibular joint (TMJ) disorders or trigeminal neuralgia.

Prognosis The key to a good prognosis for a dental trauma is taking quick steps, remaining calm and getting dental attention within the first 20 minutes. Prevention is the best method.

Health care team roles The dentist may delegate treatment to other staff members (e.g., registered dental assistants), who can take x rays and comfort the patient, while the office manager takes care of all financial matters and billing questions. The registered dental hygienist may administer an anesthetic agent where needed. All team members can alleviate patient fears during a trauma.

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Diagnosis

Dental x rays

Resources

KEY TERMS

ORGANIZATIONS

Crown—1. The natural part of the tooth covered by enamel. 2. A restorative crown is a protective shell that fits over a prepared tooth. Eruption—The process of a tooth breaking through the gum tissue to grow into place in the mouth. Evulsion—The forceful, and usually accidental, removal of a tooth from its socket in the bone. Extraction—The surgical removal of a tooth from its socket in the bone. Intrusion—A condition in which a tooth is forced upward into the bone tissue by a force outside the mouth. Lateral displacement—A condition in which a tooth is forced out of alignment forward or backward, but remains in its socket.

American Academy of Sports Dentistry. 211 East Chicago Avenue, Ste. 700, Chicago, IL 60611-2616. (312) 3372169. . American Dental Association 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-2500. . PERIODICALS

Padilla, Ray, DDS. “Oral/Facial Injury Prevention, Treatment and Related Topics” Humboldt-Del Norte Dental Society News (5 January 2001): 3-4. OTHER

Dental Emergencies Television show clip. ADA Dental Minutes, October 12, 2000. Howell, Maria Lopez “Dental Emergencies.” ADA Dental Emergencies Online, 2001. (Accessed February 2001).

Cindy F. Ovard, RDA

Luxation—The movement of a tooth still in its bony socket. Pulp—The innermost soft tissue of a tooth containing blood vessels, lymphatics, and nerves. Root canal treatment—The process of removing diseased or damaged pulp from a tooth, then filling and sealing the pulp chamber and root canals. Also known as endodontic therapy.

Prevention According to the study by the American Academy of Sports Dentistry, most dental traumas can be avoided if mouthguards are worn. They recommend that athletes, regardless of their age or gender, use mouth guards where facial impact is possible. The American Dental Association’s February 2000 news press release recommended preventive measures for avoiding a dental trauma: • Yearly dental exams (including x rays). • Teeth should be brushed and flossed thoroughly at least once a day. • A mouthguard and helmet should be worn while playing all contact sports (football, soccer, hockey, baseball, boxing, basketball). • A seatbelt should always be worn when in a moving vehicle. • Foreign objects (pencils, fingernails, pens) should be kept out of the mouth. 710

Dental x rays Definition Dental x rays are pictures taken of the mouth area using high energy photons with very short wavelengths. They show the teeth and surrounding bone.

Purpose Dental x rays are effective in discovering tooth decay, broken fillings, fractured teeth, tumors, occlusal trauma, or impacted or ectopic teeth that would otherwise be unseen by the eye, in between the teeth and below the gum tissue.

Description Dental x rays are part of the dental examination for aiding in the diagnostic process. X rays are vital in the diagnosis of root canal treatment on checking the apical of the tooth and the surrounding structures for abscesses or bone loss. Without the aid of dental x rays, 60% of dental decay would be missed. Diagnostic x rays are essential in providing accurate information. The most common x rays taken are: • bitewing x rays (vertical and horizontal bitewings) • panoramic x rays

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• occlusal x rays Each is used in its own respective degree of diagnosis, with the bitewing x ray being the most common. Bitewings are the most effective in discovering tooth decay in between the teeth and on adjacent teeth. A bitewing shows only the top crown portion of the tooth structure. It is called a bitewing due to the way the patient can bite down and hold the film securely in place. The bitewing is good in diagnosing and evaluating periodontal conditions and bone levels between the teeth. They are also good in detecting tartar buildup. The panoramic (a type of film used), or panorex (brand name) is also commonly taken on the initial visit to the dental office. This type of x ray makes a complete circle of the head from one ear to the other, to produce a complete two-dimensional representation of all the teeth. This x ray will also show bone structure beneath the teeth and the temporomandibular joint (TMJ). The panoramic is the most commonly used x ray in the aid of diagnostic decisions regarding third molar extractions (wisdom teeth) for people who are edentulous (the tooth is not there/has not erupted). This special x ray, however, has its advantages and disadvantages. One advantage of the panoramic is that a broad area is imaged, showing many structures. Furthermore, the exposure level emits low radiation. The panoramic is excellent for evaluation of trauma, tooth development, and certain anomalies. A 1999 study at the University of Buffalo School of Dental Medicine demonstrated that calcifications in the carotid arteries, which were exposed on standard panoramic x rays, served as predictors of death from cardiovascular disease. The main disadvantage of panoramic x rays is that the image shown does not provide the fine detail of a bitewing x ray. The procedure for taking a panoramic x ray is also somewhat confining to the patient, as the x ray machine takes a minute or more to fully encircle the head for the complete picture. These films are not good in aiding the diagnosis of decay, bone level, and certain types of periapical pathosis. A periapical x ray is similar to a bitewing. This type of x ray shows the entire tooth area, from crown to root, and the bone surrounding the root from a side view. This type of film will reveal any root anomalies, changes in the bone and surrounding tissue, cysts, bone tumors, and abscesses. The fine detail in the periapical film is necessary in diagnosis and treatment planning, and is commonly taken during root canal treatment and crown restoration procedures.

Dental x rays Type

Purpose

Bitewing (interproximal)

Show tooth crowns, alveolar crest, and interproximal area Check for cavities, look at previous dental work, and determine any bone loss

Edentulous (toothless)

Check for residual pathologic conditions, or foreign bodies Detect retained teeth or root tips prior to denture construction

Full mouth series

Includes a number of periapical and bitewing x rays to identify conditions in the bones around the teeth and nerve tissue in the teeth Can be used as comparison for future problems

Occlusal

Shows large areas of the maxilla, mandible, or floor of the mouth Shows entire upper or lower bite and how primary or permanent teeth are developing

Periapical

View the entire tooth from root to crown and its periodontal supporting structures Evaluate bone loss, determine causes of toothaches, and assess existing dental work

Panoramic

Supplement to periapical survey but not a substitute View general tooth development, check for specific problems such as trauma or temporomandibular joint (TMJ) pain

SOURCE: Alvarez, K.H. Williams & Wilkins’ Dental Hygiene Handbook. Baltimore: Williams & Wilkins, 1998.

Occlusal films are least common. These films show the whole bite of the lower or upper jaw. Occlusal x rays, when taken, are mainly taken on children to show the eruption order of the permanent teeth. X rays pass through hard and soft tissue in the mouth. The x ray beam is blocked by denser structures, such as teeth, fillings, jaws, and bones. Teeth appear lighter because fewer x rays go through the teeth to reach the film. Cavities and gum disease appear darker (shown by a dark spot in the tooth or loss of bone structure around the tooth) because of more x-ray penetration. On the film, the white images are the dense structures.

Operation William Roentgen, a German scientist, discovered the x ray in 1895. He found that x rays are energy in the form of waves, similar to visible light. The only difference between light and x rays is that light does not have the ability to penetrate the body as x ray energy does. Light makes pictures of the outside of objects, while x rays have the ability to make pictures of the inside of objects. The name roentgen represents the amount of

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• periapical x rays

Dental x rays

Maintenance Dental x rays are essential in diagnosing and treating oral disease, abnormal tooth development, or trauma. At the initial dental examination, a full-mouth set of x rays may be taken (bitewings and panoramic). Thereafter, it is the dentist who should determine when and how often x rays will be required. Children are usually more cavity prone than adults; x rays may be taken with regard to degree of risk, or at the check-up examination every six months.

A digitized x ray shows two molar teeth cavities. (Custom Medical Stock Photo. Reproduced by permission.)

exposure given off by one single energy photon. The amount of absorbed x ray in the body is a unit called a rad. A unit called “rem” accounts for the difference in biological effectiveness of different types of radiation, such as secondary radiation, or cosmic radiation. One rem equals one rad. One rad equals one R and one thousand milliroentgens, more commonly known as mrad; it is equal to one roentgen (R). Research conducted in 2000 by the Idaho Radiation Network sets a maximum permissible x ray dose for one year at 5R (roentgens). A full mouth set of dental x rays consists of 18 to 20 films (bitewings, periapicals, occlusalsm and panoramic x rays). The amount of radiation for receiving the full-mouth set of x rays is 10 to 20 mrads (milliroentgens). The benefits derived from x rays greatly outweigh the radiation concerns. In 1999, the National Council on Radiation Protection reported that the amount of radiation an average person receives each year from background sources (e.g., outer space, materials in the earth, foods consumed, and naturally radioactive materials in the body) is 360 mrads. Secondary radiation consists of the radiation waves left over after the source of radiation is stopped. Most secondary waves can penetrate tissue and are the most dangerous and damaging waves from radiation. Measures taken to prevent damaging rays are:

An adult presenting a dental trauma will need x rays to diagnose what the treatment should be. More x rays may be needed depending on the treatment plan and the extent of the injury. The American Dental Association (ADA) recommends basic guidelines on taking dental x rays. On average, bitewing x rays should be taken approximately once a year. This is mainly to detect and treat any conditions early in their development. If the overall general health of the mouth is good, x rays can be taken every 18 to 24 months. The ADA also recommends that the type and frequency of dental x rays taken at an examination be based upon clinical judgment after the examination and consideration of the dental health and the general health of the patient.

Health care team roles A registered dental assistant (RDA) or registered dental hygienist (RDH) commonly takes the x rays during a dental examination. They review the health and dental history, chart, and age of the patient to be x rayed. Adjustments are made to the x-ray unit depending on the size and age of the patient. The RDA then develops and mounts the x rays and presents them to the dentist. The dentist will interpret the x rays and complete the oral examination. A treatment plan will follow.

Training

• use of lead-filled aprons to shield sensitive body parts, such as thyroid glands and gonads

An RDA and an RDH must have an x-ray certification in order to take and develop x rays. To become certified, full-mouth sets of x rays need to be taken. Knowledge of the x-ray machine unit is needed, as is the number of roentgens emitted from a variety of different x-ray machines. Furthermore, a working knowledge of angles and height of the x-ray unit is needed; this is necessary for taking fine-detailed images. Certification also requires knowledge of the principles of radiation safety.

• x ray badges worn by dental staff to monitor the amount of radiation exposure in the workplace

Classes leading to certification as an RDA or RDH are available outside the work setting. Each state has dif-

• setting radiation exposure to lower settings depending on the patient’s age, height, build and structure • use of high-speed films to minimize exposure time

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Apical—Rounded end of the root of a tooth that is embedded in hard tissue (bone); toward the apex of the root. Crown—1. The upper part of the tooth, covered by enamel. 2. A dental restoration that is a protective shell fitting over a tooth. Eruption—The process of a tooth breaking through the gum tissue to grow into place in the mouth. Pulp—The soft, innermost part of a tooth containing blood and lymph vessels, and nerves. Root canal treatment—The process of removing diseased or damaged pulp tissue from a tooth, then filling and sealing the pulp chamber and root canals.

ferent bylaws regarding x-ray licensing for technicians. The rules of the state in which one is interested in working should be consulted. Resources BOOKS

Definition Denture care is the maintenance of removable artificial teeth. Full or complete dentures replace all teeth in the upper jaw (maxilla), lower jaw (mandible), or both jaws. Partial dentures replace some teeth.

Purpose Dentures replace natural teeth lost because of a health condition or injury. The artificial teeth fit in the mouth, allowing a person to eat normally. Daily denture care by the patient helps prevent conditions such as plaque. Periodic dental appointments assure that dentures fit properly and that the patient’s mouth is healthy.

Precautions Dentures are fragile and can break if dropped. The American Dental Association (ADA) advises people to hold dentures over a towel or basin of water. The patient should not try to repair dentures. Dentures should fit, so dental adhesive should be used only in an emergency. Extended adhesive use can conceal infections. Sores

Gerry D. Westcott. “Radiology Safety.” In University of California Davis Radiology News, 2001. (January 2000). PERIODICALS

Robert Seemuth, D.D.S. “Dental Health.” New Horizons Family Dentistry (February 2001): 2-3. ORGANIZATIONS

American Dental Association. 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-2500. . University of California Davis Radiology. 178 Mark Hall, University of California, Davis, CA 95616 (530) 7523710 . OTHER

Dental x rays television clip. ADA Dental Minutes, July 30, 2000. Steve D. Rima CHP, “How Much Radiation Do You Get From Dental X Rays?” Idaho State Physics Dept. 2001. (October 2000).

Cindy F. Ovard, RDA

Dentures and partial dentures can cause sores in areas such as the jaw, below the tongue, and on the roof of the mouth (palate). Sores can swell slightly and are generally red. Poor oral hygiene and wearing dentures too long can lead to denture stomatitis (denture sore mouth). Symptoms often include an inflamed palate. The dentist may prescribe antibiotics or an antiseptic rinse. Other causes of sores include poorly fitted dentures, an uneven bite, illness, and infections. Moreover, smoking, alcoholism, or oral cancer may cause sores. Furthermore, neglected sores could stimulate the growth of excess soft tissue. Tissue should be removed and a biopsy performed to detect malignant cells.

Description People have worn dentures for thousands of years. Early material for artificial teeth included whale ivory. Today, most restorative teeth are made of plastic material such as acrylic resin. Types of dentures There are two types of complete dentures. Immediate dentures are placed in a patient’s mouth after teeth are removed. These temporary dentures allow patients to have

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Denture care

KEY TERMS

Denture care

Denture repairs averaged $51 for an adjustment, $91 for a broken denture with no teeth involved, $90 for tooth replacement, and $139 to reline dentures.

Dental prostheses Appliance type

Maintenance required for oral health

Orthodontic: fixed, removable, space maintainers

Specific plaque control instructions Orthodontic brushes Interdental aids: rubber tip, toothpick/ holders, flossthreaders, proximal brushes, single tuft brushes Fluoride application: dentrifrice, brush-on gel, gel trays Oral irrigation Store in water when not in use

Fixed partial dentures: natural teeth supported; implant supported

Toothbrushing instructions Oral irrigation Floss or yarn with threader Nonabrasive dentrifrice with fluoride (do not use acidulated fluoride with composite and porcelain restorations)

Removable partial dentures, complete dentures, and overdentures

Power-assisted brush should not be used Use a separate toothbrush for dentures and natural teeth Immerse dentures in liquid cleanser after brushing Store in water when not in use

SOURCE: Alvarez, K.H. Williams & Wilkins’ Dental Hygiene Handbook. Baltimore: Williams & Wilkins, 1998.

teeth while gums heal. Healing can take up to eight weeks. Conventional dentures are worn after gums heal. Complete dentures rest on the dental ridge, the arch in the mouth that supports teeth roots. For a partial denture, artificial teeth are attached to a base that fits on the gums. Clasps and attachments link the framework to the patient’s other teeth. An overdenture fits on the roots of natural teeth. Those teeth provide stability and support. Costs for care At-home denture care involves traditional oral hygiene and denture cleaning. In the spring of 2001, athome denture products such as cleansers and toothpaste cost $7 or less. Denture care also includes dental appointments. In the United States in 2000, the average complete denture cost about $874 for the upper arch and $900 for lower arch, according to information compiled by . That information was based on statistics from sources including the ADA and the U.S. Bureau of Labor Statistics. An acrylic partial denture cost averaged $632, while a metal partial costs $983. 714

Dental plans may cover some costs. For example, the 2000 Delta Dental Plan of California assessed a patient co-pay of $395 for the upper or lower complete denture, and $495 for an immediate denture for one jaw. The copay for one partial was $300 or $395, with the higher cost for a metal framework. Repair co-pays included $20 for adjustments, $50 for repairing the denture base, and $25 for a tooth replacement. The plan allows one relining per denture in a year. The chairside reline cost was $50 per denture and $150 for laboratory relining.

Preparation The process for making dentures generally starts with the dentist taking a wax impression of the patient’s mouth. A material similar to plaster is poured into the impression to make a model of the teeth. The plaster model is sent to a lab, where a wax denture is made. The dentist fits this denture on the patient and then sends it to the lab where the permanent denture is created.

Aftercare The dental team educates new denture wearers about how to adjust to restorative teeth and clean them. Dentures should be rinsed to remove food particles. Then the patient brushes natural teeth and dentures to removes plaque and food. The ADA recommends using a toothbrush recommended for dentures or a soft bristle brush. Dentures can be cleaned with denture cleansers bearing the ADA Seal of Acceptance, mild liquid dish soap, or hand soap. The new denture wearer is usually advised to wear the full denture most or all of the time. After an adjustment period, the dentist generally tells the patient to take the dentures out before bedtime. This gives the gums a chance to rest and promotes oral health, according to the ADA. When removed, dentures are soaked in water or a cleanser solution.

Complications Bones and gums may shrink, especially during the first six months after teeth are removed. When shrinkage occurs, the dentist may need to rebase or reline the immediate dentures. The new denture wearer may experience soreness. This is caused by the pressure of hard dentures on soft tis-

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The patient may also experience a temporary increase in saliva flow. If any symptoms persist, patients should contact their dentists.

Instruction for patients with dentures Item

Important instruction

Dental hygiene

Throughly clean dentures twice each day by immersing dentures in chemical solution and brushing for plaque removal; rinse throughly. It is preferable to leave the dentures out while sleeping, or for 6–8 hours during the day. Brush and massage the gums to clean away plaque and debris and stimulate circulation.

Denture storage

After cleaning, store the dentures in water in a covered container when they are not being worn. Keep the container in a safe place inaccessible to children or house pets.

Eating

New denture wearers should cut food into small pieces, avoid foods that need incising, and avoid raw vegetables, fibrous meats, and sticky foods until experience has been gained. Practiced denture wearers may select a variety of foods, but should not expect the same efficiency as with the natural teeth. Use the canine and premolar area to bite food, and push back as the food is incised; do not pull or tear the food in a forward direction. Take small portions and try to chew with some food on each side at the same time to stablize the denture.

Over-the-counter products

Consult the dentist for advice about all denture problems, and before buying self-reline materials, adhesives, or other additives. Never attempt to alter the denture for relief of discomfort.

Speaking

Speak slowly and quietly. Practice by reading aloud at home, preferably in front of a mirror, and repeat and practice words that seem the most difficult.

Results After a patient adjusts to new dentures, the person should have no trouble eating or speaking. Subsequently, modifications to dentures may be required because the shape of the mouth changes over time as gums recede or sink. Dental adjustments include: • Relining, adding material to reshape the denture. • Rebasing, building a new base and placing the artificial teeth on it. • Replacement of teeth. A set of dentures may need to be replaced within five to 10 years.

Health care team roles The dental team monitors the patient’s mouth health during periodic check-ups. In addition, the dental staff educates the new denture wearer about oral hygiene and how to adjust to wearing artificial teeth. Advice to new denture wearers includes: • Eat soft foods and cut them into small pieces. After adapting to dentures, add other foods to the diet. • Read aloud to adjust to speaking with dentures. • Smiling, laughing, or coughing could cause dentures to slip. Gently biting down and swallowing will reposition the dentures.

SOURCE: Alvarez, K.H. Williams & Wilkins’ Dental Hygiene Handbook. Baltimore: Williams & Wilkins, 1998.

Resources BOOKS

ORGANIZATIONS

Guerini, Vicenzo. A History of Dentistry From the Most Ancient Times Until the End of the Eighteenth Century. Boston, MA: Longwood Press, 1977. McGivney, Glen P., et al. McCracken’s Removable Partial Prosthodontics. St. Louis, MO: Mosby-Yearbook, Harcourt Health Sciences, 1999. Taintor, Jerry, and Mary Jane Taintor. The Complete Guide to Better Dental Care. New York: Facts on File, Inc., 1997. Teabord, Mark, et al, eds. Development, Function and Evolution of Teeth. New York, Cambridge UK: Cambridge University Press, 2000. Zarb, George A., et al, eds. Boucher’s Prosthodontic Treatment for Edentulous Patients. St. Louis, MO: Mosby-Yearbook, Harcourt Health Sciences, 1997.

Academy of General Dentistry. 211 E. Chicago Ave., Chicago, IL 60611. (312) 440-4300. . American College of Prosthodontists. 211 E. Chicago Ave., Suite 1000, Chicago, IL 60611. (312) 573-1260. . American Dental Association. 211 E. Chicago Ave., Chicago, IL 60611. (312) 440-2500. . Centers for Disease Control and Prevention. National Center for Chronic Disease Prevention and Health Prevention. Division of Oral Health, MS F-10. 4770 Buford Highway, NE, Atlanta, GA 30341. (888) CDC-2306. . National Institute of Dental & Craniofacial Research. National Institutes of Health. Building 45, Room 4AS-18, 45

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sue and is usually temporary. However, soreness is frequently a sign that dentures need adjusting.

Depressive disorders

• major depression

KEY TERMS

• seasonal affective disorder

Plaque—A transparent material in the mouth that contains bacteria and causes tooth decay. Prosthodontics—The area of dentistry concerned with the replacement of missing teeth.

• bipolar disorder • dysthymia • depression due to a general medical condition • postpartum depression • substance-induced depression

Center Drive MSC 6400, Bethesda, MD 20892-6400. .

Liz Swain

Dentures see Dental prostheses

Major depression Major depression can be mild, moderate or severe, and the rating of its severity is based upon the number of symptoms the person has, and how seriously these symptoms affect their lives. Typical symptoms are: • lack of interest in once-enjoyable activities

Depression see Depressive disorders

• loss or gain of weight • difficulty concentrating or making decisions • feelings of worthlessness and hopelessness • changes in sleep patterns, either insomnia or hypersomnia

Depressive disorders Definition A depressive disorder is defined by the National Institute of Mental Health (NIMH) as an illness that involves the body, mood and thoughts. It encompasses feelings of overwhelming sadness and despair that persist or intensify over time.

Description Occasional feelings of unhappiness or sadness are normal, but when such feelings dominate everyday life causing physical and mental deterioration, they are termed depressive disorders. In Caring For The Mind, The Comprehensive Guide to Mental Health, Dianne and Robert Hales state that comparing everyday blues to clinical depression is like comparing a cold to pneumonia. Nearly 19 million American adults, approximately 10% of the population, suffer from depression in any given year. Less than one of three of these will ever pursue, or receive, medical care. In a survey conducted by the National Mental Health Association, it was found that nearly half of those surveyed believed that depression was not an illness, but rather a personal emotional weakness. However depressive disorders are valid illnesses that require treatment and can literally be life-threatening: Fifteen percent of all people diagnosed as being depressed actually do commit suicide. Thirty percent may make unsuccessful attempts. Categories of depression include: 716

People with major depression may be preoccupied with death or suicide. In children, it may manifest itself as irritability or acting out. According to the National Comorbidity Survey, major depression is the single most common mental illness in the United States, affecting one in ten Americans, and women twice as often as men. Ten to 15% of people over 65 and 25% of those in nursing homes show symptoms, and NIMH estimates that better than half of elderly Americans who suffer from major depression do not receive appropriate treatment. Seasonal affective disorder (SAD) The unique characteristic of SAD is when the depression occurs. Incidences usually occur at a specific time each year. SAD can be either unipolar, showing depressive symptoms only, or bipolar, having cycles of depression and elevated mood. SAD typically begins in the autumn, when the days grow shorter, and continues through the winter, ending in the spring. A less common form begins in the spring and ends in early fall. The NIMH estimates that ten million Americans have SAD. Bipolar disorder Close to two million Americans are diagnosed as having bipolar disorder, or manic depression, a mental illness that is characterized by cycles of giddy elation and despondency. Approximately one-fifth of all depressive disorders are termed bipolar. People suffering from bipolar illnesses often first exhibit hypomania, a mild state of

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Dysthymia Dysthymia, or chronic mild depression, has been described as sadness that will not end. There has been debate among mental health professionals for several years as to whether dysthymia is a truly separate entity from major depression, and the answer remains unclear. NIMH studies have shown that three-quarters of those diagnosed woth dysthymia also had other disorders, including major depression, panic or anxiety disorders, and substance abuse. The National Comorbidity Survey suggested that approximately 6% of Americans will develop this disorder in their lifetimes. Depression due to a general medical condition Many people are not aware that physical disease can cause depression. One of the significant differences in this type of depression is that patients continue to feel good about themselves, and complain that the depression is interfering with their normal life activities. Postpartum depression It is not unusual for a new mother to have what is termed baby blues shortly after giving birth. This involves feeling sadder than usual, crying easily, and typically occurs in the first seven to 10 days after birth. However, about 1% of all new mothers develop a true mental illness, postpartum depression, between a month and a year after giving birth. The symptoms are similar to major depression, but some women may develop more serious complications, including hallucinations and delusions. Substance-induced depression Many different medications, both legal and illegal, can cause depression. Alcoholism has long been linked closely with depression, but it is now known that one in four alcoholics suffered from depression before they ever drank, and will remain depressed whether they drink again or not, unless the depression is treated.

Causes and symptoms As study of the brain and nervous system has advanced, it has become known that depression is a complicated biological process that interrupts the normal balance of neurotransmitters, or messenger chemicals such as norepinephrine or serontin. Major depression Heredity appears to be strongly linked to major depression. As a rule, the rate of depression between family members of a person suffering from major depression is one to three times higher than in families where there is none. An identical twin is 66% more likely to become depressed if the other develops the illness. However therapists can often see predictable patterns of behavior that lead to depression. Life traumas such as grief also seem to lead to major depression. Seasonal affective disorder SAD is common in northern climates. It is nearly nine times more prevalent in New Hampshire as in Florida, indicating that the altered brain chemistry that produces the depression is related to the decrease in light in northern climates during the winter. However, the cause of SAD is still under investigation. Bipolar disorder Bipolar disorders are believed to be caused by abnormal functioning of the brain. Heredity is considered a major factor. Dysthymia Like other depressions, dysthymia has been related both to hereditary chemical imbalances within the brain and to traumatic events in life, often going back to childhood. Some research has linked dysthymia to attention deficit hyperactivity disorder (ADHD) and conduct and personality disorders. Depression due to a general medical condition Among the physical illnesses capable of causing depression are cancer, heart disease, hormonal problems (such as thyroid disorders), Alzheimer’s and Parkinson’s Disease, brain tumors, head injuries, infectious illnesses, and malnutrition/vitamin deficiency. Postpartum depression This type of depression appears related to changes in hormonal chemistry that affects a woman’s brain chemistry.

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mania, in which they are often able to accomplish a great deal, go without sleep, and exhibit extreme self-confidence. As the disease progresses, they may cycle into full-blown mania, and engage in much more dangerous behavior, such as wild spending sprees, promiscuous sexual activity, substance abuse, and other self-destructive behaviors. This euphoric phase is followed by the depths of classic depression.

Depressive disorders

Diagnosis Many people go to their primary care practitioner with complaints of insomnia, lack of appetite, or other physical complaints only to discover that what they actually have is depression. A thorough physical examination is needed, including a family history of depression, the person’s use of alcohol or other drugs, and medications being taken. Psychological testing and a mental status examination may be conducted. Several clinical inventories or scales may be used to assess a patient’s mental status and determine the presence of depressive symptoms. Among these tests are: the Hamilton Depression Scale (HAM-D), Child Depression Inventory (CDI), Geriatric Depression Scale (GDS), Beck Depression Inventory (BDI), and the Zung Self-Rating Scale for Depression. These tests may be administered in an outpatient or hospital setting by a general practitioner, nurse, social worker, psychiatrist, or psychologist. The guidelines for diagnosing depression are found in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV).

Treatment Major depression, dysthymia, and seasonal affective disorder are all treated effectively with psychosocial therapy of various kinds and antidepressant medications. Antidepressants Positron emission tomography (PET) scans comparing a normal brain with that of someone with a depressive disorder. (Photo Researchers, Inc. Reproduced by permission.)

Substance-induced depression Among the substances that are capable of causing depression are: • alcohol • minor tranquilizers such as valium • heroin and other narcotics • antihistamines • anticancer drugs • steroids and corticosteroids • anti-seizure medications such as dilantin or depakot • anti-inflammatory drugs • cocaine, when its initial elevation in mood has passed • estrogen • L-dopa, a drug used to treat Parkinson’s disease 718

Antidepressant medications, without any other type of treatment, are estimated to relieve the symptoms of 60–70% of clinically depressed people. Selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine (Prozac) and sertraline (Zoloft) reduce depression by increasing levels of serotonin, a neurotransmitter. Some clinicians prefer SSRIs for treatment of dysthymic disorder. Anxiety, diarrhea, drowsiness, headache, sweating, nausea, poor sexual functioning, and insomnia are all possible side effects of SSRIs. Tricyclic antidepressants (TCAs) are older and less expensive medications than SSRIs, but they have more severe side effects, including persistent dry mouth, sedation, dizziness, and irregular heartbeat. Because of these, caution is taken when prescribing TCAs to elderly patients. TCAs include amitriptyline (Elavil), imipramine (Tofranil), and nortriptyline (Aventyl, Pamelor). A 10-day supply of TCAs is potentially lethal, so these drugs are questionable treatment options for patients at risk for suicide. Monoamine oxidase inhibitors (MAOIs) such as tranylcypromine (Parnate) and phenelzine sulfate (Nardil) block the action of monoamine oxidase, a cen-

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Heterocyclics include bupropion (Wellbutrin) and trazodone (Desyrel). Bupropion should not be prescribed for patients with seizure disorder. Side effects of the drug may include agitation, anxiety, confusion, tremor, dry mouth, fast or irregular heartbeat, headache, low blood pressure, and insomnia. Because trazodone has a sedative effect, it is useful in treating depressed patients with insomnia. Psychosocial therapy Psychotherapy explores an individual’s life to bring to light possible contributing causes of the present depression. During treatment, the therapist facilitates an awareness of thought patterns and how they developed. There are several different subtypes of psychotherapy, but all have the common goal of helping the patient develop healthy problem solving and coping skills. Electroconvulsant therapy ECT, or electroconvulsive therapy, is normally employed after other treatment options have been explored. But it may be used sooner if severe depression, suicide risk, or psychosis is present, or if the person is unable or unwilling to take medication. About half of those who do not improve from other therapies recover after having ECT. The treatment consists of a series of electrical pulses that move into the brain through electrodes on the patient’s head. ECT is given under general anesthesia and patients are administered a muscle relaxant to prevent convulsions. Although the exact mechanisms behind the success of ECT therapy are not known, it is believed that the electrical current modifies the electrochemical processes of the brain, consequently relieving depression. Headaches, muscle soreness, nausea, and confusion are possible side effects immediately following ECT. Memory loss, typically transient, is reported by ECT patients.

Alternative treatment St. John’s wort (Hypericum perforatum) is used throughout the world to treat depression. In Germany, St. John’s Wort is the most widely used antidepressant. This herbal antidepressant has few reported side effects, but some users have experienced high blood pressure, headaches, stiff neck, nausea, and vomiting. NIMH is currently involved in a three-year study of its efficacy. However, in February 2000, a public health advisory was issued by the Food and Drug Administration (FDA) stating that St. John’s wort may interact with other medications commonly prescribed for heart disease, depression, seizures, and certain cancers, as well as anti-rejection drugs used for transplant patients. Healthcare providers were advised to alert their patients to the risk of this interaction. Holistic treatment can also be very therapuetic in treating depression. Good nutrition, proper sleep, exercise, and full engagement in life are very important to a healthy mental state.

Prognosis Untreated or improperly diagnosed depression is the number one cause of suicide in the United States. Yet treatment can result in dramatic improvement for between 75–80% of patients, and should be clearly evident within three to four months. Five to 10% of patients still report depression two years after initially being treated, but there are varying reasons for this, including medication noncompliance and alcohol abuse. The risk of recurrence climbs significantly with each episode.

Prevention Education is crucial for patients with depressive disorders. They must learn to recognize symptoms and to take an active part in their treatment. Extended maintenance treatment with antidepressants may be required in some patients to prevent relapse. Physical exercise and staying connected to self-help support groups have both been shown to be effective in preventing depression. Early intervention with children with depression is effective in arresting development of more severe problems.

Phototherapy Phototherapy, or exposure to fluorescent light bulbs installed in a metal box with a plastic screen ten to twenty times brighter than indoor lighting, has proven effective in treating SAD. Phototherapy is often combined with other treatments such as medication or psychosocial therapy. The person sits in front of this light box for anywhere from one-half hour to two hours.

Health care team roles Psychiatrist Psychiatrists are licensed medical doctors who have undergone a three-year psychiatric residency. They diagnose depression, determine appropriate treatment, and provide psychotherapy and support for patients.

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tral nervous system enzyme. Patients taking MAOIs must restrict foods high in tyramine (found in red wine, aged cheeses, and meats) from their diet to avoid potentially serious hypertension.

Depressive disorders

Social workers

KEY TERMS Clinical depression—Depression that is serious enough to require psychiatric intervention and treatment. Hypersomnia—The need to sleep excessively; a symptom of dysthymic and major depressive disorder. Neurotransmitter—A chemical in the brain that transmits messages between neurons, or nerve cells. Changes in the levels of certain neurotransmitters, such as serotonin, norepinephrine, and dopamine, are thought to be related to depressive disorders. Psychomotor agitation—Disturbed physical and mental processes (fidgeting, wringing of hands, racing thoughts); a symptom of major depressive disorder. Psychomotor retardation—Slowed physical and mental processes (slowed thinking, walking, and talking); a symptom of major depressive disorder.

Education on the nature of depression, and the various treatment options available, are important adjuncts to the therapy they provide. Primary care practitioner (PCP) Though depression is a mental illness, depression may be diagnosed by primary care practitioners because depressed patients often exhibit distinct physical symptoms. Psychiatrists frequently become involved only after a consultation is requested. The importance of a psychiatric referral for further evaluation cannot be overstated. It can literally save a severely depressed person’s life. Registered nurse (RN), psychiatric nurse, or licensed practical nurse (LPN) Both RNs and LPNs must complete a prescribed nursing course and pass a state examination. RNs typically have a degree in nursing, and psychiatric nurses have additional training specific to their field. Both RNs and LPNS are the health care team members who are most involved with depressed patients in outpatient clinics and in psychiatric units, where patients at risk for suicide must be monitored. Observational skills, empathy, and the ability to listen are necessary assets for nurses. Education about depression typically comes from both physicians and nurses. 720

Social workers are usually either certified (CSW) or licensed clinical social workers (LCSW). A two-year graduate degree, specialized training that includes supervised clinical work with the mentally ill, and state licensure are typical requirements. Social workers often conduct supportive groups or programs that help people vent feelings or work on ways to better be able to cope. Mental health assistants These are staff members on inpatient psychiatric units who have been provided with special training in order to assist with the care of people with mental illness. They normally aid patients with day-to-day needs, accompany them to appointments or for walks if necessary, help deal with crises, and assist professional staff in providing care. Resources BOOKS

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th ed. Washington, DC: American Psychiatric Press, Inc., 1994. Hales, Dianne, and Hales, Robert E., M. D. Caring For the Mind: The Comprehensive Guide to Mental Health. New York: Bantam Books, 1996. Maxmen, Jerrold S., and Nicholas G. Ward. “Mood Disorders.” In Essential Psychopathology and Its Treatment, 2nd ed. New York: W.W. Norton, 1995. Thompson, Tracy. The Beast: A Reckoning with Depression. New York: G.P. Putnam, 1995. Whybrow, Peter C. A Mood Apart. New York: HarperCollins, 1997. ORGANIZATIONS

American Psychiatric Association (APA). Office of Public Affairs. 1400 K Street NW, Washington, DC 20005. (202) 682-6119. . American Psychological Association (APA). Office of Public Affairs. 750 First St. NE, Washington, DC 20002-4242. (202) 336-5700. . National Alliance for the Mentally Ill (NAMI). 200 North Glebe Road, Suite 1015, Arlington, VA 22203-3754. (800) 950-6264. . National Depressive and Manic-Depressive Association (NDMDA). 730 N. Franklin St., Suite 501, Chicago, IL 60610. (800) 826-3632. . National Institute of Mental Health (NIMH). 5600 Fishers Lane, Rm. 7C-02, Bethesda, MD 20857. (301) 443-4513. .

Joan M. Schonbeck

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Definition Developmental assessment involves the measure of a child’s attainment of physical or cognitive skills that allow continued maturation, learning, and function in society.

Purpose Developmental assessment is used to observe functional ability in children and to identify any deviations from the norm. It is used to recognize whether or not a disability may exist and if so, where the specific problem areas lie. Developmental tests provide information regarding the milestones a child has attained, and can help in determining the course of intervention to attain further milestones. Results of developmental tests may also be used to indicate the level of progress achieved after intervention, and are often used by both clinicians and researchers.

Description In addition to the use of a test with established reliability and validity, a developmental assessment should include data collection in the form of an interview, history, and clinical observation. The interview should take place with the parents/caregivers and, if age-appropriate, the child, in an informal and friendly setting. The concerns and goals of the parents and child are important to note, and information regarding the child’s developmental and medical history may be obtained at this time. In addition to the parent report, it is important to look at medical records if they are available. Information regarding the mother’s pregnancy, labor, and delivery, and the child’s medical/surgical history, health status, medications, precautions, and other items of relevance is helpful in providing a background for the assessment. Clinical observation of the child is useful in determining factors that may contribute to developmental difficulties. In addition, it is helpful to watch a child moving under his or her own volition, instead of under a therapist’s directions. Observation may include, but is not limited to: the manner in which the infant or child is held by the parent (e.g. posture, support required); preferred means of mobility (e.g. wheelchair, ambulation [walking], crawling, scooting, rolling); antigravity posture and movements; equilibrium and righting reactions; balance, including base of support; compensations; and assistance required for stability or mobility.

There are a number of assessment tools available that measure gross motor development. Some, but not all, of these tools will be summarized here. Screening tests Screening tests are the most basic form of developmental assessment tool, and are used to determine whether or not a concern exists. The Alberta Infant Motor Scale (AIMS) is used during the first year of life to identify motor delay and to evaluate maturation over time. Fiftyeight items related to posture, movement, and weight bearing in prone, supine, sitting, and standing positions take 10 to 20 minutes to observe. Researchers have found predictive validity, interrater (the consistency of the rating between different people performing the test), and testretest reliability of the AIMS to be good. In addition, there is high concurrent validity with the Peabody Developmental Motor Scales’ gross motor portion. The Miller First Step Screening Test for Evaluating Preschoolers assesses cognitive and physical function in children 35 to 74 months of age. It uses 18 games that are age-appropriate and takes approximately 20 minutes. The Denver II is a comprehensive screening test encompassing 125 items in the personal-social, fine motor-adaptive, language, and gross motor domains. The test is norm-referenced from birth to six years; however, it has been criticized for poor specificity. Motor assessments The Test of Infant Motor Performance (TIMP) consists of observation of 28 items and elicitation of 31 items in infants up to four months of age. It is found to be highly sensitive to small changes in development and valid in measuring behaviors of functional relevance. Test-retest reliability has been found to be high; more research needs to be done on predictive validity. Administration takes 25 to 45 minutes. The Movement Assessment of Infants (MAI) is a criterion-referenced test for infants in the first year of life. Sixty-five items related to muscle strength/tone, primitive reflexes, automatic reactions, and volitional movement, including quality of movement, are assessed. Researchers report that interrater and test-retest reliability is good; however, the MAI has been found to overidentify infants with motor delay (i.e. produce a high rate of false positives). The Peabody Developmental Motor Scales (PDMS) is a norm- and criterion-referenced test that examines gross and fine motor function in children from birth to 83 months (the second edition includes up to 71 months). The gross motor scale includes reflexes, balance, nonlocomotor, locomotor, and receipt and propulsion of objects. The

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Development assessment

Development assessment

fine motor scale includes grasp, hand functions, eye-hand coordination, and manual dexterity. High reliability and validity have been reported; however, criticisms of the test prompted the creation of a second edition, the PDMS-2. This edition is updated with new normative data representative of the current U.S. population. Reliability and validity were studied for gender, race, and other subgroups of the normative sample. In addition, more specific scoring criteria and illustrations were added. The Bruininks-Oseretsky Test of Motor Proficiency (BOTMP) is a norm-referenced test that examines gross and fine motor function in children aged four-and-a-half to fourteen-and-a-half years. The gross motor subtests assess speed and agility, balance, bilateral coordination, and strength. The fine motor subtests assess upper-limb coordination, speed and dexterity, response speed, and visuomotor control. Administration takes 45 to 60 minutes, and reliability (interrater and test-retest) is high. Critics of the test have pointed out, however, that some of the items, e.g. “tapping feet alternately while making circles with fingers,” do not measure skills relevant to everyday function. In addition, it is important to note that failure of items may result as much from cognitive and perceptual difficulties as from motor difficulties. The Gross Motor Function Measure (GMFM) is designed to evaluate change in motor performance over time in children with cerebral palsy. The test contains 88 items in five groups: lying and rolling; sitting; crawling and kneeling; standing; and walking, running, and jumping. Interrater and test-retest reliability have been demonstrated as high.

Assessments of functional capabilities are not necessarily developmental milestone-based; however, their use is important in determining whether or not specific disabilities exist. These disabilities may be related to mobility, transfer, self-care or social function. Examples of functional assessments include the Pediatric Evaluation of Disability Inventory (PEDI) and the Functional Independence Measure for Children (WeeFIM).

Results In a norm-referenced test, the child’s score is compared to the average of a group of children. This average is obtained by collecting scores from a large population. In a criterion-referenced test, the scores are interpreted based on absolute criteria such as the number of items performed correctly. Raw scores on tests often can be converted to age equivalent scores, standard scores, motor quotients and percentile rankings. Once scores are obtained, they must be analyzed along with the information gathered during the interview, history, and observation. Although the normative populations used for the tests are representative of the U.S. population, cultural differences in motor development need to be considered as well. All of this information may be used to guide intervention and/or identify areas of progress or concern. Once specific areas of dysfunction are noted, goals and objectives may be formulated to treat these areas.

Health care team roles

Comprehensive assessments The Bayley II consists of a norm-referenced test of motor performance (manipulation, coordination of large muscle groups, dynamic movement, postural imitation, stereognosis [the ability to recognize solid objects by touch]), and mental ability (object permanence, memory, problem solving, complex language) in children from birth to 42 months. It also contains a criterion-referenced behavior scale that looks at affect, interests, activity, and fearfulness. Test-retest and interrater reliability have been found to be higher for older ages than for younger ages with this test. This test takes approximately 45 to 60 minutes to administer. The Early Intervention Developmental Profile (EIDP) consists of six scales in the following areas: perceptual/fine motor; cognition, language, social/emotional; self-care; and gross motor development. It is designed to be administered wholly by any member of a multidisciplinary team to children from birth to 36 months. 722

Content validity, in addition to interrater and test-retest reliability, have been found to be good.

Physical and occupational therapists usually perform developmental motor assessments; however, the more comprehensive scales are often designed for administration by any or all members of the health care team. This team may include any or all of the following: physician, nurse, physical therapist, occupational therapist, speech and language pathologist, special educator, psychologist, and social worker. It is important that whoever administers the test takes care to learn the test and procedure for administration. Resources BOOKS

Campbell, Suzann K., Darl W. Vander Linden and Robert J. Palisano. Physical Therapy for Children, 2nd ed. Philadelphia: W. B. Saunders Company, 2000. Folio, M. Rhonda and Rebecca R. Fewell. Peabody Developmental Motor Scales, 2nd Edition: Examiner’s Manual. Austin, TX: PRO-ED, Inc., 2000.

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Concurrent validity—Relationship between performance on a given test and another well-established test which is purported to measure the same skills. Content validity—The likelihood that the test measures what it says it is to measure. Interrater reliability—Relationship of an individual’s score on first administration of a test to the score on second administration. Predictive validity—The likelihood that a child’s performance on the test predicts an actual behavior. Specificity—Ability of a test to identify those who do not have a disorder. Test-retest reliability—Index of agreement between two different testers for the same test.

PERIODICALS

Campbell, Suzann K. and Thubi H. A. Kolobe. “Concurrent Validity of the Test of Infant Motor Performance with the Alberta Infant Motor Scale.” Pediatric Physical Therapy 12, no. 1 (Spring 2000): 2-9. Fetters, Linda and Edward Z. Tronick. “Discriminate Power of the Alberta Infant Motor Scale and the Movement Assessment of Infants for Prediction of Peabody Gross Motor Scale Scores of Infants Exposed In Utero to Cocaine.” Pediatric Physical Therapy 12, no. 1 (Spring 2000): 16-23. Ketelaar, Marjolijn and Adri Vermeer. “Functional Motor Abilities of Children with Cerebral Palsy: A Systematic Literature Review of Assessment Measures.” Clinical Rehabilitation 12 (1998): 369-80. Koseck, Karen. “Review and Evaluation of Psychometric Properties of the Revised Bayley Scales of Infant Development.” Pediatric Physical Therapy 11, no. 4 (Winter 1999): 198-204. OTHER

Levine, Kristin J. “The Bruininks-Oseretsky Test of Motor Proficiency: Usefulness for Assessing Writing Disorders.” OT-Peds website. 1995. .

Peggy Campbell Torpey, MPT

Definition Diabetes mellitus is a condition that occurs when either the pancreas does not produce enough insulin or the body’s cells stop responding to the insulin that is produced. In either case, glucose in the blood cannot be absorbed or used by the cells of the body.

Description Diabetes has been recognized as a disease since ancient times. Egyptian papyri described its symptoms in 1550 B.C., and Hindu physicians noted 500 years later that insects were drawn to the sugary urine of people afflicted with diabetes. The disease was first named in 230 B.C. by Apollonius of Memphis, who took it from the Greek diabainein (to pass through), a description of the unquenchable thirst and copious urine produced by diabetics. It was not until the latter part of the eighteenth century that the British physician John Rollo appended the Latin term mellitus (honey-sweet) to distinguish diabetes from other diseases that caused excessive urine production. Diabetes mellitus is a chronic disease that causes serious health complications including renal failure, heart disease, stroke, blindness, and peripheral neuropathy with vascular insufficiency, putting patients at risk for gangrene and subsequent amputation of the extremities. Approximately 16 million Americans have diabetes; of these, it is estimated that around 5.4 million are undiagnosed. Diabetes afflicts 120 million people worldwide, with the World Health Organization predicting that the number will reach 300 million by 2025. Physiology Every cell in the human body requires fuel to function. The body’s primary energy source is glucose, a simple sugar resulting from the digestion of foods containing carbohydrates. Glucose from the digested food circulates in the blood as a ready energy source for any cells that need it. Insulin is a protein hormone secreted into the blood by cells in the pancreas called islets of Langerhans. Insulin bonds to a receptor site on the outside of a cell, and acts like a key to open a doorway into the cell through which glucose can enter. The liver may convert excess glucose to concentrated energy sources like glycogen or fatty acids, which are stored for later use. If there is insufficient insulin production, or when the doorway no longer recognizes the insulin key, glucose stays in the blood rather than entering the cells.

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Diabetes mellitus

KEY TERMS

Diabetes mellitus

As the level of glucose in the blood rises, a condition called hyperglycemia results. The body will try to dilute this high blood glucose level by drawing water out of the cells, pumping it into the bloodstream, and excreting it in urine. It is not unusual for those with undiagnosed diabetes to complain of constant thirst, to drink large quantities of fluids, and to urinate frequently as their bodies attempt to get rid of the extra glucose. At the same time that the body is attempting to rid itself of glucose in the blood, its cells are starving for glucose and sends signals to eat more food, giving patients tremendous appetites. To provide energy for the starving cells, the body also tries to convert fats and proteins into glucose. Breaking down these substances causes acid compounds called ketones to form in the blood and to be excreted in the urine. As ketones build up in the blood, a condition called ketoacidosis can occur. If left untreated, this condition can be life threatening, eventually leading to coma and death. Types of diabetes mellitus Type 1 diabetes, sometimes called juvenile diabetes, commonly begins in childhood or adolescence. It occurs more frequently in populations descended from northern European countries than in those from southern Europe, the Middle East, or Asia. This form of diabetes is also called insulin-dependent diabetes because people who develop it need to have insulin injections at least once a day. In this form of diabetes, the body produces little or no insulin. Its onset is sudden, and it usually–but not always—occurs in people under 30. Brittle diabetics are a subgroup of type 1 in which patients have frequent and rapid blood sugar level swings, alternating between hyper- and hypoglycemia. These patients may need several injections of different types of insulin taken at specific times during the day to maintain a blood glucose level within a fairly normal range. The more common form of diabetes is type 2, sometimes called age-onset or adult-onset diabetes. It accounts for more than 90% of all diabetes in the United States. This form occurs most often in people who are over 50, as well as those who are overweight and sedentary; it is also more common in people of Native American, Hispanic, and African-American descent. People who have migrated to Western cultures from East India, Japan, and Australian Aboriginal cultures are also more likely to develop type 2 diabetes than those who remain in their native countries. Type 2, also called noninsulin-dependent diabetes, is considered a milder form of diabetes because of its gradual onset (sometimes developing over the course of several years) and because it can often be controlled with 724

diet and oral medication. The consequences of uncontrolled and untreated type 2 diabetes, however, are as serious as those caused by type 1. Many people with type 2 diabetes are able to control their blood glucose with diet and oral medications, but for those who cannot, insulin injections may be necessary. In recent years, an alarming trend was being noted in Western culture, particularly in the United States: a tendency for children, teenagers, and young adults, particularly those who are obese, to develop this type of diabetes. Another type of diabetes is gestational diabetes, which can develop during pregnancy and generally resolves after the delivery of the baby. This diabetic condition develops during the second or third trimester in approximately 2% of pregnancies. The condition is normally treated by diet, however, insulin injections may be required for periodic exacerbation control. Women who develop diabetes during pregnancy are at higher risk for developing type 2 diabetes within five to 10 years. Diabetes may also develop as a result of or in concert with pancreatic disease, alcoholism, malnutrition, or other severe illnesses that tax the body’s immune system.

Causes and symptoms The causes of diabetes mellitus are unclear, however, there appear to be both hereditary and environmental factors involved. Research has shown that some people who develop diabetes have common genetic markers. In type 1 diabetes, the immune system is probably triggered by a virus or other microorganism that destroys the cells in the pancreas that produce insulin. Type 2 diabetes is characterized by the insulin resistance syndrome, in which peripheral adipose and muscle cells fail to respond appropriately to circulating insulin, which the pancreas produces in response to food loads. Research has now shown that the insulin resistance syndrome is closely associated with dyslipidemia, an imbalance in the ratio of total cholesterol to the cholesterol fractions of either low-density lipoproteins (bad cholesterol) or to high-density lipoproteins (good cholesterol). Untreated or inadequately treated dyslipidemia leads to atherosclerosis and eventually to the microvascular complications mentioned above. Patients with type 2 diabetes and dyslipidemia are often treated with one of the drugs from the group known as statins, in addition to oral antidiabetic agents. Age, obesity, and family history may all play a role in the development of type 2 diabetes. Symptoms may begin so gradually that a person may not be aware of them. Early signs are fatigue, extreme thirst, and frequent urination. Other symptoms may include sudden weight

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loss, slow wound healing, urinary tract infections, or blurred vision. It is not unusual for type 2 diabetes to be detected while a patient is seeing a doctor for another health concern that is actually being caused by the as-yetundiagnosed diabetes. Individuals who are at high risk of developing type 2 diabetes mellitus include those who: • Are obese (more than 20% above their ideal body weight). • Have a primary relative (immediate family member) with diabetes mellitus. • Belong to a high-risk ethnic population (African American, Native American, Hispanic, or Native Hawaiian). • Have been diagnosed with gestational diabetes or have delivered a baby weighing more than 9 lbs (4 kg). • Have been diagnosed with transient diabetes at the time of a moderate to severe systemic infection (like protracted pneumonia). • Have high blood pressure (140/90 mmHg or above). • Have a high-density lipoprotein cholesterol level less than or equal to 35 mg/dL and/or a triglyceride level greater than or equal to 250 mg/dL. • Have had impaired glucose tolerance or impaired fasting glucose on previous testing. Several common medications can impair the body’s use of insulin, causing a condition known as secondary diabetes. These medications include treatments for high blood pressure (furosemide, clonidine, and thiazide diuretics), drugs with hormonal activity (oral contraceptives, thyroid hormone, progestins, and systemic gluococorticoids), and the anti-inflammation drug indomethacin. Several drugs used to treat mood disorders can also impair glucose absorption. These drugs include haloperidol, lithium carbonate, phenothiazines, tricyclic antidepressants, and adrenergic agonists. Other medications that can cause diabetes symptoms include isoniazid, nicotinic acid, cimetidine, and heparin. Symptoms Symptoms of diabetes can develop suddenly (over days or weeks) in previously healthy children or adolescents, or can develop gradually (over several years) in overweight adults past the age of 40. The classic symptoms include fatigue, frequent urination, excessive thirst, excessive hunger, tingling of hands and feet, pruritus, and weight loss. In sudden-onset diabetes, some patients may have a “fruity” odor to their breath.

Wrinkled, dehydrated skin of a person in a diabetic coma. Untreated diabetes mellitus results in elevated blood glucose levels, causing a variety of symptoms that can culminate in a diabetic coma. (Photo Researchers, Inc. Reproduced by permission.)

Ketoacidosis, a condition that results from starvation or uncontrolled diabetes, is common in patients with type 1 diabetes. Its symptoms include abdominal pain, vomiting, tachypnea, and extreme fatigue or lethargy. Patients with ketoacidosis will also have a characteristically sweet, fruity breath odor. Left untreated, this condition may lead to coma and death. With type 2 diabetes, the condition may not become evident until the patient presents for medical treatment for some other condition. A patient may have heart disease, chronic infections of the gums and urinary tract, blurred vision, numbness in the feet and legs, and slowly healing wounds. Women may experience genital itching.

Diagnosis Urine tests Diabetes is suspected based on symptoms, but many of its symptoms may also suggest other diseases. Urine tests can begin the winnowing process that leads to a definitive diagnosis. Urine tests can detect ketones and protein in the urine; they can also show urine “spill,” the renal threshold at which the kidneys will spill excess blood sugar into the urine. They can help assess how adequately the kidneys are functioning, and are used to monitor the disease once the patient is compliant with the recommended diet, oral medications, or insulin. Blood tests Although urine tests can confirm an initial suspicion of diabetes, specific blood tests are often required to make the differential diagnosis. One such diagnostic tool

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is the fasting glucose test. Blood is drawn via a venipuncture after a period of at least eight hours of fasting, usually in the morning prior to breakfast. The red blood cells are separated from the sample and the amount of glucose is measured in the remaining plasma. A plasma level of 7.8 mmol/L (200 mg/L) or greater can indicate diabetes. The fasting glucose test is usually repeated on another day to confirm the results. A postprandial glucose test involves taking blood one to two hours after the patient has eaten a meal. A glucose tolerance involves blood and urine sampling over a three- or five-hour period after a patient drinks a specially prepared syrup of glucose and other sugars. During the test the patient drinks no other fluids. When patients are healthy, the blood glucose level rises immediately after the drink and then decreases gradually as insulin is used by the body to metabolize the glucose. In patients with diabetes, the serum glucose rises and stays elevated after drinking the sweetened liquid. A plasma glucose level of 11.1mmol/L (200 mg/dL) or higher two hours after drinking the syrup and at one other point during the two-hour test period confirms the diagnosis of diabetes. During this time, the urine is tested for glucose spill. A diagnosis of diabetes is confirmed if there are symptoms of diabetes and a blood glucose level of at least 11.1 mmol/L, a fasting plasma glucose level of at least 7 mmol/L, or a two-hour plasma glucose level of at least 11.1 mmol/L during an oral glucose tolerance test. Monitoring glucose levels The blood test that gives the best indication of average blood glucose levels over time is the hemoglobin A1C (HbA1C) test. It measures the percentage of hemoglobin A that has become glycosylated (coated with glucose) during the past three months. (Red blood cells have a life span of about 100 days; after that they are recycled by the bone marrow.) A normal reading for healthy individuals is about of 4–6% glycosylated HbA1C. Diabetics whose disease is well controlled will read 7% or lower. A reading of 8% or higher indicates the need for a change in treatment or better dietary compliance; these patients are also at increased risk for such complications as eye disease, kidney disease, and nerve damage. The HbA1C test should be performed at least twice a year to be sure that blood glucose levels stay within safe and healthy levels. Home blood glucose monitoring kits are available so patients with diabetes can monitor their daily glucose readings. For decades, a small needle or lancet was used to prick the finger and a drop of blood was collected and analyzed by a monitoring device. Modern blood moni726

toring devices, however, are strapped on like a wrist watch; no finger sticks are required. This is especially helpful for patients who need to test their blood glucose levels several times during the day.

Treatment There is no cure for diabetes; it can, however, be controlled so that patients can live a relatively normal life. Treatment focuses on two goals: keeping blood glucose readings within a normal range (140 mg/dL, the standard accepted by the American Diabetes Association) and preventing the development of long-term complications. Careful monitoring of diet, exercise, and blood glucose levels are important, affecting the need for insulin replacement as well as the dose of oral antidiabetic agents. Lack of consistent control leads to complications of the disease. Dietary changes Diet and moderate exercise are the first treatments implemented in diabetes. For many type 2 diabetics, weight loss may be an especially important part of treatment. A well balanced, nutritious diet provides approximately 50% to 60% of calories from carbohydrates, around 10% to 20% from protein, and less than 30% of calories from fat. The number of calories required by an individual depends on their age, weight, and activity level. Calorie intake also needs to be distributed over the course of the entire day so that surges of glucose entering the blood are kept to a minimum. The timing of snacks must also correspond to the timing and type of insulin being used. Counting the calories in different foods can be complicated, so patients are usually advised to consult a nutritionist, who will set up an individualized, easily managed diet for each patient. Both the American Diabetes Association and the American Dietetic Association recommend diets based on the use of food-exchange lists. Each food-exchange unit contains a known amount of calories in the form of protein, fat, or carbohydrate. A patient’s diet plan will allow a certain number of exchanges from each food category (meat or protein, fruits, breads and starches, vegetables, and fats) to be eaten at mealtimes and as snacks. Patients can choose which foods they eat as long as they stick with the number of exchanges prescribed and adhere to their schedule if they take a combination of insulin types. The food exchange system, along with an exercise program, can help patients lose excess weight and improve their overall health. This may be especially important for type 2 diabetics.

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A variety of oral medications are available to help lower blood glucose in type 2 diabetics. They act in a variety ways to control postprandial (after meal) glucose levels; the particular medication or combination of drugs chosen will be based largely on the individual patient profile. Some oral medications stimulate the pancreatic beta cells to produce additional insulin. Others change the way receptors on peripheral adipose (fat) and muscle cells receive the insulin and act on it, and still others block the intestinal absorption of food byproducts that would increase blood glucose levels. All drugs have side effects that may make them inappropriate for particular patients. For example, some medications may stimulate weight gain or cause stomach irritation, so they may not be the best treatment for individuals who are already overweight or who have stomach ulcers. While these medications are an important aspect of treatment for type 2 diabetes, they are not a substitute for an appropriate diet and exercise. Oral medications are not effective for type 1 diabetes, in which the patient produces little or no insulin. Insulin Patients with type 1 diabetes need daily injections of insulin to help their bodies utilize glucose. The amount and type of insulin required depends on the individual patient’s height, weight, age, food intake (quantity and timing), and activity level. Some patients with type 2 diabetes may need to use insulin injections if their diabetes cannot be controlled with diet, exercise, and oral medication. Injections are given subcutaneously, using a small needle and syringe. Injection sites can be anywhere on the body where there is adequate subcutaneous tissue, including the upper arm, abdomen, hips, or upper thigh. Purified human insulin is most commonly used, however, insulin from beef and pork sources is also available. Insulin may be given as an injection of a single dose of one type of insulin once a day. Different types of insulin (short-acting rapid-onset, slow-onset long-acting) can be mixed and given in one dose or split into two or more doses during the day. Patients that require multiple injections over the course of a day may be able to use an insulin pump that administers small doses of insulin on demand. The small battery-operated pump is worn outside the body and is connected to a tube that is inserted into the abdomen. Pumps can be programmed to inject small doses of insulin at various times during the day, or the patient may be able to adjust the insulin doses to coincide with glucometer readings, meals, and exercise.

There are also multiple-dose insulin injection devices available that are commonly referred to as insulin pens. They are designed to hold a cartridge containing several days’ worth of insulin dosages. Regular human insulin is fast-acting and begins to work within 15–30 minutes; its peak glucose-lowering effect occurs about two hours later and its effects last approximately 4–6 hours. Neutral protamine Hagedorn (NPH) and Lente insulin are intermediate-acting insulins that start to work within 4–8 hours, and last 18–26 hours. Ultralente is a long-acting form of insulin that starts to work within four to eight hours and lasts 28 to 36 hours. Many diabetics combine a long- or intermediate acting insulin with a short-acting one to provide the proper insulin peak at mealtimes. Premixed insulins are available in standard doses. Newer forms of insulin are under investigation. Although the goal of most diabetes treatment is to lower blood glucose levels, hypoglycemia, or low blood glucose, can be caused by too much insulin, too little food, alcohol consumption, or increased exercise. A patient with symptoms of hypoglycemia may be hungry, irritable, confused, and tired. The patient may be diaphoretic (sweating profusely), pale, and shaky. Left untreated, the patient can lose consciousness or have a seizure soon after these symptoms appear. This condition, called an insulin reaction or insulin shock, should be treated by giving the conscious patient something with readily available sugar to eat or drink like orange juice, hard candy, or sugar cubes. If the patient has declined into unconsciousness, do not try to feed them. This is a critical condition and always requires emergency intravenous therapy. Surgery Transplantation of healthy pancreatic tissue into a diabetic patient can be successful. However, it is not clear if the potential benefits outweigh the risks of the surgery and drug therapy required. Alternative therapies Since uncontrolled diabetes can be life-threatening if not properly managed, patients should be instructed to not attempt treatments without medical supervision. Patients interested in alternative and herbal remedies should be instructed about the possible benefits, but cautioned to consult with a health care professional before they try them. Some alternative therapies may interact negatively with some of the oral antidiabetic agents or other drugs, such as antihypertensives or anticoagulants.

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Diabetes mellitus

Prognosis

KEY TERMS Diabetic peripheral neuropathy—Condition in which the sensitivity of nerves to pain, temperature, and pressure is dulled, particularly in the legs and feet. Diabetic retinopathy—A condition in which the tiny blood vessels to the retina are damaged, leading to blurred vision, sudden blindness, or black spots, lines, or flashing light in the field of vision. Hemoglobin A—Normal hemoglobin found in the blood of an adult. Hemoglobin A1C—One of three fractions of hemoglobin A; the other two are HBA1a and HbA1b. Because HbA1c can become glycosylated, it is an important measure of blood glucose over the past three months. Hyperglycemia—Abnormally high levels of blood glucose. Hypoglycemia—Abnormally low levels of blood glucose. Ketoacidosis—Condition that results in untreated diabetes from the body’s attempt to burn fat for fuel when carbohydrates cannot be utilized. Ketones, the byproduct of fat metabolism, enter the bloodstream and make the blood more acidic than the body’s tissues. Pruritus—Itching. Tachypnea—Rapid breathing.

For patients who are willing to consult with their physician, alternative options may include: • Fenugreek has been shown in some studies to reduce blood insulin and glucose levels while also lowering cholesterol. • Bilberry may lower blood glucose levels, as well as help to maintain healthy blood vessels. • Garlic may lower blood sugar and cholesterol levels. • Cayenne pepper may help relieve the pain of diabetic neuropathy. Any therapy that lowers stress levels may also be useful in treating diabetes by helping to reduce insulin requirements. Among the alternative treatments that aim to lower stress are hypnotherapy, biofeedback, and meditation. 728

Uncontrolled diabetes is a leading cause of blindness, end-stage renal disease, and peripheral vascular insufficiency, which leads to limb amputations. It also doubles the risks of heart disease and increases the risk of stroke. Eye problems including cataracts, glaucoma, and diabetic retinopathy are also more common in diabetics. Diabetic peripheral neuropathy is a condition where nerve endings, particularly in the legs and feet, become less sensitive. Diabetic foot ulcers are a particular problem since the patient does not feel the pain of a blister, callous, or other minor injury. Poor blood circulation in the legs and feet contribute to delayed wound healing. The inability to sense pain along with the complications of delayed wound healing can cause minor injuries, blisters, or calluses to become infected and difficult to treat. In cases of severe infection, the infected tissue begins to break down and rot away. The severe infection may further exacerbate diabetes and increase blood glucose levels, perpetuating the problem. In the most serious infection cases, toes, feet, or legs may need to be amputated. Diabetes can also affect the kidneys, a condition called diabetic nephropathy. This usually means that soft kidney tissue hardens and thickens, a process called sclerosis; this is especially true for the glomerulus (kidney membrane), which filters protein and other waste products from the blood. The ADA estimates that 35–45% of type 1 patients and 20–30% of type 2 patients have damaged kidneys. Because the symptoms of nephropathy may not appear until 80% of kidney function is gone, periodic tests of kidney function are especially important for patients with diabetes. Once renal function drops to 10–15%, kidney dialysis or a kidney transplant become necessary. The risk of heart disease for patients with diabetes is two to four times higher than that of the general population. Death from heart disease is also two to four time higher in diabetics, as is the risk of stroke. These statistics hold for people with both type 1 and type 2 diabetes. The risk of cardiovascular disease increases with age, obesity, smoking, poor blood glucose control, and family history of heart disease.

Health care team roles All members of the health care team may come into contact with diabetic patients. The nurse plays a particularly important role in teaching patients the skills necessary to manage this complex disease, and educating them about the effects of their medications.

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Diabetic retinopathy see Retinopathies

Research continues on ways to prevent diabetes and to detect those at risk for developing the disease. While the onset of type 1 diabetes is unpredictable, the risks for developing type 2 diabetes can be reduced by maintaining a healthy weight and exercising regularly. The physical and emotional stresses of surgery, illness (especially systemic infection), pregnancy, and alcoholism can all increase the risks for diabetes, so maintaining a healthy lifestyle is critical to preventing the onset of type 2 diabetes and further complications. Research is in progress to determine the usefulness of placing high-risk patients on metformin (Glucophage; an oral antidiabetic drug used to treat type 2 diabetes) prophylactically in an effort to delay or prevent the onset of type 2 diabetes. Resources BOOKS

Beers, Mark H., and Robert Berkow. The Merck Manual of Diagnosis and Therapy. 17th ed. Whitehouse Station, NJ: Merck and Company, Inc., 1999. PERIODICALS

Lincoln, Thomas A. “A1c: Know Your Value!” Diabetes Forecast (March 2001): 66. Pennachio, Dorothy L. “How to Manage Diabetes in the Older Patient.” Patient Care (January 30, 2001): 53. ORGANIZATIONS

American Diabetes Association. 1701 North Beauregard Street, Alexandria, VA 22311. 800-DIABETES. . Juvenile Diabetes Foundation International. 120 Wall Street, New York, NY 10005-4001. 800-JDF-CURE. . OTHER

American Diabetes Association. Clinical Practice Recommendatons. “Tests of Glycemia in Diabetes” Position Statement. Diabetes Care 24, no. 1. . Diabetes Manager. “History of Diabetes.” . Kentucky Department for Public Health. “The Hemoglobin A1C Test: The Best Test For Blood Sugar Control.” . Moran, David T. “Glycosylated hemoglobin.” .

Deanna M. Swartout-Corbeil, R.N.

Diabetic diet see Diet therapy

Diagnostic medical sonography Definition Diagnostic medical sonography, or ultrasound, is a technique using high frequency sound to create images of specific areas of the body to diagnose various pathologies. The diagnostic medical sonographer performs examinations, records anatomic condition and provides diagnostic information.

Description Under the supervision of a physician, the diagnostic medical sonographer provides patient services using medical ultrasound to gather data necessary to diagnose various conditions and diseases. The sonographer uses advanced computerized technology to produce images. The images are viewed on a video screen or converted by computer to produce photographs or printouts of ultrasonic patterns. The imaged patterns help the physician determine the diagnosis. The sonographer’s responsibilities include image production through patient positioning and operation of clinical instrumentation, patient care, quality control, technical assistance with interventional procedures, image manipulation and processing, and the preliminary interpretation of the ultrasound examination for the sonologist. Supporting the physician, the sonographer obtains, reviews, and integrates pertinent patient history and supporting clinical data to facilitate optimum diagnostic results. This involves performing appropriate procedures and recording anatomical, pathological, and/or physiological data for interpretation by a physician, and recording and processing sonographic data and other pertinent observations made during the procedure for presentation to the interpreting physician. Before the procedure, sonographers explain the ultrasonic procedure to patients and help patients assume the correct physical positions for required exposure to ultrasonic waves. At all times, the sonographer is required to exercise good judgment in the performance of sonographic services.

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Prevention

Diagnostic medical sonography A pregnant woman undergoes an ultrasound. (Photograph by Larry Mulvehill. Science Source/Photo Researchers. Reproduced by permission.)

Work settings Some sonographers can work in a variety of medical settings including hospitals, clinics, private offices, and other facilities performing examinations in their areas of specialization. More experienced sonographers may work on a contractual basis or for mobile services.

Education and training A sonographer must have a thorough knowledge of cross-sectional anatomy and pathology, as well as the skills to manipulate a wide variety of sophisticated instruments. Individuals entering diagnostic medical sonography are required to have a strong academic background in the basic sciences and a strong comprehension of computer technology. Diagnostic medical sonography programs vary in length from one to four years depending on the program design and the degree or certificate awarded. Program entry requirements range from a high school diploma to specific qualifications in a clinically related Allied Health profession such as nursing, radiotechnology, nuclear medicine, etc. Typical program curriculums can 730

include ultrasound physics and instrumentation, patient care procedures, professionalism and ethics, physiology and pathophysiology, and sonographic anatomy and scanning techniques. Many programs involve an internship as part of the course of study. Interns work in medical facilities to apply classroom theory and gain practical skills. Following graduation, candidates take a national qualifying exam administered by the American Registry of Diagnostic Medical Sonographers (ARDMS). Continuing education is required of all sonographers to maintain registration. Candidates become Registered Diagnostic Medical Sonographer (RDMS) when they pass the ARDMS exam.

Advanced education and training Diagnostic medical sonographers may wish to specialize through formal and/or continuing education after graduation and certification. Recent advancements in the technology have led to increased specialization. Specialties include spectral and color doppler, vascular

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Future outlook Diagnostic medical sonography is a rapidly expanding field. The non-invasive, non-ionizing nature of the technology makes it an attractive modality. Continuing advancements in the technology provide a broader application of sonography. Therefore, an increasing need exists for well-trained and dedicated sonographers. Important recent advances include the transvaginal scan that involves specially designed probes placed in the vagina that produce better images and more information in patients in the early stages of pregnancy. Transvaginal scans are becoming valuable in the early diagnosis of ectopic pregnancies and in detecting fetal abnormalities in the first trimester of pregnancy. Another recent advancement, doppler ultrasound, is useful in detecting fetal heart rates and fetal blood flow. Color doppler is useful in the diagnosis and assessment of congenital heart abnormalities. Also, three-dimensional ultrasound, which can create better scans by providing volumetric measurement, is moving from the research and development stages and into more widespread application. Graduates of diagnostic medical sonography programs can find many employment opportunities in hospitals, medical centers, and mobile services. There are many opportunities for advancement, both within an institution and within the field. Advancement can depend on continuing education, specialization, and experience. Starting salaries for recent graduates range from $28,000 to $32,000. Career opportunities also exist outside the healthcare field. Graduates can find employment in industry as education specialists, researchers and administrators and with equipment manufacturers as sales representatives. Resources BOOKS

Fleischer, Arthur C. and Kepple, Donna M. Diagnostic Sonography. Philadelphia, PA: W.B. Saunders, 1995. Hagen-Ansert, Sandra L. Textbook of Diagnostic Ultrasonography Volume Two. St. Louis, MO: Mosby, 1995. Rowland, Jeanne. Introduction to Radiologic Technology. St. Louis, MO: Mosby-Year Book, Inc. 1996. Zwiebel, William J. and Sohaey, Roya. Introduction to Ultrasound. Philadelphia, PA: W.B. Saunders, 1998. OTHER

“Diagnostic Medical Sonography (Ultrasound).” Rochester Institute of Technology Department of Allied Health

KEY TERMS Color Doppler—An ultrasound technique used to locate areas of motion, such as blood flow in vessels. Doppler—Technique for calculating the relative velocity between two points by measuring the shift in frequency of a sound wave transmitted from one point to another. Transducer—Often called probes, transducers come in different shapes and sizes for use in different ultrasonic scanning situations. Ultrasonic—A sound beyond the range of human hearing. Ultrasound—The diagnostic or therapeutic use of ultrasound and esp. a noninvasive technique involving the formation of a two-dimensional image used for the examination and measurement of internal body structures and the detection of bodily abnormalities.

Sciences Diagnostic Medical Sonography Program 1998. .

Daniel J. Harvey

Dialysis, kidney Definition Dialysis treatment replaces the function of the kidneys, which normally serve as the body’s natural filtration system. Through the use of a blood filter and a chemical solution known as dialysate, dialysis removes waste products and excess fluids from the bloodstream, while maintaining the proper chemical balance of the blood. There are two types of dialysis treatment: hemodialysis and peritoneal dialysis.

Purpose Dialysis also can be used to remove overdosed drugs or poisons from the bloodstream more quickly than normally functioning kidneys. Its most prevalent application, however, is for patients with temporary or permanent kidney failure. For patients with end-stage renal disease (ESRD), dialysis is the only renal replacement

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sonography, endocavity imaging, and intraoperative ultrasound.

Dialysis, kidney A man undergoes hemodialysis on a dialysis machine. (Giovaux Communication/Phototake NYC. Reproduced with permission.)

therapy available other than kidney transplantation. In the United States, nearly 250,000 patients receive regular dialysis treatments to manage ESRD.

Precautions Blood pressure changes during hemodialysis may pose a risk for patients with heart disease. Peritoneal dialysis may be the preferred treatment option for these patients. Peritoneal dialysis is not recommended for patients with abdominal adhesions or other abdominal defects, such as a hernia, which might compromise the efficiency of the treatment. It is also not recommended for patients who suffer frequent bouts of diverticulitis (inflammation of diverticuli, small pouches in the colon).

Description There are two types of dialysis treatment: hemodialysis and peritoneal dialysis. Hemodialysis Hemodialysis is the most frequently prescribed type of dialysis in the United States. The treatment involves 732

circulating the patient’s blood outside of the body through an extracorporeal circuit (ECC), or dialysis circuit. Two needles are inserted into the patient’s vein, or access site, and are attached to the ECC, which consists of plastic blood tubing, a filter known as a dialyzer (artificial kidney), and a dialysis machine that monitors and maintains blood flow and administers dialysate. Dialysate is a chemical bath that is used to draw waste products out of the blood. Since the 1980s, the majority of hemodialysis treatments in the United States have been performed with hollow fiber dialyzers. A hollow fiber dialyzer is composed of thousands of tube-like hollow fiber strands encased in a clear plastic cylinder several inches in diameter. There are two compartments within the dialyzer (the blood compartment and the dialysate compartment). The membrane that separates these two compartments is semipermeable; it allows the passage of certain sized molecules across it, but prevents the passage of other, larger molecules. As blood is pushed through the blood compartment in one direction, suction or vacuum pressure pulls the dialysate through the dialysate compartment in a countercurrent, or opposite direction. These opposing pressures

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machine administers and drains the dialysate solution, and sessions can take up to 24 hours.

A second process, called diffusion, moves waste products in the blood across the membrane into the dialysate compartment, where they are carried out of the body. At the same time, electrolytes and other chemicals in the dialysate solution cross the membrane into the blood compartment. The purified, chemically balanced blood is then returned to the body.

Peritoneal dialysis is often the treatment option of choice for infants and children, whose small size can make vascular access difficult to maintain. Peritoneal dialysis also may be performed outside of a clinical setting, which is more conducive to regular school attendance.

Most hemodialysis patients require treatment three times a week, for an average of three to four hours per dialysis “run.” Specific treatment schedules depend on the type of dialyzer used and the patient’s current physical condition. While the treatment prescription and regimen is usually overseen by a nephrologist (a doctor that specializes in the kidney), dialysis treatments are typically administered by a nurse or dialysis technician in outpatient clinics known as dialysis centers or in hospitalbased dialysis units. In-home hemodialysis treatment is also an option for some patients, although access to this type of treatment may be limited by financial and lifestyle factors. An investment in equipment is required and another person in the household should be available for support and assistance with treatments.

A dialysis technologist, nurse, or nursing assistant weighs patients immediately before and after each hemodialysis treatment to assess their fluid balance. The dialysis technologist, nurse, or nursing assistant also measures and records blood pressure and temperature and assesses patients for any physical changes since their last dialysis run. Regular blood tests, performed by laboratory technologists, monitor chemical and waste levels in the blood. Prior to treatment, patients are typically administered a dose of heparin (an anticoagulant that prevents blood clotting) to ensure the free flow of blood through the dialyzer and an uninterrupted dialysis run.

Peritoneal dialysis In peritoneal dialysis, the patient’s peritoneum (lining of the abdomen) acts as a blood filter. A catheter is surgically inserted into the patient’s abdomen. During treatment, the catheter is used to fill the abdominal cavity with dialysate. Waste products and excess fluids move from the patient’s bloodstream into the dialysate solution. After a waiting period of six to 24 hours, depending on the treatment method used, the waste-filled dialysate is drained from the abdomen and replaced with clean dialysate. There are three types of peritoneal dialysis: • Continuous ambulatory peritoneal dialysis (CAPD). This treatment is self-administered and requires no machine. The patient inserts fresh dialysate solution into the abdominal cavity, waits four to six hours, and removes the used solution. The solution is immediately replaced with fresh dialysate. A bag attached to the catheter is worn under clothing. • Continuous cyclic peritoneal dialysis (CCPD). An overnight treatment that uses a machine to drain and refill the abdominal cavity, CCPD takes 10–12 hours per session. • Intermittent peritoneal dialysis (IPD). This hospitalbased treatment is performed several times a week. A

Preparation

Aftercare Both hemodialysis and peritoneal dialysis patients must be vigilant about keeping their access sites and catheters clean and infection-free during and between dialysis runs. Dialysis is just one facet of a comprehensive treatment approach for ESRD. Although dialysis treatment is very effective in removing toxins and fluids from the body, there are several functions of the kidney it cannot mimic, such as regulating high blood pressure and red blood cell production. Patients with ESRD need to watch their diet and fluid intake carefully and adhere to prescribed medications to effectively manage their disease.

Complications Many of the risks and side effects associated with dialysis are a combined result of both the treatment and the poor physical condition of the ESRD patient. Dialysis patients should be instructed to report side effects to their healthcare provider. Anemia Hematocrit (Hct) levels, the percentage of whole blood comprised of red blood cells, are typically low in ESRD patients. This deficiency is caused by a lack of the hormone erythropoietin, which is normally produced by the kidneys. The problem is exacerbated in hemodialysis patients, who may incur blood loss during hemodialysis

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work to drain excess fluids out of the bloodstream and into the dialysate, a process called ultrafiltration.

Dialysis, kidney

rate of the treatment. Adjustment of the dialysis prescription often helps alleviate symptoms.

KEY TERMS Access site—The vein tapped for vascular access in hemodialysis treatments. For patients with temporary treatment needs, access to the bloodstream is gained by inserting a catheter into the subclavian vein. Patients in long-term dialysis require stronger, more durable access sites, called fistulas or grafts, that are surgically-created. Dialysate—A chemical bath used in dialysis to draw fluids and toxins out of the bloodstream and supply electrolytes and other chemicals to the bloodstream. Dialysis prescription—The general parameters of dialysis treatment that vary according to each patient’s individual needs. Treatment length, type of dialyzer and dialysate used, and rate of ultrafiltration are all part of the dialysis prescription. Dialyzer—An artificial kidney usually composed of hollow fiber that is used in hemodialysis to eliminate waste products from the blood and remove excess fluids from the bloodstream. Erythropoietin—A hormone produced by the kidneys that stimulates the production of red blood cells by bone marrow. ESRD—End-stage renal disease; chronic or permanent kidney failure. Extracorporeal circuit (ECC)—The path the hemodialysis patient’s blood takes outside of the body. It typically consists of plastic tubing, a hemodialysis machine, and a dialyzer. Hematocrit (Hct) level—A measure of red blood cells. Peritoneum—The abdominal cavity; the peritoneum acts as a blood filter in peritoneal dialysis.

treatments. Epoetin alfa, a hormone therapy also known as EPO (sold under the trade name Epogen), and intravenous or oral iron supplements are used to manage anemia in dialysis patients.

Because of the stress placed on the cardiovascular system with regular hemodialysis treatments, patients are at risk for hypotension, a sudden drop in blood pressure. This can often be controlled by medication and adjustment of the patients’ dialysis prescription. Infection Both hemodialysis and peritoneal dialysis patients are at risk for infection. Hemodialysis patients should keep their access sites clean and watch for signs of redness and warmth that could indicate infection. Peritoneal dialysis patients must follow the same precautions with their catheters in order to prevent peritonitis. Peritonitis, an infection of the peritoneum, causes flu-like symptoms and can disrupt dialysis treatments if not detected promptly. Infectious diseases Because there is a great deal of blood exposure involved in dialysis treatment, a slight risk of contracting hepatitis B and hepatitis C exists. The hepatitis B vaccination is recommended for most hemodialysis patients. As of 1997, there has only been one documented case of HIV being transmitted in a United States dialysis unit to a staff member, and no documented cases of HIV ever being transmitted between dialysis patients in the United States. The strict standards of infection control practiced in modern hemodialysis units makes the chance of contracting one of these diseases very small.

Results Fluid retention may be relieved after dialysis treatment. The patient’s overall sense of physical well being may also be improved. Because dialysis is an ongoing treatment process for many patients, a baseline for normalcy can be difficult to gauge.

Health care team roles

Cramps, nausea, vomiting, and headaches Some hemodialysis patients experience cramps and flu-like symptoms during treatment. These may be caused by a number of factors, including the type of dialysate used, composition of the dialyzer membrane, water quality in the dialysis unit, and the ultrafiltration 734

Hypotension

Patients receiving dialysis treatments are cared for by a team that includes nephrologists, dialysis technicians, nurses, radiology technicians, and laboratory technicians. Registered dietitians, nutritionists, and nurses instruct patients about dietary changes to manage their disease.

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BOOKS

Cameron, J. S. Kidney Failure: The Facts. New York, NY: Oxford Univ. Press, 1996. The Washington Manual of Medical Therapeutics. 30th ed. Philadelphia: Lippincott Williams & Wilkins, 2001. ORGANIZATIONS

American Association of Kidney Patients (AAKP). 100 S. Ashley Drive, Suite 280, Tampa, FL 33602. (800)7492257. . American Kidney Fund (AKF). Suite 1010, 6110 Executive Boulevard, Rockville, MD 20852. (800)638-8299. . National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Natcher Building, 6AS-13K, 45 Center Drive, Bethesda, MD 20892-6600. . National Kidney Foundation (NKF). 30 East 33rd Street, New York, NY 10016. (800)622-9020. . United States Renal Data System (USRDS). USRDS Coordinating Center, 315 W. Huron, Suite 240, Ann Arbor, MI 48103. (313)998-6611. .

Barbara Wexler

Dialysis technology

Hemodialysis, performed by dialysis technologists, is the most frequently prescribed type of dialysis in the United States. The treatment involves circulating the patient’s blood outside of the body through an extracorporeal circuit (ECC), or dialysis circuit. Two needles are inserted into the patient’s vein, or access site, and are attached to the ECC, which consists of plastic blood tubing, a filter known as a dialyzer (artificial kidney), and a dialysis machine that monitors and maintains blood flow and administers dialysate. Dialysate is a chemical bath that is used to draw waste products out of the blood. Dialysis technology involves health care workers with a variety of job titles—dialysis technologist, hemodialysis technician, renal dialysis technician, clinical nephrology technologist. All of these allied health professionals are trained to provide direct patient care to people who must undergo hemodialysis because their kidneys no longer adequately rid their bodies of waste products. Dialysis technologists assess patients’ vital signs prior to dialysis, perform dialysis, monitor patients during and after treatment, and document clinical findings. They administer drugs, including local anesthetics, and are trained to provide emergency medical intervention such as administering oxygen or performing cardiopulmonary resuscitation (CPR). Dialysis technologists also are responsible for ensuring the proper functioning of dialysis machines; in some settings they perform routine equipment maintenance and repairs. Dialysis technologists are often involved in patient education, instructing patients and families about in-home dialysis treatment and reinforcing the importance of adherence to prescribed treatment.

Definition Dialysis technology is a highly specialized field of nephrology (care of the kidneys). In clinical practice settings dialysis technologists provide dialysis treatment under the supervision of a physician or registered nurse. The dialysis technologist is responsible for all medical devices and equipment involved in renal replacement therapies, such as reprocessing and water treatment equipment. Along with patient care and equipment operation, maintenance, and repair, dialysis technologists act to ensure regulatory compliance.

Work settings Dialysis technologists may work in hospitals, outpatient clinics, or freestanding dialysis centers. Work environments must be scrupulously clean and well maintained to prevent infection of patients and health care workers. In the work setting, there must be strict adherence to safety standards since dialysis technologists routinely handle dangerous chemicals during the course of performing their responsibilities.

Education and training Description Dialysis is treatment for patients with temporary or permanent kidney failure. For patients with end-stage renal disease (ESRD) dialysis is the only renal replacement therapy available other than kidney transplantation. In the United States, nearly 250,000 patients receive regular dialysis treatments to manage ESRD.

Dialysis technologist trainees generally require at least a high school diploma; in some states, prior patient care experience and/or college course work in health sciences may be required. The areas of study addressed during course work may include: • hazard communications and safety; specific risks of peracetic acid solution

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Resources

Dialysis technology

• prevention of occupational injuries

KEY TERMS

• power failure/manual dialysis • managing chemical agents and chemical emergencies • water safety, testing, treatment • monitoring dialysis patients; dialysis process • pathophysiology of kidney and urinary system; hypo/hyperkalemia • machine preparation and operation • medication, documentation, and quality assurance Since 1996, the National Nephrology Technology Certification Organization (NNCO) has offered certification examinations for nephrology clinical technicians and nephrology biomedical technicians. To take the NNCO certification examination, candidates must have a high school diploma or its equivalent, and at least one year or 2,000 hours of experience in nephrology technology or they must have completed a year-long educational program in nephrology technology. The certification exam in biomedical nephrology technology measures candidates’ knowledge in the following areas:

Dialysate—A chemical bath used in dialysis to draw fluids and toxins out of the bloodstream and supply electrolytes and other chemicals to the bloodstream. Dialysis prescription—The general parameters of dialysis treatment that vary according to each patient’s individual needs. Treatment length, type of dialyzer and dialysate used, and rate of ultrafiltration are all part of the dialysis prescription. Dialyzer—An artificial kidney usually composed of hollow fiber that is used in hemodialysis to eliminate waste products from the blood and remove excess fluids from the bloodstream. Erythropoietin—A hormone produced by the kidneys that stimulates the production of red blood cells by bone marrow. ESRD—End-stage renal disease; chronic or permanent kidney failure. Extracorporeal circuit (ECC)—The path the hemodialysis patient’s blood takes outside of the body. It typically consists of plastic tubing, a hemodialysis machine, and a dialyzer.

• principles of dialysis • scientific concepts • electronic applications • water treatment • equipment functions

Future outlook

• environmental/regulatory issues Candidates who pass the national certification examination in clinical nephrology technology may use the designation CCNT after their names. Those who pass the certification examination in biomedical nephrology technology use the designation CBNT after their names. To retain certification, candidates must retake the examination every four years or meet alternative certification requirements. State licensure requirements vary, however, most states require from 15–35 hours of continuing medical education annually.

Advanced education and training Dialysis technologists can advance from trainee positions to chief technologist posts at major medical centers. Some dialysis technologists participate in clinical research and teaching. Others work closely with biomedical engineers to improve hydraulic and electrical systems used in dialysis equipment. Some medical facilities encourage dialysis technologists to continue their education and advance to become licensed vocational nurses, registered nurses, or other specialized health care therapists or practitioners. 736

Throughout the United States, the employment prospects for dialysis technologists are excellent. The number of patients on dialysis continues to increase, and the average duration (the length of time patients remain on dialysis) is also increasing. Advances in medical technology, the increasing prevalence of end stage renal disease (ESRD), and the aging population all point to an increasing need for renal care practitioners, especially dialysis workers. For example, according to the California Labor Market Information Division, in the state of California, projected growth in opportunities between 1990–2005 is 42%. Resources BOOKS

The Washington Manual of Medical Therapeutics. 30th ed. Philadelphia: Lippincott Williams & Wilkins, 2001. PERIODICALS

“Dialysis: Need for Artificial Kidney Treatment Is Increasing.” Mayo Clinic Health Letter, 15 (Feb 1997): 1–4. Favero, Martin S. “Infection Control.” Dialysis and Transplantation 25 (October 1996): 699-702.

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American Association of Kidney Patients (AAKP). 100 S. Ashley Drive, Suite 280, Tampa, FL 33602. (800) 7492257. . American Kidney Fund (AKF). Suite 1010, 6110 Executive Boulevard, Rockville, MD 20852. (800) 638-8299. . National Association of Nephrology Technicians/Technologists (NANT). P.O. Box 2307 Dayton, OH 45401-2307. (877) 607-6268. . National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Natcher Building. 6AS-13K, 45 Center Drive, Bethesda, MD 20892-6600. . National Kidney Foundation (NKF). 30 East 33rd Street, New York, NY 10016. (800) 622-9020. . United States Renal Data System (USRDS). USRDS Coordinating Center, 315 W. Huron, Suite 240, Ann Arbor, MI 48103. (313) 998-6611. .

Barbara Wexler

ry diarrhea is a bacterium that produces a toxin. Common examples of non-inflammatory bacteria include Escherichia coli, Staphylococcus aureus, Bacillus cereus and Clostridium perfringens. Some viruses and amoeba such as Giardia lamblia also cause non-inflammatory diarrhea. This diarrhea is typically mild but may be voluminous, involving large amounts of fluid (10 to 200 mL/kg/day). Such fluid loss results in dehydration and loss of electrolytes. There is usually no blood loss. • Inflammatory diarrhea. This is usually characterized by the presence of fever and blood in the stool and is associated with left lower quadrant cramps, urgency and tenesmus (anal spasms). Common causes of inflammatory diarrhea include infection with Campylobacter or Yersinia species or infection with some species of Escherichia coli. Diarrhea due to these pathogens tends to be less voluminous, less than 1 liter per day. • Enteric fever. This is characterized by abdominal tenderness, confusion, prolonged high fever, prostration and occasionally a rash. Common causes of enteric fever-related diarrhea include Salmonella typhi or Salmonella paratyphi. Multi-organ disease is frequently encountered. Inflammatory diarrhea must be distinguished from ulcerative colitis.

Diarrhea Definition Diarrhea is an increased frequency of stools or bowel movements (more than two or three per day) or liquidity of feces.

Description In a normal adult, about 10 quarts (liters) of fluid waste leaves the stomach each day. All but a liter and a half is absorbed in the small intestine. The unabsorbed contents enter the large bowel or colon. Most of the fluid in the feces is reabsorbed by the large intestine. The fluid loss is about 100 milliliters each day. From a strictly medical perspective, diarrhea is defined as stool weight of more than 250 grams in 24 hours. In practice, the calculation of stool weights is restricted to persons with chronic diarrhea. There are three broad classes that encompass most cases of diarrhea. • Non-inflammatory diarrhea. This is described as a watery, non-bloody bowel movement that is associated with diffuse abdominal cramping, nausea, vomiting or bloating. The most common cause of non-inflammato-

Non-professionals may use the term diarrhea in reference to increased incidence of bowel movements, a sense of fecal urgency, increased stool liquidity or fecal incontinence.

Causes and symptoms Many cases of non-inflammatory diarrhea are caused by the organisms listed in the description section. The symptoms of diarrhea include nausea, weakness and dehydration. After more that three of four episodes of diarrhea, lethargy develops. Occasionally, diffuse abdominal cramping is experienced. Inflammatory diarrhea is characterized by fever, nausea, sweating (diaphoresis) and lower abdominal tenderness and cramping. Tenesmus is common but not always present. Weakness and dehydration are often present. Lethargy develops after three or four episodes of diarrhea. Diarrhea that is associated with enteric illness will be accompanied by prolonged high fever, confusion, prostration, respiratory distress and abdominal tenderness. Organisms that cause diarrhea have been described. In babies and young children, dehydration is a significant problem that must be rapidly corrected to avoid

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ORGANIZATIONS

Diarrhea

severe consequences. Lethargy may be the most prominent symptom in these children.

• 1.0 teaspoon baking soda

In cases of chronic diarrhea, anemia may be present due to blood loss. Fatigue and lethargy are the most common observable symptoms. Laboratory tests can be used to confirm anemia due to blood loss. The same persons should be tested for ova and parasites in the stool.

• 8 ounces orange juice

Diagnosis The causative agent of diarrhea may be recovered from a stool sample. Once recovered, it is grown in a laboratory, using standard culture techniques and procedures. Among persons with dysentery, the rate of positive identification of agents using bacterial culture is 60 to 75%. Persons with a recent history of possible exposure to amoeba, whether through travel or from sexual preference, should have a wet mount examination of stool for amoeba. Laboratories should be alerted to the possibility of exposure to E. coli if exposure to improperly prepared food is suspected. Stool should be examined for ova and parasites in persons with diarrhea that persists for more than 10 days. Three such examinations for ova and parasites should be performed. Rectal swabs should be considered for persons suspected of having Neisseria gonorrhoeae, Chlamydia or herpes simplex virus. Sigmoidoscopy should be considered for persons with severe rectal pain, tenesmus or rectal discharge. Sigmoidoscopy is often useful for differentiating infective diarrhea from ischemic or ulcerative colitis.

There are four main elements of treatment: rehydration, diet, antidiarrheal agents, and antibiotic therapy. Rehydration Drinking fluids such as tea, sport drinks, fruit juices and some mildly carbonated beverages, augmented with water, will rapidly replace fluid lost through diarrhea. Fluids should be consumed as rapidly as affected persons will tolerate them. Experts recommend fluid intake levels of 50-200 mL/kg/day. Severely dehydrated individuals may require hospitalization and intravenous fluid therapy with lactated Ringer’s solution. Persons who do not require hospitalization can make a similar solution that can be taken orally at home. Combine the following:

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• water to equal 1 quart Diet If persons with diarrhea consume adequate carbohydrates and fluids, most will avoid dehydration. Fluids that contain electrolytes are especially useful. Brothbased soups with crackers, sport drinks and some soft drinks contain salt, potassium, sugar and bicarbonate. These substances are lost with diarrhea. The bowel should not be stressed during recovery from diarrhea. This can be accomplished by avoiding foods that are high in fiber, fatty foods, milk and dairy foods, alcohol and caffeine. Eating relatively small meals on a frequent basis is helpful. Tea and fruit juices provide nourishment without stressing the digestive system. Antidiarrheal agents Persons with mild to moderate diarrhea usually benefit from antidiarrheal preparations. If diarrhea does not subside or worsens with the use of such agents, they should be discontinued and competent medical assistance sought. Preparations containing opioids (such as loperamide) should not be used by persons with bloody diarrhea or high fevers. In others, they will decrease stool liquidity, quantity and tenesmus. The following preparations are generally useful: • bismuth subsalicylate (Pepto-Bismol) • loperamide (Imodium AD) Antibiotic therapy

Treatment

• 0.5 teaspoon salt

• 8 teaspoons water

For the majority of persons with diarrhea, the condition is self-limiting. As such, antibiotic therapy is not indicated. For persons with moderate to severe diarrhea, antibiotic therapy may be helpful. Symptoms of bloody stools, fever and tenesmus are indications for the use of an antibiotic. The following are often used while awaiting the results of a stool culture. Because they are used without accurately identifying a causative agent for the diarrhea, their use is characterized as empirical. • a fluoroquinolone such as ciprofloxacin • erythromycin • trimethoprim/sulfamethoxazole Antibiotics are indicated for persons with so-called traveler’s diarrhea or for diarrhea that is caused by cholera, shigellosis or salmonellosis.

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Most cases of diarrhea are self limiting. Once the causative agent or toxin is discharged with the fecal flow, recovery can begin. Over 90% of persons with acute diarrhea will recover fully with adequate rehydration or the use of antidiarrheal agents. Laboratory determination of the cause in such instances is infrequently required. The cost is not justified. Laboratories identify approximately 3% of causative agents from stool cultures. Laboratories will frequently examine stool samples for the presence of blood to differentiate inflammatory and non-inflammatory causes of diarrhea. After a diagnosis of inflammatory diarrhea has been made, stool cultures are needed to determine appropriate antimicrobial therapy. Hospitalization for diarrhea is uncommon but warranted for severe diarrhea. Babies and older persons are at increased risk for adverse outcomes, including death, from diarrhea. Each day, more than 1,700 babies around the world die from diarrheal diseases. Most of these are due to a lack of potable drinking water. With adequate hydration using non-contaminated water, most of these deaths could be prevented. Without clean drinking water, their prognosis is often poor.

Health care team roles Diarrhea is usually diagnosed by someone other than a professional member of a health care team. Treatment is often provided by the same person. When professional advice is sought, a family physician, internist, pediatrician, physician’s assistant or nurse practitioner is most likely to be consulted. A laboratory technician may process stool samples and identify a causative agent. In unusual circumstances, a pathologist may be called upon to identify a causative pathogen. A specialist in infectious diseases may provide assistance. Epidemiologists and sanitarians have an interest in diarrhea outbreaks or clusters of cases. Health officers may be called upon to take preventive measures if food sources, public restaurants or day care centers are shown to be the causes of a diarrhea outbreak.

Prevention Handwashing and personal hygiene are critical methods for preventing diarrhea. Adequate handwashing alone will prevent a majority of diarrhea cases. Adequate sanitation and attention to cleanliness are the best ways to prevent outbreaks of diarrhea disease. Persons handling food must always wash their hands

Diarrhea

Prognosis

KEY TERMS Diaphoresis—An alternative for sweating. Incontinence—The inability to voluntarily control elimination of bodily wastes. Inflammation—A physiological response to stress on the body that is characterized by redness, tenderness, increased temperature, swelling and decrease or loss of function. Ova—Eggs. Sigmoidoscopy—Procedure to visualize the interior of the colon. A flexible tube is inserted in the anus. An operator looks into the colon that is illuminated by a light at the end of the tube. Stool—An alternative name for feces. Tenesmus—A feeling that a bowel movement is imminent.

before touching any food. Food, especially poultry and shellfish, must be stored at appropriate temperatures and thoroughly washed before being prepared for consumption. Food must be properly prepared and held or stored at proper temperatures. Prior to cooking, foods should be kept at temperatures below 40°F (4.4°C). During cooking, the internal temperature of foods should exceed 160°F (71°C) to ensure the destruction of pathogens. While being served, food should be held at temperatures between 40 and 140°F (4.4 and 60°C). The total time that food should be allowed to remain within these temperatures is four hours. After four hours total time, including original serving and subsequent reheating, the food should be discarded. Foods that contain eggs such as mayonnaise and salads should be kept cold and protected from heat and sunlight. Day care facilities must be constantly cleaned and disinfected. Employees who change diapers must wash their hands before returning to work. Persons should drink only potable water. Water that is used for washing dishes or personal uses such as tooth brushing should also be boiled before use if the source of the water is not assured to be potable and safe. Resources BOOKS

Bass, Doesey M. “Rotavirus and other agents of viral gastroenteritis.” In Nelson Textbook of Pediatrics, 16th ed.

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Edited by Richard E. Behrman et al., Philadelphia: Saunders, 2000, 996-998. Blaser, Martin J. “Infections due to Campylobacter and related species.” In Harrison’s Principles of Internal Medicine, 14th ed. Edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 960-962. Butler, Thomas. “Shigellosis.” In Cecil Textbook of Medicine, 21st ed. Edited by Goldman, Lee and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, 1685-1687. Cleary, Thomas G. “Salmonella.” In Nelson Textbook of Pediatrics, 16th ed. Edited by Richard E. Behrman et al., Philadelphia: Saunders, 2000, 842-848. Ghishan, Fayez K. “Chronic diarrhea.” In Nelson Textbook of Pediatrics, 16th ed. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2000, 1171-1176. Gomez, Henry F. and Thomas G. Cleary. “Shigella.” In Nelson Textbook of Pediatrics, 16th ed. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2000, 848-850. Greenberg, Harry B. “Viral gastroenteritis.” In Harrison’s Principles of Internal Medicine, 14th ed. Edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 1116-1118. Guerrant, Richard L. “Campylobacter enteritis.” In Cecil Textbook of Medicine, 21st ed. Edited by Goldman, Lee and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, 1687-1690. Kapikian, Albert Z. “Viral gastroenteritis.” In Cecil Textbook of Medicine, 21st ed. Edited by Goldman, Lee and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, 1835-1840. Kaye, Donald. “Salmonella infections other than typhoid fever.” In Cecil Textbook of Medicine, 21st ed. Edited by Goldman, Lee and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, 1683-1685. Keusch, Gerald T. “Salmonellosis.” In Harrison’s Principles of Internal Medicine, 14th ed. Edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 950-957. Keusch, Gerald T. “Schigellosis.” In Harrison’s Principles of Internal Medicine, 14th ed. Edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 957-960. Pearson, Richard D. “Advice to travelers.” In Cecil Textbook of Medicine, 21st ed. Edited by Goldman, Lee and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, 1586-1590. Powell, Don W. “Approach to the patient with diarrhea.” In Cecil Textbook of Medicine, 21st ed. Edited by Goldman, Lee and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, 702-712. Ratnaike, Ranjit N. Diarrhoea and Constipation in Geriatric Practice. Cambridge (UK): Cambridge University Press, 1999. Sack, R. Bradley. “The diarrhea of travellers.” In Cecil Textbook of Medicine, 21st ed. Edited by Goldman, Lee and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, 1696-1697. 740

Weissman, Sharon B., and Robert A. Salata. “Amebiasis.” In Nelson Textbook of Pediatrics, 16th ed. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2000, 1035-1036. PERIODICALS

Ahmed F., M. Ansaruzzaman, E. Haque, M. R. Rao, J. D. Clemens. “Epidemiology of postshigellosis persistent diarrhea in young children.” Pediatric Infectious Disease Journal vol. 20 no. 5 (2001): 525-530. Fontaine O., C. Newton. “A revolution in the management of diarrhoea.” Bulletin of the World Health Organization vol. 79 no. 5 (2001): 471-472. Holt P. R. “Diarrhea and malabsorption in the elderly.” Gastroenterology Clinics of North America vol. 30 no. 2 (2001): 427-444. Mahalanabis D., A. B. Choudhuri, N. G. Bagchi, A. K. Bhattacharya, and T. W. Simpson. “Oral fluid therapy of cholera among Bangladesh refugees.” Bulletin of the World Health Organization vol. 79 no. 5 (2001): 473479. Mangala S., D. Gopinath, N. S. Narasimhamurthy, and C. Shivaram. “Impact of educational intervention on knowledge of mothers regarding home management of diarrhoea.” Indian Journal of Pediatrics vol. 68 no. 5 (2001): 393-397. Nakajima H., T. Nakagomi, T. Kamisawa, N. Sakaki, K. Muramoto, T. Mikami, H. Nara, and O. Nakagomi. “Winter seasonality and rotavirus diarrhoea in adults.” Lancet vol. 357 no. 9272 (2001): 1950-1953. Okhuysen, P. C. “Traveler’s diarrhea due to intestinal protozoa.” Clinical Infectious Disease vol. 33 no. 1 (2001): 110-114. Scheidler M.D., R. A. Giannella. “Practical management of acute diarrhea.” Hospital Practice vol. 36 no. 7 (2001): 49-56. Spencer, D.C. “Are antibiotics effective for travelers’ diarrhea?” Journal of Family Practice vol. 50 no. 6 (2001): 495-496. ORGANIZATIONS

American Academy of Emergency Medicine, 611 East Wells Street, Milwaukee, WI 53202. (800) 884-2236. Fax: (414) 276-3349. . American College of Gastroenterology, 4900 B South 31st Street, Arlington VA 22206. (703) 820-7400. Fax: (703) 931-4520. . American College of Osteopathic Emergency Physicians, 142 E. Ontario Street, Suite 550, Chicago, IL 60611. 312-5873709 or 800-521-3709. Fax: 312-587-9951. . Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30333. (404) 639-3534 or (800) 3113435. . . College of American Pathologists, 325 Waukegan Road, Northfield, IL 60093. (800) 323-4040. .

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OTHER

American Academy of Family Physicians. . Boston University: . Centers for Disease Control and Prevention. . National Digestive Diseases Clearinghouse. . National Library of Medicine. and . Quick Care. . Rehydration Project. .

L. Fleming Fallon, Jr., MD, DrPH

Diathermy see Heat treatments

Diet and health Definition Diet has a tremendous effect on health. Diet plays a role in promoting health and reducing chronic disease for many conditions such as preventing obesity, diabetes mellitus, coronary heart disease, and cancer, as well as low birth weight in babies.

Description The concept of diet quality in relation to health has changed over time. Nutrition scientists focused on preventing nutrient deficiencies early in this century, but now the shift has changed, exploring diets and chronic disease prevention and treatment. Adequate nutrition is essential to reduce morbidity and mortality from acute and chronic disease. Well-nourished people are more resistant to disease and are better able to tolerate other therapy and to recover from acute illnesses, surgery, and trauma. Nutrition also plays a key part in a patient’s recovery from a disease or treatment.

Consumption of a wide variety of foods, with appropriate amounts of protein, carbohydrate, fat, vitamins and minerals is the basis of a healthy diet. However, today’s major health care problems are increasingly the result of acute and chronic conditions related to dietary intake. In fact, eight of the 10 leading causes of death, including coronary heart disease, stroke, diabetes mellitus, and some cancers, can be attributed to diet and alcohol. Some chronic diseases continue to increase due to factors such as the rise in obesity in Western populations, Americans in particular. There is no disputing that a healthy diet can help to prevent illness and promotes a feeling of well-being. A research study reported in the Journal of the American Medical Association suggested that by following the current dietary guidelines, women are able to live longer. Women whose diets included large amounts of fruits, vegetables, whole grains, low-fat dairy, and lean meats had a lower risk of death. Women who were considered to have the best diets (those eating the highest intake level of recommended foods from the current dietary guidelines) had a 30% lower risk of death from any cause compared with those eating the lowest level of recommended foods.

Viewpoints The position of the American Dietetics Association on the role of nutrition and diet in health promotion and disease prevention programs includes steps for primary, secondary, and tertiary prevention. These steps include the following guidelines: • Primary prevention (health promotion): Health promotion is a population-based approach that encourages behaviors for better health. For example, nutrition classes at a local adult education center could be considered a primary prevention measure. • Secondary prevention (risk appraisal and risk reduction): For people at risk of illness who are beginning to encounter health-related problems, secondary prevention encompasses risk appraisal and screening to detect preclinical disease, and early intervention to promote health and well-being. For example, cholesterol screening for people with a family history of cardiovascular disease could be considered a secondary prevention measure. • Tertiary prevention (treatment and rehabilitation): For people experiencing illness or injury, tertiary prevention includes treatment and rehabilitation to promote maximum health and prevent further disability and secondary conditions resulting from the initial health problem. Examples of tertiary prevention include medical

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Pan American Health Organization, 525 Twenty-third Street, NW, Washington, D.C. 20037. (202)974-3000. Fax: (202)974-3663. . E-mail: [email protected]. World Health Organization, 20 Avenue Appia, 1211 Geneva 27, Switzerland. +41 (22) 791 4140. Fax: +41 (22) 791 4268. . [email protected].

Diet and health

nutrition therapy or diabetes education for people diagnosed with type 2 diabetes mellitus. Experts in nutrition recommend a variety of foods and the maintenance of an ideal weight. Large amounts of fat, saturated fat, and cholesterol should be avoided. Individuals should consume adequate starch and fiber and avoid excess sugar and sodium. Dietary guidelines The Dietary Guidelines for Americans, published by the U.S. Department of Agriculture and Health and Human Services, can provide a broad overall view of good nutrition. These dietary guidelines include these basic recommendations: • Eat a variety of foods; let the food pyramid guide your food choices. • Control your weight. • Be physically active each day. • Eat a diet low in saturated fat and cholesterol, and moderate in total fat. • Eat a variety of vegetables, fruits, and grains. • Eat sugar in moderation. • Use salt in moderation. • If you drink alcohol, do so in moderation; no more than two drinks per day of wine, beer, or spirits. • Keep food safe to eat; follow the government safety precautions as outlined on the food package. The Food Guide Pyramid was created by the U.S. Department of Agriculture to help Americans choose foods from each food grouping. It focuses on fat intake, which is too high in most Americans. The food pyramid, developed by nutritionists, provides a visual guide to healthy eating. At its base are those foods that should be eaten numerous times each day, while at its apex are those foods that should be used sparingly. The pyramid suggests a range of servings in each group so that the number of servings can be adjusted to suit each individual’s caloric requirements. The daily recommendations (from bottom to top) of the food pyramid include: • bread, cereal, rice, and pasta: 6–11 servings • vegetables: 3–5 servings • fruits: 2–4 servings • milk, yogurt, and cheese: 2–3 servings • meat, poultry, fish, dried beans, eggs, and nuts: 2–3 servings • fats, oils, and sweets: use sparingly 742

Other programs use the National Cholesterol Education Program Step 1 Diet guidelines, which may be followed to assist in controlling weight. The guidelines provided by the National Cholesterol Education Program can be followed for maintaining optimal blood lipid levels [total cholesterol, low-density lipoproteins (LDL), high-density lipoproteins (HDL), and triglycerides]. Health promotion and disease prevention are central components of national recommendations to improve the health of Americans in an initiative called Healthy People 2000. This program is a series of national health promotion and disease prevention objectives that examine the association between nutrition and chronic disease. A program called Healthy People 2010 is planned. National and international trends Major diet and health targets in the United States include: • Obesity. Obesity has become a major problem for Americans due to inactive lifestyles and poor diets. Estimates suggest that over 50% of Americans are overweight. Dietary modification can reduce obesity, in turn decreasing conditions and diseases such as coronary heart disease, atherosclerosis, hypertension, cancer, diabetes, and high blood cholesterol. • Diabetes. Since 1990, type 2 diabetes has jumped by 33% nationwide in the United States. Being overweight and contracting diabetes are closely linked. • Fat and cholesterol intakes. These are still too high. Since the 1960s, the average blood cholesterol level has decreased, mostly due to a shift from red meat to poultry, from whole to lower-fat milk, and from butter and lard to margarine and vegetable oils. Cholesterol has dropped to about an average of 205 mg/dl from the peak of the coronary epidemic in the 1960s of 220 to 230 mg/dl. Intake of saturated fat was about 16% in the 1960s; it has now been reduced to approximately 12%. Fat intake is too still too high. It is estimated that the average American consumes about 40% of their calories from fat. Fat source (i.e. saturated, monounsaturated, or polyunsaturated) is an important issue to consider when reducing overall fat in the diet, as some fats reduce cholesterol while others raise cholesterol. • Stroke incidence. Stroke incidence and related deaths have dropped in the last 30 to 40 years, likely due to better blood pressure control, less smoking and drinking, and possibly an increase in fruits and vegetable consumption. • Lack of exercise. Energy expenditure has declined due to more sedentary lifestyles. Those who sit at a com-

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• “Fad” and herbal diets. Throughout the 1990s and into this century, the market for dietary supplements and herbal remedies has exploded. The nutritional implications of many of these compounds has not been established with scientific research, and therefore the health implications are unknown in many cases. • Health supplements. There are a great many claims about particular vitamins, minerals, and/or antioxidants having beneficial health effects on the market today. Proper nutrition with an adequate diet is the best way to achieve vitamins, but a supplement may be required when intake is inadequate. It is important to check with a dietitian or doctor before taking nutritional supplements or alternative therapies if other medications are taken for chronic illness, because they may cause a drug interaction. Dietary recommendations in Europe and Australasia are comparable with those in the United States. The European guidelines suggest, as do those in the United States, that total fat should provide 30% or less total energy, which implies that complex carbohydrates, fruits, cereals, and vegetables should be increased to replace the foods rich in total and saturated fat which have been eliminated. The European Atherosclerosis Society states that for those with total cholesterol levels of 200-250 mg/dl (5.2-6.5 mmol/L), dietary modification to reduce the risk of coronary heart disease (CHD) is required. While CHD incidence is declining in western Europe, Australia, and the United States, it is rapidly rising in central and eastern Europe and in some Asian countries. These regions are undergoing unprecedented economic growth and rapidly changing lifestyles in many aspects including dietary intake. These changes have led to an increase in CHD incidence and death. Singapore, the most economically developed country in Asia, also has the highest prevalence of CHD deaths, at rates similar to those of the United States and Australia. This region may serve as a warning that Asia may expect an escalation in CHD. Although cholesterol levels vary widely over Asia, CHD mortality is evidenced where cholesterol levels have increased from previously low levels and in regions where the highest cholesterol levels predominate. Australasian (National Heart Foundation of New Zealand Scientific Committee and the National Heart Foundation of Australia) and European (British Hyperlipidaemia Association, British Hypertension Society) guidelines for the prevention of CHD in clinical practice emphasize the need to determine the absolute CHD risk for any individual in order to decide the most appropriate therapy. This, of course, includes

dietary management to control fat intake and cholesterol. Clearer statements and guidelines on the prevention and control of diabetes and hypertension as well as diet, obesity, exercise, and smoking may be appropriate.

Professional implications Qualified dietetics professionals assist in encouraging good nutrition and/or dietary change as a method of promoting health and preventing chronic disease. Nursing and allied health professionals can reinforce good dietary choices and provide nutrition guidance for patients in hospitals, long-term care facilities, or in community settings. In general, only registered dietitians (R.D.) have sufficient training and knowledge to accurately assess the nutritional adequacy of a patient’s diet, especially if chronic disease is present. A doctor may also have a nutrition background or specialization and may thus be able to conduct a dietary assessment or to provide general nutrition advice and/or diet therapy. When an individual or patient is using dietary means to help recover or control a disease or condition, it is often called medical nutritional therapy. To maintain health in a patient with a nutrition-related illness, all health care team members and especially the patient must commit to achieving optimum health through medical nutritional therapy. Prioritized goals are critical when developing the nutrition treatment plan. Continuous assessment is made by the patient and health care team members to evaluate the importance of these and other goals. Physicians must understand the dietary approaches an individual is using and reinforce this diet therapy when interacting with the individual. The position of the American Dietetic Association is that medical nutritional therapy is effective in treating disease and preventing disease complications. Resources BOOKS

Institute of Medicine. Dietary Reference Intakes: Applications in Dietary Assessment. Washington, D.C.: National Academy Press, 2001. Institute of Medicine, ed. Dietary Reference Intakes: Risk Assessment (Compass Series). Washington, D.C.: National Academy Press, 1999. Larson-Duyff, Roberta. The American Dietetic Association’s Complete Food & Nutrition Guide. New York: John Wiley & Sons, 1998. Mahan, L. Kathleen, and Sylvia Escott-Stump., eds. Krause’s Food, Nutrition, & Diet Therapy. London: W.B. Saunders Co, 2000.

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puter all day expend fewer calories than in physicallabor jobs.

Diet therapy

OTHER

KEY TERMS

Food and Nutrition Professionals Network .

Dietitian—A health professional who has a bachelor’s degree, specializing in foods and nutrition, and in addition undergoes a period of practical training in a hospital or community setting. Many dietitians further their knowledge by pursuing master’s or doctoral degrees. The title “dietitian” is protected by law so that only qualified practitioners who have met education qualifications can use that title.

Crystal Heather Kaczkowski, MSc.

Diet pills see Fad diets

Diet therapy Definition

Netzer, Corinne T. The Complete Book of Food Counts. New York: Dell Publishing Company, 2000. Nutrition and Your Health: Dietary Guidelines for Americans. 5th edition. Hyattsville, MD: U.S. Department of Agriculture, U.S. Department of Health and Human Services, 2000. Rodwell-Williams, Sue. Essentials of Nutrition and Diet Therapy (With CD-ROM for Windows and Macintosh). London: Mosby-Year Book, 1999. PERIODICALS

American Dietetics Association. “Women’s health and nutrition—Position of ADA and Dietitians of Canada.” Journal of the American Dietetic Association 99 (1999): 738–751. Hu F.B., et al. “Trends in the incidence of coronary heart disease and changes in diet and lifestyle in women.” New England Journal of Medicine 343 (2000): 530–537. Kant, Ashima K., et al. “A Prospective Study of Diet Quality and Mortality in Women.” Journal of the American Medical Association 283 (2000): 2109–2115. Patterson, Ruth E. “Is there a consumer backlash against the diet and health message?” Journal of the American Dietetic Association 101 (2001): 3741. Stampfer M.J., et al. “Primary prevention of coronary heart disease in women through diet and lifestyle.” New England Journal of Medicine 343 (2000): 16–22. ORGANIZATIONS

American Dietetic Association. 216 W. Jackson Blvd. Chicago, IL 60606-6995. (312) 899–0040. . American Heart Association National Center. 7272 Greenville Avenue, Dallas, Texas 75231. (800) AHA-USA1. . Food and Nutrition Information Center Agricultural Research Service, USDA. National Agricultural Library, Room 304, 10301 Baltimore Avenue, Beltsville, MD 207052351. (301) 504–5719, Fax (301) 504–6409. . [email protected].

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Diet therapies are specially designed and prescribed for medical and/or general nutritional reasons.

Purpose Diet therapy promotes a balanced selection of foods vital for good health. By combining foods appropriate for each individual and drinking the proper amount of water, one can help maintain the best possible health. Eating the proper diet is critical for the health of individuals, groups with special medical and dietary needs, and entire populations afflicted with malnutrition.

Precautions A particular modified diet is prescribed specifically for each individual. Those individuals who have medical conditions or who are sensitive to certain foods need to be very compliant and cautious about what they eat. Individuals should not follow a “fad” diet without first consulting a registered dietitian or physician. Popular (but sometimes dangerous) low-carbohydrate diets, for example, may deprive the body of the glucose it needs for central nervous system and brain functions.

Description Nutrition is the science concerned with the human body’s use of nutrients and food substances. Proper nutrition decisions are important for the optimal health of each individual. This is especially true for those individuals with specific dietary needs and acute or chronic diseases. The nutrients necessary to maintain normal growth and health include proteins, carbohydrates, fats, vitamins, and minerals. Included in these nutrients are eight amino acids the body cannot produce but that must be derived from proteins, four fat-soluble and ten watersoluble vitamins, ten minerals, and three electrolytes.

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PROTEIN. Protein is important for building body tissue and synthesizing enzymes. Enzymes are specialized organic substances that act to regulate the speed of chemical reactions in human metabolism. Twenty amino acids of the 100 or more occurring in nature make up proteins. Animals and plants are quick and available sources of what are termed “essential” amino acids; they are called essential because the body cannot build them internally. Normal growth and health are dependent upon these essential amino acids. Dietitians recommend that a healthy diet includes 10–20% of daily calories from protein (poultry, fish, dairy, and vegetable sources). CARBOHYDRATES. Carbohydrates provide most of

the energy in the majority of human diets. Foods rich in carbohydrates are usually the most abundant and cheapest. The carbohydrates containing the most nutrients are the complex carbohydrates, such as unrefined grains, tubers, vegetables, and fruits. Simple carbohydrates or sugars should be eaten in moderation, since they are high in calories but low in nutrients. Carbohydrates are needed in the form of glucose by the brain and central nervous system (CNS). A minimum of 1.6 oz (50 g) of glucose is required daily for proper functioning of the CNS. If the body is denied carbohydrates, it will use ketone bodies for energy, but this is not a good energy source for the body, and may have unfavorable health effects. FATS. Fats supply energy and essential fatty acids and promote absorption of the fat-soluble vitamins A, D, E, and K. The accumulation of body fat has become a serious health concern; over 50% of Americans are considered overweight. Fats are compact fuels efficiently stored in the body for later use when carbohydrates are in short supply. Fats produce more than twice as much energy as carbohydrates, approximately 9 Kcals/gram versus about 4 Kcals/gram for carbohydrate and protein. Dietary fats are broken down into fatty acids that pass into the blood. These fatty acids are either saturated or unsaturated (mono-unsaturated, polyunsaturated, or trans-unsaturated). Saturated fats, derived mostly from animal sources, have been found to raise the level of total cholesterol in the bloodstream, and certain unsaturated fats tend to lower the level of total cholesterol in the blood stream. For example, mono-unsaturated fats like oleic acid in olive oil reduce low-density lipoprotein cholesterol (bad cholesterol) and increase high-density lipoprotein cholesterol (good cholesterol), thus reducing the risk of heart disease. Saturated and trans-unsaturated fatty acids both raise serum cholesterol; in contrast, neither mono-unsaturated nor polyunsaturated fats have this effect.

INORGANIC MINERAL NUTRIENTS. Inorganic mineral nutrients are required to build tissues. They are also important for muscle contractions, nerve reactions, and blood clotting. All of these mineral nutrients must be supplied in the diet. Minerals are categorized as major elements or trace elements. Major elements consist of calcium, phosphorus, magnesium, iron, iodine, and potassium. Trace elements include copper, cobalt, manganese, fluorine, and zinc. VITAMINS. Vitamins increase the breakdown and absorption of proteins, carbohydrates, and fats. Certain vitamins help form blood cells, hormones, nervous system chemicals, and genetic materials. Vitamins are classified into two groups: fat-soluble vitamins, such as A, D, E, and K; and water-soluble vitamins, such as vitamin C and the B-vitamin complex. Fat-soluble vitamins are usually found in foods that contain fat. Because excess amounts are stored in the body’s fat and in the liver and kidneys, fat-soluble vitamins do not have to be consumed every day. The water-soluble vitamins, C and B complex, cannot be stored and must be consumed daily to replenish the body’s supply.

Food types Foods can be widely grouped into breads and cereals; legumes, tubers or starchy roots; vegetables and fruits; meat, fish, and eggs; milk and milk products; fats and oils; and sugars. Breads and cereals are high in starches (carbohydrates), but whole cereals also often supply significant amounts of protein. However, these cereals should be eaten in conjunction with other protein foods to supply all the essential amino acids. Meat, fish, and eggs supply all the essential amino acids that the body needs to build its own proteins. Milk and milk products also provide a plentiful amount of protein, phosphorus, calcium, and vitamins. Legumes are rich in starch but also furnish more protein than cereals or tubers. Tubers provide a variety of minerals and vitamins. Vegetables and fruits are a direct source of many minerals and vitamins. Fats and oils are high in calories but usually contain few nutrients. Sugars, which are heavily consumed in more affluent countries, contain few nutrients and can cause tooth decay. Dietary guidelines The Food and Nutrition Board of the National Research Council of the National Academy of Sciences has determined dietary standards called Recommended Dietary Allowances (RDA). These standards explain the daily amounts of energy, protein, minerals, and fat-soluble and water-soluble vitamins needed by healthy males and females, from infancy to old age. The RDA has been

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under revision and is replaced by the Dietary Reference Intakes (DRI) as of 2001. The DRI will be applicable to Canadians and Americans. Like the RDA, the DRI recommends an average daily intake for a nutrient, but the DRI is more comprehensive than the RDA. It incorporates updated scientific research into providing expert guidance for issues such as risk reduction for chronic disease and upper limits of intake for nutrients with adverse health effects. Experts in nutrition recommend a variety of foods and the maintenance of an ideal weight. Large amounts of fat, saturated fat, and cholesterol should be avoided. Individuals should consume adequate starch and fiber and avoid excess sugar and sodium. The U.S. Department of Agriculture and the U.S. Department of Health and Human Services have developed official dietary guidelines that include these seven basic recommendations: • Eat a variety of foods. • Control your weight. • Eat a low-fat, low-cholesterol diet. • Eat plenty of vegetables, fruits, and grains. • Eat sugar in moderation. • Use salt in moderation. • If you drink alcohol, do so in moderation; no more than 2 drinks per day of wine, beer, or spirits. The food pyramid, developed by nutritionists, provides a visual guide to healthy eating. At its base are those foods that should be eaten numerous times each day, while at its apex are those foods that should be used sparingly. The pyramid suggests a range of servings in each group so that the number of servings can be adjusted to suit each individual’s caloric requirements. The daily recommendations (from bottom to top) of the food pyramid include: • bread, cereal, rice, and pasta: 6–11 servings • vegetables: 3–5 servings • fruits: 2–4 servings • milk, yogurt, and cheese: 2–3 servings • meat, poultry, fish, dried beans, eggs, and nuts: 2–3 servings • fats, oils, and sweets: use sparingly Energy requirements Carbohydrates, proteins, and fats provide energy in the form of calories to fuel the body for metabolic processes, growth, and activity. When an individual consumes as many calories each day as the body uses, they 746

are in a state of energy balance and will neither gain nor lose weight. When more calories are eaten than the body uses, the excess calories are stored as fat and weight increases. On the other hand, when fewer calories are consumed than the body needs, stored fat is burned and weight decreases. Using the metric system nomenclature, a kilojoule (kJ) is used instead of a kilocalorie (kcal), where 1 kcal=4.184 kJ and 1 megajoule (MJ)=1000 kJ. The amount of energy required depends on such factors as an individual’s weight, gender, age, and activity level, so an estimation should be made based on these parameters. Some dietary guidelines do suggest an average energy intake for people in different age groups, but many of the guidelines do not base the estimations on measures such as activity level. The Food and Agriculture Organization/World Health Organization uses a more accurate method for estimating energy requirements for populations and individuals. They define energy requirement as “... the amount of energy needed to maintain health, growth, and an appropriate level of physical activity.” The “appropriate level of physical activity” is not a standardized level, but is dependent on social, cultural, and lifestyle factors. Physical activity categories for light, moderate activity or heavy work are used to provide a better energy estimation. For example, a 143 lb (65 kg) woman between the ages of 30-60 years who participates in light activity would require about 2190 kcal/day (9.2 MJ/day). At a moderate activity level, this same woman would require approximately 2300 kcal/day (9.6 MJ/day) and 2550 kcal/day (10.7 MJ/day) for heavy activity. Calorie-modified diet Calorie-modified diets are prescribed to correct weight problems with a healthy diet. Low-calorie diets are designed for weight reduction and are prescribed for people who are overweight or obese. High-calorie diets are recommended for people with greatly increased energy needs such as athletes in training or individuals fighting diseases such as cancer, AIDS, or cystic fibrosis. Highcalorie diets are also prescribed to treat anorexia nervosa. Calorie-modified diets are planned by dietitians and should be prescribed following a complete physical examination and dietary assessment or dietary history. A low-calorie diet provides enough energy to meet the person’s metabolic needs and activity level. It includes a balanced variety of foods, but limits carbohydrates and alcohol. A low-calorie diet should not aim to promote a weight loss of more than approximately 1–2 lb (500 grams to one kilogram) per week. In general, for a slightly overweight person, it is not wise to lose more than 1 lb (about 500 grams) per week. A high-calorie diet usually

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When caloric limits allow, have no more than two drinks of wine, beer or liquor per day. Fiber-modified diet Fruits and vegetables are excellent sources of fiber. Fiber has important nutritional benefits such as facilitating the movement of food through the digestive tract, helping to prevent constipation. Research suggests low dietary fiber may be responsible for increasing the incidence of diverticulosis and may also be associated with cancer of the colon. High-fiber diets, including whole grains (especially bran), raw vegetables, unpeeled fresh fruits, nuts, and seeds, are recommended to: • increase fecal bulk • increase intestinal movement • prevent or treat constipation, diverticulosis, Crohn’s disease, or irritable bowel syndrome • help lower cholesterol • assist with weight loss in people who are overweight and improve sugar tolerance in diabetics Low-fiber diets exclude raw fruits and vegetables, whole grains, nuts, and seeds, while emphasizing soft, mild foods. They are recommended to: • decrease fecal bulk • slow intestinal movement • decrease stomach acid secretion • treat a variety of disorders including indigestion, diarrhea, bowel inflammation, and heart attack Protein-modified diet High-protein diets are designed to provide about 0.05 oz (1.5 g) of protein for each kilogram of a person’s body weight. Complex proteins, such as milk and meats, should make up one-half to two-thirds of the daily protein requirement. High-protein diets are recommended for people who: • have an increased need for protein due to protein-calorie malnutrition, severe stress, or conditions such as AIDS, cancer, or burns with high metabolic rates that lead to the loss of large amounts of protein

• have malabsorption syndromes, celiac disease, or other disorders characterized by poor food absorption A low-protein diet excludes dairy products and meats, and requires that about three-fourths of the daily allowance of protein come from high-value protein sources. Supplements may be prescribed to prevent amino acid deficiencies. Low-protein diets are used in treatment of cirrhosis and kidney disease. Low-cholesterol diet Dietary modification is the first weapon in the fight against the high cholesterol levels that contribute to heart disease and atherosclerosis. Low-cholesterol diets are prescribed to reduce the risk of heart disease and to treat atherosclerosis, diabetes, high cholesterol (which may be hereditary and might also require cholesterol-reducing drugs), and high blood pressure. A low-cholesterol diet is not a cure for the conditions it is prescribed to treat, so most people must stay on the diet for the rest of their lives. The American Heart Association eating plan recommends that total cholesterol intake should be less than 0.01 oz (300 mg) per day and total fat intake should be 30% or less of total calories. Saturated fatty acid intake should be less than 10% of calories or for anyone with elevated blood cholesterol levels or heart disease, saturated fat and cholesterol intake is limited even further to 7% of total calories per day. The AHA eating plan also suggests: • Polyunsaturated fatty acid intake should be 8–10% of calories. • Mono-unsaturated fatty acids should make up the rest of the total fat intake, up to 15% of total calories. These guidelines apply to all healthy individuals over two years of age. Low-fat diet Most American diets contain too much fat. Fat often makes up about 40% of total calories consumed each day. Registered dieticians recommend limiting fat to 30% or less of daily calories, since consumption of too much fat has been linked to obesity, heart disease, and several types of cancer. A low-fat diet usually limits daily fat intake to 1.76 oz (50 g), while an extremely low-fat diet limits fat consumed each day to 0.88–1.05 oz (25–30 g). The grams of fat in your diet will depend on the calories you need. Low-fat diets are recommended to: • help prevent heart disease • help prevent colon, prostate, and breast cancers

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provides an extra 500–1,000 calories, leading to a weight gain of about 1 lb (500 grams) per week for most people. It has a high protein content, normal fat content, and emphasizes foods that pack many calories into a small volume. Snacking between meals is encouraged as a way to increase the calories consumed.

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• help treat a variety of conditions including gout, AIDS, gallbladder disease, liver disease, celiac disease, inflammatory bowel disease, and heartburn • lose or control weight Some fat is required in the diet to prevent essential fatty acid deficiencies, but most people consume more than enough fat to meet these needs. Cutting back on fat will likely help you eat fewer calories. Make sure to read the nutrition facts label on foods. The Dietary Guidelines recommend limiting fat intake to 30% of calories or less, which corresponds to 1.87 oz (53 g) of fat in a 1,600 kcal diet, 2.57 oz (73 g) of fat in a 2,200 kcal diet, and 3.28 oz (93 g) of fat in a 2,800 kcal diet. Gluten-free diet Gluten and gliadin are proteins found in certain grains and grain-containing products. These proteins are toxic to cells within the intestinal tract of an individual who is “intolerant” and cause difficulty in food absorption. Celiac disease is caused by intolerance to these proteins. This intolerance causes patients with celiac disease to suffer weight loss, diarrhea, malnutrition, and bloating. By eliminating foods containing gluten from the diet, further damage to the intestines can be prevented, symptoms are relieved, and malabsorption of nutrients is corrected. A gluten-free diet eliminates all foods containing wheat, rye, barley, and malt, and must be followed for life. Low-purine diet This diet restricts food, such as sardines, liver, and eggs, that cause the body to produce uric acid. It is usually prescribed as part of a treatment program for gout (a disease usually caused by having too much uric acid in the body) and kidney stones, which also includes exercise and medication. In addition to excluding organ meats (sweetbreads, liver, kidney) and certain types of fish (anchovies, sardines, mackerel) and limiting the amount of other purine-containing foods such as shrimp, meats, and dairy products, this diet emphasizes drinking about 2 qt (1.89 l) of water and fruit juice daily, to promote the excretion of uric acid, and eating fruits and vegetables that increase urine alkalinity and the solubility of uric acid. Low-salt diet On the average, Americans consume about 0.17 oz (5 g) of salt or sodium daily. Dietary guidelines suggest that 0.08 oz (2.4 g) of sodium should be the upper limit, even if there are no signs of heart disease. Most people 748

with heart disease should limit their sodium intake to less than 0.07 oz (2 g) a day, and some low-salt diets restrict sodium to as little as 0.008 oz (250 mg) per day. The amount of salt in the diet is important for people who have high blood pressure or congestive heart failure. Some experts believe excessive intake of salt is a major reason for high blood pressure, especially in Western countries. Excess sodium encourages the body to retain fluid, thereby increasing fluid pumped by the heart and circulating in the bloodstream. Diets high in salt also can be harmful to people with congestive heart failure because the excess fluid backs up into the lungs, causing congestion. Potassium chloride is a common ingredient in salt substitutes. But too much potassium can be harmful for people with kidney problems. One way to enhance the flavor of food while eliminating salt is to add lemon juice, herbs, spices, or flavored vinegar. Low phenylalanine diet A low phenylalanine diet is normal treatment for phenylketonuria (PKU). PKU is a rare genetic disorder in the degradation of dietary phenylalanine that if left untreated, can result in severe progressive mental retardation. The diet is extremely restrictive, and rigorous dietary compliance is necessary to reduce or prevent mental retardation. Close supervision by a registered dietitian or physician is necessary. A normal diet cannot be tolerated by people with PKU. Dietary treatment necessitates avoiding foods containing high levels of protein. A diet contains only the amount of phenylalanine which is essential for the body. Basic principles of the PKU diet state that: • Meat, fish, cheese, eggs, milk and nuts are not allowed because they are rich in protein and thus phenylalanine. • Other foods which contain moderate amounts of protein (i.e. potato and cereals) are given in small measured quantities. These foods are spread out between the day’s meals to keep the phenylalanine levels steady. • Most fruits, some vegetables, and salads can be taken in normal quantities but excessive use should be avoided. • Sugar, jam, syrups, and fats such as butter, lard, and cooking oil can be used fairly freely. • There are many low protein manufactured foods available on prescription. These can all be taken freely to provide variety in the diet. Foods include pasta, low protein bread, biscuits, flour, and spaghetti, etc. • Infants can be fed phenylalanine-free formulas.

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Diabetic diet For the most part, dietary management is the key to keeping diabetes in check. There is controversy regarding dietary recommendations for diabetes control and at present, there is no single diet that meets the needs of all diabetics. The general rules for healthy eating as discussed previously apply to diabetics as well. Several dietary methods are available for controlling blood sugar levels. The Food Guide Pyramid is recommended by the U.S. government for everyone including diabetics. Some experts believe these dietary guidelines may be sufficient for diabetics, although there are more detailed dietary methods available for controlling blood sugar. These methods may be complex, however, which deters many diabetics from using them. The American Diabetic Association and American Dietetic Association developed the Diabetic Exchange Lists, the most common system used for controlling blood sugar. Other nutrition experts recommend adopting a Mediterranean diet because they point out the food pyramid has some drawbacks; for example, there is little focus on meal planning. Carbohydrate counting plans may assist but may also be complicated and require a committed learner; the concepts of the Diabetic Exchange Lists may be difficult to understand for some people. Type 1 and type 2 diabetics on insulin or oral medication must focus on controlling blood glucose levels by coordinating food intake with insulin administration or medication, or other variables such as exercise. Nutrition habits that assist in glucose control: • Stick to a meal plan. • Appropriately treat hypoglycemia (low blood sugar). • Quickly respond to hyperglycemia (high blood sugar). • Maintain consistent snacking habits. The recommendation given by the American Diabetes Association is to eat more starches. This is the opposite of what has been advised in past years. Current research studies now show it is healthiest for everyone to eat more grains, beans, and starchy vegetables to control fat and cholesterol. Total carbohydrate intake has greater impact on blood glucose control than the source of carbohydrate. However, consumption of complex carbohydrates (i.e. whole grain bread, beans, etc.) are better than eating foods that are sucrose (simple sugar) based.

Both weight loss and blood sugar control are particularly important for overweight type 2 diabetics who are not taking medication. Health effects are most beneficial after initial weight loss. A 10% decrease in body weight can control the progression of type 2 diabetes. Other important issues are controlling lipid (cholesterol and triglyceride) levels, and blood pressure. Controlling fat intake is important because diabetics are about twice as likely to get cardiovascular disease compared to other people. Research shows that diabetics have the same protein requirements as other people, but with onset of nephropathy, protein should be limited to 0.8 grams/kg per day for adults, with 80% coming from high biological value protein. Traditional diets may offer some health advantages Certain populations have dietary habits that are much healthier than the typical Western diet, which is often too high in fat and cholesterol. Research has shown that the traditional Mediterranean diet, Japanese diet, or “hunter-gatherer” diets have health advantages. The dietary habits characteristic of Mediterranean countries with the consumption of olive oil (mono-unsaturated fatty acid) as the main fat source appear to provide optimal health benefits with a low incidence of coronary heart disease. The Mediterranean diet consists of large amounts fruit, vegetables, pulses, nuts, cereal products, and fish, while generally only small amounts of meat and dairy foods are consumed.

Preparation Effective estimation of an individual’s diet is required in order to provide dietary counseling and guidance. If a dietary assessment is not conducted in preparation, using proper methodologies, it will be difficult for the dietitian to draw any conclusions regarding the need for diet therapy. Despite the diet type, all foods should be prepared appropriately. This includes adequate cooking time and proper storage. Some diets must be phased-in gradually.

Aftercare Regular physician follow-up is always important when the individual has been placed on a special diet because of a health condition. One cannot live on “a diet” permanently, because strict guidelines are difficult and painstaking to follow. Therefore, dietary modifications have to be lifestyle

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There is a high incidence of tooth decay among individuals affected by PKU because of the increased amounts of CHOs consumed.

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changes in food selection and more healthy attitudes about nutrition and wellness.

KEY TERMS Calorie—Commonly referred to as a calorie, but is actually a kilocalorie (kcal). A kilocalorie is the energy required to raise the temperature of one kilogram of water one degree Celsius. It is how the energy content of food is measured. Dietary assessment—An estimation of food and nutrients eaten over a particular time point. Some of the most common dietary assessment methods are food records, dietary recalls, food frequency questionnaires, and diet histories. Dietitian—A dietitian is a health professional who has a bachelor’s degree, specializing in foods and nutrition, and in addition undergoes a period of practical training in a hospital or community setting. Many dietitians further their knowledge by pursuing master’s or doctoral degrees. The title “dietitian” is protected by law so that only qualified practitioners who have met education qualifications can use that title. Electrolytes—Any of the various ions, such as sodium, potassium, or chloride, required by cells to regulate the electric charge and flow of water molecules across the cell membrane. Kilojoule—In Europe and other countries, food energy values are frequently given in kilojoules (kJ), the metric unit of energy. Using the metric system nomenclature, a calorie is converted into a kilojoule (kJ), where 1 kcal=4.184 kJ and 1 megajoule (MJ)=1000 kJ. To convert kilojoules to kcals, divide by 4.184. Legumes—A pod, such as a pea or bean, that splits into two valves with the seeds attached to one edge of the valves. Nutritionist—Some dietitians call themselves “nutritionists” but in general, the term “nutritionist” is not protected by law, therefore anyone can call themselves a nutritionist. Trans-unsaturated fatty acids (also called transfatty acids or trans-fat)—To make foods that will stay fresh on the shelf or to get a solid fat product, such as margarine, food manufacturers hydrogenate (i.e. add hydrogen) to polyunsaturated oils. This changes the double bond on the carbon atom from a cis configuration to a trans configuration, making the fatty acid saturated, and more of a health concern. For example, stick margarines are known to contain more trans fatty acids than liquid oils.

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Risks There is always the possible risk of non-compliance of any diet. However, when the individual is placed on the appropriate diet and the primary physician is aware of any known allergies, there are very few risks involved, if any.

Results When special diets are followed as prescribed, better health is the expected outcome, with a decreased risk of acquiring many diseases. However, it is up to an individual to implement the necessary dietary modifications. If a patient does not follow the recommended dietary guidance, then they will not receive a benefit. Typically, modest effects are seen in weight loss or reduction in serum lipids (i.e. cholesterol) often due to failure to fully comply with the dietary recommendations provided by a dietitian or doctor. The outcome of any diet therapy will be better when combined with exercise unless the patient is unable to exercise for medical reasons. If the appropriate diet is prescribed by medical professionals, abnormal results are very rare.

Health care team roles A certified nutrition professional such as a registered dietician (R.D.) should be seen for a dietary assessment and professional dietary counseling prior to commencing diet therapy. Beware of individuals prescribing diets without an education in dietetics and nutrition. In general, only registered dietitians have sufficient training and knowledge to accurately assess the nutritional adequacy of a patient’s diet, especially if chronic disease is present. Some dietitians call themselves nutritionists, but the term “nutritionist” is not regulated by law; therefore anyone can call themselves a nutritionist. A doctor may also have a nutrition background or specialization and may thus be able to conduct a dietary assessment or to provide general nutrition advice and/or diet therapy. Resources BOOKS

Institute of Medicine, ed. Dietary Reference Intakes: Risk Assessment (Compass Series). Washington, D.C.: National Academy Press, 1999. Institute of Medicine. Dietary Reference Intakes: Applications in Dietary Assessment. Washington, D.C.: National Academy Press, 2001.

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PERIODICALS

Hu F.B., et al. “Trends in the incidence of coronary heart disease and changes in diet and lifestyle in women.” New England Journal of Medicine 343 (2000): 530–537. Stampfer, M. J., et al. “Primary prevention of coronary heart disease in women through diet and lifestyle.” New England Journal of Medicine 343 (2000): 16–22. ORGANIZATIONS

American Dietetic Association. 216 W. Jackson Blvd. Chicago, IL 60606-6995. (312) 899–0040. . American Heart Association National Center. 7272 Greenville Avenue, Dallas, Texas 75231. (800) AHA-USA1. . Food and Nutrition Information Center Agricultural Research Service, USDA. National Agricultural Library, Room 304, 10301 Baltimore Avenue, Beltsville, MD 207052351. (301) 504–5719. Fax (301) 504–6409. . [email protected]. National Society for Phenylketonuria. P.O. Box 26642, London, UK, N14 4ZF. . OTHER

Food and Nutrition Professionals Network. .

Crystal Heather Kaczkowski, MSc.

• food frequency questionnaires (FFQs) • dietary histories • observed intakes • chemical analyses of duplicate collections of foods consumed • biological assessments (e.g. doubly-labelled water, plasma carotene, etc.)

Purpose A dietary assessment is often conducted to determine the macronutrient (energy or caloric, protein, and fat) content and the micronutrient (vitamin and mineral) content of the diet to assist in providing dietary counseling. The validation of dietary assessment instruments is important to evaluate the diet in terms of a chronic disease risk factor. It is often used as a tool to help the patient lose weight, or to prevent or treat conditions or diseases that are influenced by food intake and nutritional status (i.e. cardiovascular disease, cancer, obesity, diabetes, hyperlipidemia). A guide to the amount an average person needs each day to remain healthy has been determined for each vitamin and mineral as well as macronutrients. In the United States, this guide is called the recommended daily allowance (RDA). Consumption of too little or too much of certain vitamins and minerals may lead to a nutrient deficiency or a nutrient toxicity respectively. The RDA suggests a level of vitamin and minerals that is adequate for approximately 98% of healthy people in the population. The dietitian may use the dietary assessment to compare it to population requirements for nutrients (such as the RDA) to ensure the diet has proper intakes of energy, protein, fat, vitamins, and minerals. The RDA is under revision and will become the Dietary Reference Intakes, and will be applicable to Canadians and Americans.

Precautions

Dietary assessment Definition A dietary assessment is an estimation of food and nutrients eaten over a particular time point. There are a number of dietary assessment tools used by dietitians, nutritionists, and doctors that aid in dietary counseling. These include: • food records or diaries (including weighed intakes) • dietary recalls

Dietary assessments are estimations based on an intake of a particular time point and cannot generalize that the diet is adequate or inadequate since intake varies day to day. For example, fruit and vegetables may be lacking on a day that was surveyed for the dietary assessment while overall the diet may be adequate in fruit and vegetable intake. Thus, care must be taken regarding generalizations about deficiencies or adequacy of nutrient intake. Intake of energy, carbohydrates, and protein varies less from day to day and may be estimated more closely than vitamin and mineral intakes.

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Larson-Duyff, Roberta. The American Dietetic Association’s Complete Food & Nutrition Guide. New York: John Wiley & Sons, 1998. Mahan, L. Kathleen, and Sylvia Escott-Stump, eds. Krause’s Food, Nutrition, & Diet Therapy. London: W.B. Saunders Co, 2000. Netzer, Corinne T. The Complete Book of Food Counts. New York: Dell Publishing Company, 2000. Rodwell-Williams, Sue. Essentials of Nutrition and Diet Therapy (With CD-ROM for Windows and Macintosh). London: Mosby-Year Book, 1999.

Dietary assessment

Description Some of the most common tools that assist in providing dietary advice include food records, 24 hour dietary recalls, food frequency questionnaires, diet histories, and several other methods including biochemical indices. These tools are explained in greater detail below. Furthermore, a scientific assessment of nutritional status may be made by using a combination of the information collected from clinical evaluations, biochemical tests, and dietary information. The clinical evaluation includes measurements of various anthropometric parameters such as height, weight, and percent body fat (determined by skinfolds or hydrostatic weighing). In addition, a clinical evaluation may also include observations for signs of nutrient deficiencies in the mouth, skin, eyes, and nails. The information collected from a clinical evaluation can be compared with that obtained from the dietary assessment and biochemical tests to provide a comprehensive picture of the patient’s current nutritional status and relative risk factors for diet-related illnesses.

provide sufficient information on nutrient intakes and cannot account for day to day variation in intake, however, repeated 24 hour recalls can be used to more precisely estimate intake. Food frequency questionnaire A food frequency questionnaire (FFQ) is generally designed to provide qualitative data regarding food consumption patterns rather than nutrient composition and intake. The aim is to assess the frequency at which certain foods are consumed, for example, daily, weekly, monthly or yearly. Advantages of the FFQ are that it is quick, inexpensive, and can be administered by patients themselves. Disadvantages are that it cannot provide adequate quantitative data to use for individuals, although semi-quantitative FFQs provide some measure of quantity. As well, it does not address culture-specific foods since it primarily contains lists of somewhat standard North-American type foods. Accuracy and validation in specific cultures necessitates the use of another dietary assessment tool.

Food records This method instructs subjects to record at the time of consumption all foods and beverages consumed for a specified duration, typically one to seven days, in order to quantify intake. Three or seven day food records are the most common. Food records can be estimated or weighed, the latter providing a more precise measure of intake. Portion sizes can be obtained through the use of household measures, cups, spoons, and scales. All days of the week should be proportionally included to avoid day of the week effects on nutrient and compositional intake. The weighed food record is the preferred method for assessing individual requirements because of its ability to determine intake quantitatively. Disadvantages of the method are that it is laborious and it may be a considerable burden to correctly measure and record intake. 24-hour recall The 24-hour recall is a method for quantifying dietary intake for a group average and is not suited for individual dietary characterization although it is often used for this purpose. A person’s previous 24-hour food intake is probed by an interviewer to provide detailed descriptions of portion sizes, condiments used, cooking method, and brand names. Quantities are often estimated in household measures or using food models for assistance to more accurately quantify intake. Recalls can be repeated on several occasions in the same person in order to increase accuracy and precision. Advantages of the 24hour recall is that it is inexpensive, quick, and places little burden on the patient. Single 24-hour recalls do not 752

Diet history The diet history attempts to measure usual intake in the past over a longer time period than other methods of dietary assessment. It consists of three parts, although it is often modified, including a 24 hour recall, a food frequency questionnaire, and a 3 day food record. Portion sizes are estimated by a variety of methods including household measures, food models, household utensils, photographs, or actual food. An advantage of the diet history is that it provides qualitative and quantitative data of food intake. It also considers seasonal and day to day variations. Disadvantages are that the method is labor-intensive. Other methods The use of a portable electronic set of tape recording scales (PETRA), photographs, voice-taped, and videotaped recordings have been used as dietary assessment tools. Biochemical tests may also be used to further identify a patient’s nutritional status. Serum albumin, hemoglobin or hematocrit are used to measure plasma protein. Lymphocytes and various skin tests are used to measure immune system integrity, and various urine tests such as a calculation of urinary nitrogen are used as an indication of protein metabolism. Other indices include urinary potassium, serum concentrations of carotenoids, and stable isotopes that measure water turnover which is an indicator of energy expenditure. These indices are often more reliable and representative of true intake than methods which rely on the subject’s ability to record or recall intake.

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There are also a number of internet websites where food records or recalls can be self-administered by patients for dietary assessment. Some of these websites are listed in the resources sections below.

Preparation Systematic problems exist in the quantification of food intake using dietary assessment tools that depend on self-reported measures (i.e. when the patient subjectively reports their own food intake). This is due to the fact that these methods rely on the patient’s ability to recall or record food intake accurately. Therefore, selection of the appropriate method for dietary assessment is important to meet the goals of dietary counseling.

Complications Measurement of dietary intake typically relies on self-reported data. Most dietary collection tools using self-reported intake have not included a test for accuracy or bias to validate the data collected. These validations are difficult to conduct because in an individual who is eating at home, there are few methods to use as a reference to validate the dietary intake data. There are subgroups of the population that are more likely to provide inaccurate intake data, creating error. In general, obese people are more apt to underestimate their food consumption because they may go on “a diet” or deliberately omit foods during the food-recording period. Individuals may alter their food intake temporarily as they are cognizant that their food intake is being monitored, possibly to conform to socially acceptable foods and food habits. For example, during a 24 hour recall, an obese person may not want to admit to a dietitian that they overate the previous day, therefore, they may underreport their food intake. Another source of error comes from weighing and measuring foods. Errors involved in the estimation of food portions can reach 90% but are typically 20-50% when scales are not used to weigh foods.

KEY TERMS Dietary assessment—An estimation of food and nutrients eaten over a particular time point. Some of the most common dietary assessment methods are food records, dietary recalls, food frequency questionnaire, and diet histories. Dietitian—A dietitian is a health professional who has a bachelor’s degree, specializing in foods and nutrition, and undergoes a period of practical training in a hospital or community setting. Many dietitians further their knowledge by pursuing master’s or doctoral degrees. The title “dietitian” is protected by law so that only qualified practitioners who have met education qualifications can use that title. Macronutrient—A nutrient such as protein, carbohydrate, or fat. Micronutrient—An organic compound such as vitamins or minerals essential in small amounts and necessary to growth and health of humans and animals. Nutritionist—Some dietitians call themselves “nutritionists,” but in general, the term “nutritionist” is not protected by law, therefore anyone can call themselves a nutritionist.

Results A dietary assessment may indicate where a nutritional problem or inadequacy may lie, but it is up to an individual to implement the necessary dietary modifications. If a patient does not follow the recommended dietary guidance following dietary assessment, then they will not receive any benefit from dietary assessment. Typically, modest effects are seen in weight loss or reduction in serum lipids often due to failure to fully comply with the dietary recommendations provided.

Health care team roles In general, only registered dietitians (R.D.s) have sufficient training and knowledge to accurately assess the clinical evaluation and nutritional adequacy of a patient’s diet. Although there are many websites and software programs that provide guidance for self-use for conducting a basic dietary assessment, these should be used with caution. The term “nutritionist” is not regulated by law; therefore anyone can call themselves a nutritionist. A doctor may also have a nutrition background or special-

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Other sources that can be used for dietary reference and guidance for food choices are “The Dietary Guidelines for Americans” which is published by the U.S. Department of Agriculture and Health and Human Services. The “Food Guide Pyramid” was created by the U.S. Department of Agriculture to help Americans choose foods from each food grouping. It focuses on fat intake, which is too high in most Americans.

Dietary counseling

ization and may thus be able to conduct a dietary assessment or to provide general nutrition advice. However, one research study demonstrated that even though most doctors admitted they had ready access to a publicly funded dietician, 50% of doctors refer less than a quarter of their patients to dieticians. Major barriers for doctors to improving dietary counseling for patients include short visit times, limited nutrition coursework in medical schools, and poor patient compliance with physicians’ dietary prescriptions. Resources BOOKS

Institute of Medicine, ed. Dietary Reference Intakes: Applications in Dietary Assessment. Washington: National Academy Press, 2001. Institute of Medicine, ed. Dietary Reference Intakes: Risk Assessment (Compass Series). Washington: National Academy Press, 1999. Larson-Duyff, Roberta. The American Dietetic Association’s Complete Food & Nutrition Guide. New York: John Wiley & Sons, 1998. Netzer, Corinne T. The Complete Book of Food Counts. New York: Dell Publishing Co., 2000. ORGANIZATIONS

American Dietetic Association. 216 W. Jackson Blvd. Chicago, IL 60606-6995. (312) 899-0040. . Food and Nutrition Information Center Agricultural Research Service, USDA. National Agricultural Library, Room 304, 10301 Baltimore Avenue, Beltsville, MD 207052351. (301) 504-5719. Fax: (301) 504-6409. . . U.S. Department of Agriculture, Agricultural Research Service. “USDA Nutrient Database for Standard Reference, Release 13.” Nutrient Data Laboratory Homepage 1999. . OTHER

Food and Nutrition Professionals Network .

Crystal Heather Kaczkowski, MSc.

Dietary counseling

Purpose Today’s major health care problems are increasingly the result of acute and chronic conditions related to poor nutrition and/or overconsumption. A large proportion of coronary disease and cancer can be attributed to unhealthy eating habits and obesity. Chronic diseases continue to increase due to such factors as the rise in obesity in the American population. Individualized nutritional counseling can provide the patient important insight into food-related illnesses and education regarding how various nutrients (protein, carbohydrate, fat, alcohol) affect illnesses or obesity. Alternatively, dietary counseling can provide prevention of nutrition-related conditions such as the need for weight management. Dietary counseling can be tailored to meet the treatment needs of patients at diagnosis of specific illnesses, can help reduce complications and/or side effects, and can improve general well-being. Prevention at all levels: primary (preventing disease), secondary (early diagnosis), and tertiary (preventing or slowing deterioration) requires active patient participation and guidance and support from the dietician or physician. Education, motivation, and counseling are needed for effective patient participation. In addition to patient education, dietary counseling often includes meal planning. A guide to the amount an average person needs each day to remain healthy has been determined for each vitamin and mineral as well as macronutrients. In the United States, this guide is called the recommended daily allowance (RDA). The RDA is under revision and will become the Dietary Reference Intakes, and will be applicable to Canadians and Americans. Dietary counselors may use the RDA as a guide when providing counseling. Consumption of too little or too much of certain vitamins and minerals may lead to a nutrient deficiency or a nutrient toxicity respectively. A dietitian can advise the patient about any vitamin or mineral inadequacy concerns during the dietary counseling session.

Precautions

Definition Dietary counseling provides individualizing nutritional care for encouraging modification of eating habits. It may also assist in prevention or treatment of nutrition754

related illnesses such as cardiovascular disease, cancer, obesity, diabetes, and hyperlipidemia.

When providing dietary counseling, registered dietitians and nutritionists should recognize the benefit of individualizing nutritional care and that a “one-size-fits-all” approach to modifying eating habits cannot be effective.

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Effective dietary counseling includes a comprehensive evaluation that considers presence of disease, lipid profile, blood pressure, and weight history and goals. In addition, factors such as lifestyle, time available for food preparation, work schedule, and personal food preferences must be considered. Food choices are driven not only by the physiological necessity for nutrients, but also by the social aspects of food consumption, i.e. gathering with friends at a restaurant. This complex relationship concerning food choices often makes dietary counseling a challenge for managing specific nutrition-related disease or conditions. For example, a patient with cardiovascular disease may need to select low-fat foods when attending a social dinner or party. There are many issues related to nutrition goal outcomes that need to be considered when planning appropriate dietary counseling. When considering the appropriate counseling approach for an individual with a specific illness, particular attention needs to be given to usual food choices, food likes and dislikes, learning style, cultural issues, and socioeconomic status. Other factors that may be assessed during dietary counseling include: • medical history, including assessment of any nutritionrelated illnesses, and biochemical and anthropometric measures • dietary assessment (dietary analyses) • psychosocial evaluation, including food-related attitudes and behaviors • sociological evaluation, including cultural practices, housing, cooking facilities, financial resources, and support of family and friends • nutrition knowledge • readiness to learn or change; as well as learning style analyses • current exercise and activity level

Preparation A dietary assessment is often conducted to determine the macronutrient (energy or caloric, protein, and fat) content and the micronutrient (vitamin and mineral) content of the diet to assist in providing dietary counseling. The validation of dietary assessment instruments is important to evaluate the diet in terms of chronic disease risk factors such as a high fat diet or a diet low in antioxidants and/or fruits and vegetables. Some of the most common dietary assessment tools that assist in providing dietary counseling include food

records, dietary recalls, food frequency questionnaires, diet histories, and several other methods including biochemical indices. A scientific assessment of nutritional status may be made by using a combination of the information collected from clinical evaluations, biochemical tests, and dietary information. The clinical evaluation includes measurements of various anthropometric parameters such as height, weight, and percent body fat (determined by skinfolds or hydrostatic weighing). In addition, a clinical evaluation may also include observations for signs of nutrient deficiencies in the mouth, skin, eyes, and nails. The information collected from a clinical evaluation can be compared with that obtained from the dietary assessment and biochemical tests to provide a comprehensive picture of the patient’s current nutritional status and relative risk factors for diet-related illnesses.

Aftercare Dietary counseling is only effective if the individual is willing to implement the necessary dietary modifications. If patients do not follow the recommended dietary guidance, they will not receive a benefit from counseling. Typically, modest effects seen in weight loss or reduction in serum lipids are often due to failure to comply fully with the dietary recommendations provided.

Complications Systematic problems exist in the quantification of food intake using dietary assessment tools and selfreported measures (i.e. when the patients subjectively report their own food intake). This is due to the fact that these methods rely on the patient’s ability to recall or record food intake accurately. Therefore, selection of the appropriate method for dietary assessment is important to meet the goals of dietary counseling.

Results Goals of dietary counseling for preventative nutrition or treatment of nutrition-related illness: • Providing adequate calories for attaining reasonable weights for adults, ensuring normal growth and development rates for children and adolescents, and meeting increased metabolic needs during pregnancy and lactation or recovery from catabolic illness. Reasonable weight for adults is defined by considering weight history and is a weight that both the individual and health professional determine is attainable and can be maintained long term. • Achieving optimal lipid levels. The guidelines provided by the National Cholesterol Education Program can be followed for maintaining optimal blood lipid levels

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Description

Dietary counseling

KEY TERMS Dietary assessment—An estimation of food and nutrients eaten over a particular time point. Some of the most common dietary assessment methods are food records, dietary recalls, food frequency questionnaires, and diet histories. Dietary counseling—Individual nutritional advice provided to a patient by a registered dietitian, nutritionist, or doctor for encouraging modification of eating habits. Dietitian—A dietitian is a health professional who has a bachelor’s degree, specializing in foods and nutrition, and undergoes a period of practical training in a hospital or community setting. Many dietitians further their knowledge by pursuing master’s or doctoral degrees. The title “dietitian” is protected by law so that only qualified practitioners who have met education qualifications can use that title. Macronutrient—A nutrient such as protein, carbohydrate, or fat. Micronutrient—An organic compound such as vitamins or minerals essential in small amounts and necessary to growth and health of humans and animals. Nutritionist—A general term for someone who works with the principles of nutrition. Some dietitians call themselves “nutritionists,” but the term “nutritionist” is not protected by law, and therefore anyone can call themselves a nutritionist.

[total cholesterol, low-density lipoproteins (LDL), high-density lipoproteins (HDL), and triglycerides]. Nutrition intervention plays an important role in reaching recommended lipid levels through maintenance of a low-fat diet. • Ensuring the diet contains appropriate or reasonable amounts of protein, carbohydrates, fat, vitamins, and minerals. • Preventing, delaying, or treating nutrition-related risk factors and complications. • Improving overall health through optimal nutrition. What methods are most helpful for dietary modifications? Clearly, dietary advice tailored to suit individual needs and tastes is more appropriate than general dietary 756

advice. The issue is how to elicit a beneficial change in dietary habits and how to encourage a patient to stick to the dietary recommendations provided. Typically, dietary modifications have demonstrated limited success especially regarding weight control. Several methods have been used to induce behavioral change in individuals such as the Transtheoretical (Stages of Change) Model. It is one of most popular models of health behavior change that classifies individuals into stages according to their degree of readiness to consider change, and identifies the factors that can induce transitions from one stage to the next. The model suggests change in health behavior involves progression through six stages including precontemplation, contemplation, preparation, action, maintenance, and termination. It utilizes different types of skills training and advice at different stages and has shown promising success in diet modification interventions. It may be easier to introduce new behaviors than to eliminate established behaviors. Therefore, if weight loss is a concern, recommending the patient start exercising regularly may be more effective than changing current dietary patterns. Positive feedback or implementation of a reward system may be advantageous in helping some patients follow dietary advice. In general, changing behaviors such as making healthier food choices and increasing exercise will be much more successful and pleasurable in the long-term than dieting. Furthermore, an individual cannot live on a diet permanently; therefore, when food intake increases, weight gain will follow unless energy expenditure is increased through exercise or by other means. Dieting may encourage a “yo-yo” weight loss/gain where often even more weight is gained back than was lost and often in less favorable proportions of a fat to muscle ratio. When weight is lost, muscle and fat are both lost. Sometimes the weight that is regained after weight loss has a higher content of “fat” (adipose tissue) than the weight previously lost (which may have contained a significant percent of skeletal muscle). This is only one of the reasons why exercise is so important in maintaining body weight. In fact, because muscle is metabolically active tissue, the body actually needs more energy or calories to feed the muscles even when at rest (for example, sitting still or sleeping). Dietary counseling may help reinforce dietary modifications and assist in achieving permanent weight control. Other sources that can be used for dietary reference and self-counseling for individuals are The Dietary Guidelines for Americans which is published by the U.S. Department of Agriculture and Health and Human Services. The Food Guide Pyramid was created by the

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Health care team roles In general, only registered dietitians (R.D.s) have sufficient training and knowledge to accurately assess the nutritional adequacy of a patient’s diet. The term “nutritionist” is not regulated by law; therefore anyone can call themselves a nutritionist. A doctor may also have a nutrition background or specialization and may thus be able to provide general nutrition counseling. However, one research study demonstrated that even though most doctors admitted they had ready access to a publicly funded dietician, 50% of doctors refer less than a quarter of their patients to dieticians. Major barriers to improving dietary counseling for patients include short visit times, limited nutrition coursework in medical schools, and poor compliance with physicians’ dietary prescriptions. For effective therapy to occur, all health care team members and especially the patient with the nutritionrelated illness must commit to the goals of counseling. The prioritized goals are critical when developing the nutrition treatment plan. Continuous assessment is made by the patient and health care team members to evaluate the importance of these and other goals. Physicians must understand the nutrition approaches an individual is using and reinforce this therapy when interacting with the individual. Resources BOOKS

Institute of Medicine, ed. Dietary Reference Intakes: Risk Assessment (Compass Series). Washington: National Academy Press, 1999. Larson-Duyff, Roberta. The American Dietetic Association’s Complete Food & Nutrition Guide. New York: John Wiley & Sons., 1998. Netzer, Corinne T. The Complete Book of Food Counts. New York: Dell Publishing Co., 2000. ORGANIZATIONS

American Dietetic Association. 216 W. Jackson Blvd. Chicago, IL 60606-6995. (312) 899-0040. . Food and Nutrition Information Center Agricultural Research Service, USDA. National Agricultural Library, Room 304, 10301 Baltimore Avenue, Beltsville, MD 207052351. (301) 504-5719. Fax: (301) 504-6409. . .

Dietetics

U.S. Department of Agriculture to help Americans choose foods from each food grouping. It focuses on fat intake, which is too high in most Americans. In addition, the National Cholesterol Education Program provides a Step 1 diet that may be followed to assist in controlling weight.

OTHER

Food and Nutrition Professionals Network .

Crystal Heather Kaczkowski, MSc.

Dietary fats see Fats, dietary

Dietetics Definition Dietetics professionals are responsible for educating individual clients in developing healthy lifestyles, as well as for providing quality nutritional services to the public. Standards of professional practice have been developed by the American Dietetic Association to ensure that dietetics professionals are the most reliable sources of information regarding food and nutrition.

Description Registered dietitians (RD) and dietetic technicians (DTR) receive their credentials from the Commission on Dietetic Registration, which ensures that these professionals have fulfilled all academic requirements and completed a registration examination. Dietetics professionals work in a variety of settings involving foodservice management, clinical nutrition, and community nutrition. They work to provide nutrition education classes on topics such as breastfeeding, food safety, and diet fads. They may counsel hospital patients on health-related conditions and facilitating weight loss. They are also qualified to educate the public on proper nutrition for people of all ages including infants and the elderly.

Work settings Registered dietitians and dietetic technicians are qualified to work in a variety of settings including hospitals, nursing homes, schools, and health clinics. In hospitals and nursing homes, dietetics professionals usually perform more clinical duties such as assessing the nutritional status of patients to aid in their treatment and recovery. They must demonstrate an understanding of a variety of nutrition topics, including calculating nutrient and tube feeding needs, and various nutrition-related diseases, such as diabetes, Crohn’s disease, and cardiovascular disease. In schools, dietitians can provide services to cafeterias in helping them develop healthy meals and snacks, as well as conduct nutrition education classes for

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students and teachers. Dietitians also play a very prominent role in health clinics such as WIC (Supplemental Program for Women, Infants, and Children), in which they advocate the healthy development of children by educating women on the importance of breastfeeding and infant nutrition. Many dietetics professionals also become certified as dietary managers in which they are responsible for supervising in a foodservice setting.

Education and training To become a registered dietitian, a bachelor’s or master’s degree in dietetics may be received from a school that is a Coordinated Program (CP) accredited by the Commission on Accreditation for Dietetics Education (CADE) in which academics and supervised practical experience are combined. A graduate of a Coordinated Program may then take the Registration Examination for Dietitians to become an RD. Individuals may also enroll in a Didactic Program in Dietetics (DPD) that is also approved by CADE. After graduating with a bachelor’s degree, the supervised practical experience may be completed either at a CADE-accredited Dietetic Internship or a CADE-approved Preprofessional Practice Program (AP4). This also qualifies the individual to take the Registration Examination for Dietitians. To become a registered dietetic technician, an associate’s degree must be received from a CADE-accredited Dietetic Technician Program or a baccalaureate degree from a CADE-approved DPD. DTRs must also participate in a supervised practical experience at the Dietetic Technician Program, but it is not required that they take a registration examination. The academics involved in the undergraduate study of dietetics includes generalized courses such as biology, chemistry, statistics, and management. More detailed courses are devoted to topics such as general nutrition, food science, nutritional assessment, advanced nutrition, experimental foods, and diet therapy. Undergraduate work also consists of clinical experience in work settings in which students gain a more hands-on experience in the field of dietetics. This allows students to get a new perspective on the field that goes beyond traditional teaching methods. By encouraging active participation, students will gain a better understanding of what is necessary to develop the counseling skills and research capabilities essential to dietetics.

Advanced education and training Dietitians can further enhance their education and abilities by receiving a master’s degree in dietetics or another field related to nutrition. Some CADE-accredit758

ed/approved programs also offer graduate coursework that can be completed at the same time as the dietetic internship. Dietetics professionals are also responsible for keeping up to date with the latest information regarding nutrition and utilizing the available technology that can enhance learning.

Future outlook Dietetics is a constantly changing field in which new information is being uncovered and advances in technology are being made. While technology has become an integral part of nutrition education, it is likely to become even more prominent in years to come. Many dietitians have even designed web sites in order to market their practice. Dietitians have begun utilizing services such as email and the Internet to communicate with clients. This also allows them to communicate with people who travel or are too busy to schedule an appointment. Using the Internet to communicate with clients has its advantages as well as its disadvantages though. While it offers more flexibility for both the client and the professional and allows dietitians to reach a wide geographical range of people, it also limits dietetics professionals in accurately assessing patients because they are not seen in person. One of the major drawbacks to using the web for nutrition information is that much of the information tends to be inaccurate or exaggerated. This will give dietetics professionals an even bigger role in working to ensure that the public is getting the most accurate and upto-date information from the web and has resulted in more career opportunities for dietetics professionals. Since most nutrition information comes from search engines like <www.yahoo.com> or <www.medscape. com>, these companies have begun hiring dietetics and nutrition professionals to edit content and develop appropriate health-related messages for consumers. Many dietitians also work as consultants for Web sites who may need expert advice on nutrition-related topics. With the advances in technology and development of new computer programs for nutrition education, the role of dietitians will continue to grow as the need for the most upto-date information continues to grow. Resources PERIODICALS

Brehm, Bonnie J., Rourke, Kathleen M., and Cynthia Cassell. “Enhancing Didactic Education through Participation in a Clinical Research Project.” Journal of the American Dietetic Association (September 1999): 1090-1093. Palumbo, Christine. “Using New Technology for Nutrition Counseling.” Journal of the American Dietetic Association (November 1999): 1363-1364.

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OTHER

“Frequently Asked Questions (FAQ) about Careers in Dietetics.” American Dietetic Association Online 28 April 2001. . “Standards of Professional Practice for Dietetics Professionals.” American Dietetic Association Online 28 April 2001. .

Lisa M. Gourley

Differential count see White blood cell count and differential

Digestive system Definition The digestive system is a group of organs and tissues responsible for the conversion of food into absorbable chemicals which are then used to provide energy for growth and repair.

Description The digestive system is also known by a number of other names, including the gut, the digestive tube, the alimentary canal, the gastrointestinal (GI) tract, the intestinal tract, and the intestinal tube. The digestive system consists of the mouth, esophagus, stomach, and small and large intestines, along with several glands, such as the salivary glands, liver, gall bladder, and pancreas.

Function and role in human health The glands in the digestive system secrete digestive juices containing enzymes that break down the food chemically into smaller, more absorbable molecules. In addition to providing the body with the nutrients and energy it needs to function, the digestive system also separates and disposes of waste products ingested with the food. Food is moved through the alimentary canal by a wavelike muscular motion known as peristalsis, which consists of the alternate contraction and relaxation of the smooth muscles lining the tract. In this way, food is passed through the gut in much the same manner as toothpaste is squeezed from a tube. Churning is another

type of movement that takes place in the stomach and small intestine, which mixes the food so that the digestive enzymes can break down the food molecules. Food in the human diet consists of carbohydrates, proteins, fats, vitamins, and minerals. The remainder of the food is fiber and water. The majority of minerals and vitamins pass through to the bloodstream without the need for further digestive changes, but other nutrient molecules must be broken down to simpler substances before they can be absorbed and used. Ingestion Food taken into the mouth is first prepared for digestion in a two-step process known as mastication. In the first stage, the teeth tear and break down food into smaller pieces. In the second stage, the tongue rolls these pieces into balls (boluses). Sensory receptors on the tongue (taste buds) detect taste sensations of sweet, salt, bitter, and sour, or cause the rejection of bad-testing food. The olfactory nerves contribute to the sensation of taste by picking up the aroma of the food and passing the sensation of smell on to the brain. The sight of the food also stimulates the salivary glands. Altogether, the sensations of sight, taste, and smell cause the salivary glands, located in the mouth, to produce saliva, which then pours into the mouth to soften the food. An enzyme in the saliva called amylase begins the break down of carbohydrates (starch) into simple sugars, such as maltose. Ptyalin is one of the main amylase enzymes found in the mouth; ptyalin is also secreted by the pancreas. The bolus of food, which is now a battered, moistened, and partially digested ball of food, is swallowed, moving to the throat at the back of the mouth (pharynx). In the throat, rings of muscles force the food into the esophagus, the first part of the upper digestive tube. The esophagus extends from the bottom part of the throat to the upper part of the stomach. The esophagus does not take part in digestion. Its job is to get the bolus into the stomach. There is a powerful muscle (the esophageal sphincter), at the junction of the esophagus and stomach, which acts as a valve to keep food, stomach acids, and bile from flowing back into the esophagus and mouth. Digestion in the stomach Chemical digestion begins in the stomach. The stomach, a large, hollow, pouched-shaped muscular organ, is shaped like a lima bean. When empty, the stomach becomes elongated; when filled, it balloons out.

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Sutherland, Lisa A. “Nutrition Professionals in Cyberspace: Getting Wired for the New Millennium.” Journal of the American Dietetic Association (November 1999): 13651366.

Digestive system

Gastric juice is needed mainly for the digestion of protein by pepsin. If a hamburger and bun reach the stomach, there is no need for extra gastric juice for the bun (carbohydrate), but the hamburger (protein) will require a much greater supply of gastric juice. The gastric juice already present will begin the break down of the large protein molecules of the hamburger into smaller molecules: polypeptides and peptides. These smaller molecules in turn stimulate the cells of the stomach lining to release the hormone gastrin into the bloodstream.

Lips Mouth

Pharynx

Tongue Esophagus

Liver

Stomach Pancreas

Gallbladder Duodenum

Transverse colon Jejunum

Ascending colon Descending colon Ileum

Gastrin then circulates throughout the body, and eventually reaches the stomach, where it stimulates the cells of the stomach lining to produce more gastric juice. The more protein there is in the stomach, the more gastrin will be produced, and the greater the production of gastric juice. The secretion of more gastric juice by the increased amount of protein in the stomach represents the third mechanism of gastric juice secretion. Digestion and absorption in the small intestine

Appendix

Rectum

While digestion continues in the small intestine, it also becomes a major site for the process of absorption, that is, the passage of digested food into the bloodstream, and its transport to the rest of the body.

The parts of the human gastrointestinal tract. (Delmar Publishers, Inc. Reproduced by permission.)

Food in the stomach is broken down by the action of the gastric juice containing hydrochloric acid and a protein-digesting enzyme called pepsin. Gastric juice is secreted from the lining of the stomach walls, along with mucus, which helps to protect the stomach lining from the action of the acid. The three layers of powerful stomach muscles churn the food into a fine semiliquid paste called chyme. The chyme (pronounced “kime”) is periodically passed through an opening (the pyloric sphincter), which controls the passage of chyme between the stomach and the beginning of the small intestine. Gastric juice There are several mechanisms responsible for the secretion of gastric juice in the stomach. The stomach begins its production of gastric juice while the food is still in the mouth. Nerves from the cheeks and tongue are stimulated and send messages to the brain. The brain in turn sends messages to nerves in the stomach wall, stimulating the secretion of gastric juice before the arrival of the food. The second signal for gastric juice production occurs when the food arrives in the stomach and touches the lining. This mechanism provides for only a moderate addition to the amount of gastric juice that was secreted when the food was in the mouth. 760

The small intestine is a long, narrow tube, about 20 ft (6 m) long, running from the stomach to the large intestine. The small intestine occupies the area of the abdomen between the diaphragm and hips, and is greatly coiled and twisted. The small intestine is lined with muscles that move the chyme toward the large intestine. The mucosa, which lines the entire small intestine, contains millions of glands that aid in the digestive and absorptive processes of the digestive system. The small intestine, or small bowel, is sub-divided into three sections, the duodenum, the jejunum, and the ileum. The duodenum is about 1 ft (0.3 m) long and connects with the lower portion of the stomach. When fluid food reaches the duodenum it undergoes further enzymatic digestion and is subjected to pancreatic juice, intestinal juice, and bile. The pancreas is a large gland located below the stomach that secretes pancreatic juice into the duodenum via the pancreatic duct. There are three enzymes in pancreatic juice which digest carbohydrates, lipids, and proteins. Amylase, (the enzyme found in saliva) breaks down starch into simple sugars such as maltose. The enzyme maltase in intestinal juice completes the break down of maltose into glucose. Lipases in pancreatic juice break down fats into fatty acids and glycerol, while proteinases continue the breakdown of proteins into amino acids. The gallbladder,

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Chyme passing from the duodenum next reaches the jejunum of the small intestine, which is about 3 ft (0.91 m) long. Here, in the jejunum, the digested breakdown products of carbohydrates, fats, proteins, and most of the vitamins, minerals, and iron are absorbed. The inner lining of the small intestine is composed of up to five million tiny, finger-like projections called villi. The villi increase the rate of absorption of the nutrients into the bloodstream by extending the surface of the small intestine to about five times that of the surface area of the skin. There are two transport systems that pick up the nutrients from the small intestine. Simple sugars, amino acids, glycerol, and some vitamins and salts are conveyed to the liver in the bloodstream. Fatty acids and vitamins are absorbed and then transported through the lymphatic system, the network of vessels that carry lymph and white blood cells throughout the body. Lymph eventually drains back into the bloodstream and circulates throughout the body. The last section of the small intestine is the ileum. It is smaller and thinner-walled than the jejunum, and it is the preferred site for vitamin B12 absorption and bile acids derived from the bile juice. Absorption and elimination in the large intestine The large intestine, or colon, is wider and heavier then the small intestine, but much shorter—only about 4 ft (1.2 m) long. It rises up on one side of the body (the ascending colon), crosses over to the other side (the transverse colon), descends (the descending colon), forms an s-shape (the sigmoid colon), reaches the rectum, and anus, from which the waste products of digestion (feces or stool), are passed out, along with gas. The muscular rectum, about 5 in (13 cm) long, expels the feces through the anus, which has a large muscular sphincter that controls the passage of waste matter. The large intestine extracts water from the waste products of digestion and returns some of it to the bloodstream, along with some salts. Fecal matter contains undigested food, bacteria, and cells from the walls of the digestive tract. Certain types of bacteria of the large intestine help to synthesize the vitamins needed by the body. These vitamins find their way to the bloodstream along with the water absorbed from the colon, while excess fluids are passed out with the feces.

Liver The liver is the largest organ in the body and plays a number of vital roles, including metabolizing the brokendown products of digestion, and detoxifying substances that are harmful to the body. The liver also provides a quick source of energy when the need arises and it produces new proteins. Along with the regulation of stored fats, the liver also stores vitamins, minerals, and sugars. The liver controls the excretion and production of cholesterol and metabolizes alcohol into a mild toxin. The liver also stores iron, maintains the hormone balance, produces immune factors to fight infections, regulates blood clotting, and produces bile. Gallbladder The gallbladder lies under the liver and is connected by various ducts to the liver and the duodenum. The gallbladder is a small hollow organ; its main function is to store bile until it is concentrated enough to be used by the small intestine. The gallbladder can store about 2 oz of bile. Bile consists of bile salts, bile acids, and bile pigments. In addition, bile contains cholesterol dissolved in the bile acids. Appendix The appendix is a hollow finger-like projection that hangs from the cecum at the junction between the small intestine and the large intestine. The appendix does not function in humans; however, in some animals, such as rabbits, the appendix is rather large and helps in the digestion of cellulose from bark and wood, which rabbits eat. The appendix in humans is therefore a vestigial organ, which may have had uses for earlier types of ancestral human digestive processes before the evolution of Homo sapiens.

Pancreas When food reaches the small intestine, the pancreas secretes pancreatic juices. When there is no food in the small intestine, the pancreas does not secrete its juices. Insulin is another important hormone secreted by a group of cells within the pancreas called the islets of Langerhans, which are part of the endocrine system, rather than the digestive system. Insulin released into the bloodstream targets liver and muscle cells, and allows them to take excess sugar from the blood and store it in the form of glycogen.

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located next to the liver, secretes bile into the duodenum. While bile does not contain enzymes, it contains bile salts and other substances that help to emulsify (dissolve) fats, which are otherwise insoluble in water. Breaking the fat down into small globules allows the lipase enzymes a greater surface area for their action.

Digestive system

KEY TERMS Amylase—A digestive enzyme found in saliva and the pancreas that breaks down carbohydrates to simple sugars. Bile—Liquid produced in the liver and stored in the gallbladder that emulsifies fats. Gastric juice—Digestive juice produced by the stomach wall that contains hydrochloric acid and the enzyme pepsin. Gastrin—A hormone produced by the stomach lining in response to protein in the stomach that produces increased gastric juice. Helicobacter pylori—Recently discovered bacteria that live in gastric acids and are believed to be a major cause of most stomach ulcers. Lower esophageal sphincter—A strong muscle ring between the esophagus and the stomach that keeps gastric juice and even duodenal bile from flowing upwards out of the stomach. Lymphatic system—The system that produces, transports, and filters lymph throughout the body. It also transports fats, proteins, and some vitamins to the blood system. Mucosa—The digestive lining of the intestines. Nutrients—Vitamins, minerals, proteins, lipids, and carbohydrates needed by the body. Peristalsis—The wavelike motion of the digestive system that moves food through the digestive system. Villi—Fingerlike projections found in the small intestine that add to the absorptive area for the passage of digested food to the bloodstream and lymphatic system.

Common diseases and disorders Several disorders of the esophagus are esophagitis, esophageal spasm, and esophageal cancer. Esophagitis (heartburn) is an inflammation of the esophagus usually caused by the reflux of gastric acids into the esophagus and is treated with antacid (alkalis). Esophageal spasm is also caused by acid reflux. Esophageal cancer can be caused by smoking and is generally fatal. Disorders of the stomach include hiatal hernia, ulcers, and gastric cancer. A hiatal hernia occurs when a portion of the stomach extends upwards into the thorax through a large opening in the diaphragm. It is a condi762

tion that commonly occurs in people over the age of 50. Stomach ulcers are sores that form in the lining of the stomach. They may vary in size from a small sore to a deep cavity, surrounded by an inflamed area, sometimes called ulcer craters. Stomach ulcers and ulcers that form in the esophagus and in the lining of the duodenum are called peptic ulcers because they need stomach acid and the enzyme pepsin to form. Duodenal ulcers are the most common type. They tend to be smaller than stomach ulcers and heal more quickly. Ulcers that form in the stomach lining are called gastric ulcers. About 4 million people have ulcers, and 20% of those have gastric ulcers. Those people who are at most risk for ulcers are those who smoke, are middle-age and older men, are chronic users of alcohol, and those who take anti-inflammatory drugs, such as aspirin and ibuprofen. It is believed that about 80% of stomach ulcers may be caused by the bacterial infection, while about 20% may be from other causes, such as the use of anti-inflammatory medicines. The most common liver disorder in the United States and other developed countries is cirrhosis of the liver. The main cause for this disease is alcoholism. Cirrhosis is characterized by the replacement of healthy liver cells by fibrous tissue. The replacement process is gradual and takes a period of two to 10 years to complete. There is no cure for the disease. Symptoms may not be noticed in its early development, but in its advanced stages there are a number of symptoms and the condition can lead to coma. Close medical attention is required to treat the disease. Another common liver disorder is hepatitis. It is an inflammation of the liver caused by viruses. The most noticeable symptom of this disease is jaundice, that is, the skin, eyes, and urine turn yellow. The nine viruses known to cause hepatitis include hepatitis A, B, C, D, and E; the recently discovered F and G viruses; and two herpes viruses (Epstine-Barr and cytomegalovirus). Gallstones may form in the gallbladder. If the amount of cholesterol in the bile acids increases or the amount of acid decreases, then some of the cholesterol will settle out of the acid to form gallstones that accumulate and block the ducts to the gallbladder. Infection in the gallbladder may lead to gallstones. Gallstones may be in the gallbladder for years without giving any signs of the condition, but when they obstruct the bile duct they cause considerable pain and inflammation. Infection and blockage of the bile flow may follow. Surgical removal of the gallbladder may be necessary to treat this condition. Since the liver both produces and stores sufficient amounts of bile, the loss of the gallbladder does not interfere with the digestive process provided fat intake in the diet is regulated. If the gallstones contain mainly cholesterol, drug treatment for the stones may be possible. But if there is too much other material in the gallstones, sur-

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If food gets trapped in the appendix, an irritation of its membranes may occur leading to swelling and inflammation, a condition known as appendicitis. If the condition becomes serious, removal of the appendix is necessary to avoid a life-threatening condition if it were to rupture. When the pancreas does not produce sufficient insulin to store dietary sugar, the blood and urine levels of sugar reach dangerous levels. Diabetes mellitus is the resultant disease. Mild cases can be controlled by a properly regulated diet, but severe cases require the regular injection of insulin. Resources BOOKS

Greenspan, Francis S., and David G. Gardner, eds. Basic & Clinical Endocrinology, 6th ed. Stamford, CT: Appleton & Lange, 2000. Johnson, Leonard R., and Thomas A. Gerwin, eds. Gastrointestinal Physiology, 6th ed. London: Mosby, Inc. Morrison, Ben. The Digestive System (Insider’s Guide to the Body). New York: Rosen Publishing Group, 2001. PERIODICALS

“Digestive Disorders.” US News and World Report 131, no. 3 (July 23, 2001): 74. Voelker, Rebecca. “Digestive Health in Children.” Journal of the American Medical Association 284, no. 10 (Sept. 13, 2000): 1235. OTHER

“Pathophysiology of the Digestive System.” Colorado State University. .

Crystal Heather Kaczkowski, MSc.

Diphenhydramine see Antihistamines Diplegia see Paralysis

Disease transmission Definition Disease transmission is the means by which contagious, pathogenic microorganisms are spread from one person to another.

Description There are four major pathways by which pathogenic organisms may be spread to an individual: contact transmission, airborne transmission, vehicle transmission, and vector transmission. Contact transmission Infectious particles may be spread through direct or indirect contact with an infected individual, animal, or inanimate object. Direct contact refers to instances in which there is direct person-to-person spread of a disease. This occurs in the case of sexually transmitted diseases (STDs), when the genitals of one individual come into direct contact with the genitals of a person suffering from an STD such as herpes simplex virus (HSV). Contact of an uninfected person with infected wounds or blood may result in direct transmission, such as in the case of human immunodeficiency virus (HIV), if he/she is not protected by universal precautions. A very common form of direct contact transmission occurs when infectious particles in the form of airborne droplets are expelled by an infected individual by sneezing or coughing and inhaled by another individual. Expelled droplets may travel for several meters before falling and therefore are easily spread to surrounding individuals. Examples of diseases that are caused by inhalation of infectious droplets are influenza (caused by the influenza virus) and tuberculosis (caused by the bacterium Mycobacterium tuberculosis). Indirect contact results in the transmission of infectious particles from person to person via an intermediary carrier. Inanimate objects such as eating utensils, medical instruments, or equipment used in food preparation may become contaminated with a pathogenic microorganism and in turn spread the disease to other individuals. Infected needles may be the source of indirect transmission of pathogens between intravenous drug users. The hands of a health care worker may also cause the transmission of infectious particles from patient to patient if adequate handwashing practices are not enforced. Organ transplantation presents a unique mode by which disease may be transmitted. Microorganisms that have disseminated to the donor organ may be transplanted to the recipient and subsequently cause disease. For example, hepatitis C virus (HCV) may be transmitted by liver transplantation if the donor organ is infected. Similarly, transmission of cytomegalovirus (CMV) from infected donor kidneys may occur.

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gery may still be necessary. Even after being treated successfully by drugs and diet, the condition can return. The drug treatment takes years to dissolve gallstones.

Disease transmission

water. For example, the diarrheal disease cholera (caused by the bacterium Vibrio cholerae) is often spread by drinking water contaminated by infected fecal matter.

KEY TERMS Cleaning—The physical removal of microorganisms from an object, usually with water with or without a detergent. Disinfection—Treatment which destroys most microorganisms from an object. Droplet nuclei—Tiny particles on which microorganisms may be carried in airborne transmission. Sterilization—The complete removal of all living microorganisms from an object or fluid. Universal precautions—An infection-control technique designed to prevent the transmission of blood-borne diseases. These guidelines were initially developed by the Centers for Disease Control in 1987.

Airborne transmission Airborne transmission differs from droplet transmission in that infectious particles are carried on tiny particles called droplet nuclei and may remain suspended or carried in the air for hours or days. These aerosolized particles may be widely dispersed before settling, therefore increasing the chance that they will be inhaled. Organisms that survive well under dry conditions (e.g. Staphylococcus aureus) are often spread by the airborne route. There are many ways in which infectious microorganisms remain airborne. Droplet nuclei may be dispersed by ventilation and respiratory equipment, such as nebulizers, humidifiers, and air conditioners. S. aureus may be shed on skin scales from contaminated skin. Mycobacterium tuberculosis may be transmitted by droplet or airborne transmission and may survive for years in dust particles. Other organisms may be transmitted by disrupted soil or dried fecal matter. Vehicle transmission The spread of infectious agents through a common reservoir such as food or water supply is referred to as vehicle or common supply transmission. Food products may become contaminated after being handled by unwashed hands or processed by unclean equipment. Cattle infected with bovine spongiform encephalopathy (BSE, also known as mad cow disease) may cause Creutzfeldt-Jakob disease in humans who consume the cow’s nervous system tissue. Water may be contaminated by infected feces, urine, or other body fluids, and diseases can be spread by drinking or bathing in this contaminated 764

The blood supply is another means of vehicle transmission. Donated blood may be infected with any number of microorganisms (HIV, HCV, etc.) that could be transmitted upon transfusion. Contaminated drugs or intravenous fluid supplies at hospitals may also result in vehicle transmission of disease. Vector transmission Vector transmission occurs when an insect, arthropod, or rodent is the source of infection. Often the source of infection is an animal reservoir and the vector serves as an intermediate in the chain of infection. In the case of Lyme disease, the vector is a deer tick that transmits the spirochete Borrelia burgdorferi from deer to humans. Malaria is spread by the bite of female Anopheles mosquitoes infected with the protozoan Plasmodium. Rodents may also act as a vector—hantavirus infects many species of wild mice without causing disease but it causes disease in humans who inhale virus particles in aerosolized feces or urine.

Role in human health There are numerous practices that can be adopted in a home, business, or health care setting in order to reduce the risk of disease transmission. These include: • Handwashing: Good hand hygiene is the simplest and most effective method for preventing hospital-acquired (nosocomial) infections. Antiseptic agents that have both detergent and antimicrobial effects are recommended. • Food preparation: Common causes of food contamination are Salmonella, Staphylococcus aureus, and Clostridium perfringens. To reduce the risk of foodborne illness, it is recommended that food be cooked to a temperature of 74°C (165°F) or greater and then stored at 4°C (40°F) or cooler. • Waste disposal: Serious enteric (intestinal) diseases are common in less developed countries where adequate drainage and treatment of sewage is not available. For example, cholera is often spread in areas where there is no clean water supply or sanitary disposal of sewage. • Sterilization: An object is sterile when it is free of living organisms. There are multiple techniques that can be used to sterilize an object or fluid, including heat (moist or dry), irradiation, chemical treatment, or filtration. It is almost always recommended that critical items (those that enter normally sterile areas of the body) be sterilized.

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Resources BOOKS

Ayliffe, G. A. J., J. R. Babb, and Lynda J. Taylor. Hospitalacquired Infection: Principles and Prevention. Woburn, MA: Butterworth-Heinemann, 1999. Greenwood, David, Richard C. B. Slack, and John F. Peutherer. “Epidemiology and Control of Community Infections.” In Medical Microbiology. Edinburgh, UK: Churchill Livingstone, 1997. Palmer, Sue, Jean Giddens, and Darwin Palmer. Infection Control Outline. El Paso, TX: Skidmore-Roth Publishing, Inc., 1996. Rhinehart, Emily. Infection Control in Home Care. Gaithersburg, MD: Aspen Publishers, Ltd., 1999. Schaechter, Moselio, and Barry I. Eisenstein. Mechanisms of Microbial Disease. Philadelphia: Williams and Wilkins, 1999. PERIODICALS

Fishman, Jay, and Robert Rubin. “Infection in Organ-transplant Recipients.” New England Journal of Medicine (June 1998): 1741-1751. Pittet, Didier. “Improving Adherence to Hand Hygiene Practice: A Multidisciplinary Approach.” Emerging Infectious Diseases (March-April 2001). ORGANIZATIONS

Centers for Disease Control and Prevention. 1600 Clifton Road, Atlanta, GA 30333. (800) 311-3435. . OTHER

Centers for Disease Control and Prevention. “Universal Precautions for Prevention of Transmission of HIV and Other Bloodborne Infections.” .

Stéphanie Islane Dionne

Dislocations and subluxations Definition Dislocation is the displacement of bones that form a joint. A joint is where two or more bones meet. In a dislocation, the surfaces of the bones that normally articulate with each other (i.e., join together to allow movement) no longer line up correctly, and none of the joint surfaces are touching. Subluxation is a partial dislocation, so some contact remains between the joint surfaces.

Description Ligaments and joint capsules are tough bands of connective tissue that hold the bones together. Muscles and tendons also help strengthen joints. Any event that subjects a joint to unusual force may cause a dislocation by stretching and tearing these supporting structures. This trauma allows one or more of the bones to go out of alignment, so that the articular (joint) surfaces of the bones no longer have their correct relationship with each other. A dislocation may affect any size joint in the body. The most common dislocations of the major joints involve the shoulder, patella (i.e., kneecap), and elbow. The process of restoring the bones to their correct alignment is known as reduction. Several important problems that may arise from a dislocation require urgent attention. First, the injury is almost always very painful until the dislocation is reduced. Second, the deformity produced by the dislocation may stretch, kink, or tear adjacent major blood vessels or nerves. This effect on the neurovascular structures may severely threaten the circulation or nerve function in the more distal part of the limb, and may cause irreversible damage if not corrected in time. Complete dislocation of the knee (i.e., not just the kneecap) is especially dangerous in this regard. A different problem, which particularly affects the hip, is that part of the bone may receive its normal blood supply through the joint itself; when the joint dislocates, that part of the bone may lose its blood supply and become ischemic. Finally, hemorrhage and swelling progressively develop in the joint and the surrounding structures, so relocating the bones may become more difficult as time elapses. For all these reasons, prompt reduction of a dislocation is important. Physicians describe a dislocation by referring to the movement of the more distal of the bones involved. Thus, an anterior dislocation of the shoulder is one in which the humerus shifts anteriorly with respect to the shoulder socket. Additionally, a dislocation may be open or closed.

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• Cleaning and disinfecting: Cleaning is the physical removal of microbes from an object, while disinfection is defined as treatment to destroy microorganisms (although this does not normally lead to sterile conditions). Semicritical or noncritical items (those that do not enter sterile areas of the body) may be cleaned or disinfected based on the degree of risk of infection. • Protective barriers: The Centers for Disease Control and Prevention (CDC) recommend that universal precautions be used by all health care workers in contact with the body fluids of patients. These precautions include the following: wearing gloves when in contact with the blood, body fluids, mucous membranes, or non-intact skin of patients; wearing masks and/or protective eyewear during procedures that are likely to generate droplets of blood; and placing all disposable sharp items (needles, scalpel blades, etc.) in punctureresistant containers for disposal.

Dislocations and subluxations

• previous joint replacement surgery • medical diseases that contribute to falls

Diagnosis History A thorough history is important to determine: • the circumstances that led to the injury • the time at which the injury occurred • the type of force applied to the joint • the likelihood of other associated injuries • other medical and orthopedic history • medications and allergies • use of alcohol and illicit drugs • time of the last oral intake • tetanus status, if there are any open wounds Physical examination

This x ray shows the dislocation between two bones in a finger. (Photo Researchers, Inc. Reproduced by permission.)

This refers to the skin overlying the joint, meaning that an open injury is one in which the joint surfaces are exposed to the environment outside the body. An open injury creates a serious risk of bacterial infection of the joint. In a closed dislocation the skin remains intact.

Causes and symptoms Common causes of dislocations and subluxations include falls, motor vehicle accidents, sports, and horseplay. These activities may apply isolated or combined forces such as stretching, twisting, and compression to the affected joint. The force involved may be as minor as yawning, which may allow the mandible to slip out of the temporomandibular joint. Conditions that predispose to dislocation include: • shallow or abnormally formed joints • joints weakened by disease or previous dislocation 766

The examination must always start with the ABCs of resuscitation: airway, breathing, and circulation. Doctors and nurses must not allow a painful, deformed joint to distract them from potentially life-threatening injuries to the head, neck, chest, or abdomen. The examination of a dislocated joint typically will show deformity, tenderness, and resistance to movement. There may not be visible swelling. The distal neurovascular examination is very important—a dislocation that causes loss of the pulse in a limb is a far greater emergency than one in which the circulation is intact. Also, later exams will determine whether efforts to reduce the dislocation have affected the neurovascular function. The nurse must frequently inspect the injured limb for color, pulse, and function of motor and sensory nerves. X-ray studies Standard x-ray pictures of a joint usually will show a dislocation, and may show the additional presence of a fracture or other injury. Occasionally, special views or even advanced techniques such as computerized tomography (CT) may be necessary to demonstrate the problem. Shoulder dislocation A shoulder dislocation is a condition in which the head of the upper arm bone (humerus) is dislocated from the socket (glenoid). It can dislocate forward, backward, or downward. The injury is extremely painful, and may happen when throwing an object forcefully. The affected arm will be put in a sling, and instructions for the care of

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Shoulder separation A different condition that may be mistaken for a dislocation is acromioclavicular separation, often called AC separation or shoulder separation. This is technically a sprain, involving the stretching and tearing of ligaments that hold the tips of the acromion (i.e., part of the scapula) and the clavicle near each other. Shoulder separation typically results from a direct blow to the top of the shoulder, often in a young man, as may occur in contact sports or a motorcycle accident. The injury is painful, the patient will not want to move the shoulder, and the shoulder may lose its normal contour. The part of the shoulder just beyond the tip of the clavicle will be very tender. Regular x-ray pictures may not demonstrate a widening of the space between these two bony areas. Knee dislocation A patellar or patellofemoral dislocation (dislocation of the knee cap) is another common injury. In this condition, the knee cap moves laterally (to the outside of the leg) due to sideways motion of the lower leg while the upper leg is stationary. The injury will present with swelling and pain in the knee area. On palpation, the patella is discovered to be in the wrong position. Weakness of the joint makes it more susceptible to reinjury, and certain exercises may be prescribed to strengthen the area. Patellar injury also makes a person more likely to develop arthritis in the joint. Nursemaid’s elbow Another injury, common only in children between the ages of one to four, is subluxation of the radial head, or Nursemaid’s elbow. This condition may also cause damage to the annular ligament. The case of Nursemaid’s elbow demonstrates some of the challenges and pitfalls of diagnosing dislocation or subluxation. The cause is a simple, direct pull on the outstretched hand or wrist of a small child; this may occur when dangling a toddler by the hands in play, or when lifting a child who has fallen. The pulling action causes the head of the radius to move slightly out of position at the elbow. Often the caregiver may not associate such an innocent act with the onset of the problem. The child keeps the arm still against the body and cries if someone moves it. Often, the caregiver and even the medical staff will mistakenly believe that the problem lies in the wrist or the shoulder. The nurse and doctor must question the caregiver in detail about the

events leading to the onset of pain. Then, a careful examination will show that even slight supination of the forearm, which rotates the radius, is the motion that causes pain and resistance. X-ray studies are of little use in this condition, because the head of the radius is not displaced enough to appear abnormal.

Treatment Initial treatment Immediate treatment of a dislocation involves splinting the affected area. Splinting diminishes pain, protects the joint and nearby structures from further injury, and assists in transporting the patient. The patient may effectively splint the joint by supporting it with the hand; otherwise, the initial care provider may use pillows, a sling, folded cardboard, or other handy material to fit around the area. Application of ice helps control swelling and pain. The patient must receive nothing by mouth, in case anesthesia is necessary. Care providers should remove any rings or other constricting items distal to the site of injury. The patient will appreciate prompt medication for pain. Emergency department reduction Successful reduction of many dislocations and subluxations is possible in the emergency department (ED). Often, the physician will order intravenous (IV) medications such as narcotics (i.e., fentanyl) or morphine sulfate (Morphine) and benzodiazepines (i.e., lorazepam [Ativan] or midazolam [Versed]) to relieve pain, sedate the patient, and relax the surrounding muscles. Then the physician will employ a suitable technique of manipulating the joint in order to bring the bones back into alignment. Operative reduction Reduction in the ED is not always successful, sometimes due to the patient’s severe pain or anxiety. In other cases, swelling and entrapment of structures around the joint prevent the bones from returning to their proper position. In these instances, the patient will require general anesthesia in the operating room (OR). Also, in cases of open dislocation, the orthopedist usually will take the patient to the OR in order to thoroughly flush contamination from the joint. Post-reduction care The pain and limitation of joint movement will improve substantially after successful reduction. After any manipulation the nurse and physician must recheck and document the neurovascular function in the limb. In almost all cases the physician will request repeat x-ray studies in order to demonstrate that the reduction was

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the injury will be given to the patient. The area should be iced three or four times every day, and the shoulder should be exercised to speed healing and prevent reinjury in the future.

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Prognosis

KEY TERMS Anterior—Toward the front of the body. Benzodiazepines—The class of drugs related to diazepam (Valium), used to relax muscles and cause sedation. Clavicle—The collarbone. Distal—Farther from the center of the body. Humerus—The arm bone, connecting the shoulder and the elbow. Ischemic—Suffering from lack of arterial blood supply. Narcotics—The class of drugs related to morphine, used to relieve pain. Neurovascular—Pertaining to the function of nerves and blood vessels. Prosthetic—Referring to an artificial part of the body. Radius—The bone of the forearm which joins the wrist on the same side as the thumb. Reduction—The restoring of bones to their correct alignment. Scapula—The shoulder blade. Splinting—Preventing movement of a joint. Supination—The twisting motion of the forearm, wrist, and hand that turns the palm upward. Temporomandibular—Relating to the meeting point of the skull and the lower jaw.

successful. The physician will usually order pain medicine and a splint or support for the injured area. Most patients will be able to go home after reduction of a dislocation, although a patient who receives heavy sedation or anesthesia may require several hours of recovery before discharge. The nurse will need to instruct the patient and caregivers regarding: • allowable movement of the injured area • proper application of a splint or other support • use of ice (Heat treatments are contraindicated in acute and subacute stages.) • dosing and side effects of medications • warning signs of impending problems with neurovascular function • plans for follow-up appointments 768

Almost all patients who have a dislocation will need follow-up with an orthopedist. The injured ligaments and other joint structures may require many weeks to heal. Exercises and physical therapy will help improve function and decrease pain. Recurring dislocation or persistent loss of function may lead to surgical reconstruction, or even replacement of a joint. Numerous factors influence the ultimate outcome of a dislocation. These include: • extent of the original injury to the joint • presence of associated injuries • time delay to reduction of the dislocation • the patient’s prior overall fitness as well as previous function of the affected joint • the patient’s motivation to exercise and strengthen the injured area • the patient’s ability to modify behavior and avoid re-injury For some patients, especially athletes, decrease in limb function and time lost from normal activities may jeopardize career prospects and future earning potential. The patient, family, or coaches may put pressure on the doctor and support staff for a rapid and complete recovery, although this may not always be possible.

Health care team roles Emergency medical technicians perform initial rescue, begin to stabilize the patient, splint the injured area, and transport the patient to the hospital. The nurse receives the patient at the ED, performs further assessment, and orders x-ray tests directly or after consulting with the physician, depending on local policies. Later, the nurse carries out orders for medications and other treatments as directed by the physician, monitors the patient throughout the hospital stay, and prepares the patient for discharge. The aide assists the nurse. A radiology technician performs the x-ray studies ordered by the doctor or nurse. Later, a social worker may help coordinate care after discharge. The physical therapist works to rehabilitate the patient through exercise, massage, and other treatments. A certified athletic trainer (ATC) is sometimes employed in an effort to reduce the possibility of repeated injury in susceptible persons.

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Description

Prevention of dislocations and subluxations starts with awareness of inherently dangerous activities (e.g., riding motorcycles, climbing ladders, consuming alcohol) and avoidance of behavior that may cause specific injuries (e.g., crossing the legs for prosthetic hip dislocation, pulling toddler by hand for Nursemaid’s elbow). Participants should use appropriate protective equipment for work or sports, maintain good overall fitness, and allow sufficient time for healing of a previously injured body part before resuming full activity. Resources

Diverticula tend to occur most frequently in the last segment of the large intestine, the sigmoid colon. They occur with decreasing frequency toward the beginning of the colon. The chance of developing diverticula increases with age, so that by the age of 50, about 20–50% of all people will have some diverticula. By the age of 90, virtually everyone will have developed some diverticula. Most diverticula measure about 3 mm (0.19 inches) to just over 3 cm (1.18 inches) in diameter. Larger, or giant diverticula, are extremely rare, but may measure as large as 15 cm (5.9 inches) in diameter.

Causes and symptoms

BOOKS

Menkes, Jeffrey S. “Initial Evaluation and Management of Orthopedic Injuries.” In Emergency Medicine: A Comprehensive Study Guide, edited by Tintinalli, Judith E., Gabor D. Kelen, and J. Stephan Stapczynski. 5th ed. New York: McGraw-Hill, 2000, pp.1739-53. ORGANIZATIONS

American Academy of Orthopedic Surgeons. 6300 North River Road, Rosemont, IL 60018-4262. (800) 346AAOS. . OTHER

American Academy of Orthopedic Surgeons. “Dislocated Shoulder.” . Medline Plus. “Knee Cap Dislocation.” Medical Encyclopedia. .

Kenneth J. Berniker, M.D.

Diverticulitis see Diverticulosis and diverticulitis

Diverticulosis and diverticulitis Definition Diverticulosis is a condition in which the inner layer of the colon herniates (bulges out) through the outer, muscular layer, creating pouches called diverticula. Diverticulitis refers to inflammation and infection in one or more diverticula.

Diverticula are believed to be caused by overly forceful contractions of the muscular wall of the large intestine, often caused by straining to produce a bowel movement. As areas of this wall spasm, they become progressively weaker, allowing the inner lining to bulge through. The anatomically weakest areas of the intestinal wall occur next to blood vessels which course through the wall, so diverticula commonly occur in this location. Diverticula are most common in the developed countries of the West (North America, Great Britain, northern and western Europe). This is thought to be due to the diet of these countries, which tends to be low in fiber. This produces smaller volumes of stool. In order to move this smaller stool along the colon and out of the rectum, the colon must narrow itself significantly, and does so by contracting forcefully. This causes an increase in pressure, which, over time, weakens the muscular wall of the intestine and allows diverticular pockets to develop. The origin of giant diverticula development is not completely understood; one theory involves gas repeatedly entering and becoming trapped in an already existing diverticulum, causing it to stretch and expand. The great majority of people with diverticulosis will remain symptom-free. Many diverticula are incidentally discovered during examinations for other conditions of the intestinal tract. Some patients with diverticulosis have symptoms such as constipation, cramping, and bloating. It is unclear whether these symptoms are actually caused by the diverticula themselves, or whether some other gastrointestinal condition, such as irritable bowel syndrome, might be responsible. Because many diverticula develop in areas near blood vessels, one serious, although infrequent, risk of diverticulosis is intestinal bleeding. Seventy-five percent of such bleeding episodes occur in diverticula located on the right side of the colon. About 50% of the time the bleeding will stop on its own.

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Prevention

Diverticulosis and diverticulitis

diverticulitis include the formation of fistulas and colonic strictures.

Diagnosis The majority of diverticula do not cause any symptoms, and are often found during an examination being performed for some other medical condition. When diverticula are suspected because a patient begins to have sudden rectal bleeding, the location of the bleeding can be identified with colonoscopy. In this procedure a colonoscope, a small, flexible tube, is inserted through the rectum and into the colon. The tip of the scope has a fiber-optic camera, which allows the view through this colonoscope to be projected onto a television screen. The operator can introduce the colonoscope through the entire colon to find the source of the bleeding.

Perforation 18% Hemorrhage 25%

Illustration of diverticula in the sigmoid colon. Diverticulosis is almost always located in the descending or sigmoid colon. (Delmar Publishers, Inc. Reproduced by permission.)

One of the most common and potentially serious complications of diverticulosis is inflammation and infection of a particular diverticulum, a condition called diverticulitis. Diverticulitis is usually found in the sigmoid colon, the final segment of the large intestine that empties into the rectum where most diverticula are found. Older adults have the most serious complications from diverticulitis, although very severe infections also may occur in patients under the age of 50. Men are three times as likely as women to be stricken with diverticulitis. Diverticulitis is believed to occur when a hardened piece of stool, undigested food, and bacteria (called a fecalith) becomes lodged in a diverticulum. This blockage interferes with the blood supply to the area, and infection sets in. The patient with diverticulitis experiences pain (especially in the lower left side of the abdomen) and fever. In response to the infection and the irritation of nearby tissues within the abdomen, the abdominal wall muscles may begin to spasm. About 25% of all patients with diverticulitis have some rectal bleeding, although this rarely becomes severe. Abscesses (pockets of infection) may appear within the wall of the intestine, or even on the exterior surface of the intestine. When a diverticulum weakens sufficiently, and is filled to bulging with pus, a perforation in the intestinal wall may develop. When the infected contents of the intestine spill into the abdomen, peritonitis may occur. Other complications of 770

Angiography can also trace the source of intestinal bleeding, although it is used less often. It involves inserting a tiny tube through the femoral artery in the groin, and advancing it into one of the major arteries that supplies the colon. Contrast medium that will appear on xray films is injected, and the area of bleeding is located by looking for an area where the contrast is leaking into the lumen of the colon. Diagnosis of diverticulitis is not difficult in patients with previously diagnosed diverticulosis. The presence of left-lower quadrant abdominal pain and fever in such patients should prompt suspicion of diverticulitis. Examination of the abdomen will usually reveal tenderness to touch, with the patient’s abdominal muscles contracting strongly to protect the tender area. During a rectal exam, the clinician may be able to feel an abnormal mass if there has been perforation and abscess formation at the site of the perforation. Palpating this mass may prove painful to the patient. When diverticulitis is the suspected cause of the patient’s symptoms, tests traditionally used to diagnose colonic disorders such as barium enema and endoscopy are contraindicated during the acute phase of the illness. The concern is that the increased pressure exerted on the colon during these exams may increase the likelihood of perforation of the diverticula. After several weeks, when the diverticulitis has resolved, these examinations may be performed in order to confirm the diagnosis and extent of the disease.

Treatment Only about 20% of patients with diverticulosis experience symptoms that prompt them to seek medical care. Most people never know that they have diverticula. For those individuals with cramping pain and constipation

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While there are almost no situations when uncomplicated diverticulosis requires surgery, giant diverticula always require removal due to the high risk of infection and perforation. The usual treatment involves removing that portion of the intestine. Treatment for uncomplicated diverticulitis usually requires hospitalization to rest the bowel. This involves keeping the patient from eating and drinking anything. The patient receives IV (intravenous) fluids and antibiotics. Some physicians treat mildly ill patients at home with a liquid-only diet and oral antibiotics. The complications of diverticulitis need to be treated aggressively, because mortality (death rate) from perforation and peritonitis is quite high. Abscesses may be drained of their infected contents by inserting a needle through the skin of the abdomen and into the abscess. If this is unsuccessful, laparotomy (open abdominal surgery) is required to resect the segment of the colon that contains the abscess. Fistulas require surgical repair by removing a segment of the colon that contains the origin of the fistula, followed by immediate anastomosis (reconnection) of the two free ends of colon. Peritonitis requires open surgery. The entire abdominal cavity is irrigated (washed) with a warmed sterile saltwater solution, and the damaged piece of intestine is removed. Obstructions require immediate surgery to prevent perforation. Massive, uncontrollable bleeding is rare, and may require removal of part or all of the large intestine. During any of these procedures, the surgeon must decide how much of the intestine must be removed. When the amount of intestine removed is great, it may be necessary to perform a colostomy, which involves pulling the end of the remaining intestine through the abdominal wall, to the outside. This bit of intestine is then fashioned so that a bag can be fitted over it. The patient’s feces collect in the bag, because the intestine no longer connects with the rectum. The colostomy may be temporary, in which case another operation will be required to reconnect the intestine, after substantial healing has occurred. Otherwise the colostomy is permanent, and the patient must adjust to living permanently with the

colostomy bag. Most patients with colostomies are able to lead full, active lives. Occasionally, a patient has such severe diverticular disease that the surgeon recommends removal of a portion of the colon as a preventive measure, to avoid the high risk of surgery performed after a complication has set in. It is recommended for patients identified as at very high risk of experiencing dangerous complications of diverticulosis. Such elective surgery may be recommended: • for older patients who have had several attacks of diverticulitis • for patients under age 50 who have had even one attack • when treatment does not get rid of a painful mass • when the intestine appears to be strictured on colonoscopic or barium enema (This could suggest the presence of cancer.) • when certain patients begin to regularly experience painful urination or urinary infections (this suggests that there may be a connection between the intestine and the bladder) • when there is any question of cancer • when the diverticular disease appears to be progressing rapidly

Prognosis The prognosis for people with diverticula is excellent, with only 20% of such patients ever seeking any medical care for their condition. While diverticulitis can be a difficult and painful disease, it is usually quite treatable. Prognosis is worse for individuals who have coexisting medical problems, particularly those requiring the use of steroids, which increase the chances of developing a serious infection. Prognosis is also worse in the elderly.

Health care team roles Diverticulitis and diverticulosis are often diagnosed by primary care practitioners and gastroenterologists during the course of examinations for other problems. In some instances, patients may require surgical intervention. Imaging studies to assist in diagnosis are performed by x-ray technologists; laboratory technologists may be involved in obtaining blood and stool samples for analysis. Patient education Nurses, dietitians, and nutritional counselors have important roles in teaching patients about dietary

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due to diverticulosis, the usual treatment involves increasing the fiber in the diet. This may be done with dietary supplements of bran or psyllium seed to increase stool volume, or by increasing the patient’s intake of fruits, vegetables, legumes, and whole-grain foods. Bleeding diverticula are usually treated by bed rest, with blood transfusion if needed for hemorrhaging. In cases of very heavy hemorrhaging, medications to encourage clotting may be injected during the course of a diagnostic angiography.

DNA typing

Resources

KEY TERMS

BOOKS

Angiography—An x-ray study of the arteries in a particular part of the body. Angiography is often performed in order to localize internal bleeding. Bowel obstruction—A blockage in the intestine which prevents the normal flow of waste down the length of the intestine. Colonic stricture—Strictures that form after a bout of diverticulitis resolves, leaving scar tissue that narrows the colon lumen. Colostomy—A procedure performed when a large quantity of intestine is removed. The end piece of the intestine leading to the rectum is closed. Diverticula—Outpouchings in the large intestine caused when the inner, lining layer of the large intestine (colon) bulges out (herniates) through the outer, muscular layer. Endoscopy—Examination of an area of the gastrointestinal tract by putting a lighted scope, usually bearing a fiber-optic camera, into the rectum, and passing it through the intestine. Fistula—An abnormal connection formed between two organs which usually have no connection whatsoever (e.g. the colon and bladder). Peritonitis—A potentially life-threatening infection and inflammation of the lining of the abdominal cavity, the peritoneum. Sigmoid colon—The final portion of the large intestine which empties into the rectum.

changes to prevent these conditions. Nurses, social workers, and ostomy specialists also may be involved in educating patients pre- and postoperatively about colostomy care.

Prevention While there is no absolutely certain way to prevent the development of diverticula, it is believed that highfiber diets are beneficial. Foods recommended for their high-fiber content include whole-grain breads and cereals, and all types of fruits and vegetables. Most experts suggest that individuals consume about 20–35 grams of fiber daily. If this is not possible to achieve through diet, there are fiber products that can be mixed into 8 ounces of water or juice, and which provide about 4–6 grams of fiber per dose. 772

Isselbacher, Kurt J., and Alan Epstein. “Diverticular, Vascular, and Other Disorders of the Intestine and Peritoneum.” In Harrison’s Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998. PERIODICALS

Cerda, James J., et al. “Diverticulitis: Current Management Strategies.” Patient Care 31 no. 12 (July 15, 1997): 170 ff. Cunningham, Mark A., et al. “Medical Versus Surgical Management of Diverticulitis in Patients Under Age 40.” American Journal of Surgery 174 no. 6 (December 1997): 733 ff. “Diet and Diverticular Disease in Men.” Nutrition Research Newsletter 14 no. 2 (November 1994): 28. “Diet for Diverticulosis.”Consumer Reports on Health 8, no. 11 (November 1996): 132. “Keeping Diverticulosis Silent.” Berkeley Wellness Letter 12, no. 4 (January 1996): 6 ff. Munson, Marty, and Teresa Yeykal. “Outrun Trouble: Running and Bran Cereal in the Prevention of Diverticular Disease.” Prevention 47 no. 9 (September 1995): 38 ff. ORGANIZATIONS

National Digestive Diseases Information Clearinghouse. 2 Information Way, Bethesda, MD, 20892-3570.

Barbara Wexler

DNA see Inheritance, principles of DNA test see Genetic testing

DNA typing Definition DNA typing is a laboratory procedure that detects normal variations in a sample of DNA (deoxyribonucleic acid). DNA typing is most often used to establish identity, parentage, family relationship and appropriate matches for transplantation of organs and tissues.

Description DNA DNA is a molecule that stores genetic information required for the development of the body and the control of cellular processes. Each strand of DNA is made of individual nucleotides that are joined together. Each nucleotide is made up of a phosphate group, a five-car-

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The DNA sequence is made up of coding and noncoding regions. A coding region is a section of DNA, called an exon, that contains the instructions for the production of a particular protein. The primary structure of proteins is determined by the sequence of bases in the exons of a gene. Exons are located within the genes but are separated by non-coding regions called introns. Genes make up about 5% of human DNA and the other 95% consists of non-coding regions. The function of the non-coding regions is for the most part unknown. Normal variations can occur in the DNA sequence of the coding and non-coding regions. Sequence polymorphism and length polymorphism are the two main forms of DNA variation. Sequence polymorphism results from differences in the sequence of bases at a particular locus. A locus is a specific location on a DNA molecule. Length polymorphism results from differences in the length of DNA at a particular locus. Differences in the length of the DNA are due to variations in the number of times that a certain sequence of bases is repeated. The number of times that a certain sequence is repeated at a specific locus will often vary between individuals. A locus that has a repeated unit of nine to ninety-eight bases is called a variable number tandem repeat locus (VNTR) or minisatellite. Loci that have a repeating unit of only two to seven bases are called short tandem repeats (STRs) or microsatellites. For example CAGACAGACAGA is an STR of four bases that is repeated three times. Nuclear and mitochondrial DNA Two strands of single stranded DNA wind together to form double stranded DNA in the form of a double helix. The DNA strands are held together by hydrogen bonds that form between the bases. Adenine joins with thymine and guanine joins with cytosine. Two sequences are said to be complementary if they have a sequence that allows them to join together to form double stranded DNA. Most DNA is packaged with proteins to form microscopic structures called chromosomes. Chromosomes are found in the nucleus of each cell of the body and can be visualized under the microscope. Each cell of the body, except for the egg and the sperm cells, normally contains 22 pairs of chromosomes and two sex chromosomes (46 chromosomes in total). The egg and sperm cells each contain 23 chromosomes.

DNA is also found in the mitochondria. The mitochondria are energy producing organelles found in most cells. There are many mitochondria found in each cell. Each mitochondria contains one copy of circular DNA. Since there are many mitochondria in each cell, a lot of mitochondrial DNA may be present in only a small sample of cells. Mitochondrial DNA is found in the egg cells but not the sperm cells. Mitochondrial DNA is, therefore, only passed down from a mother to her offspring. Methods of DNA typing for identity, parentage, and family relationships RESTRICTION FRAGMENT LENGTH POLYMORPHISM (RFLP) ANALYSIS. RFLP analysis was the first technique

used for forensic DNA typing. During RFLP analysis, DNA that has been isolated from a sample is cut into short sections by an enzyme called a restriction endonuclease. An enzyme is selected that will make a cut in the DNA at a specific sequence of bases on either side of a VNTR locus. This results in different sized fragments of DNA. Different people will have fragments of DNA of different lengths due to differences in the number of repeating units at a particular DNA locus. After the DNA is cut into pieces, the fragments are separated according to size by a process known as gel electrophoresis. DNA fragments are negatively charged at an alkaline pH owing to the phosphate groups. The smaller the fragment, the faster it will migrate to the positive electrode (anode). After separating the DNA fragments, the gel is soaked in a solution of sodium hydroxide and sodium chloride which separates the double stranded DNA into single stranded DNA, a process called denaturation. The single stranded DNA is transferred from the gel to a nylon membrane. A piece of DNA called a probe is added to the DNA that is affixed to the membrane. The probe will attach to a section of DNA on the membrane that has a complementary base sequence. The probe chosen corresponds to a specific locus that has a variable number of repeats containing the bases complementary to the probe. Either a florescent or radioactive material is bound to the probe so that it can be visualized. Either one or two bands will be visualized for each probe used. If the person has inherited the same length DNA fragment at a locus from both parents then only one band will be seen. If two different sized DNA fragments are inherited then two bands will be visualized. The DNA is analyzed using a panel of probes each specific for a different locus. A DNA type is made up of a pattern of different sized bands at different loci. The frequencies of the VNTRs that are inherited at each locus determines the probability of a DNA match. POLYMERASE CHAIN REACTION (PCR). PCR based STR analysis is a more modern approach to DNA typing. The first step of the process is to isolate DNA from a

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bon sugar (deoxyribose), and an organic base. Adenine, thymine, guanine, and cytosine are the four bases found in DNA. The sequence of bases in DNA determines the genetic code of an individual. Every person excluding identical twins has a different sequence of bases.

DNA typing

sample of tissue such as blood or semen. The isolated DNA, called the template, is mixed with a heat-stable form of DNA polymerase (e.g., Taq polymerase), deoxynucleotide triphosphates, and DNA primers. These reagents are suspended in a buffer and together are called the master mix. The template and master mix are added to a tube and the tube is placed into an incubator called a thermal cycler. The purpose of the thermal cycler is to control the temperature of each of the three phases of DNA amplification. The first step in PCR is denaturation. This is accomplished by heating the mixture to 94°C, which separates the strands. After denaturation, the temperature of the thermal cycle is automatically lowered to 64°C. The primers are short sequences of DNA that can bind to one of the DNA strands on either side of the target sequence to be amplified. Four primers are required for each section of DNA that is being analyzed. The primers are selected so that they flank an STR region. The binding of the primers to complementary base sequences on the target DNA is called annealing, and requires a lower temperature. After the annealing step, the temperature is increased to 72°C, which is the optimal temperature for DNA polymerase. Once the primers have annealed, the DNA polymerase binds to single stranded DNA between the primers and fills in the sequence with the deoxynucleotide triphosphates. This results in synthesis of a new piece of double stranded DNA consisting of the STR locus and the primer regions. This process is called primer extension. After extension, the new double strands of target DNA are denatured by heating the mixture to 94°C again. After a suitable incubation, the temperature is lowered to 64°C to facilitate annealing of primers, and then is adjusted to 72°C for extension of new complementary strands. Each cycle increases the number of DNA pieces containing the STR locus. Each time this process is repeated the amount of target DNA doubles. After 20 cycles (about two hours) there will be over one million identical copies of the STR locus. DNA typing for identification, parentage and familial studies uses probes that encompass various STR loci. If a person has inherited the same number of repeats from his or her mother and father, then only one band will appear for that locus. If the person has inherited a different number of repeats from his or her mother and father, then two bands will be seen for that locus. DNA typing to establish identity, parentage, and family relationship DNA typing used for identification purposes and the establishment of parentage and family relationships looks for variation within the non-coding regions of the 774

DNA. It relies on the presence of length polymorphisms such as VNTRs and STRs. DNA typing determines the number of times that a particular sequence is repeated at a particular locus. DNA typing usually analyzes the number of repeats at four or more separate loci. The loci chosen for DNA typing have a high degree of variability and are usually found on different chromosomes. It is possible that two unrelated individuals will possess the same number of repeats at a particular locus. It is less likely, however, that two unrelated individuals will have the same number of repeats at a number of different loci. In order to determine the possibility that a match in DNA types occurred by chance, the frequency of the determined number of repeats in the individual’s ethnic group is calculated. For example, if the frequency of the repeat number in the ethnic group is 1 in 10,000, then there is a 1 in 10,000 chance that the match occurred by chance. By using a number of different loci, one can decrease the chances that the match occurred by chance and increase the chances that the two DNA samples are from the same individual. While it is mathematically impossible to prove that two samples are identical using this procedure, it is possible to prove absolutely that two samples are not identical. This occurs when a different number of repeats is found at a locus. Mitochondrial DNA typing may be performed if nuclear DNA typing is not successful or when there is insufficient nuclear DNA for typing. It is also sometimes used to help establish maternity. Variations in mitochondrial DNA are typically discovered by sequencing (determining the order of bases). PARENTAGE AND FAMILY RELATIONSHIP. DNA typing used for establishment of parentage and family relationships uses either RFLP analysis or PCR based STR analysis. DNA typing is the method most often used to establish paternity. It may also be used to establish parentage in cases where neonates have been mistakenly switched in the nursery. DNA typing can be used to resolve immigration cases when family relationships are disputed.

The basis for DNA typing in parentage and family relationship cases is that each child inherits one of each chromosome from their mother and one of each chromosome from their father. The child should, therefore, inherit a set number of repeats at a particular locus from their mother and a set number of repeats at that locus from their father. At some loci they may inherit the same number of repeats from their mother and from their father. During parentage analysis the number of repeats found at different loci is compared between the child and the alleged parent. It is helpful, but not absolutely necessary,

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If the alleged parent’s repeat numbers do not match with the child’s repeat numbers then parentage can usually be ruled out. What can make this analysis tricky is that sometimes a small alteration can occur in the DNA of the child that is not present in the parent. This can cause the child to have a different repeat number then their true parent at a specific locus. It is therefore important that more than one loci be analyzed. Forensic and non-forensic identification Modern day DNA typing for identification purposes usually uses PCR and STRs rather than RFLP analysis. DNA typing can be used to help identify a victim of a homicide. The DNA type of the victim can be compared to the DNA types of alleged family members to see if there is a match. DNA typing has also been used to identify soldiers killed in battle. The U.S. Department of Defense has a collection of tissue samples from soldiers so that, if necessary, they can be identified through DNA typing. DNA typing can also help to determine whether a suspect was at a particular crime scene. DNA can be isolated from tissue such as skin, blood, hair and semen left at the scene. The DNA type of the sample at the crime site can be compared to the DNA type of the suspect. If there is a difference in the DNA type at any locus then the DNA obtained is definitely not from the suspect. If the DNA type is identical at all loci then the probability that this occurred by chance must be determined. Transplantation matches DNA typing for transplantation matches looks at normal variation in the coding region of the DNA. DNA typing can be used to identify an appropriate match for a transplant such as a bone marrow transplant. A successful transplant requires a close match of human leukocyte (HLA) antigens between donor and recipient. The HLA antigens are proteins that are located on the surface of most cells. There are six subregions on chromosome number six that each contain at least one HLA locus. The

subregions are divided into two classes. HLA-A, HLA-B, and HLA-C comprise Class I and HLA-DR, HLA-DP, and HLA-DQ comprise class II. Each subregion has at least one gene that has a number of different genetic variants (allels). The HLA gene products mediate the recognition and the destruction of foreign cells such as bacteria and viruses. They also mediate the destruction (rejection) of transplanted cells that do not express the same HLA allels as the recepient. Therefore, a transplant from a donor with very different HLA antigens is likely to be rejected by the body’s immune system. Conversely, if the donor and recipient have a close HLA match then the transplant has a better chance of being successful. DNA typing looks for characteristic sequence differences in the genes that produce the HLA antigens. For example, there are more than fifty HLA-A variants. Each HLA-A variant is produced by a different gene. The HLA variants inherited by an individual can be determined by extracting DNA from blood cells and using PCR to amplify the HLA loci. Specific primers or probes are used to identify the variants for each of the six subregions.

Viewpoints Early use of DNA typing for forensic evidence was marred by technical difficulties. By the year 2001, however, DNA typing techniques had improved considerably and had become highly accurate tools for forensic evidence. DNA typing evidence is now widely used in most North American and European courts. The quality of the evidence is still dependent, however on the methodology used, the number of loci examined and the quality of the laboratory where the typing is performed. Contamination of the DNA sample collected from the crime site is also a concern if proper techniques are not followed. The increasing use of DNA typing has led to the formation of databases that contain DNA typing information. DNA data banks of convicted criminals exist in each of the 50 states and in many other countries. The FBI has also created a national DNA data bank of convicted criminals called CODIS (combined DNA index system). These DNA data banks require convicted felons to donate blood samples for DNA typing prior to parole. The type of felonies for which DNA typing is required varies from state to state. It is anticipated that most laws will be amended to require DNA typing of all convicted felons. It is also possible that laws may be enacted to force all people arrested for a crime to donate a DNA sample to the database. Many countries obtain DNA samples from ordinary citizens when trying to eliminate suspects of a particular

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to perform DNA typing on the known parent as a comparison. Sometimes the DNA of siblings and other family members will also be typed for comparison. If the alleged parent is the true biological parent, then at each locus analyzed, the child should have the same repeat number as the parent. Since a match can occur by chance it is necessary to calculate the frequency of the repeat number in the alleged parent’s ethnic group. Usually when a match is found the chance of parentage is greater than 99%. For example a 1/1000 chance that the match occurred by chance corresponds to a 99.9% chance that the alleged parent is the true biological parent.

DNA typing

KEY TERMS Amniocentesis—Prenatal testing performed at 1620 weeks of pregnancy which involves inserting a needle through the abdomen of a pregnant mother and obtaining a small sample of fluid from the amniotic sack. Can be used to obtain a sample of the baby’s cells for DNA typing. Antibody—Protein produced by the body in response to the presence of a foreign antigen. Antigen—A substance that induces an immune response. Chorionic villus sampling (CVS)—Prenatal testing performed at 10-12 weeks of pregnancy which involves inserting a catheter through the vagina of a pregnant mother or inserting a needle through the abdomen of the mother and obtaining a sample of placenta. Can be used to obtain a sample of cells for DNA typing. Chromosome—A microscopic structure, made of a complex of proteins and DNA, that is found within each cell of the body. DNA (deoxyribonucleic acid)—The hereditary material that influences the development and functioning of the body. Eugenics—A discredited movement which attempts to improve the human race by preventing the creation of offspring in individuals with undesirable traits and promoting the creation of offspring in those with desirable traits. Forensic—Related to or used in the courts of law. Gene—A functional segment of DNA that contains the instructions for the production of a particular protein. Each gene is found on a specific location on a chromosome. HLA typing—The determination of the type of human leukocyte antigens possessed by an individual. Locus—Specific physical location on a DNA molecule. Nucleus—A membrane bound spherical structure that contains the chromosomes and is found in most cells. Polymorphism—Genetic variation. STR (short tandem repeats)—A locus of DNA that has a repeating unit of two to seven bases. VNTR (variable number tandem repeats)—A locus of DNA that has a repeating unit of 9 to 98 bases.

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crime. For example DNA samples may be collected on hundreds of men in a rural area where a sexual assault has occurred. Although citizens are not required by law to donate their DNA, it is likely that they experience a great deal of social coercion. The United States does not currently allow DNA typing of those who are not convicted of a crime. There are concerns, however, that the databases could be expanded to include all citizens and be used as a method of identification similar to a social security number. Commercial databanks exist which store DNA samples or DNA typing results of children. If the child is later kidnapped then DNA samples obtained from such items as gum and licked stamps can be used to try and locate and identify the child. Some people would argue that these databanks are unnecessary since a child’s DNA type can be deduced from that of other family members should it become necessary. This stored information could also be used later as evidence against the child. If the commercial data bank becomes bankrupt or changes ownership then there may be concerns about the control, availability and ownership of the DNA. In addition, issues of non-paternity can be discovered during this process. The existence of DNA databanks raise concerns about privacy and discrimination. There is a concern that DNA typing may yield other unintended genetic information about the individual and his or her family. There has been some discussion about donating DNA samples that have been collected for forensic DNA typing to researchers. This research could yield very specific genetic information on the individual. There is a concern that the genetic information obtained could be used for discriminatory purposes. For example, the information could result in the discrimination of citizens by employers and health insurance companies.

Professional implications DNA typing results often become evidence in a court of law. It is, therefore, important that health care professionals involved in collecting samples for DNA typing follow strict protocols that prevent contamination and insure that samples are obtained from the correct person. It is also important that a chain-of-evidence is established. A chain-of-evidence documents who has handled the evidence and when it was transferred to another person. A chain-of-evidence can help to demonstrate that evidence was not altered prior to its introduction in court. Often, laboratories that perform DNA typing for parentage have kits designed to insure that proper protocols are followed. They may also have designated blood collection centers that will obtain the samples required for DNA typing. Many hospitals have specific protocols,

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It is important that health care professionals try to help prepare their patients for paternity test results since the results can sometimes be unexpected and can often be quite devastating. It can be helpful to explore the motivation behind the testing and discuss the implications of possible test results. The limitations of the testing should also be adequately discussed. The quality of the laboratory chosen for paternity testing should also be evaluated. Some health care professionals may be called upon to offer paternity testing prenatally. The patient needs to be informed about the risks of losing a normal pregnancy if prenatal testing methods such as amniocentesis and chorionic villus sampling are performed. It is also typically more expensive to perform paternity testing prenatally. Many patients when provided with complete information about prenatal paternity testing choose to have the tests performed after the child is born. Resources BOOKS

Butler, John. Forensic DNA Typing. San Diego, CA: Academic Press, 2001. Hancock, JT. Molecular Genetics. Woburn, MA: Reed Educational and Professional Publishing Ltd., 1999. Inman, Keith and Norah Rudin. An Introduction to Forensic DNA Analysis. Boca Raton, Florida: CRC Press, 1997. Winter, P.C., G.I. Hickey, and H.L. Fletcher. Instant Notes in Genetics. New York, New York: Bios Scientific Publishers, 1998. PERIODICALS

Carracedo, A., W. Bar, W. Lincoln et al. “DNA Commission of the International Society for Forensic Genetics: Guidelines for Mitochondrial DNA Typing.” Forensic Science International 110 (2000): 79-85. Guillen, Margarita, Maria Lareu, Carmela Pestoni, et al. “Ethical-legal problems of DNA databases in criminal investigation.” Journal of Medical Ethics 26 (2000): 266271. Hallenberg, Charlotte, and Niels Morling. “A Report of the 1997, 1998 and 1999 Paternity Testing Workshops of the English Speaking Working Group of the International Society for Forensic Genetics.” Forensic Science International 116 (2001): 23-33. Hoyle, Russ. “The FBI’s national DNA database.” Nature Biotechnology 16 (November 1998): 987. Reilly, Phil. “Legal and public policy issues in DNA forensics.” Nature Reviews Genetics 2 (April 2001): 313-317.

OTHER

Benecke, Mark. “DNA typing in forensic medicine and in criminal investigations: a current survey.” Naturwissenschaftenaufsatze. 84 (1997):181-188. “DNA analysis laboratory.” Human DNA typing. .

Lisa Maria Andres, MS, CGC

Doctor-patient relationship see Professional-patient relationship Docusate see Laxatives Doppler echocardiography see Echocardiography

Doppler ultrasonography Definition Doppler ultrasonography, also called Doppler ultrasound, is a noninvasive diagnostic procedure that uses an ultrasound scanner to convert sound waves into images of blood flow in body tissue and organs. Doppler ultrasonography does not use ionizing radiation and is used for a variety of clinical applications.

Purpose Doppler ultrasonography is used during an ultrasound examination to assess the direction, velocity, and turbulence of blood flow. It is frequently used in cardiac and vascular scanning to evaluate blood flow and diagnose abnormalities in flow. Cardiac applications include the detection of heart valve problems, the determination of arterial vessel narrowing (stenosis) or blockage, the diagnosis of congenital cardiac defects, and the evaluation of damage following myocardial infarction (heart attack). Vascular applications include the work-up of stroke patients, the assessment of blood flow in the major abdominal arteries, and the evaluation of vessels in the arms, legs, and neck. Vascular conditions that can be diagnosed using Doppler ultrasonography include deep vein thrombosis (DVT), a blocked carotid artery, blood clots, tumors with vascular involvement, and abdominal aortic aneurysm. Doppler ultasonography can also be used to determine whether a patient is a candidate for a surgical or other interventional procedure, such as vascular grafting, or it can be used during and after cardiac and

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kits, and chain-of-evidence procedures in place to insure that samples for DNA typing are collected and handled properly. In some cases special training programs are offered to health care professionals who are involved in collecting samples for DNA typing used as forensic evidence.

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Precautions The test is widely used because it is noninvasive, uses no x rays, and gives excellent images. It is harmless, painless, and widely available. Because smoking can cause constriction of blood vessels, patients should not smoke before an ultrasound examination of the blood vessels.

Description Doppler ultrasonography is performed using an ultrasound scanner with Doppler imaging capabilities; most scanners used for general-purpose abdominal, cardiac, and vascular scanning are equipped with Doppler. Ultrasonography involves the use of sound waves above the level of human hearing, and works similarly to sonar or radar. Sound waves are transmitted through the body and echoed back to produce an image of the area of interest. Ultrasound waves used for diagnostic imaging are typically in the range of 2 to 10 megahertz (MHz).

A physician can monitor blood flowing through a patient’s carotid artery using the Doppler technique. (Science Source/Photo Researchers. Reproduced by permission.)

vascular surgical procedures to assess blood flow and the success of the procedure. In obstetric ultrasound, Doppler ultrasonography is used to check fetal cardiac activity. Doppler ultrasonography can be performed in a hospital radiology or cardiology department, a hospital vascular laboratory, at the patient’s bedside, in the emergency department, in an operating room, or in an outpatient imaging center, depending on the patient’s medical condition. Doppler ultrasonography is a noninvasive, safer, and faster alternative to x-ray angiography, which involves radiation exposure, the injection of a contrast dye, and catheterization of blood vessels, although ultrasound may not yield images that are as detailed as those from x rays during catheterization. A new device introduced in 2000 combines Doppler ultrasonography with endoscopy. The Doppler ultrasound scanner is interfaced with an endoscopy system, and the Doppler ultrasound images can be simultaneously displayed with the endoscopic images on one monitor, like a picture-in-picture display. Clinical applications include the evaluation of ulcers and hemorrhaging, vascular abnormalities of the intestinal tract, and enlarged vessels in the digestive tract, as well as assessment during endoscopic surgical procedures. 778

Doppler ultrasonography uses the frequency shift caused by the Doppler effect to produce images of blood flow. The Doppler effect is a principle of physics involving light and sound; relative to an observer, the frequency of any light or sound wave will vary as the source of the wave approaches or moves away. With regard to medical ultrasound, the Doppler principle states that sound waves increase in frequency when they echo from objects (in this case, red blood cells) moving toward the transducer and decrease in frequency when they echo from objects moving away from it. This change in frequency, which is related to the velocity of the moving red blood cells, is then measured and used to determine blood flow velocity. Therefore, Doppler imaging allows the frequency of the speed of blood flow to be calculated relative to a computer marker placed by the sonographer. There are several different modes of Doppler ultrasound. Most ultrasound scanners include both continuous- and pulsed-wave Doppler. Continuous-wave Doppler is the simplest mode, and is commonly used in cardiac studies for blood flow analysis. This mode receives flow information from all the moving reflectors in the path of the beam and can provide maximum velocity through the target area. Pulsed-wave Doppler allows the operator to select the area of interest for flow analysis using cursors superimposed on the 2-D image. Depthselective information is obtained by acoustic pulses emitted from the transducer, allowing the precise location of the target area, as well as the flow, to be determined. Most ultrasound scanners also have color Doppler imaging capability, which superimposes color over moving structures on the gray-scale images. For example, red and

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During an ultrasound examination, the patient is positioned on a bed or table so the area to be imaged can be easily accessed. An acoustic coupling gel, a special gel that enhances the transmission of ultrasound waves, is spread on the skin over the area of interest. A handheld ultrasound probe with a transducer (a crystal that transmits and receives the sound waves) is placed on the skin and positioned appropriately to acquire images of the blood vessels. Usually gray-scale images, which use different shades of gray to indicate differences in the strength of echoes (echoes from blood are of lower strength and appear darker than surrounding tissue) are acquired first, and then the Doppler mode is selected to acquire Doppler images that are superimposed over the gray-scale images. The sonographer is able to use the scanner’s computer to mark areas and calculate parameters of interest, such as blood flow velocity in vessels with narrowing or blockage. Ultrasound scanners are usually equipped with a videotape recorder or digital image acquisition system to record the Doppler examination, as well as a medical image printer for hard copies of still images.

Preparation There is no special preparation needed for this test, other than removing clothing and jewelry covering the area to be imaged.

KEY TERMS Angiography—During cardiac catheterization, the procedure of acquiring x rays of the heart and coronary arteries after injection of a radiopaque substance (often referred to as a dye or contrast agent). Catheter—A flexible or preshaped curved tube, usually made of plastic, used to evacuate or inject fluids into the body. In cardiac catheterization, a long, fine catheter is inserted through a blood vessel into the chambers of the heart. Doppler imaging—A mode of ultrasound imaging that uses the physics principle of the Doppler effect (sound frequency waves shift relative to the observer, allowing velocity measurement) to produce color or gray-scale images of blood flow velocity and heart motion. Endoscopy—A minimally invasive procedure that uses a scope with a camera on the end to examine the inside of a body cavity or organ. Grafting—Implantation of a biological or artificial portion of a blood vessel to repair the vessel and restore flow. Doppler ultrasound is used to evaluate the patency of the grafted area. Noninvasive—Pertaining to a diagnostic procedure or treatment that does not require the skin to be broken or a body cavity to be entered. Transducer—A device that converts electrical signals into ultrasound waves and ultrasound waves back into electrical impulses, also called a probe. Ultrasound—Sound waves at high frequencies beyond the level of human hearing; frequencies of approximately 2 to 10 megahertz are often used for diagnostic imaging.

Aftercare No special aftercare is necessary.

Results A Doppler ultrasonography test that shows no restricted blood flow or other abnormalities is a normal finding. Findings indicating restricted blood flow or other cardiovascular abnormalities are abnormal results. Disrupted or obstructed blood flow through the carotid artery or other neck arteries may indicate the person is at risk of having a stroke. Narrowed arterial flow or clots in

the legs may also be imaged. Abnormal findings are then used to plan further diagnostic tests and/or treatment.

Health care team roles Doppler ultrasonography is performed by an ultrasonographer with special training in ultrasound techniques, particularly cardiac and vascular imaging. The sonographer should be a registered vascular technologist or a registered cardiac sonographer. A radiologist, cardiologist, or other physician experienced in ultrasound imaging techniques interprets the ultrasound examination results. During some examinations, the sonographer may

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yellow in a blood vessel image indicate flow away from the probe, while blue and green indicate flow toward the probe. Color Doppler imaging can be used to identify areas of arterial narrowing. Another Doppler feature is power Doppler, which is more sensitive than color Doppler imaging and can produce images of structures not normally able to be depicted with ultrasound, for example, inflammation or signs of congenital heart disease in a fetus. Power Doppler mode may only be included on advanced ultrasound scanners.

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print out images and consult with the radiologist or cardiologist; alternatively the radiologist or cardiologist may perform some of the scanning. Resources BOOKS

Whittingham, T.A. “Diagnostic Ultrasound.” In Physics for Diagnostic Radiology. 2nd ed. Edited by P.P. Dendy, and B. Heaton. Philadelphia: Institute of Physics Publishing, 1999. pp.330-375. PERIODICALS

Kosoff, George. “Basic Physics and Imaging Characteristics of Ultrasound.” World Journal of Surgery 24 (February 2000):134-142. ORGANIZATIONS

American Institute of Ultrasound in Medicine. 14750 Sweitzer Lane, Suite 100, Laurel, MD 20707-5906. (301) 4984100. . American Registry of Diagnostic Medical Sonographers. 600 Jefferson Plaza, Suite 360, Rockville, MD 20852-1150. (800) 541-9754. . American Society of Radiologic Technologists (ASRT). 15000 Central Avenue SE, Albuquerque, NM 87123-2778. (800) 444-2778. . Society of Diagnostic Medical Sonography. 12770 Coit Road, Suite 708, Dallas, TX 75251-1319. (972) 239-7367. . Society of Vascular Technology. 4601 Presidents Drive, Suite 260, Lanham, MD 20706. (301) 459-7550. . OTHER

“New Endoscopic Doppler Device Combines Endoscopy and Doppler Ultrasound.” . “Vascular Ultrasound Imaging.” .

Jennifer E. Sisk, M.A.

Down syndrome

Chromosomes are the units of genetic information that exist within every cell of the body. Twenty-three distinctive pairs, or 46 total chromosomes, are located within the nucleus (central structure) of each cell. When the sperm cells from the father and egg cell from the mother are formed, they both undergo a reduction of their total number of chromosomes from 46 to 23. This process is called meiosis. When a baby is conceived by the combination of one sperm cell with one egg cell, the baby receives 23 chromosomes from each parent, for a total of 46 chromosomes. Occasionally, an error occurs in the reduction process. Instead of passing on 23 chromosomes to the baby, a parent will pass on 24 chromosomes. This event is called non-disjunction and occurs in 95% of Down syndrome cases. The baby, therefore, receives an extra chromosome at conception. In Down syndrome, this is an extra chromosome 21. The total number of chromosomes in individuals affected with Down syndrome is 47 instead of 46. In approximately 1-2% of Down syndrome cases, the original egg and sperm cells cells contain the correct number of chromosomes, 23 each. The problem occurs sometime shortly after fertilization; during the phase where cells are dividing rapidly. One cell divides abnormally, creating a line of cells with an extra copy of chromosome 21. This form of genetic disorder is called mosaicism. An individual with this type of Down syndrome has two types of cells: those with 46 chromosomes (the normal number), and those with 47 chromosomes (as occurs in Down syndrome). Individuals affected with this mosaic form of Down syndrome generally have less severe signs and symptoms of the disorder. Another relatively rare genetic accident that causes Down syndrome is called translocation. During cell division, chromosome 21 somehow breaks. The broken off piece of this chromosome then becomes attached to another chromosome. Each cell still has 46 chromosomes, but the extra piece of chromosome 21 results in the signs and symptoms of Down syndrome. Translocations occur in about 3 to 4% of cases of Down syndrome. Genetic profile

Definition Down syndrome is the most common chromosome disorder and genetic cause of mental retardation. It occurs because of the presence of an extra copy of chromosome 21. For this reason, it is also called trisomy 21. 780

Description

Down syndrome is usually the result of an extra copy of chromosome 21 (trisomy 21). As described earlier, Down syndrome may occur because of: nondisjunction within the sperm, or more commonly, the egg cell; genetic mosaicism, which occurs after conception; or translocation, which also occurs after conception.

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This chart shows the abnormality in chromosome 21 present in Down syndrome. (Account Phototake/NYC. Reproduced by permission.)

Once a couple has had one baby with Down syndrome, they are often concerned about the likelihood of future offspring also being born with the disorder. Women who are 34 and younger have a recurrence rate of 1% for having another Down syndrome child. Women who are 35 and older are at increased risk. The specific risk varies and increases as their age increases. When a baby with Down syndrome has the type that results from a translocation, it is possible that one of the two parents is a carrier of a balanced translocation. When one parent is a carrier of a balanced translocation, the chance of future offspring having Down syndrome is greatly increased. Specific risks must be assessed by a genetic counselor. Demographics The incidence of Down syndrome is about 1 in 800 live births. It affects an equal number of male and female

babies. The majority of cases of Down syndrome occur due to an extra chromosome 21 within the egg cell supplied by the mother (nondisjunction). As a woman’s age (maternal age) increases, the risk of having a Down syndrome baby significantly increases. By the time the woman is age 35, the risk increases to one in 400; by age 40 the risk increases to one in 110; and, by age 45 the risk becomes one in 35. There is no increased risk of either mosaicism or translocation with increased maternal age.

Causes and symptoms While Down syndrome is a chromosomal disorder, a baby is usually identified at birth through observation of a set of common physical characteristics. It is important to remember that not all children with Down syndrome will exhibit all of the features discussed. There is great variability in both the number and severity of character-

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istics. Babies with Down syndrome tend to be overly quiet, less responsive to stimuli, and have weak, floppy muscles. A number of physical signs may also be present. These include: a flat appearing face; brighter sparkles in the iris of the eye (Brushfield spots); a small head; a flat bridge of the nose; a smaller than normal, low-set nose; small mouth. This causes the tongue to stick out and to appear overly large. They have upward slanting eyes; extra folds of skin located at the inside corner of each eye, near the nose (epicanthal folds); rounded cheeks; and small, misshapen ears. They tend to have small, wide hands; an unusual deep crease across the center of the palm (simian crease); a curved little finger; a wide space between the great and the second toes; unusual creases on the soles of the feet; overly-flexible joints (sometimes referred to as being double-jointed); and, a shorter than normal length. Other types of problems often accompany Down syndrome. Approximately 30 to 50% of all children with Down syndrome are found to have heart defects. Malformations of the gastrointestinal tract are present in about 5 to 7% of children with Down syndrome. The most common malformation is a narrowed, obstructed duodenum (the part of the intestine into which the stomach empties). This disorder, called duodenal atresia, interferes with the baby’s milk or formula leaving the stomach and entering the intestine for digestion. The baby often vomits forcibly after feeding, and cannot gain weight appropriately until the defect is repaired. Another relatively common problem is a tracheo-esophageal fistula. This is an abnormal connection between the trachea (windpipe) and esophagus that interferes with both eating and breathing. Other medical conditions occurring in persons with Down syndrome include an increased chance of developing infections, especially ear infections and pneumonia; certain kidney disorders; thyroid disease (especially low or hypothyroidism); hearing loss; vision impairment requiring glasses (corrective lenses); and a 20 times greater chance than the population as a whole of developing leukemia. Development in a baby and child affected with Down syndrome occurs at a much slower than normal rate. Because of weak, floppy muscles (hypotonia), babies learn to sit up, crawl, and walk much later than their unaffected peers. Talking is also quite delayed. The level of mental retardation is considered to be mild-tomoderate in people with Down syndrome. The degree of mental retardation varies greatly among children with Down syndrome. While it is impossible to predict the severity of Down syndrome at birth, with proper education, children who have Down syndrome are capable of 782

learning. Most children with Down syndrome can read and write and are placed in special education classes at school. The majority of individuals with Down syndrome become semi-independent, meaning that they can take care of their own needs with some assistance. Many hold non-complex jobs. As people with Down syndrome age, they face an increased chance of developing the brain disease called Alzheimer’s (sometimes referred to as dementia or senility). People without Down syndrome have a lifetime risk of 12% for developing Alzheimer’s disease. In contrast, by age 40-50, almost all persons with Down syndrome will also develop Alzheimer’s disease. As people with Down syndrome age, they also have an increased chance of developing a number of other illnesses, including cataracts, thyroid problems, diabetes, and seizure disorders.

Diagnosis Diagnosis is usually suspected at birth, when the characteristic physical signs of Down syndrome are noted. Once this suspicion has been raised, genetic testing (chromosome analysis) can be undertaken in order to verify the presence of the disorder. This testing is usually done on a blood sample, although chromosome analysis can also be performed on other types of tissue, including the skin. The cells to be studied are prepared in a laboratory. Chemical stain is added to make the characteristics of the cells and the chromosomes stand out. Chemicals are added to prompt the cells to go through normal development, up to the point where the chromosomes are most visible, prior to cell division. At this point, they are examined under a microscope and photographed. The photograph is used to sort the different sizes and shapes of chromosomes into pairs. In most cases of Down syndrome, one extra chromosome 21 will be revealed. The final result of such testing, with the photographed chromosomes paired and organized by shape and size, is called the individual’s karyotype. A female with Down syndrome will have a 47, XX+21 karyotype; a male with Down syndrome will have a 47 XY+21 karyotype. Women who are over the age of 35 are offered prenatal tests to determine if their developing baby is affected with Down syndrome. A genetic counselor meets with these families to inform them of the risks and to discuss the tests that are available to make a diagnosis prior to delivery. Because there is a slight risk of miscarriage following some prenatal tests, all testing is optional. Couples must decide whether or not they desire to take this risk to learn the status of their unborn baby. Couples must also decide if they wish to know whether or not the

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Ultrasound is now available for prenatal screening. Some abnormalities associated with Down syndrome, including intrauterine growth retardation, may be detected using ultrasound. The use of ultrasound as a screening test for Down syndrome is limited by the difficulty of producing reliable sonographic images of critical fetal structures. A counselor needs to inform a woman that her risk of having a baby with Down syndrome increases with her increasing age. Two types of testing are available during a pregnancy to determine if the baby being carried has Down syndrome. Screening tests are used to estimate the chance that an individual woman will have a baby with Down syndrome. All pregnant women under the age of 35 are offered a maternal serum alpha-fetoprotein (MSAFP) screen. This test is normally performed at 15-22 weeks of pregnancy. The MSAFP screen measures a protein and two hormones normally found in maternal blood during pregnancy. A specific pattern of these hormones and protein can give a pregnant woman an increased risk for having a baby born with Down syndrome. Carrying a baby with Down syndrome often causes MSAFP to be lower than normal. Test results reveal only an increased risk and cannot diagnose a baby born with Down syndrome. The MSAFP test can detect up to 60% of all babies who will be born with Down syndrome. Women with an increased risk are offered amniocentesis. The only way to definitively (with about 99% accuracy) establish the presence or absence of Down syndrome in a developing baby is to test tissue from the pregnancy itself. This is usually done either by amniocentesis or chorionic villus sampling (CVS). In chorionic villus sampling, usually performed at 10-12 weeks of pregnancy, a tiny tube is inserted into the opening of the uterus to retrieve a small sample of the placenta (the organ which attaches the growing baby to the mother via the umbilical cord, and provides oxygen and nutrition). In amniocentesis, a small amount of the fluid in which the baby is floating is withdrawn with a long, thin needle. Both amniocentesis and CVS allow the baby’s own karyotype to be determined. Both tests carry a small risk of causing miscarriage. The risk from CVS is 1% and the risk from amniocentesis is 0.5%. This small risk must be considered when deciding to perform these tests. If test information is positive for Down syndrome, a couple must then decide how to use this information to begin to prepare for the arrival of a baby with Down syndrome, to

consider adoption for the baby or to terminate the pregnancy. It must be noted that while the results of prenatal tests can diagnose Down syndrome, they are unable to predict the severity of symptoms.

Treatment No treatment is available to cure Down syndrome. Treatment is directed at addressing the individual concerns of a particular person. For example, heart defects will many times require surgical repair, as will duodenal atresia or a tracheo-esophageal fistula. Many persons with Down syndrome will need to wear glasses to correct vision. Persons with hearing impairment benefit from hearing aids. While some decades ago, all Down syndrome children were quickly placed into institutions for lifelong care, research shows very clearly that the best outlook for children with Down syndrome is a normal family life in their own homes. This requires careful support and education of both parents and siblings. It is a life-changing event to learn that a new baby has a permanent condition that will affect essentially all aspects of development. Some community groups exist to help families deal with the emotional effects of this new information, and to help plan for the baby’s future. Schools are required to provide services for children with Down syndrome, sometimes in separate special education classrooms, and sometimes in regular classrooms (this is called mainstreaming or inclusion). As of 2001, the genetic sequence for chromosome 21 was fully determined, which may open the door to new approaches to the treatment of Down syndrome through the development of gene-specific therapies.

Prognosis The prognosis in Down syndrome is quite variable, depending on the types of complications (heart defects, susceptibility to infections, development of leukemia) of each individual baby. The severity of the retardation can also significantly vary. Without the presence of heart defects, about 90% of children with Down syndrome live into their teens. People with Down syndrome appear to go through the normal physical changes of aging more rapidly, however. The average age of death for an individual with Down syndrome is about 50 to 55 years. The prognosis for a baby born with Down syndrome continues to improve. Due to modern medical treatments, including antibiotics to treat infections, and surgery to correct heart defects, duodenal atresia and tracheoesophageal fistula, life expectancy has greatly increased. Community and family support allows people with

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baby the mother carries has Down syndrome. Some couples choose not to have the test because they are certain they would not choose an abortion if they find theirs is a Down syndrome baby.

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KEY TERMS Cell—A fundamental unit of living tissue. The specialized nature of organs and tissues in a human body reflects the specialized structure and function of its constituent cells. Chromosome—The structures that carry genetic information. Chromosomes are located within every cell and are responsible for directing the development and functioning of all the cells in the body. The normal number is 46 (23 pairs). Genetic counseling—A communication process by which personal genetic risk information is translated into practical information for families. Genetic counselors are health care professionals with specialized training and experience in the areas of medical genetics and counseling. Karyotype—The specific chromosomal makeup of a particular cell. Mental retardation—A condition where an individual has a significantly lower-than-normal IQ, and thus is developmentally delayed. Mosaic—A term referring to a genetic situation in which all of an individual’s cells do not have the same composition of chromosomes. In Down syndrome, this may mean that some of an individual’s cells have a normal 46 chromosomes, while other cells have 47 chromosomes. Nondisjunction—A genetic term referring to an event that takes place during cell division in which a genetic accident causes an egg or sperm cell to have 24 chromosomes, rather than the normal 23. Translocation—A genetic term referring to a situation during cell division in which a piece of one chromosome breaks off and sticks to another chromosome. Trisomy—The condition of having three identical chromosomes, instead of the normal two.

Down syndrome to have rich, meaningful relationships. Because of educational programs, some people with Down syndrome are able to hold jobs. Most men with Down syndrome appear to be sterile (meaning that they are unable to have offspring). There has been at least one report of a male with Down syndrome who fathered a child. Some women with Down syndrome, however, are capable of having babies. 784

Approximately 40% of women with Down syndrome are unable to become pregnant. The risk of a woman with trisomy 21 to have a child with Down syndrome is approximately 50%.

Health care team roles Obstetricians, nurse practitioners, or family doctors often make an initial recommendation that a woman be screened for Down syndrome. Depending on the test, a physician, phlebotomist or ultrasonographer may obtain sample materials. A laboratory technician will process sample materials. A genetic counselor, physician or other person with specialized training usually provides test results to a couple or woman. Counselors must be available to assist a woman or couple to make appropriate decisions about their baby. Pediatricians, family doctors, internists, and geriatric physicians provide care throughout the life of an individual with Down syndrome. Other health professionals, including surgeons, eye specialists and hearing experts, provide services as needed.

Prevention As of 2001, there is no known way to prevent Down syndrome. Resources BOOKS

Girod, Christina M. Down Syndrome. Farmington Hills, MI: Lucent Books, 2001. Jones, Kenneth L. “Down syndrome.” In Smith’s Recognizable Patterns of Human Malformation, 5th ed. Richard E. Behrman et al., Philadelphia: Saunders, 1997, 8-14. Miller, Jon F, Mark Leddy and Lewis A. Leavitt. Improving the Communication of People With Down Syndrome. Baltimore, MD: Paul H Brookes Publishers, 1999. Pueschel, Sigfried M. A Parent’s Guide to Down Syndrome: Toward a Brighter Future, 2nd ed. Baltimore, MD: Paul H Brookes Publishers, 2000. Van Allen, Margot and Judith C. Hill. “Congenital anomalies.” In Cecil Textbook of Medicine, 21st ed. Goldman, Lee and Bennett, J. Claude. Philadelphia: W.B. Saunders, 2000, 150-153. Weeks, Daniel J. Perceptual-Motor Behavior in Down Syndrome. Champaign, IL: Human Kinetics Publishing, 2000. PERIODICALS

Kaiser, A. P., P. P. Hester, and A. S. McDuffie. “Supporting communication in young children with developmental disabilities.” Mental Retardation and Developmental Disability Research Review 7, no. 2 (2001): 143-150. Maymon, R., E. Dreazen, I. Buckovsky, Z. Weinraub, and A. Herman. “Does a ‘notched’ nuchal translucency indicate

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Resources for Children with Special Needs. .

L. Fleming Fallon, Jr., MD, DrPH

Dressings see Bandages and dressings Drowning see Near-drowning Drug abuse see Substance abuse and dependence Drug addiction see Substance abuse and dependence Drug dependence see Substance abuse and dependence

ORGANIZATIONS

American Academy of Neurology, 1080 Montreal Avenue, St. Paul, Minnesota 55116. (651) 695-1940. Fax: (651) 6952791. . [email protected]. American Academy of Pediatrics, 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. (847) 434-4000. Fax: (847) 434-8000. . [email protected]. American Association on Mental Retardation, 444 North Capitol Street, NW, Suite 846, Washington, D.C. 200011512. (202) 387-1968 or (800) 424-3688. Fax: (202) 387-2193. . American Speech-Language Hearing Association, 10801 Rockville Pike, Rockville, MD 20852. (800) 638-8255. . [email protected]. Association of Retarded Citizens of the United States, PO Box 6109, 2501 Avenue J, Arlington, TX 76011. National Association for Down Syndrome, PO Box 4542, Oak Brook, IL 60522. (630) 325-9112. . National Down Syndrome Congress, 7000 PeachtreeDunwoody Road, NE, Lake Ridge 400 Office Park, Building #5, Suite 100, Atlanta, GA 30328-1655. (800) 232-6372 or (770) 604-9500. . [email protected]. National Down Syndrome Society, 666 Broadway, New York, NY 10012. (212) 460-9330 or (800) 221-4602. Fax: (212) 979-2873. . OTHER

Administration on Developmental Disabilities (Dept of Health and Human Services). . Arc. . Children With Disabilities. . Disability Solutions. . National Council on Disability. .

Drug dosages Definition Drug dosage refers to the determination and regulation of the amount, frequency, and number of times a specific quantity of medication is to be administered. For legal purposes in the United States, a drug is considered to be any substance (other than a food or a device) intended for use in diagnosis, cure, relief, treatment, or prevention of disease, or to affect the structure or function of the body. However, a simple, working definition of a drug is any chemical that affects the processes of the mind or body, and the dose is the amount to be administered at one time.

Purpose The selection of a drug for use in an individual requires two primary considerations: pharmacodynamics (what the drug does to the body) and pharmacokinetics (what the body does to the drug over time). Pharmacodynamics not only involves considering what the drug does as in lowering blood pressure, relieving pain, or fighting an infection, but where (the site) and how (mechanism of action) the drug acts on the body. Often, what the drug does is immediately obvious, but the exact site and mechanism of action may not be understood until after many years of use. For a drug to work, it has to get to the place in the body where it is needed, and this requires the science of pharmacokinetics. Sufficient amounts of a drug must stay at the site of its required action until the job is completed, but not so much that severe side effects or toxic reac-

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Down syndrome fetuses or other adverse pregnancy outcome?” Prenatal Diagnosis 21, no. 5 (2001): 403-408. Palisano R. J., S. D. Walter, D. J. Russell, P. L. Rosenbaum, M. Gemus, B. E. Galuppi, and L. Cunningham. “Gross motor function of children with down syndrome: creation of motor growth curves.” Archives of Physical Medicine and Rehabilitation 82, no. 4 (2001): 494-500. Savulescu, J. “Resources, Down’s syndrome, and cardiac surgery.” British Medical Journal 322, no. 7291 (2001): 875-876. Van Riper, M., and W. I. Cohen. “Caring for children with Down syndrome and their families.” Journal of Pediatric Health Care 15, no. 3 (2001): 123-131. Varela, A. M., L. B. Sardinha, and K. H. Pitetti. “Effects of an aerobic rowing training regimen in young adults with Down syndrome.” American Journal of Mental Retardation 106, no. 2 (2001): 135-144.

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process, they cannot re-establish a system that is injured beyond repair.

KEY TERMS Conjugations—The joining of a chemical substance with another to form a new product. Hydrolysis—The breaking up of a chemical compound by the addition of water. Lipids—A group of substances composed of fatty, greasy, oily, and waxy compounds that are insoluble in water and soluble in nonpolar solvents or most organic solvents. Metabolism—The sum of the physical and chemical processes by which living organized substance is built up and maintained and by which large molecules are broken down into smaller molecules to make energy available to the organism. Oxidation—The chemical reaction whereby electrons are removed from the atoms of a substance for transferal. Perfused—The act of the passage of a fluid through the vessels of a specific organ or tissue. Phospholipids—Any lipid or fatty substance that contains phosphorus; the major lipids in cell membranes. Reduction—The gaining of electrons during a chemical reaction. Semi-permeable—Permitting passage only of certain molecules. Therapeutic window—A drug’s ability to maintain a specific level of action over a specific period of time.

tions are produced. Many drugs get to their site of action through the bloodstream. Therefore, how much time they need to work and how long their effects will last can depend on how fast they get into the bloodstream, how much gets into the bloodstream, how fast they leave the bloodstream, how easily and efficiently they are broken down (metabolized) by the liver, and how soon they are eliminated by the kidneys and intestines. Drugs affect only the speed of biologic functions and do not change the basic character of existing processes nor generate new functions. This means that drugs can either speed up or slow down biochemical reactions in the body, as in how fast or slow a nerve may transmit a message, or how fast or slow a muscle may contract. Although drugs can change the rate of a biological 786

Every person responds to a drug differently. Thus, it is difficult to determine what dosage of a drug should be administered to each individual. Since drugs undergo testing in animals and trials in humans, an average dose is determined from these studies. An appropriate response to a drug requires the appropriate concentration of the drug at the site of action. The appropriate concentration and dosage regimen depend on individuals’ clinical state, the severity of their disorder, the presence of a diseased state, the use of other drugs, as well as other considerations. Drug administration must be determined by each individual’s needs, which requires an accurate evaluation of drug dosage.

Precautions All drugs can harm as well as help, so the safety and effectiveness (efficacy) of a drug are relative. Since most drugs cannot maintain a specific level of action for a certain period of time (therapeutic window), their effect can sometimes be either too strong or too weak, depending on the individual’s condition who is receiving the drug. Unwanted drug effects are called side effects or adverse reactions. A drug may affect several functions even though it is prescribed for only one. As an example, most antihistamines are targeted for the function of relieving allergy symptoms, yet one of the many side effects is sleepiness. In turn, this side effect is utilized to target the function of an inability to sleep when offered as a sleep aid. The best drugs are both safe and effective. However, some drugs may be used despite having a very narrow margin of safety because there might be no safer alternative. Although it is impossible to know everything about every drug, understanding the general principles of drug action is an essential precaution in drug administration.

Description Utilization of drug treatment for any condition requires the drug to be capable of getting into the body’s system (administration), moving into the bloodstream (absorption), and traveling to the specific site where it is needed (distribution). Following the administration, absorption, and distribution, the drug leaves the body (elimination) either in the urine or by conversion to another substance. Administration of drugs can occur by many different means. Drugs be taken by mouth (oral/p.o.); by injection into a vein (intravenous/IV); by injection into a muscle (intramuscular/IM); beneath the skin (subcutaneous/SQ);

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Absorption is the process of drug movement from the administration site to the general (systemic) circulation. Although oral administration is the most convenient, the safest, the least expensive, and the most common route, it has its restrictions. The presence of other drugs and food in the stomach affect how drugs are absorbed. Some drugs must be taken on an empty stomach, while others should be taken with food. For distribution into the general circulation, a drug taken orally is absorbed from the gastrointestinal tract by passing through the intestinal wall and then to the liver. Whereas a drug given IV immediately passes into the general circulation to produce a quicker and more consistent effect, a drug given by most other routes must travel across several semi-permeable cell membranes before reaching the systemic circulation. These membranes are biologic barriers that selectively prevent the passage of drug molecules and are composed of mostly cholesterol and phospholipids. These lipids provide stability to the membrane and determine its permeability characteristics. Drugs cross a biologic barrier by passive diffusion (moving from an area of high concentration to one of low concentration), facilitated passive diffusion (a carrier component combines with the drug to cause rapid diffusion across the membrane), active transport (the cell expends energy to move a drug), or pinocytosis (the cells ingest extracellular fluid and its contents). Bioavailability refers to the rate and extent to which a drug is absorbed into the bloodstream and thereby gains access to the site of action. The properties of the actual dosage form of a drug, either tablet, capsule, suppository, transdermal patch, or solution, largely determine drug bioavailability. Drug products may be chemically equivalent, containing the same compound in the same amount, but have dissimilar effects even at the same dose, due to different inactive ingredients, which affect absorption. When drug products contain the same active ingredients and also produce virtually the same blood levels over time, they are termed bioequivalent. If drug products given to the same person in the same dosage regimen produce the same therapeutic effect, they are therapeutically equivalent. Bioequivalent products are expected to be therapeutically equivalent. A drug product is the actual dosage form of a drug. Drug products contain other substances (additives) that are adjusted to affect the rate and extent of the drug’s

absorption. Some drug products are designed to release the active ingredient slowly over a long period of time and are called controlled-release dosage forms. This occurs by coating the drug product with a polymer (a chemical substance) of varying thickness that dissolves layer by layer at different times in the gastrointestinal tract. Other additives such as enteric coatings prevent the drug from irritating the stomach lining. Drugs filled with liquids are usually absorbed faster than those filled with solids. Although a drug rapidly circulates through the body in the bloodstream, this does not mean that it immediately moves into the tissues. Drugs are distributed to different tissues at different rates, depending on their ability to cross membranes, the rate of blood flow to a particular tissue, and the tissue mass. Most drugs do not spread evenly throughout the body; some tend to stay in the plasma (watery tissue of the blood) and muscle, others concentrate in specific areas such as the kidneys, liver, and thyroid. A balance between entry and exit rates (distribution equilibrium) is reached more rapidly in highly vascularized areas than in areas that are poorly perfused. There are drugs that bind tightly to blood proteins and leave the bloodstream very slowly, and others that exit quickly to the tissues. Some tissues build up high levels of a drug and serve as reservoirs of extra drug, which prolongs their distribution. Those drugs that accumulate in fatty tissues exit slowly and will continue to circulate in the bloodstream for days following the last administration. It is possible for drugs to reach the central nervous system (CNS) through the brain capillaries and the cerebral spinal fluid (CSF). However, despite the fact that the brain receives approximately one-sixth of the blood circulation, distribution of drugs to brain tissues is restricted. Fat-soluble drugs can enter the brain and exert their effects rapidly, but the water-soluble drugs enter the brain slowly. The CNS is well perfused so the major factor of drug distribution rate in it is permeability, whereas for most tissues, perfusion is the major determinant of distribution. The liver is the principal site of drug metabolism, and some of the metabolites are active forms of the drug administered. An inactive substance that produces an active metabolite, once it is absorbed, is called a prodrug. All drugs are either metabolized or excreted intact. Enzymes in the liver assist with chemical reactions (oxidation, reduction, hydrolysis), and some enzymes attach substances to the drugs, producing reactions called conjugations, which enable a drug to be excreted in the urine. Excretion refers to the processes by which the body eliminates a drug without further chemical change, and

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placed under the tongue (sublingual); inserted in the rectum (rectal); instilled in the eye (ocular); sprayed into the nose (nasal); sprayed into the mouth (inhalation); applied directly to the skin for a local effect (topical); or applied to the skin for a systemic effect by a patch (transdermal).

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the major organ of excretion is the kidney. The kidneys filter drugs from the bloodstream and excrete them into the urine. Thus, the major limiting factor of excretion is kidney function, and decreasing kidney function is seen in the elderly, or people with high blood pressure, diabetes, and recurring kidney infections. A laboratory determination of kidney function permits the dosage of a drug to be altered as necessary. The liver does excrete some drugs through bile. These particular drugs enter the gastrointestinal tract and end up in the feces if they are not reabsorbed into the bloodstream or decomposed. Individuals with liver disease may need to have the drug dosage adjusted accordingly, although there is no corresponding liver function test comparable to that for kidney function. Likewise, some drugs can be excreted in breast milk, saliva, sweat, or exhaled air. Once in the body, drugs can affect it in many ways. Interactions with other cells, tissues, or organs may result in side effects or adverse drug reactions. Many drugs bind or attach to cells by means of receptors on the cell surface. Receptors have a specific structure, which permits only those substances that fit it precisely to attach to it. The majority of cells have these surface receptors with which drugs can selectively bind to change the activity of the cell. These receptors possess a natural, physiologic purpose, and drugs take advantage of them. A class of drugs called agonists activates or stimulates the receptors to trigger a response that either increases or decreases the cell’s function. Another class of drugs called antagonists blocks the access of agonists to the receptors. Antagonists are used primarily to block or diminish cell responses to agonists normally present in the body, and this is usually in reference to neurotransmitters. Other targets of drug action are enzymes, protein substances needed in the body to assist with the control of chemical reactions during metabolism. Drugs that target enzymes are classified as inhibitors or inducers (activators). Affinity and intrinsic activity are two other drug properties that must be considered in dosage. Affinity refers to the attraction or strength of the bond between a drug and its target, regardless of whether it is a receptor or an enzyme. Intrinsic activity refers to the ability of the drug to produce its desired effect after it is bound to its target. Agonists drugs have both properties because they must bind effectively and produce a response. Antagonists drugs, however, only have an affinity for a target site since their purpose is to block agonists. Other properties that are important in determining drug dosage include potency, efficacy, tolerance, and 788

resistance. Potency refers to the amount of drug needed to produce a certain effect; it is usually expressed in milligrams (mg). Greater potency does not necessarily mean that one drug is better than another because side effects, toxicity, duration of effectiveness, and cost must also be considered. Efficacy refers to the maximum therapeutic response that a drug can produce and, once again, this is only one factor in the consideration of which drug to use at what dosage. Tolerance to a drug can occur when the body adapts to the continued presence of the drug. It is also possible for tolerance to occur if the number of receptors decreases or their affinity for the drug decreases. The term resistance is generally used to refer to a situation in which an individual no longer responds well to a drug. In these cases, the drug dosage may be increased or an alternative drug may be utilized.

Preparation Before administering a new drug or a medication that is prescribed on an as-needed basis, a patient must be assessed in terms of factors that may be pertinent. An initial prediction of increased risk for adverse drug effects can be made by the patient assessment. It is essential to double check the medication ordered, the dosage to be given, the times the drug is to be administered, how it is to be administered, the expiration date on the drug, and that the correct patient receives the correct drug. Many IV medications are now being mixed in the pharmacy to prevent errors in calculations for a patient. It is important that the health care provider discusses with the patient what the medication is, why it is being given, and reviews some potential side effects.

Aftercare A patient should be continually assessed during the administration of a medication for signs and symptoms of any untoward reaction, as well as to determine if the medication has had the desired effect.

Complications Adverse reactions are one of the main complications of drug administration. Some patients may experience an allergic reaction to a medication that could range from mild to severe. They may experience itching, exhibit a rash, have localized swelling, difficulty breathing, or suffer a complete vascular collapse. Other complications could include a resistance to the drug with a subsequent progression of the initial condition. If the patient’s status does not seem to be improving, this should be reported to the physician or nurse practitioner. Severe side effects

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Results Results expected with drug administration will vary according to why the drug was given. In all cases, it is essential to determine what end result is expected from the administration of a drug.

Health care team roles The health care team shares responsibility for providing optimal intervention in the administration of drugs. Since nurses spend more time with patients and are more likely to focus on the patient as an individual, this places them in an optimal position to assess a patient’s response to a drug. Any pertinent changes should be immediately reported to the physician or nurse practitioner. The nurse must also ensure that the patient is well informed about the drug being administered. Resources BOOKS

Hovsepian, Movses. Modell’s Current Use and New Drugs. New York: Springer Publishing Co., Inc., 2001. Liska, Ken. Drugs and the Human Body: With Implications for Society. New York: Prentice Hall, 2000. Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals. Merck & Company, Inc., 2001. ORGANIZATIONS

American Pharmaceutical Association. 2215 Constitution Avenue, N.W., Washington, DC 20037-2985. (202) 6284410. . OTHER

Annual Reviews: Pharmacology & Toxicology. . DrKoop.com, Inc. .

Linda K. Bennington, C.N.S.

Drug interactions Definition Drug interactions are changes in the effect of one drug due to the effect of either another drug taken at the same time (drug-drug interactions) or food consumed while the drug is being taken (drug-food interactions).

Description Some drugs are deliberately combined for administration because there are beneficial effects to be derived. Generally, drug interactions are unwanted and harmful. They may either serve to intensify or diminish the desired effect of a particular drug, or worsen its side effects. Although most drug-drug interactions involve prescription drugs, they can occur with nonprescription or overthe-counter (OTC) medications—the most common of these being aspirin, antacids, and decongestants. Individuals under the care of more than one health care practitioner are at highest risk for drug interactions because each practitioner may not be aware of drugs being prescribed by the other. The patient needs to make each practitioner fully aware of all medications being taken. This includes prescription and nonprescription medications, and herbal remedies. A practitioner may not think to ask a patient about OCT medications or herbal supplements, and the patient may not think to inform their practitioner they are taking these substances because they do not think of OTCs or herbals as medications. The more drugs being consumed, the greater the risk of developing a drug interaction. This risk also increases with the amount of drug taken and the tendency of particular drugs to interact adversely with each other. The incidence of adverse drug reactions increases with the age of the patient; the risk is three times greater for older people than for younger adults. When the effect of one drug in the body is altered by the presence of another, one drug may increase or decrease the effects of the other with harmful results. Two drugs taken together may produce a new and dangerous reaction, or they may be in opposition to each other in their actions. Two similar drugs taken together may produce an effect that is greater than would be expected from one drug. This effect is called potentiation. One drug may also affect the rate at which the kidneys excrete another drug by altering the acidity of the urine. This, in turn, affects the excretion of other drugs. Vitamin C in large doses can do this. Although not considered a drug by some, alcohol is a drug that does affect bodily processes and is often responsible for drug interactions. OCT drugs can interact with each other as well as with prescription drugs. For example, many cough medicines contain alcohol which, if taken with antihistamine medications, could increase sleepiness and decrease alertness. Examples of drug interactions include: • salt substitutes interacting with potassium-sparing diuretics (agents that promote urine secretion) to increase blood potassium levels and cause nausea,

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could be detrimental to the patient, necessitating laboratory tests to monitor the patient’s condition.

Drug interactions

Interactions between drugs and commonly used modalities Modality

Use

Drugs with complementary/synergistic effects

Drugs with antagonistic effects

Cryotherapy: cold/ice packs, ice massage, cold baths, vapocoolant sprays

Decreased pain, edema, and inflamation

Anti-inflammatory steroids (glucocorticoids); nonsteroidal anti-inflamatory analgesics (aspirin and similar NSAIDs) Skeletal muscle relaxants

Peripheal vasodilators may exacerbate acute local edema.

Muscle relaxation and decreased spacticity

Nonselective cholinergic agonists may stimulate the neuromuscular junction.

Superficial and deep heat (local application): hot packs, parafin, infrared, fluidotherapy, diathermy, ultrasound

Decreased muscle/ joint pain and stiffness Decreased muscle spasms

NSAIDs; opioid analgesics; local anesthetics

—

Skeletal muscle relaxants

Increased blood flow to improve tissue healing

Peripheral vasodilators

Nonselective cholinergic agonists may stimulate the neuromuscular junction. Systemic vasocontrictors (e.g., α-1 agonists) may decrease perfusion of peripheral tissues.

Systemic heat: large whirlpool, Hubbard tank

Decreased muscle/ joint stiffness in large areas of the body

Opioid and nonpioid analgesics; skeletal muscle relaxants

Nonselective cholinergic agonists may stimulate the neuromuscular junction.

Ultraviolet radiation

Increased wound healing Management of skin disorders (acne, rashes)

Various systemic and topical antibiotics Systemic and topical antibiotics and anti– inflammatory steroids (glucocortroids)

— Many drugs may cause hypersensitivity reactions that result in skin rashes, itching.

Transcutaneous electrical nerve stimulation (TENS)

Decreased pain

Opioid and nonopioid analgesics

Opioid antagonists (naloxone)

Functional neuromuscular electrical stimulation

Increased skeletal muscle strength and endurance Decreased spasticity and muscle spasms

—

Skeletal muscle relaxants.

Skeletal muscle relaxants

Nonselective cholinergic agonists may stimulate the neuromuscular junction.

SOURCE:

Ciccone, C.D. Pharmacology in Rehabilitation. 2nd ed. Philadelphia: F.A. Davis Co., 1996.

vomiting, diarrhea, muscle weakness, and possibly cardiac arrest • decongestants interacting with diuretics to increase blood pressure • antacids interacting with anticoagulants (blood thinning drugs) to slow down absorption of the prescribed drug or interacting with absorption of other drugs— such as the antibiotic tetracycline—and thus prolonging an infection • aspirin increasing the effect of blood thinning drugs • antihistamines increasing the sedative effects of barbiturates (sleeping pills), tranquilizers, and some pain relievers • iron supplements binding with antibiotics in the stomach, preventing absorption of the antibiotic into the bloodstream • antihypertensive medications mixed with digitalis (Lanoxin) resulting in abnormal heart rhythms • anticoagulants mixed with sleeping pills resulting in decreased effectiveness of the anticoagulant • antibiotics taken by women on the low-dose birth control pill causing decreased effectiveness of the pill 790

• nonsteroidal antiinflammatory drugs (NSAIDs) causing the body to retain salt and fluid that can oppose or antagonize the effectiveness of a diuretic • beta-blockers, such as propanolol, counteracting certain drugs taken for asthma Certain drug-food combinations can produce dangerous side effects as well. Food can speed up or slow down the action of a medication, and some drugs may prevent the absorption of vitamins and minerals from food. Drugs may also alter the way the body uses nutrients, as well as altering the taste sensation. Chemicals in cigarette smoke can increase the enzyme activity of some liver enzymes, which, in turn, reduces the effectiveness of some pain relievers and some drugs used for lung conditions. The antibiotic tetracycline is not absorbed appropriately if it is taken within an hour of drinking milk or eating other dairy products or foods containing calcium. To help avoid drug interactions, patients should inform their health care practitioners of any medical problems they have or have had, maintain a list of drugs—both prescription and nonprescription—taken during the few weeks prior to their visit to their practitioner, and give the list to their practitioner. They should also advise their practitioner of any allergies or unusual reactions to drugs, food, or other substances, and make

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KEY TERMS Potentiation—Making effective or active, or more effective or active; synergistically augmenting the activity of one drug with another.

note of any special dietary or food restrictions. A woman should always inform her practitioner if she is pregnant, plans to become pregnant in the near future, and if breastfeeding.

Dr Koop.com. . Pharmacy and Toxicology Annual Reviews. .

Linda K. Bennington, C.N.S.

Drug monitoring see Therapeutic drug monitoring Drug overdose see Overdose

Viewpoints Although drug interactions can create serious health risks, they can be avoided with appropriate education (of the patient) and history-taking (by the health care practitioner). The health care practitioner needs to take the time to ask pertinent questions about an individual’s history, including diet, nutritional intake, and medication regimen which should include nonprescription drugs and herbal remedies. Although it is often difficult for the practitioner to spend an appropriate amount of time with patients in this era of health care management, it could ultimately save time and money and prevent serious consequences to the health of the patient. Healthcare providers need to stay informed and up-to-date regarding drug-drug and drug-food interactions.

Drug testing Definition Drug testing is the assessing of drug use (or non-use) by a person. The drugs for which one tests fall into three main types: illegal drugs, alcohol, and performanceenhancing drugs. Illegal drugs include marijuana, cocaine, amphetamines, and phencyclidine (PCP, the hallucinogen known as “angel dust”). Alcohol is, of course, a legal drug for adults, but since such activities as driving under its influence are illegal, it is sometimes very important to test for the level of alcohol in the bloodstream. Performance-enhancing drugs may be legal, but their use by athletes may be forbidden by the rules of an athletic association sponsoring a competition, rules designed to be fair to all the players.

Professional implications Healthcare professionals are capable of exerting a measurable impact on the lives of individuals who are taking drugs for either medical or nonmedical reasons. Education is the foundation for patient care with regards to potential drug interactions. It is the responsibility of the care provider to take the time to inform patients of potential interactions with drugs and food, as well as to take a complete patient history. A patient’s family should be included in the educational process so they may recognizing possible interactions by changes in behavioral patterns or demeanor. Resources BOOKS

Hovsepian, Movses. Modell’s Current Use and New Drugs. New York: Springer Pub. Co., Inc., 2001. Liska, Ken. Drugs and the Human Body: With Implications for Society. New York: Prentice Hall, 2000. Merck Index: An Encyclopedia of Chemicals, Drugs and Biologicals. Merck & Company, Inc., 2001.

Description One line of attack in the “war against drugs” in the United States involves compulsory drug testing. Specific drug-test laws vary from state to state, but drug tests are commonly administered in schools, athletic competitions, and the workplace. When results of some tests are being evaluated, it is important to keep in mind the fact that sometimes legitimate prescription drugs for such conditions as arthritis and asthma can produce test results that falsely suggest illegal drug use. Some schools test students in general for drug use; others focus on student athletes because drug use increases the risk of sports-related injury, and also because the use of performance-enhancing drugs would give the athletes who use them an unfair advantage over the other athletes. The United States Supreme Court ruled in 1995 that schools may test entire teams of student athletes, even if individual team members are not suspected of using drugs. On the state level, courts are divided on the circumstances under which such testing can legally

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OTHER

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as for an airplane pilot, a truck driver, or a person producing atomic weapons. Much workplace testing is conducted under such circumstances as the following: • Pre-employment. Employers offer employment on condition of a negative drug test. • Reasonable suspicion. Employers test an employee after direct observation of drug use or possession, patterns of erratic behavior, or drug-related arrests. • Post-accident. Employees involved in accidents are sometimes asked to take a drug test immediately after an incident to determine whether alcohol or drug use was a factor. • Treatment follow-up. Employees returning to work after treatment for substance abuse are often subject to follow-up testing.

A technician performs laboratory urine drug testing. (Photograph by Edward L. Lallo. The Picture Cube. Reproduced by permission.)

occur. Some states provide more protection than others for the rights of students to privacy and due process. In the 1970s, the issue of performance-enhancing drug use among athletes came into the forefront. Many athletes use performance-enhancing drugs (ergogenic drugs) such as anabolic steroids, growth hormone, and erythropoietin. Some athletes also use stimulants because of their ability to mask fatigue. Athletes are tested for use of forbidden drugs at many major meets.

Urine is the most common sample used in drug testing. Urine tests for federal employees are first analyzed by laboratories certified by the Substance Abuse and Mental Health Services Administration (SAMHSA), and any samples that come up positive are double-checked by gas chromatograph mass spectrometry, the “gold standard” test that identifies the exact molecular structure of a substance. Some private employers also follow SAMHSA procedures and use federal laboratories for testing, but others use commercial drug-testing kits. These commercial kits have often been criticized for generating a high rate of false positives. The problems associated with urine testing have sparked interest in alternative techniques, such as the testing of hair, sweat, or saliva.

Viewpoints

The federal government laid the groundwork for drug testing in the workplace when, in the late 1980s, it initiated mandatory drug testing of federal employees, and began to require that government contractors establish drug-testing programs for their workers. Today, many large companies in the United States administer drug tests to their employees, but testing in smaller organizations is significantly less common.

SAMHSA advocates drug testing in order to help businesses achieve a drug-free workplace. A survey from the United States National Institute on Drug Abuse (NIDA) estimated that employee drug misuse cost the country billions of dollars in lost productivity, as well as in medical expenses and in worker-compensation claims. Mandatory drug testing in the workplace deters those who abuse drugs and alcohol from engaging in this unhealthy behavior at least while they are on the job, and it may deter non-users from ever starting to abuse drugs and alcohol. Also, it can sometimes help those with abuse problems to admit them and so to start getting help, but some abusers are in such deep denial that they cannot be helped in this way.

Some workplace drug-testing policies are considerably stricter than others. Federal employees can be subject to compulsory random drug tests, as can private-sector employees with responsibility for the lives and safety of others. It is obviously not as dangerous to the public for the person raking leaves in a park to take illegal drugs

Opponents of these views point out problems with drug testing. Workplace testing may actually dampen company productivity because it is time-consuming, has the potential to violate the confidentiality that medical personnel are obliged to practice, and undermines staff morale and loyalty. More importantly, it may needlessly

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Amphetamine—A chemical mixture that can strongly stimulate the central nervous system. Over time, users tend to need stronger doses, and eventually they may develop a physical dependence on it and thus become addicted. Anabolic steroid—A synthetic or semisynthetic substance that promotes the production within the body of the proteins that build up tissues, especially muscle tissues. Cocaine—An alkaloid chemical obtained from the leaves of the coca plant (or from some related species). It is addictive, it can cause mental and physical problems, and an overdose can lead to coma and death. Ergogenic—Giving rise to, or enhancing, work, activity, functioning, and the like. Erythropoietin—A protein produced mostly in the kidneys, and now available synthetically, that stimulates the production of red blood cells in the bone marrow. False negative—A test result that erroneously gives a negative finding when the actual condition should have given a positive finding.

ments. First, a gas chromatograph heats the compounds until they vaporize into gases which ascend a column and emerge one at a time. Then, each separate fraction of these gases is sent to a mass spectrograph which identifies the fragments of the molecules according to their mass. One thus gets a kind of chemical fingerprint of the substance being tested, and checks in a data base of thousands of such fingerprints of known substances to see which substance one has just tested. Growth hormone—A substance produced naturally in the body, and now available synthetically, that promotes the development of flesh and bone, and influences the metabolism of proteins, carbohydrates, and fats. Hallucinogen—A drug that can cause false sensations, such as hearing voices when there are no voices and no other sounds that could reasonably be confused with voices, or seeing persons or things that are not present.

False positive—A test result that erroneously gives a positive finding when the actual condition should have given a negative finding.

Marijuana—The dried leaves, stems, and flowers of plants of the cannabis family. It is often smoked, sometimes eaten. It can produce distorted perceptions (which the users consider to be a form of elevated consciousness) and sometimes causes outright hallucinations.

Gas chromatograph mass spectrometry—A technique by which complex organic compounds are identified by the use of two sophisticated instru-

Phencyclidine—A chemical used legally as a veterinary anesthetic and illegally as a drug that alters consciousness (a psychedelic drug).

harm the careers of employees whose legitimate use of prescription medicines causes confusing or ambiguous test results. Also, it may identify substances at insignificant doses because of recreational drug use outside working hours, use that has no bearing on employee performance, according to civil-rights groups such as the American Civil Liberties Union (ACLU). The ACLU advises that employees in safety-sensitive positions such as airline pilots should indeed be tested for impairment, and that any individuals found to be impaired should then be referred to special programs called Employee Assistance Programs (EAPs). EAPs can in turn direct these persons to the appropriate substance-abuse programs. The ACLU also recommends more rigorous reference-checking to avoid hiring someone with a history of drug-abuse problems in the first place. However, if the

person no longer has a drug problem, such an approach could illegally and unfairly violate this person’s rights. Many health-care organizations that provide qualified support for drug testing oppose its more radical uses, such as random testing or testing without suspicion. The American Nurses Association (ANA) opposes random drug testing of health-care workers, viewing it in violation of the basic principle of “innocent until proven guilty,” but provides qualified support for testing under reasonable suspicion, and with evidence that job performance has been impaired by alcohol or drug usage. Employees who initially test positive for drugs should be offered a reassessment of the test results and should be given the chance to explain what legitimate medications they are taking which might have produced false-positive results. Even when the drug use is confirmed, counseling

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KEY TERMS

Drug tests

and treatment are recommended before any disciplinary action is taken, according to the ANA. The American Hospital Association (AHA) advocates pre-employment testing, suspicion-based testing, testing after certain incidents or injuries, and testing following drug rehabilitation, but not random testing without cause. Some health-care organizations have also issued position statements on drug-testing policies in the community. The American Academy of Pediatrics has stated opposition to drug testing without cause as a prerequisite to student participation in school activities. And the American Medical Association (AMA) is opposed to the practice of reporting positive drug results for pregnant women to law-enforcement officials. Proponents say such practices protect unborn children, but the AMA states they are an invasion of medical confidentiality and a violation of the provider/patient relationship. Such practices may also discourage some women from seeking prenatal care.

Professional implications Nurses may draw blood samples, for example, when testing for alcohol level. They must be certain that they have the informed consent of the person from whom they are drawing blood, or else that they have clear-cut legal authorization, such as a court order, to do so. In the case of testing of urine, hair, saliva, and sweat, nurses should instruct the person being tested and then properly store and label the specimen provided. Medical technologists or clinical-laboratory scientists are responsible for running the tests, for reporting the results accurately, and in some cases for estimating the margin of error or assessing the likelihood that the result is a false positive or a false negative. All health personnel must see that the results of such tests are disclosed only to those authorized to have them, and must otherwise maintain strict professional confidentiality.

International Commission on Occupational Health 7, no. 2 (April–June 2001): 103–108. Kunsman, K. “Oral Fluid Testing Arrives.” Occupational Health and Safety (Waco, TX) 69, no. 4 (April 2000): 28–30, 34. Laws, J. “Rewriting the Testing Rulebook.” Occupational Health and Safety (Waco, TX) 69, no. 4 (April 2000): 36–38. ORGANIZATIONS

American Civil Liberties Union. 125 Broad Street, New York, NY 10004-2400. (212) 549-2500. [email protected]. . American Medical Association. The Council on Ethical and Judicial Affairs. 515 North State Street, Chicago, IL 60610-4320. (312) 464-4823. . American Nurses Association, ANA, 600 Maryland Avenue, SW, Suite 100 West, Washington, DC 20024-2571. (800) 274-4ANA. . American Society of Addiction Medicine. 4601 North Park Avenue, Arcade Suite 101, Chevy Chase, MD 208154520. (301) 656-3920. . Division of Workplace Programs, Center for Substance Abuse Prevention, Substance Abuse and Mental Health Services Administration. 5600 Fishers Lane, Rockwall II Building, Room 815, Rockville, MD 20857. (301) 443-6780. . National Clearinghouse for Alcohol and Drug Abuse Information (NCADI) Center for Substance Abuse Prevention. 5600 Fishers Lane, Rockville, MD 20857. (301) 443-0365. . National Institute on Drug Abuse. 6001 Executive Boulevard, Bethesda, MD 20892. (301) 443-1124. www.nida.nih.gov. NSNA, National Student Nurses Association, 555 West 57th Street, New York, NY 10019. (212) 581-2211. .

Ann Quigley

Resources PERIODICALS

Annas, G. J. “Testing Poor Pregnant Women for Cocaine— Physicians as Police Investigators.” New England Journal of Medicine 344, no. 22 (31 May 2001): 1729–1732. Kennedy, M. M. and R. B. Pickett. “An Uncomfortable Issue: Dealing with Substance Abuse.” Clinical Laboratory Management Review: Official Publication of the Clinical Laboratory Management Association/CLMA 15, no. 3 (May–June 2001): 183–184. Kraus, J. F. “The Effects of Certain Drug-Testing Programs on Injury Reduction in the Workplace: An Evidence-Based Review.” International Journal of Occupational and Environmental Health: Official Journal of the 794

Drug tests Definition Drug tests are analytical procedures that may be performed on blood, urine, or gastric fluid for the purpose of identifying an unknown drug or measuring the concentration of a specific drug.

Purpose Drug tests are usually performed for three reasons. 1) To identify an abuse drug. The majority of drug abuse

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Description Drug abuse testing Drug screening may be performed on urine, blood serum or plasma, or gastric fluid, but urine is the sample of choice for symptomatic cases because drugs and their metabolites concentrate in the urine. Clinical or emergency department settings require the use of a screening method because the identity of the drug is not usually known. Drug screening methods may be designed to detect a class of related drugs. For example, a drug test for amphetamines may detect methamphetamine, dexamphetamine, methylenedeoxymethamphetamine (Ectasy), and phenylpropanolamine. The latter drug is a decongestant that sometimes cross reacts with the antibodies used in the amphetamine assay (analysis). Although drug screening may be sufficient to treat the patient, medicolegal implications are usually involved and this necessitates the need for positive sample identification and confirmatory drug testing. The confirmatory test need not be more specific than the screening test, but must utilize a different method of detection. This obviates the chance of a false positive test result caused by an interfering substance unless the interferent affects both methods. Drug screening programs are also used in occupational settings as a condition of employment, and extensively by the criminal justice system for criminal investigations and monitoring persons who have been convicted of drug related offenses. These situations require stringent adherence to procedures for documenting chain-of-custody of

the specimen and confirmatory testing. Federal drug testing worksites must follow the Department of Transportation (DOT) chain-of-custody procedures for collection and transport of urine samples for drug testing. Labor-atories certified by the U.S. Substance Abuse and Mental Health Services Administration (SAMHSA) must use the gas chromatography with mass spectroscopy (GC-MS) method to confirm a positive drug screening test. This method is the gold standard for drug identification because it determines the mass spectrum of the drug which is a fingerprint of its chemical composition. Specimen collection and transport Urine specimens should be collected in a room with separate areas for workspace and toilet. The sink should be located in the workspace area. The patient or client must be positively identified via two forms of photoidentification or a passport. A form such as a DOT Custody Control Form should be used for chain-of-custody documentation. This form should include labels for the collection bottle and bag, and signature lines for all persons who will receive the specimen. At minimum the client must be observed entering and leaving the toilet area and should be instructed to remove outer garments and empty his or her pockets. The toilet should contain a bluing agent and the client should be instructed not to flush the toilet. The collection container should be unwrapped in the client’s presence and affixed with a temperature measuring strip. The sample should be examined by the collector for adulteration and rejected if not within perscribed limits for volume (at least 30 mL) and temperature (90-100°F). An acceptable sample is labeled across the lid and side so the seal will be broken if the lid is removed. The laboratory should perform a test for urinary creatinine, pH, or specific gravity to check specimen integrity. Blood samples are collected by venipuncture using standard precautions for reducing exposure to bloodborne pathogens. It is not necessary to restrict fluids or food prior to collection. Blood should be collected in tubes containing no additive. Risks of venipuncture include bruising of the skin or bleeding into the skin. The EMIT principle The most commonly used drug screening method is immunoassay. There are several immunoassay methods available including the enzyme multiplied immunoassay technique (EMIT), solid phase immunoassay fluorescence polarization immunoassay (FPIA), and cloned enzyme donor immunoassay (CEDIA). In addition, thin layer chromatography is sometimes used as a screening test. This method is more time consuming than immunoassay but is more comprehensive. The EMIT

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involves one or more of the following substances and these comprise a typical drug of abuse panel: amphetamines, cannabinoids, cocaine, ethanol, opiates (morphine and codeine compounds), and phencyclidine (PCP). Over 85% of drug abuse cases involve those drugs or one of the following: barbiturates, benzodiazepines, methadone, propoxyhene, LSD, methaqualone, and antidepressants. 2) To identify a drug which may have been ingested or administered in a toxic or lethal dose either accidentally or on purpose. In addition to poisons such as pesticides and heavy metals such as arsenic, drugs are often implicated in accidental overdose and suicide situations. The three most commonly encountered drugs seen in overdose situations are ethanol, salicylate (aspirin), and acetaminophen. 3) To determine whether the amount of a drug in the blood is within therapeutic limits. This process, called therapeutic drug monitoring (TDM), is used to insure that the dose and dose interval of the drug are sufficient to maintain a therapeutic blood concentration throughout drug therapy without risk of toxicity. TDM is also performed to verify that a patient is complying with the physician’s orders.

Drug tests

method is the most commonly used platform for drug of abuse screening. All EMIT assays follow the same scheme regardless of the drug being tested. EMIT assays measure enzyme activity. In a typical EMIT assay, urine is mixed with an antibody specific for the drug (e.g., methadone) and an enzyme-conjugated form of the drug. The enzyme used in EMIT testing is glucose-6-phosphate dehydrogenase. If not bound by the antibody, the enzyme will catalyze the oxidation of glucose-6-phosphate in the reagent forming 6-phosphogluconate and NADH. The production of NADH causes an increase in the absorption of 340 nm light. If no drug is present in the urine sample, all of the antibody will bind to the enzymeconjugated drug. The antibody will block the catalytic site of the enzyme preventing the formation of NADH. If the drug is present in the urine sample, it will bind to some of the antibody, reducing the amount of antibody available to bind to the enzyme-conjugated drug. Therefore, the activity of the enzyme will be proportional to the concentration of drug in the urine sample. In order to give maximum sensitivity the concentration of antibody is less than the concentration of the enzyme-conjugated drug. The labeled drug competes with any drug in the urine for binding sites on the antibody. If no drug is present in the sample, there will still be some unbound enzyme-conjugated drug that will produce NADH. However, the rate of enzyme activity will be less than that of the cutoff calibrator solution. The enzyme activity of the sample is compared to that of a cutoff calibrator. The concentration of drug in the calibrator is set to a level recommended by SAMHSA for a positive test result. If the patient’s sample result is greater than that of the cutoff calibrator, the drug test is presumed to be positive. Results below the cutoff calibrator are interpreted as negative. Activity less than the cutoff can result from endogenous drug present at very low levels in the absence of substance abuse. For example, poppy seeds used in baking contain minute amounts of opiates that cause some reactivity with enzyme immunoassays for opiates. Generally, the level of opiate detected will be below the cutoff value. Typically, the low calibrator and positive and negative urine control samples are assayed at least once per day along with the urine specimens. EMIT is approved by the FDA only for urine specimens. Samples should be collected in clean plastic containers and refrigerated if not run within one hour. They can be refrigerated for up to three days or frozen, if longer storage is required. The pH of the sample must be between five and eight. 796

Confirmatory drug testing Confirmation of a positive drug test by immunoassay is performed by a chromatographic method. Confirmatory methods include gas chromatography (GC), gas chromatography with mass spectroscopy detection (GC-MS), thin layer chromatography (TLC), and high performance liquid chromatography (HPLC). The methods most commonly employed in clinical practice are GC and TLC. In forensic laboratories and SAMHSA approved toxicology laboratories confirmation is done using GC-MS. All chromatography techniques require extraction of the drug from the biological fluid. This is accomplished by adjusting the pH of the sample to minimize ionization of the drug and addition of an organic solvent. The nonionized drug molecules will be more soluble in the organic phase and can be separated from water-soluble interfering substances. Extraction also serves to concentrate the drugs. In general, a pH of nine promotes extraction of alkaline and neutral drugs, and a pH of 4.5 promotes extraction of neutral or acidic drugs. Most abuse drugs with the exception of barbiturates and some benzodiazepines are extracted at an alkaline pH. Chromatography is a method used to separate molecules of similar structure. The process of separation depends upon nature of the chromatographic medium. Separation can result from partitioning (solubility differences), adsorption, size exclusion, ion exchange, and affinity bonding. Gas chromatography Gas chromatography is performed using a glass column packed with a liquid separation medium such as polyethylene glycol or an open glass capillary that is coated with a liquid polymer separation medium. GC measures only those substances that are volatile or can be separated into volatile compounds. GC separates molecules primarily on the basis of solubility. The sample is introduced into the instrument injection port and is vaporized by a high temperature. The vapors are carried by an inert gas (usually nitrogen) into a temperature-controlled column where they separate based upon their boiling point. Molecules of low boiling move faster through the column and elute first. When the drugs leave the column they are most often detected by a process called flame ionization. A small hydrogen-air flame is used to excite the molecule, causing release of an outer shell electron. This produces a current that is proportional to the concentration of the molecules. The instrument produces a recorder tracing of a peak when a compound is detected. The peak height or area is proportional to the drug concentration. The time between introduction of the sample and the appearance of the peak is called the retention time. Under standardized conditions, the retention

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GC-MS is a form of gas chromatography. The detector used is a mass spectrometer. This device usually uses an electron beam to break the eluted drug into ion fragments. The ions are kept apart by application of a vacuum and are separated according to their mass to charge (m/z) ratio in the mass analyzer, which is usually a quadrupole mass filter. This device produces alternating direct current voltage and radio frequency waves that attract and repel the ions. Ions of different m/z ratios move at different rates as the frequencies change and leave the filter at different times. The ions are detected by a dynode as they leave the filter. When the ion strikes the dynode it causes the element to release a shower of electrons. This current is used to produce a peak corresponding in height to the concentration of the ion. A recorder tracing of all of the ion fragments constitute the mass spectrum of the drug. As no two drugs have the identical mass spectrum this method conclusively identifies the drug. For drug identification the GC-MS is used in a mode called total ion chromatography, which displays the complete mass spectrum of the eluate and allows comparison to a computerized library of drug standards. For quantitative analysis the selected ion monitoring (SIM) mode is used. This mode measures the principal ions of the drug and can more accurately quantify the drug at lower concentrations. When testing for abuse substances the timing of specimen collection is very important because drugs are metabolized and eliminated at different rates. Dosage, length of use, and individual differences in absorption, metabolism, and elimination cause the window of detection to vary. Approximate detection times are shown below for some commonly abused drugs: • amphetamines: one to two days • short acting barbiturates (eg. Seconal): one day • long-acting barbiturates (eg. Phenobarbital): two to three weeks • benzodiazepines: three days • THC: three days for acute intermittent use; up to one month for heavy, chronic use • cocaine: two to four days • ethanol: three to four hours • morphine and codeine: two days • phencyclidine: one to two days • propoxyphene: six to 48 hours

Therapeutic drug monitoring (TDM) The same dose and dosing schedule for a drug can be therapeutic for some patients, and subtherapeutic or toxic for others. Age, gender, smoking, genetics, protein binding, concurrent medications, and renal and hepatic function cause variation in drug absorption, distribution, and clearance, which affects blood levels of the drug. The study of the behavior of a drug in the body is called pharmacokinetics. Pharmacokinetics describes the relationship between drug dose and blood concentrations. When two or more measurements are made after the drug reaches steady state, the results can be used to determine the dose and dosing interval needed to achieve the desired blood level. Tests for therapeutic drugs are performed for four reasons. 1) To determine whether the dose and dosing interval are able to maintain the desired blood level of the drug. 2) To permit empirical adjustment of the dose when the drug level falls outside the therapeutic range. 3) To verify that the patient is complying with the prescribed treatment. 4) To evaluate the magnitude of an intentional or accidental drug overdose. In practice, only those drugs that have toxic potential near the therapeutic range need to be monitored. Drugs that should be monitored include many anticonvulsants, aminoglycoside antibiotics, antiasthmatics, antiarrhythmics, antineoplastics, antidepressants, and immunosuppressive drugs used in organ transplantation. As orally ingested drugs are metabolized and eliminated between doses, blood levels are time dependent. Shortly following absorption and distribution of the drug in the body, the blood level will peak. As the drug is metabolized and eliminated the blood level will fall until replaced by the next oral dose. When serial measurements of drug are plotted, the result is a dose response curve made up of repeating peaks and troughs. Accurate timing of sample collection is required to properly interpret blood drug test results. For most drugs, there is not a great difference between peak and trough blood drug levels, and measurement of trough drug concentration is sufficient to evaluate the patient. In cases where the trough-peak range is large, both trough and peak levels need to be considered. This is the case when monitoring aminoglycoside antibiotics. When measuring trough blood levels of a drug the sample should be collected just before the next dose is given. Collection time for peak blood levels depends upon the drug and route of administration. For aminoglycoside antibiotics peak levels are usually drawn 30 minutes following an IV (intravenous) dose and 60 minutes following an IM (intramuscular) dose.

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times of unknown substances can be compared to those of drug standards to identify the drug in the sample. GC is the reference method for measuring ethanol in blood and is sufficiently sensitive and specific to identify most drugs extracted from biological samples.

Drug tests

Therapeutic drug measurements

KEY TERMS Immunoassay—A method for measuring biological substances such as drugs, proteins, and hormones. It utilizes antibodies specific for the substance being tested. Enzyme—A protein that accelerates the rate of a biochemical reaction. Enzyme immunoassay—A procedure employing an enzyme bound to an antigen or antibody. The antibody binds to the antigen of interest and the enzymatic reaction measures the concentration of the antigen. Chromatography—A technique used to separate closely related biological molecules which exploits one or more of the following differences: solubility, molecular size, adsorption, ion exchange, affinity bonding. Gas chromatography—A chromatographic method that utilizes a gas for the carrier or mobile phase and a liquid for the stationary phase. Gas chromatography with mass spectroscopy—A method that employs a gas chromatograph to separate the molecules and a mass spectrometer to identify and quantify the separated compounds. High performance liquid chromatography—A chromatographic method that utilizes a liquid mobile phase or carrier and a liquid stationary phase. Sample is forced through the stationary phase by a high pressure pump. Thin layer chromatography—A chromatographic method that uses a thin layer of silica gel and a liquid mobile phase which migrates upward through the silica gel by capillary action. Molecules are carried by the mobile phase and separate on the basis of solubility. Therapeutic drug monitoring—The measurement of a drug in blood serum or plasma in order to determine the adequacy of dosing and prevent drug toxicity. Trough level—A drug assay performed on a sample collected before the next dose is absorbed. Peak level—A drug assay performed on a sample following complete absorption and distribution.

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Both immunoassay and chromatographic methods are used to quantify therapeutic drugs. EMIT, CEDIA, and FPIA assays are the most commonly used immunoassays. Gas chromatography and high-performance liquid chromatography are the most commonly used chromatographic methods. FLUORESCENCE POLARIZATION IMMUNOASSAY (FPIA). This method measures the plane polarized fluores-

cence of fluorscein-labeled antigen without the need for an enzyme conjugate. Fluorscein conjugated to a drug competes with the drug in the sample for a limited number of antibody molcecules. Plane-polarized UV light is transmitted through the sample. Both the unbound and antibody-bound, fluorscein-labeled drug absorb the UV light and the fluorescein becomes excited. The unbound labeled drug is rotating rapidly and emits light that is unpolarized. The labeled drug that is bound by antibody rotates more slowly and will emit light that is plane polarized. The detector responds to plane-polarized light only because a polarizing filter is placed between the cuvet and detector. Antibody binds to more fluorescein labeled drug when there is less drug in the patient’s serum. This slows down its rotation giving a greater plane polarized signal. Therefore, plane-polarized fluorescent intensity is inversely proportional to the drug concentration in the patient’s sample. CLONED ENZYME DONOR IMMUNOASSAY (CEDIA).

A technique related to EMIT is CEDIA (cloned enzyme donor immunoassay). The method uses a drug conjugated to a fragment of the enzyme β−galactosidase which is called the enzyme donor (ED). The ED reagent also contains the substrate, cholorophenol red-β-D-galactopyranose. This is mixed with urine or serum and a second reagent containing a monoclonal antibody against the drug and a second fragment of β-galactosidase called the enzyme acceptor (EA). If drug is present in the sample it neutralizes the antibody. The two enzyme fragments associate forming an active enzyme which splits the substrate, liberating the red dye. Absorbance is directly proportional to drug concentration. If drug is not present, the antibody binds to the ED fragment preventing formation of active enzyme. HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (HPLC). HPLC is a chromatography method that uses liq-

uid mobile and stationary phases. The mobile phase is usually a buffer to which a polarity modifier such as acetonitrile has been added. The stationary phase consists of a stainless steel column of silica gel that is bonded to a nonpolar liquid. The most common column packing for clinical use is octadecylsilane (C18). The stationary phase is less polar than the mobile phase, and this causes

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Results Results for drug of abuse tests should be negative (ie. below the low calibrator cutoff). Results for therapeutic drugs should fall within the published therapeutic range for the drug and treatment. Some typical therapeutic limits for commonly measured drugs are shown below: • Acetaminophen: 10-30 mg/L; toxic level >200 mg/L. • Amikacin: trough 1-4 mg/L; peak 25-35 mg/L; toxic trough >10 mg/L; toxic peak >35 mg/L. • Carbamazepine: 4-12 mg/L; toxic level >15 mg/L. • Digoxin: 1.5-2.0 µg/L; toxic level >2.5 µg/L. • Ethosuximide: 40-100 mg/L; toxic level >150 mg/L. • Gentamicin: trough 1-2 mg/L; peak 8-10 mg/L; toxic trough >2 mg/L; toxic peak >12 mg/L. • Kanamycin: trough 4-8 mg/L; peak 25-35 mg/L; toxic trough >10 mg/L; toxic peak >35 mg/L.

• Tobramycin: trough 1-2 mg/L; peak 8-10 mg/L; toxic trough >2 mg/L; toxic peak >12 mg/L • Valproic acid: 50 - 100 mg/L; toxic level >100 mg/L. • Vancomycin: trough 5-10 mg/L; peak 20-40 mg/L: toxic peak >80 mg/L.

Health care team roles Therapeutic drug tests are ordered by physicians. Blood and urine samples may be collected by a nurse or phlebotomist. In the case of drug of abuse testing performed on behalf of an employer or government agency, drug testing is supervised by a medical officer appointed by the institution. Urine samples are collected and transported by nontesting personnel who should have special training in chain-of-custody procedures. Drug testing is performed by a clinical laboratory scientist, CLS (NCA) or medical technologist, MT (ASCP) or by a clinical laboratory technician, CLT (NCA) or medical laboratory technician, MLT (ASCP). Clinical toxicologists, clinical chemists, and clinical pharmacologists may be responsible for interpreting therapeutic drug tests and recommending doseage adjustments to the physician. Psychiatrists, psychologists, nurses, and social workers who are trained in drug abuse treatment are involved in evaluation, treatment, and counseling of drug abusers. Resources BOOKS

Burtis, C.A. and E.R. Ashwood(eds). Tietz Fundamentals of Clinical Chemistry, 5th ed. Philadelphia: W.B. Saunders, 2001. Henry, J.B. (ed).Clinical Diagnosis and Management by Laboratory Methods, 20th ed. Philadelphia: W.B. Saunders, 2001. Kaplan, L.A. and A.J. Pesce (eds). Clinical Chemistry Theory Analysis and Correlation, 3rd ed. St. Louis: C.V. Mosby, 1999. OTHER

Substance Abuse and Mental Health Services Administration. .

• Lidocaine: 1.5 - 6 mg/L: toxic level >6 mg/L. • Netilmicin: trough 1-2 mg/L; peak 8-10 mg/L; toxic trough >2 mg/L; toxic peak >12 mg/L. • Phenobarbital: 15-40 mg/L; toxic level >40 mg/L. • Primidone: 5-12 mg/L; toxic level >15 mg/L. • Procainamide: 4-10 mg/L; toxic level >12 mg/L. • Salicylates: 100-300 mg/L; toxic level >400 mg/L. • Theophylline: 8-20 mg/L; toxic level >20 mg/L.

Robert Harr

Drugs used in labor see Uterine stimulants Dual energy x-ray absorptiometry (DXA) scan see Bone densitometry Duchenne muscular dystrophy see Muscular dystrophy

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compounds which are lower in polarity to be retained longer than more polar molecules. The column is packed very tightly to give thousands of surfaces upon which partitioning can occur. Therefore, a pump is used to move the mobile phase through the column. To obtain a flow rate of 1.5 2.0 mL/min it is not uncommon to develop a pressure of 1,200-2,500 pounds per square inch at the start of the column. The separated molecules enter an optical flowcell after eluting from the column. UV (ultraviolet) light is passed through the flowcell and a photomultiplier tube or photodiode array detects the transmitted light. When a drug enters the flowcell it will absorb a portion of the incident UV light causing an increase in absorbance (optical density). This signal is applied to a chart recorder, which produces a peak that is proportional in height and area to the concentration of the drug. HPLC is time consuming and is usually reserved for assays of drugs for which there is no available immunoassay. It has the advantage of being able to separate drug metabolites from parent compounds and separate compounds that are nonvolatile (for example, anabolic steroids).

Dynamic spatial reconstructor

point sources directly opposite them at a frequency of 1/60 second, which happens to be a physiologically appropriate frequency for internal investigations involving moving organs such as the heart.

Dynamic spatial reconstructor Definition The dynamic spatial reconstructor (DSR) is a unique computed tomography (CT)-based scanner valuable for three-dimensional imaging and visualization of high temporal resolution three-dimensional cardiac cycles. Developed in the 1970s and early 1980s, the DSR is the “multi-source, multi-detector high speed synchronous 3D CT scanner for high temporal and spatial resolution scanning of the heart, lungs, and circulation” according to the Mayo Clinic, where the scanner was developed and is located. It is considered a research prototype and is not available commercially.

Purpose The DSR was developed as a non-invasive diagnostic device to detect lung cancer and heart disease in their early stages. It emerged as an answer to the tremendous challenge of using CT to provide 3D reconstruction of moving objects such as the cyclic motion of the beating heart. Due to its efficacy, it has become the standard in the field of three-dimensional real-time imaging by which other non-invasive imaging modalities are measured in their effectiveness for achieving various diagnoses.

Description Only a single DSR exists, at the Mayo Clinic site (Rochester, Minnesota), due to its prohibitive cost and size. The physical machine comprises: • a gantry 15 ft (4.57 m) in diameter and 20.5 ft (6.24 m) in length, weighing about 17 U.S. tons • fourteen x-ray guns featured within a hemicylindrical arrangement (surrounding the patient or subject overhead and on the sides) and targeted at an adjacent hemicylindrical fluorescent screen • fourteen rotating two-dimensional television cameras and eight video disc recorders for recording the x-rays • electronics and software algorithms for image acquisition The DSR is theoretically capable of acquiring image data for up to 240 contiguous 0.9 mm thick segments in time periods down as far as 1/60 of a second. The process can then be repeated as rapidly as 60 times per second. Due to limiting physical factors of the machine, however, these values are somewhat diminished in practice. The 14 rotating television cameras, possessing 240 scan lines apiece, receive x-ray photons from the 14 x-ray 800

Though the DSR is capable of diagnosing a myriad of heart and lung disorders, its cost (and thus limited capability for service) has prevented it from becoming a routinely useful clinically diagnostic tool. Nevertheless, over the years since its inception in 1983, the DSR has made possible the collection and analysis of unique, important data that has been especially employed in cardiac dynamics research and in assuring the legitimacy of other imaging modalities. An example of typical research usage is estimating the spatio-temporal distribution of the velocity of the left ventricular wall from experimental data obtained on the DSR. Essentially, a dense velocity field may be computed by applying a differential technique. This velocity field is obtained by mathematically applying the three following assumptions to the images: conservation of mass, incompressibility, and smoothness of the velocity field. In the case of this study, the results were in terms of the evolution of the field over time and maximum velocities, which were found to be in good agreement with the known physiological behavior of the heart. The DSR is not without its problems, however. In addition to its enormous cost and size, another difficulty plaguing the machine is that the gantry rotates only 1.5° per 1/60 second, which hinders the homogeneous distribution in orientation angle of images per time period. In order to keep the DSR more modern, some alterations have been implemented over the years since its launch, such as converting the old cameras (image isocon) to CCD (charge coupled device) cameras, larger lenses, and utilizing digitized images with corresponding algorithms. The DSR has thus been used to examine cardiopulmonary mechanics and pulmonary ventilation. Studies have confirmed the functionality of volumetric CT (DSR) in accurately resolving lung volumes, cardiac chamber volumes, myocardial muscle mass, and regional lung density, among others.

Operation In general, the greater the number of viewing angles used in collecting data tends to generate better images, at least up to a point. At least 4/60 of a second of scanning is typically desirable for creation of a reasonably good image reconstruction by the DSR. However, the DSR operator, or the research team doing the experiment, must consider the organ of interest in terms of its speed of movement within the body. This is so that interesting and

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KEY TERMS Computed tomography (CT)—Also known as CAT (computed axial tomography) scans. Computed tomography scans are completed with the use of a 360-degree x-ray beam and computer reconstruction of images using appropriate algorithms. Two-dimensional slices are acquired and stacked up computationally to yield a threedimensional density map of areas of interest. These scans allow for high resolution cross-sectional views of body organs and tissues.

The Mayo Clinic. 200 First Street SW, Rochester, MN 55905 507-284-2511. . OTHER

The Dynamic Spatial Reconstructor. .

Bryan Ronain Smith

Dysarthria Definition

relevant data can be taken at an appropriate rate, based on the similarity between the DSR temporal resolution and the tissue velocities and periodicity, in order to obtain optimal images.

Maintenance Maintenance is performed as needed on this unique instrument.

Health care team roles The DSR is mainly a research machine, so health care roles are generally relegated to interpretation of data sets by a doctor or technician trained to work with the apparatus. The DSR is used at its sole site in the Mayo Clinic. It is generally used by researchers in fields such as cardiac dynamics which require in vivo 3D data for specific studies or by doctors who wish to measure how well another imaging modality (i.e. electron CT) performs in comparison. It is used on humans as well as a wide range of animals for research.

Training Very few people are needed to operate the DSR since there is only one. Operating the scanner requires very specialized training that would be provided by technicians and technologists on site at Mayo if the need arises for its use. Resources PERIODICALS

Gorce, J.M., D. Friboulet, and I.E. Magnin. “Estimation of three-dimensional cardiac velocity fields: Assessment of a differential method and application to 3d ct data.” Medical Image Analysis. 1, no. 3 (1997): 245-261.

Dysarthria is a group of speech impairments due to weakness, incoordination, spasticity, rigidity, or irregular movements caused by damage to the nervous system.

Description Speech abilities depend on the coordinated function of muscles of respiration, phonation (larynx), and articulation. These functions are controlled by a complex neural circuitry involving the structures and pathways of the peripheral nervous system (cranial and spinal nerves) and central nervous system (cerebral cortex, basal ganglia, substantia nigra, cerebellum, brainstem). Damage to any portion of the speech neural circuitry can lead to dysarthria. As a result, speech may be distorted and difficult to understand. Dysarthria is frequently accompanied by dysphagia, or swallowing difficulty, as similar neural circuits are necessary for swallowing function. Depending on which portion of the nervous system is affected, dysarthria can be accompanied by other speech, language, motor and sensory disturbances. Dysarthria can occur in adults and children who have neurologic conditions affecting the speech circuitry.

Causes and symptoms Many neurologic etiologies that affect the speech neural circuitry can lead to dysarthria. Among the most common etiologies are stroke, degenerative conditions (e.g., Parkinson’s disease, amyotrophic lateral sclerosis, Huntington’s disease, cerebellar degeneration, multiple sclerosis), trauma, cerebral palsy, tumor, infections, and toxic conditions. Because dysarthria can arise from so many different neurologic conditions, the prevalence of the disorder is difficult to estimate. The symptoms of dysarthria vary depending upon which portion of the neural circuitry is damaged.

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ORGANIZATIONS

Dysarthria

KEY TERMS Articulation—The pronunciation of speech sounds. Central nervous system—Portions of the nervous system within the confines of the meninges and bones. Dysphagia—Swallowing difficulty. Dysphonia—Hoarse, breathy, or strained voice. Etiology—The cause or causes of a disease or condition. Peripheral nervous system—Portions of the nervous system that exit the meninges; the nerves. Phonation—Sound that emanates from the larynx; voice. Prosody—Intonation and rhythm of speech. Resonance—The nasal quality of speech.

Articulation may be slurred, imprecise, distorted, or irregular. The resonance quality of speech may be hypernasal (over nasally sounding) or hyponasal (under nasally sounding). The voice may be breathy, strained, hoarse, or strangled to the point of stopping. Selective dysphonia (strained or breathy voice quality) can be observed. The prosody or melody of speech may be flattened, excessive, or choppy. The rate of speaking is usually slowed, but some individuals may actually speak at an excessive rate. Respiration for speech may be weak or forced. Tremor, spasms, or excessive movements of the speech muscles may disrupt the flow of speaking. Different combinations of symptoms can lead to significant loss of speech intelligibility (how easily speech is understood). Patterns of these symptoms tend to be observed in relation to the part of the nervous system that is damaged.

Diagnosis A physician will perform a clinical neurological examination to determine a diagnosis in individuals with suspected neurologic disease. When an accompanying speech disorder is noted, the physician will refer the patient to a speech-language pathologist trained in the administration of speech examination protocols to identify the pattern of dysarthria and determine a course of treatment if warranted. Although most dysarthria tests depend on the clinician’s perceptual analysis and judgment of the patient’s speech characteristics, some acoustic and physiologic measurements can be complet802

ed using computerized analyses. Clinicians evaluate patterns of speech characteristics related to articulation, resonance, phonation, respiration, and prosody to determine a course of intervention. Assessment of dysarthria, which occurs in acute through chronic stages of the neurologic condition, takes one to two hours to complete.

Treatment Treatments provided by physicians that may improve aspects of dysarthria include pharmacologic treatments for neurologic conditions, surgical intervention (e.g., injection of botulinum toxin into the vocal folds), or prosthetic management (for example, palatal lift, a prosthesis used to improve speech for a patient with an incompetent soft palate). Patients with dysarthria often work with a speech-language pathologist who will use behavioral methods to alleviate the consequences of dysarthria for communication. When patients have a neurologic condition from which recovery is anticipated (e.g., stroke), clinicians will use drills and practice with speech activities to restore speech skills or identify strategies to improve speech intelligibility. In degenerative neurologic conditions, when it often becomes impossible to rehabilitate speech, patients with dysarthria may adopt alternative and augmentative communication strategies including writing, communication pointing boards, computers, or speech-generation devices to compensate for the severe speech impairment.

Prognosis The prognosis for recovery of dysarthria relates to the nature of the neurologic disorder that has caused the disease. When patients develop degenerative neurologic conditions, speech is likely to deteriorate as well. When the patient has a static or recovering neurologic condition (e.g., stroke), some improvement in speech abilities is likely depending on the extent of the nervous system injury.

Health care team roles Nursing and medical staff providing medical care for individuals with dysarthria implement strategies recommended by speech-language pathologists to foster communication with patients. The rehabilitation team (e.g., physical therapist, occupational therapist, physiatrist, social worker) assists with neurological recovery and implements strategies to maximize communication skills.

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The way to prevent dysarthria is to prevent the neurologic event that causes dysarthria. Resources BOOKS

Duffy, J.R. Motor speech disorders. St. Louis: Mosby, 1995. Weiner, W.J., and Goetz, C.G., eds. Neurology for the NonNeurologist. Philadelphia: Lippincott, Williams, & Wilkins, 1999. ORGANIZATIONS

American Academy of Neurology. 1080 Montreal Avenue, St. Paul, MN, 55116. (651) 695-1940. . American Speech-Language-Hearing Association. 10801 Rockville Pike, Rockville, MD 20852. (800) 638-8255, . National Institute of Deafness and other Communicative Disorders: Health Information: Aphasia. National Institutes of Health, 31 Center Drive, MSC 2320, Bethesda, MD, 20892-2320, . National Parkinson Foundation. Bob Hope Parkinson Research Center, 1501 N.W. 9th. Avenue, Bob Hope Road, Miami, FL, 33136-1494. (305) 547-6666. (800)327-4545. .

Anastasia Marie Raymer, Ph.D.

Dyslexia see Language disorders Dysmetria see Movement disorders

Dysphagia Definition Dysphagia is a disorder of swallowing.

Description Dysphagia is a disruption in the ability to move food or liquid from the mouth through the pharynx and esophagus into the stomach safely and efficiently. Swallowing disorders can occur at any point in the life span from infancy through old age. It is estimated that approximately 6,228,000 Americans over age 60 have dysphagia, and that it occurs in 32% of all patients in intensive care units. If untreated, dysphagia can result in dehydration, weight loss, malnutrition, pneumonia, and, in rare cases, death.

In order to understand dysphagia, it helps to understand the normal swallow. A normal swallow rapidly carries a bolus of food or liquid through the mouth, pharynx, and esophagus, leaving these structures substantially clear of residue at its completion. It involves a complex interaction of sensory stimuli and motor responses that encompass both voluntary and involuntary behaviors. A normal swallow consists of four phases: the oral preparatory phase, the oral phase, the pharyngeal phase, and the esophageal phase. The oral preparatory phase readies the food or liquid for swallowing. The lips close and seal to contain the material in the mouth. Solid food is chewed and mixed with saliva. The tongue gathers the liquid or solid material into a bolus and holds it. During this phase, the entry into the airway is open and nasal breathing continues. The oral phase begins when the tongue starts to move the bolus backward toward the pharynx. It ends when the head of the bolus passes into the pharynx. The pharyngeal phase begins when the bolus enters the pharynx and ends when it passes into the esophagus. In this phase, sensory stimuli interact with reflex and volitional movements to trigger the swallow response, which includes: • elevation and retraction of the soft palate to prevent material from entering the nose • elevation and forward movement of the hyoid and larynx, which moves them out of the path of the bolus as it travels downward, thus helping to prevent it from entering the airway below • closure of the larynx, which stops respiration momentarily and prevents the bolus from entering the airway below • retraction of the tongue base and contraction of the posterior pharyngeal wall, which build pressure to propel the bolus downward • progressive top to bottom contraction of the pharyngeal constrictor muscles, placing additional downward pressure on the bolus • opening of the pharyngoesophageal segment to allow the bolus to pass into the esophagus The esophageal phase of the swallow begins when the bolus enters the esophagus and ends when it passes into the stomach. Muscular contractions push the bolus downward through the lower esophageal sphincter into the stomach.

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Prevention

Dysphagia

Causes and symptoms

• gurgly or wet vocal quality associated with swallowing

Causes

• unexplained weight loss

Dysphagia occurs when any element of the normal swallow is disrupted. Oral structural abnormalities, muscular weakness, or incoordination may interfere with holding material in the mouth, forming it into a cohesive bolus, and propelling it backward into the pharynx. Lack of control over the material in the mouth might cause it to fall over the back of the tongue prematurely, while the airway is unprotected, or it might result in material remaining in the mouth after the swallow, when it could fall into the pharynx. If the bolus enters the pharynx before or after the swallow, while the airway is open and unprotected, there is a danger that aspiration will occur. Similarly, structural abnormalities, weakness, or incoordination in the pharynx or larynx may interfere with protection of the airway during the swallow or with the downward propulsion and emptying of the bolus into the esophagus. Finally, structural abnormalities, weakness, or incoordination in the esophagus may interfere with the progress of the bolus through the esophagus into the stomach. Common etiologies of dysphagia include: • strokes • head injuries • cervical spinal cord injuries • progressive neurologic diseases • head and neck cancer and the surgery or radiation used to treat it • congenital syndromes and abnormalities • esophageal stenosis • esophageal tumors • esophageal motility disorders

• increased time to consume a meal • complaints of globus • recurring pneumonia • heartburn

Diagnosis Diagnosis of dysphagia generally involves a clinical screening evaluation (sometimes called a bedside evaluation) and an instrumental evaluation. The clinical screening evaluation includes review of the medical history; current medical status; examination of oral anatomy and oral motor functioning; perceptual evaluation of laryngeal functioning; and observation of eating and drinking unless the risk of aspiration is very high and the individual is deemed too medically fragile to tolerate it. If the clinical screening evaluation suggests the presence of a dysphagia, it is usually followed by an instrumental evaluation. The instrumental evaluation that is most widely used for diagnosing oropharyngeal dysphagia is the videofluoroscopic modified barium swallow (MBS) study. The MBS study allows the observation of structures and movements as the individual swallows controlled amounts of various consistencies (usually thin and thick liquid, a paste or pudding consistency, and solid food) while seated in an upright position. It provides information about transit times through the mouth and pharynx, motility problems, and the presence and etiology of aspiration. The MBS is done in the radiology department and requires the patient’s cooperation. Thus, it may be contraindicated for patients who are unable to cooperate with instructions, or who are too medically fragile to be transported.

• achalasia • gastroesophageal reflux disease Medications may also cause or exacerbate dysphagia. Antipsychotic drugs that cause extrapyramidal symptoms like tardive dyskinesia may cause dysphagia, and some anticholinergic drugs may impair swallowing ability. Symptoms Common symptoms of dysphagia include: • inability to control food or saliva in the mouth • residue in the mouth after the swallow • coughing during or after the swallow 804

Videoendoscopy, or flexible fiberoptic examination of swallowing (FEES), is another procedure used to examine for oropharyngeal dysphagia. A flexible scope is inserted through the nose into the pharynx, allowing observation of the pharynx before and after the pharyngeal swallow is triggered. It does not allow observation of the oral or esophageal phases of the swallow, and, because the image is blocked by the constriction of the pharynx around the scope during the pharyngeal swallow, the presence and etiology of aspiration may be inferred but cannot be observed. This procedure can be done at the bedside and requires minimal cooperation from the patient, making it useful for patients who cannot tolerate an MBS study.

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Achalasia—Failure of the pharyngoesophageal segment to relax sufficiently to allow swallowed material to pass from the esophagus into the stomach. Anterior faucial arches—Also called the glossopalatine arches, these pillar-like structures run from the palate down to the tongue laterally in the back of the mouth. Anticholinergic drugs—Drugs that affect the parasympathetic system. Aspiration—Entry of food or liquid into the airway below the level of the true vocal folds. Aspiration of large amounts or of small amounts over a period of time may result in pneumonia. Cervical auscultation—Listening to the sounds of swallowing, usually via a stethoscope. Dilatation—The stretching of a structure by swallowing increasingly larger sized rubber catheters filled with mercury. Electromyography—Measures the timing and amplitude of selected muscle contractions. Esophageal stenosis—Narrowing of the esophagus. Esophagus—The tube that carries food or liquid from the pharynx to the stomach. Globus—The feeling that there is a lump in the throat. Hyoid—A small bone at the root of the tongue to which many lingual muscles are attached. It provides a stable base for tongue movement.

The instrumental evaluation most frequently used for esophageal dysphagia is the standard barium swallow or upper gastrointestinal series. This differs from the MBS study in that the patient is required to swallow a much larger amount of barium, typically while lying in the prone position. It allows observation of structures and of the movement of the material through the esophagus and into the stomach. When gastroesophageal reflux disease is suspected, continuous pH monitoring that measures the pH level of the contents of the lower esophagus is considered the best single test for its diagnosis. Other instrumental evaluations that are sometimes used, either alone or in combination with the more standard techniques, include: ultrasound of the oral cavity, scintigraphy, electromyography, cervical auscultation, and manometry.

Larynx—Commonly called the voice box, this structure of muscle and cartilage sits at the top of the trachea. Manometry—Measures of pressure changes that occur in the pharynx and/or esophagus during the swallow. Motility—Movement. Pharyngoesophageal segment—Also called the cricopharyngeal muscle or the upper esophageal sphincter (UES), this segment is normally in tonic contraction in awake individuals to prevent air from entering the esophagus during respiration and to reduce the risk of reflux from the pharynx into the esophagus. Pharynx—The hollow muscular tube, commonly called the throat, that runs from the base of the skull to the opening of the esophagus. Reflux—Backward flow of food and stomach acid from the stomach into the esophagus. Scintigraphy—A nuclear medicine test requiring the patient to swallow measured amounts of radioactive substance. It can reveal the amount of aspiration and residue, but does not allow visualization of structures or movements. Tardive dyskinesia—A disorder characterized by abnormal involuntary movements.

Treatment Treatment of oropharyngeal dysphagia depends on the etiology and the severity of the problem. An essential component of treatment is education of the patient, family, and other caregivers regarding the nature of the swallowing problem, its potential complications, and the importance of following recommendations to prevent such complications. Treatment may also involve one or more of the following: • An exercise program to improve the strength, range of motion, speed, and/or coordination of movements. • Diet modifications that eliminate food or liquids of consistencies that are at high risk of being aspirated. • Teaching of specific postures or strategies designed to reduce or eliminate the risk of aspiration when swallowing.

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Dysphagia

KEY TERMS

Dysphagia

• Use of an alternate means of feeding, such as a gastric tube, either temporarily while other treatment strategies are attempted, or permanently if other treatment is unsuccessful. • Esophageal dysphagia is usually medically, rather than behaviorally, managed. Dilatation is the typical treatment for esophageal stenosis. Surgery is most often used for esophageal tumors. Medications are used to treat motility disorders. Achalasia may be treated with smooth muscle relaxant drugs, dilatation, or surgery. Gastroesophageal reflux disease may be managed through dietary and lifestyle modifications, specifically: decreasing or eliminating certain foods from the diet, elevating the head of the bed for sleeping, avoiding lying down within two hours of eating, and eliminating smoking. Drugs and surgery are also used to treat this disorder.

Prevention Prevention of dysphagia requires prevention of the conditions that cause dyphagia, such as stroke, head trauma, or head and neck cancer. Prevention of complications from dysphagia involves adherence to the individualized treatment program, which usually specifies the precautions that should be taken. Although these will vary for each individual, they generally include eating and drinking only those foods and liquids of the recommended consistencies, sitting upright for oral intake, taking small amounts at a slow rate, ensuring that the mouth is clear after a swallow and at the end of a meal, using recommended strategies on every swallow, maintaining good oral hygiene, and remaining upright for 30 minutes after eating or longer if there is an esophageal dysphagia. Resources BOOKS

Prognosis The prognosis for recovery from dysphagia varies from excellent to poor depending on its severity, etiology, and the ability of the individual to comply with treatment recommendations.

Health care team roles Identification, diagnosis, and management of dysphagia is a multidisciplinary effort. In most settings, speech-language pathologists perform screening evaluations, collaborate with a physician (usually a radiologist or otolaryngologist) in instrumental evaluations, design and implement a treatment program for oropharyngeal dysphagia, and provide education to the patient, family, and other staff members. The dietitian monitors the patient’s nutritional status. The nursing staff, often the first to recognize dysphagic symptoms, encourages daily compliance with the recommended treatment program. Occupational and physical therapists work on feeding, adaptive devices, and sitting balance. (In some settings an occupational therapist is the primary swallowing therapist.) Physicians monitor and treat the patient’s overall medical status. They are typically the primary treatment providers for esophageal dysphagia.

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Johnson, Alex F. and Jacobson, Barbara H. Medical SpeechLanguage Pathology: A Practitioner’s Guide. New York: Thieme, 1998. Logemann, Jeri A. Evaluation and Treatment of Swallowing Disorders 2nd ed. Austin: Pro-ed, 1998. PERIODICALS

Zorowitz, Richard D. and K. Robinson. “Pathophysiology of Dysphagia and Aspiration.” Topics in Stroke Rehabilitation 6, no. 3 (Fall 1999): 1-16. ORGANIZATIONS

American Speech Language Hearing Association. 10801 Rockville Pk., Rockville, MD 20852. (888) 321-ASHA. . Center for Swallowing Research. Massachusetts Institute of Technology, Cambridge, MA. . OTHER

Agency for Health Care Policy and Research. Diagnosis and Treatment of Swallowing Disorders (Dysphagia) in Acute-Care Stroke Patients: Evidence Report/Technology Assessment Number 8. Rockville, MD: U.S. Department of Health and Human Services, July 1999.

Mary Boyle, Ph.D., CCC-SLP, BC-NCD

Dystonia see Movement disorders

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E E. coli food poisoning see Food poisoning Ear exam with an otoscope see Otoscopic examination

Ear instillation

Preparation The hands should be washed before administering ear drops. Check the medication label each time to avoid medication errors. Be sure it is the right medicine, the right dose (strength), the right time, the right person and the right method. Look at the expiration date on the label. Do not use outdated medicine. Warm the eardrops to body temperature by rolling the bottle in the hands for several minutes before the instillation.

Definition An ear instillation is a solution of topical medicine prepared for administration into the ear canal. Medicine instilled into the ear is absorbed through the skin of the ear canal and membranes of the eardrum.

Purpose Ear instillations are used primarily to treat wax build-up and inflammations or infections of the ear.

Precautions Do not place the medicine dropper tip or cotton swabs directly into the ear canal, as this can traumatize the skin of the ear canal. Do not touch anything with the tip of the medicine dropper to prevent contamination. If the patient experiences pain from eardrops, stop using the medicine and contact the physician.

Description To instill eardrops, have the patient lie on his or her side with the affected ear up. Gently pull the lobe of the ear up and back to open the ear canal (down and back for children under the age of three). Hold the medicine dropper just above the entrance to the ear canal and squeeze out the correct number of drops. Release the ear and have the patient remain still for five minutes to allow absorption of the eardrops. Repeat the procedure on the other ear if ordered.

Aftercare Have tissues or a warm washcloth available to wipe off residual medicine that may drip out of the ear when the patient sits up. A small piece of clean cotton ball may be placed into the outer portion of the ear canal to absorb excess medicine if desired. Discard soiled tissues and cotton in a bag that can be closed and discarded. Wipe the tip of the ear dropper with a clean tissue and recap the bottle. The hands should be washed again after completing the procedure.

Complications Excessive use of eardrops can cause irritation and inflammation of the skin and membranes of the ear.

Results Ear instillations will produce the desired results within a few days. Contact the physician if the patient experiences ear pain at the time of medicine instillation, or if the condition does not improve.

Health care team roles Ear instillations are usually administered by a licensed nurse (R.N. or L.P.N.) in the health care setting. The patient or members of the patient’s family can be taught to instill ear medicines in the home setting.

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Ear irrigation

Resources OTHER

“General Information About Otic (Ear) Medicines.” InteliHealth Online. 2001. . “Gentamicin (Otic).” Web MD Health Online. 2000. . “How to Use Ear Drops.” Pharm Web. 2001. . Nancy Sculerati, M.D. “Topical Ear Drops.” CEF Homepage Online. 2001. . “Swimmer’s Ear.” ENT Associates of Corpus Christi Online 1993. .

Mary Elizabeth Martelli, R.N.,B.S.

Ear irrigation Definition Ear irrigation is the process of flushing the external ear canal with sterile water or sterile saline. It is used to treat patients who complain of foreign body or cerumen (ear wax) impaction.

Purpose The purpose of ear irrigation is to remove earwax that is obstructing the ear canal or to remove a foreign object lodged in the ear canal. Ear irrigation is most commonly performed on those who experience a wax buildup that has impaired hearing and irritated the outer ear canal. Ear irrigation is performed in the emergency department as a first-line treatment for a foreign object in the ear canal, because it is less invasive than using an instrument. If the object is a live insect, oil is inserted into the ear to kill the insect; then, the ear canal is irrigated to remove the dead insect. Some foreign objects may be removed from the ear using irrigation alone, but most require a combination of both irrigation and the use of instruments by the physician.

Precautions The ear canal should be examined with an otoscope prior to ear irrigation. Ear irrigation is contraindicated if the eardrum is ruptured, because the procedure may force bacteria through the perforation into the inner ear. Ear irrigation is also contraindicated in patients with fever 808

and ear pain, as these symptoms may indicate an inner ear infection. If a foreign object is made of vegetable matter (e.g., a bean or pea), irrigation is contraindicated because the water will cause the object to swell and complicate extraction of the object.

Description Ear irrigation can be performed using a 50–60-cc syringe (20–30-cc syringe for children). Some nurses prefer to attach a large bore IV (intravenous) catheter (with the needle removed) to the syringe for easier direction of the fluid. Using this method, the fluid is aspirated into the syringe and squirted into the ear canal. Another method uses IV solution and tubing, with a disposable ear irrigation connector that fits onto and over the outer ear. When using this method, the IV is turned on and the fluid flows by gravity into the ear to create the irrigation. When using the IV method, the bag should be about 6 inches (15 cm) or less above the patient’s head to create the proper fluid pressure. After positioning the patient, the earlobe of the affected ear should be held back, and up (back and down for an infant). The tip of the irrigation syringe or catheter should be placed at the entrance to the ear. The tissue of the ear should not be touched. The ear canal should not be occluded, or the solution will not be able to run back out of the ear. Gently aiming the flow of the irrigation solution towards the upper aspect of the external ear canal, the nurse should syringe or run in the IV fluid at a slow, steady rate, allowing the fluid to escape out of the ear canal and into the basin. If using a dental pik apparatus, the lowest setting should be used. Exerting too much pressure can force the foreign object or the wax occlusion deeper into the ear canal. The return fluid should then be checked before the syringe is refilled—or after 100cc of fluid for an adult, and 30cc of fluid for a child. The nurse should investigate whether the wax or foreign object has been flushed from the ear. When the occlusion has been removed, 500cc of irrigation fluid should be used for an adult—100cc for a child, or as ordered by the physician. The procedure should be interrupted if the patient complains of pain or dizziness.

Preparation The patient should be positioned with his or her head bent slightly forward and tilted toward the unaffected ear. His or her shoulder and neck should be covered with a water-resistant pad and a bath towel. The patient should be given kidney-shaped basin to hold under the affected ear. Children, the elderly, or patients who cannot sit up may be positioned on the back with the head tilted slightly toward the unaffected ear. Again, the shoulder should be covered

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The nurse should wash his or her hands and put on gloves. The normal saline or sterile water irrigation solution should be heated. This can be accomplished by placement of the solution bag (bottle) in hot water, or using a microwave. Then, the temperature of the solution should be checked before the irrigation is started. The solution should be body temperature or slightly warmer (98.6–100°F [37-37.8°C]). Cool irrigation solution is more likely to make the patient dizzy. If using an irrigation syringe, the cap should be removed, and the first 60 cc should be drawn into the syringe. If using an IV catheter, the needle should be removed and the plastic catheter attached to the syringe or the IV tubing. All air from the syringe and tubing must be removed. Further, when an ear irrigation kit is used, the pieces should be opened and assembled. The IV tubing must be primed and filled, and the irrigation apparatus should be connected. The patient should have a dry wash cloth on hand in case the irrigation fluid runs toward his or her face or eyes. The patient should be informed before the irrigation begins. The patient should be instructed to speak up if he or she experiences pain or discomfort.

Aftercare The patient should tilt his or her head toward the affected ear for a few minutes. This will allow excess fluid to run out. The irrigation apparatus should be removed and the patient assisted with drying off. The outer ear should be wiped with cotton balls or cotton swabs. However, the swabs should not be placed into the ear canal. Irrigation fluid should be discarded into a hopper. Disposable equipment and gloves should be placed in a trash bag that can be sealed and discarded. Finally, the nurse should wash his or her hands once the procedure is completed.

be used for several days, to soften the earwax before further irrigation. If foreign bodies cannot be removed with ear irrigation, suction or instruments to remove the foreign object may be employed by the physician.

Health care team roles Ear irrigations are performed by a registered nurse (R.N.) in the health care setting. The patient or family of the patient may be taught, by the physician or nurse, to do ear irrigations in the home setting if a patient has frequent problems with ear wax build-up. Resources BOOKS

“Ear Irrigation.” In Nurse’s Clinical Guide. PA: Springhouse Corporation, 2000. OTHER

Bemis, Patricia R.N., C.E.N. “Ear, Nose, Throat and Dental Emergencies.” Wild Iris Medical Education Online, August 2001. . “Foreign Body in Ear.” Common Simple Emergencies. NCEMI Online, 2001. . Rudy, Susan F., MSN. “What Precautions Are Necessary When Irrigating the Ear Canals.” Ask the Expert. Medscape Online, June 2000. . “Temperature of Saline Solution for Ear Irrigation: Tips From Other Journals.” American Family Physician Online, January 2000. .

Mary Elizabeth Martelli, R.N., B.S.

ECG see Electrocardiography ECG unit see Electrocardiography unit

Complications Complications of an ear irrigation are rare, but may include trauma to the external ear canal, external ear infection, pain, nausea, or vertigo. Forceful irrigation with high pressure can rupture the eardrum and force bacteria into the inner ear.

Results Proper ear irrigation will most often result in the removal of the impacted earwax. If the wax is not washed out with 500cc of irrigation fluid, ear drops containing peroxide will be prescribed by the physician; these are to

Echocardiography Definition Echocardiography is a diagnostic test that uses ultrasound waves to produce an image of the heart muscle and the heart’s valves.

Purpose Echocardiography is used to diagnose certain cardiovascular diseases, and is one of the most widely used

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and/or the pillow with a water resistant pad and a bath towel. If necessary, the nurse should obtain assistance to hold the basin under the ear during the ear irrigation.

Echocardiography

echocardiography are portable (handheld) or mobile, echocardiography can be performed in the emergency department or at the bedside of patients who cannot be transported to the cardiology department.

Precautions Echocardiography is a safe, noninvasive procedure, and there are no special precautions.

Description

Echocardiogram, in which one can see the four chambers of the heart. (Photograph by Ken Eward. Science Source/Photo Researchers. Reproduced by permission.)

diagnostic tests for heart disease. Ultrasound waves that rebound or echo off the heart can show the size, shape, and movement of the heart’s valves and chambers, as well as the flow of blood through the heart. Echocardiography may show abnormalities such as a poorly functioning heart valve or damage to the heart tissue from a heart attack. Echocardiography is especially useful for assessing disorders of the heart valves. It not only allows doctors to evaluate the heart valves, but can also detect abnormalities in the pattern of blood flow. For example, echocardiography can show the backward flow of blood through partially open heart valves (that should be fully closed). This backward flow of blood through a valve is known as regurgitation. By assessing the motion of the heart wall, echocardiography can help detect the presence and assess the severity of coronary artery disease, as well as help determine whether chest pain is related to heart disease. Additionally, echocardiography can help detect hypertrophic cardiomyopathy, in which the walls of the heart thicken in an attempt to compensate for heart muscle weakness. Echocardiography is also used to evaluate heart murmurs (abnormal heart sounds), determine the causes of congestive heart failure, assess enlarged hearts or hearts with septal defects (holes between pumping chambers), and to monitor the heart in patients with diseases that may affect heart function (e.g., lupus, lung diseases). The biggest advantage to echocardiography is that it is noninvasive (it doesn’t involve breaking the skin or entering body cavities) and has no known risks or side effects. Echocardiography is often used in conjunction with other diagnostic tests for the heart, such as electrocardiography. Echocardiography is usually performed in the cardiology department at a hospital, but may also be performed in a cardiologist’s office or an outpatient imaging center. Because the ultrasound scanners used to perform 810

Echocardiography creates an image of the heart using ultra-high-frequency sound waves—sound waves that are too high in frequency to be heard by the human ear. The technique is very similar to ultrasound scanning commonly used to visualize the fetus during pregnancy. An echocardiography examination generally lasts between 15-30 minutes. The patient lies bare-chested on an examination table. A special gel is spread over the chest to help the transducer make good contact and slide smoothly over the skin. The transducer, also called a probe, is a small handheld device at the end of a flexible cable. The transducer, essentially a modified microphone, is placed against the chest and directs ultrasound waves into the chest. Some of the waves get echoed (or reflected) back to the transducer. Since different tissues and blood reflect ultrasound waves differently, these sound waves can be translated into a meaningful image of the heart that can be displayed on a monitor or recorded on paper or tape. The patient does not feel the sound waves, and the entire procedure is painless. Occasionally, variations of the echocardiography test are used. For example, Doppler echocardiography employs a special microphone that allows technicians to measure and analyze the direction and speed of blood flow through blood vessels and heart valves. This makes it especially useful for detecting and evaluating regurgitation through the heart valves. By assessing the speed of blood flow at different locations around an obstruction, it can also help to precisely locate the obstruction. An exercise echocardiogram, or stress echo, is an echocardiogram performed during exercise, when the heart muscle must work harder to supply blood to the body. This allows doctors to detect heart problems that might not be evident when the body is at rest and needs less blood. For patients who are unable to exercise, certain drugs can be used to mimic the effects of exercise by dilating the blood vessels and making the heart beat faster. During the examination the sonographer can take measurements and, using the ultrasound scanner’s computer, make calculations, including calculating blood

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Preparation The patient removes any clothing and jewelry above the chest.

Aftercare No special measures need to be taken following echocardiography.

Complications There are no known complications associated with the use of echocardiography. There is a slight risk of having a heart attack during an exercise echocardiogram, due to the stress put on the heart during the test, mostly for patients with a history of heart attack or other risk factors.

Results A normal echocardiogram shows a normal heart structure and the normal flow of blood through the heart chambers and heart valves. However, a normal echocardiogram does not rule out the possibility of heart disease. An echocardiogram may show a number of abnormalities in the structure and function of the heart, such as: • thickening of the wall of the heart muscle (especially the left ventricle) • abnormal motion of the heart muscle • blood leaking backward through the heart valves (regurgitation) • decreased blood flow through a heart valve (stenosis)

Health care team roles Echocardiography should be performed by a registered diagnostic cardiac sonographer—an ultrasonographer specially trained in cardiac ultrasound. The results should be interpreted by a cardiologist trained in the application of cardiac sonography. The Intersocietal Commission for the Accreditation of Echocardiography Laboratories provides a self-evaluation process for echocardiography labs to become accredited. Accreditation involves staff evaluation and training, equipment assessment, and peer review.

KEY TERMS Doppler imaging—A mode of ultrasound imaging that uses the physics principle of the Doppler effect (sound frequency waves shift relative to the observer, allowing velocity measurement) to produce color or gray-scale images of blood flow velocity and heart motion. Heart murmur—An abnormal sound originating from the heart, usually detected by stethoscope. Murmurs are often caused by abnormalities of the heart valves. Lupus—Also known as systemic lupus erythematosus, it is an autoimmune disease that may affect connective tissues and possibly the heart. Noninvasive—Pertaining to a diagnostic procedure or treatment that does not require the skin to be broken or a body cavity to be entered. Regurgitation—Backward flow of blood through a partially closed heart valve. Transducer—A device that converts electrical signals into ultrasound waves and ultrasound waves back into electrical impulses; also called a probe. Ultrasound—Sound waves at high frequencies beyond the level of human hearing; frequencies of approximately 2 to 10 megahertz are often used for diagnostic ultrasound imaging.

Resources BOOKS

Faculty Members of the Yale University School of Medicine. The Patient’s Book of Medical Tests. Boston, New York: Houghton Mifflin Company, 1997. PERIODICALS

Kosoff, George. “Basic Physics and Imaging Characteristics of Ultrasound.” World Journal of Surgery 24 (February 2000):134-142. Lee, Thomas H. and Charles A. Boucher. “Noninvasive tests in patients with stable coronary artery disease.” New England Journal of Medicine 344, no. 24 (June 14, 2001):1840-6. ORGANIZATIONS

American College of Cardiology. Heart House, 9111 Old Georgetown Road, Bethesda, MD 20814-1699. (800) 253-4636. . American Heart Association National Center. 7272 Greenville Avenue, Dallas, Texas 75231. (800) AHA-USA1. .

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flow speed. Most ultrasound scanners are equipped with videotape recorders or digital imaging/archiving devices to record the real-time examination, and with medical image printers to print out hard copies of still images.

Edema

American Institute of Ultrasound in Medicine. 14750 Sweitzer Lane, Suite 100, Laurel, MD 20707-5906. (301) 4984100. . American Registry of Diagnostic Medical Sonographers. 600 Jefferson Plaza, Suite 360, Rockville, MD 20852-1150. (800) 541-9754. . American Society of Echocardiography. 1500 Sunday Drive, Suite 102, Raleigh, NC 27607. (919) 787-5181. . OTHER

Barasch, Eddy. “Why Doctors Use Echocardiography.” .

Jennifer E. Sisk, M.A.

Echoencephalography see Ultrasonic encephalography

• mild edema that accompanies female hormone imbalance during the menstrual cycle • allergies in which the chemical histamine is released by the immune system, resulting in fluid leaking into the tissues, which creates swelling • injuries that do damage to capillaries, causing fluids to seep out into the tissue and not be reabsorbed by the damaged capillaries • hormonal imbalance caused by taking certain hormonal medications such as corticosteroids, high estrogen contraceptives, or androgens (male hormones) • beriberi (vitamin B1 deficiency) and dietary protein deficiency, often found with malnutrition • the venous congestion that accompanies cirrhosis of the liver and eventually decreases osmotic pressure • kidney failure, which eventually allows salts and water to be retained in the tissues rather than being excreted • nephritic syndrome, a condition in which large amounts of blood protein are lost and the blood loses its ability to draw fluid back out of the tissues

Edema Definition Edema is the medical term for swelling. It is an abnormal retention of fluid in body tissue.

Description Edema that is visible and localized often accompanies a soft-tissue injury, a sprain, or a fracture. However, it is also a component of generalized retention of fluid such as occurs in congestive heart failure (CHF). By weight, 60% of the human body is composed of water. In a remarkable process that is, under normal circumstances, a nearly perfect balance, water is exchanged between the blood and the tissues. As it circulates blood through the body, the pressure from the heart presses water out of capillaries and into body tissues. Osmotic (water-drawing) properties of certain blood proteins cause this process to reverse and fluid to be reabsorbed from the tissues back into the capillaries. To maintain equilibrium, the kidneys draw off excess fluid and salt, which are then excreted as part of the urine. When fluid is not released from the tissues, the result is edema.

Other than traumatic injuries or allergic reactions, swelling typically develops quite slowly and often goes unnoticed at its onset. It is estimated that fluid in the body can increase by 15% without being visible. Frequently it is manifested at that point only by an increase in weight. When edema does become apparent, it is usually found in the lower part of the body, in the feet, ankles, legs, and lower back. A finger pressed into edematous skin will leave an imprint that slowly disappears as the fluid again refills that tissue. Severe edematous conditions can cause fluid to gather in body cavities. Ascites, common with cirrhosis of the liver, is characterized by large amounts of fluid amassing in the peritoneal cavity of the abdomen. When liquid fills the pleural cavity adjacent to the lungs, it is termed pleural effusion; the liquid presses upon the lungs, causing difficulty in breathing. Pulmonary edema, which occurs when air sacs in the lungs become waterlogged, also causes respiratory complications.

Diagnosis

Causes and symptoms The causes and severity of edema cover a wide spectrum, including: 812

• congestive heart failure, a common condition, especially in the elderly, in which the heart functions less efficiently due to coronary artery disease, high blood pressure, or congenital or disease-caused abnormality in the heart

Diagnosis of the cause of edema is based upon physical examination and laboratory testing, plus a complete medical history. For patients with a history of CHF or

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Edema Gross lymphoedema in the arm of an elderly woman following radiotherapy treatment for breast cancer. (Photograph by Dr. P. Marazzi. National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.)

kidney disease, weights are frequently taken to watch for fluid retention.

Treatment The simple act of elevating the legs sometimes will reduce edema. However, the primary means of treating edema is in determining the cause of the fluid retention and attempting to remedy that. Giving antihypertensive drugs to people with high blood pressure will sometimes eliminate the edema. Often, though, the underlying cause of the edema is not easily remedied, such as in the case of CHF. Treatment of CHF may include: • limiting the salt in the diet • taking diuretics, medications that stimulate the kidneys to excrete the excess salt and water • taking angiotensin-converting enzyme inhibitors (ACE inhibitors) and vasodilator drugs, which cause blood vessels to expand and allow blood to flow easier, decreasing the work required of the heart • taking beta blockers, which improve the functioning of the left ventricle of the heart

• taking digitalis, a drug that expands the ability of the heart to pump blood through the body • having surgery to replace abnormal heart valves; in extreme cases, heart transplant may be needed

Prognosis The outcome for edema depends heavily upon its cause. The best outlook for the relief of edema is when the underlying condition is treatable.

Health care team roles Edema is most often noticed by either the patient, by a primary care physician or nurse-practitioner during a routine examination, or by nursing staff caring for the patient in a health care facility or at home. Both registered nurses (RNs) and licensed practical nurses (LPNs) must complete a prescribed course in nursing and pass a state examination. RNs typically have a degree in nursing. Good nursing care of the patient with edema will include observation, elevating the legs if the

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Resources

KEY TERMS

BOOKS

Capillaries—The term for any of the vessels that carry blood between the smallest arteries, or arterioles, and the smallest veins, venules. Congestive heart failure—A condition in which the heart cannot circulate enough blood to meet the needs of the body.

Weir, E. K. and Reeves, S. L., editors. Pulmonary Edema (American Heart Association Monograph Series). Futura, 1998. ORGANIZATIONS

American Heart Association. Congestive Heart Failure 2000. .

Joan M. Schonbeck

Corticosteroids—A group of medications that have similar properties to the corticosteroid hormones that the adrenal glands produce naturally.

EEG see Electroencephalography

Fracture—A partial break in a bone.

EEG unit see Electroencephalography unit

Histamine—A chemical present in cells that is released during an allergic reaction and that causes the symptoms of inflammation, including swelling.

EKG see Electrocardiography EKG unit see Electrocardiography unit Electrical stimulation see Electrotherapy

Osmosis—The passage of a fluid such as water through a sieve-like tissue called a semipermeable membrane from a less concentrated, or weaker, solution to a more concentrated, or stronger one. Soft-tissue injury—Damage to tissue that encloses bones or joints, such as muscles, tendons, or ligaments. Sprain—The tearing or stretching of ligaments holding bone ends together in a joint, usually caused by sudden, violent pulling.

Electroanalgesia Definition Electroanalgesia is a method of pain management that involves the introduction of a weak electric current at the site of pain.

Purpose lower extremities are swollen, monitoring vital signs and weights, and providing education about the cause of the edema. Clinical laboratory scientists have specialized training and must pass a state examination. They draw blood samples or do the necessary tests on fluids withdrawn from fluid-filled body cavities. Radiologic technologists have specialized training and must pass a state examination. They take x rays and other tests to visualize and monitor the course of disease processes that contribute to the edema.

Prevention Prevention of edema is dependent upon treatment of the basic reason for the edema. Losing weight, stopping smoking, and reducing stress can all aid in reducing blood pressure. Proper nutrition can help to maintain a healthy circulatory system. 814

The purpose of electroanalgesia is to reduce or eliminate pain.

Precautions There are few contraindications for the use of electroanalgesia. It should not be used with pregnant women or patients with pacemakers, heart problems, hearing aids or hearing-aid implants. The low-level current can often interfere with the working of pacemakers and hearing aids.

Description Electroanalgesia is a relatively new treatment method (since the late 1960s) to mitigate or eliminate pain. The concept, however, dates to the time of Aristotle, when patients who were experiencing pain were urged to stand in shallow water on top of electric fish (probably rays). It was not until 1965 when Dr. Ronald Melzack and Dr. Patrick Wall suggested the gate control theory that a legitimate scientific basis for electroanalgesia was

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found. This theory, and the endorphin release theory, became the foundational rationale of electroanalgesia. The gate control theory is the most widely held explanation for why electroanalgesia works. It says that by stimulating nerve sensors in the skin through electricity, a gate is closed in a part of the spinal cord, preventing pain messages from being carried to the brain. The patient has no perception of pain, although the message of pain at its site of origin still exists. The endorphin release theory, in contrast, says that electricity stimulates the production of endorphins and enkaphalins—natural, morphine-like protein peptides— in the brain. These peptides block pain messages like conventional medications do but without the side effects associated with introducing pain control with opioids, for instance. Electroanalgesia cannot create a physical dependency like pain medications can. Electroanalgesia may be used to relieve pain found in migraine and tension headaches, lower back, phantom limb syndrome, various forms of arthritis, cancer, angina pectoris, dysmenorrhea, posthepatic neuralgia, diabetic neuropathy, bursitis, sports injury, wounds, and after surgery. It can also be used to mitigate dental pain. There are two forms of electroanalgesia: transcutaneous electrical nerve stimulation (TENS) and percutaneous electrical nerve stimulation (PENS). Electrical dental analgesia (EDA) is a form of TENS therapy and has been approved by the FDA since 1996. TENS therapy uses one-inch (2.5 cm) diameter conductor electrode pads with adhesive backings. These electrode pads are placed on the skin near the site of the pain. The locus of the pain is the only reference for placement of these electrode pads. Studies have shown that endorphins are only released at pulse repetition rates (PPR)—or frequencies—of 8 Hz or less. Wider pulses spread the current over a greater area; most TENS units emit pulse widths ranging from 50–400 microseconds. Each TENS treatment will consist of the determined frequency (number of Hz) delivered for a certain length of time (perhaps one or two hours a day and sometimes more often at night) for a specified period of time (seven days; 14 days; 24 days). In low-frequency high-intensity stimulation, “quick probe treatments” may be delivered for 10 seconds each time; however, one “treatment” consists of several sets of five or six of these 10-second stimulations, and several “treatments” may be given consecutively. High-frequency TENS has been shown to suppress spontaneous and abnormal activity in a damaged nerve, and frequencies of 80 Hz or higher may be the treatment of choice in certain circumstances. PENS therapy is a combination of acupuncture and electroanalgesia. In PENS treatment, fine stainless steel

An electrical current is passed between the two transcutaneous electrical nerve stimulation (TENS) pads on the skin. The current blocks the nerve signaling pathway and prevents pain signals from reaching the brain and being felt. (Photograph by Sheila Terry. Science Source/Photo Researchers. Reproduced by permission.)

acupuncture probes (rather than electrode pads) are attached to bipolar leads coming from an electrical generator. These probes are inserted into the soft tissue like acupuncture needles and the electricity running through them stimulates the pain sensors within and just beneath the skin. As with TENS, the level and length of stimulation, number of treatments, and number of treatment days, is determined. (In one study an alternating frequency of 15 Hz and 30 Hz was administered for 30 minutes three times a week.) Also as in TENS, the probes are inserted at or near the locus of pain rather than at traditional acupuncture points. Because a patient’s skin is punctured, universal sterile procedures must be used. A similar therapy to PENS is electroacupuncture. In this treatment method probes carrying the electric current are inserted at traditional acupuncture sites rather than at the pain locus.

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patient will need repeated treatments which are often taken at home under the patient’s control.

KEY TERMS Dysmenorrhea—Painful menstruation. EDA—Electrical dental analgesia. Endorphins—Natural, morphine-like substances in the brain. Enkaphalins—Natural, morphine-like substances in the brain. PENS—Percutaneous electrical nerve stimulation. TENS—Transcutaneous electrical nerve stimulation.

EDA is administered through small pads placed inside the mouth or on the outside of the cheeks. The patient controls the amount of electroanalgesic administered and feels only a pins-and-needles sensation rather than pain. Once the dental procedure is over and the EDA pads are removed, the patient has no residual numbing as often occurs with the use of local anesthetics. Neither PENS nor electroacupuncture were approved by the FDA by 2001, and often are not covered by standard medical insurance. TENS and EDA have been approved. However, all of these electroanalgesic therapies should be used as a supplement to conventional treatment and should not be the primary or alternate course of treatment. Since pain is an indication of many serious conditions, pain should not be ignored or eliminated until the source of the disorder is found. Then, any number of pain management therapies including electroanalgesia may be used.

Preparation There is no preparation for this procedure, except to identify the location of the pain. For TENS treatment, the patient should be given three separate treatments in the practitioner’s office. An assessment of the patient’s pain level after treatment, measured against a standard scale, must be discussed and recorded. The patient can then be instructed in the use of the apparatus for self-treatment at home. Once several treatments are completed, the patient should be evaluated. If the pain has stopped or reached a plateau, treatment should cease. If the pain is gone, even after only one minute of treatment during the first treatment, treatment should cease for that day. Often the patient feels immediate relief; sometimes, it is delayed over a day or two. It is important to remember that with progressive pathologies such as cancer and degenerative diseases like arthritis, pain most likely will return. The 816

For PENS therapy, the patient receives treatment in the practitioner’s office. The practitioner must locate the areas of pain and place the steel probes into the soft tissue at specific points near the pain.

Aftercare With proper use, there is no need for aftercare from these procedures.

Complications The only complications with electroanalgesic therapies are the risk of infection in invasive techniques (probes) and continuation of therapy after pain is eliminated or has reached it’s lowest threshold. In these instances, continuing treatment may cause the pain to return.

Results Before treatments begin, the physician and patient must come to an agreement on the goals of therapy. Normal expected results are to diminish or eliminate pain; however, goals must be reasonable and workable according to the patient’s condition. Often, patients report more freedom of movement, better sleep patterns, and considerable reduction in the need to use oral analgesics following electroanalgesic therapies.

Health care team roles PENS therapists require special training in the use of the equipment and insertion of probes. There is an art to the therapy, much like the art associated with acupuncture. TENS training is less delicate but still necessary. Since this therapy is relatively new, many physicians have written a prescription for a TENS unit, or given a unit to a patient without proper patient education about the use of the unit and the necessity for determining the appropriate frequency to obtain the necessary results. By administering the first three treatments in the office, the practitioner can determine the appropriate settings for the patient and his or her particular type of pain before sending the unit home with the patient. Because dental patients control the amount of electronic anesthesia they receive, dentists and dental assistants must be trained in the use of the EDA units so they can instruct the patient how to dispense their individual level of pain suppression.

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Resources PERIODICALS

Author unspecified. “PENS for Relief of Low Back Pain.” Internal Medicine Alert 21, no. 3 (July 15, 1999): 100. Hamilton, Kendall, and Joan Raymond. “More Lasers, Less Lidocaine: Meet Dr. Friendly, D.D.S.” Newsweek 131, no. 15 (April 13, 1998): 14. Hamza, Mohamed A., Paul F. White, William F. Graig, ElSayed A. Ghoname, Hesham E. Ahmed, Timothy J. Proctor, Carl E. Noe, Akshay S. Vakharia, and Noor Gajraj. “Percutaneous Electrical Nerve Stimulation.” Diabetes Care 23, no. 13 (March 2000): 365. Somers, David L, and Martha F. Somers. “Treatment of Neuropathic Pain in a Patient with Diabetic Neuropathy Using Transcutaneous Electrical Nerve Stimulation Applied to the Skin of the Lumbar Region.” Physical Therapy 79, no. i8 (August 1999): 767.

Janie F. Franz

Electrocardiography Definition Electrocardiography is a commonly used, noninvasive procedure for recording electrical changes in the heart. The record, which is called an electrocardiogram (ECG or EKG), shows the series of waves that relate to the electrical impulses which occur during each beat of the heart. The results are printed on paper or displayed on a monitor. The waves in a normal record are named P, Q, R, S, and T, and follow in alphabetical order. The number of waves may vary, and other waves may be present.

Purpose Electrocardiography is a starting point for detecting many cardiac problems. It is used routinely in physical examinations and for monitoring a patient’s condition during and after surgery, as well as in the intensive care setting. It is the basic measurement used in exercise tolerance tests and is also used to evaluate symptoms such as chest pain, shortness of breath, and palpitations.

Precautions No special precautions are required; however, patients are asked not to eat for several hours before a stress test.

An EKG strip indicating atrial flutter. (Custom Medical Stock Photo. Reproduced by permission.)

Description The patient disrobes from the waist up, and electrodes (tiny wires in adhesive pads) are applied to specific sites on the arms, legs, and chest. When attached, these electrodes are called leads; three to twelve leads may be employed. Muscle movement may interfere with the recording, which lasts for several beats of the heart. In cases where rhythm disturbances are suspected to be infrequent, the patient may wear a small Holter monitor in order to record continuously over a 24-hour period. This is known as ambulatory monitoring. In 2001, the role of prehospital EKG in caring for patients with acute coronary syndromes was examined by the University of California San Diego School of Medicine, University of California San Diego Medical Center, San Diego, California, USA. Reported benefits of the prehospital 12-lead EKG include prompt initiation of reperfusion therapy (restoration of blood flow), and overall improved management and outcome of patients with acute myocardial infarction. Concerns remain regarding the best means of providing real-time field interpretation of the prehospital EKG and the potential for field time delay, triage concerns, and treatment of patients. Questions are raised regarding the overall clinical and cost benefit of expanding this resource.

Preparation The skin is cleaned to obtain good electrical contact at the electrode positions and, occasionally, shaving the chest may be necessary.

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KEY TERMS Ambulatory monitoring—ECG recording over a prolonged period during which the patient can move around. Arrhythmia or dysrhythmia—Abnormal rhythm in hearts that contract in an irregular way. ECG or EKG—A record of the waves which relate to the electrical impulses produced at each beat of the heart. Ectopic beat—Abnormal heart beat arising elsewhere than from the sinoatrial node. Electrodes—Tiny wires in adhesive pads that are applied to the body for ECG measurement. Fibrillation—Rapid, uncoordinated contractions of the upper or the lower chambers of the heart. Lead—Name given the electrode when it is attached to the skin. Reperfusion therapy—Restoration of blood flow to an organ or tissue; following a heart attack, quickly opening blocked arteries to reperfuse the heart muscles to minimize damage.

Aftercare To avoid skin irritation from the salty gel used to obtain good electrical contact, the skin should be thoroughly cleaned after removal of the electrodes.

Complications No complications from this procedure have been observed.

Results Normal results When the heart is operating normally, each part contracts in a specific order. Contraction of the muscle is triggered by an electrical impulse. These electrical impulses travel through specialized cells that form a conduction system. Following this pathway ensures that contractions will occur in a coordinated manner. When the presence of all waves is observed in the electrocardiogram, and these waves follow the order defined alphabetically, the heart is said to show a normal sinus rhythm, and impulses may be assumed to be following the regular conduction pathway. 818

The heart is described as showing arrhythmia or dysrhythmia when time intervals between waves, or the order or the number of waves do not fit this pattern. Other features that may be altered include the direction of wave deflection and wave widths. In the normal heart, electrical impulses—at a rate of 60–100 times per minute—originate in the sinus node. The sinus node is located in the first chamber of the heart, known as the right atrium, where blood reenters the heart after circulating through the body. After traveling down to the junction between the upper and lower chambers, the signal stimulates the atrioventricular node. From here, after a delay, it passes by specialized routes through the lower chambers or ventricles. In many disease states, the passage of the electrical impulse can be interrupted in a variety of ways, causing the heart to perform less efficiently. Abnormal results Special training is required for interpretation of the electrocardiogram. To summarize in the simplest manner the features used in interpretations, the P wave of the electrocardiogram is associated with the contraction of the atria. The QRS series of waves, or QRS complex, is associated with ventricular contraction, with the T wave coming after the contraction. Finally, the P-Q or P-R interval gives a value for the time taken for the electrical impulse to travel from the atria to the ventricle (normally less than 0.2 seconds). The cause of dysrhythmia is ectopic beats. Ectopic beats are premature heart beats that arise from a site other than the sinus node—commonly from the atria, atrioventricular node, or the ventricle. When these dysrhythmias are only occasional, they may produce no symptoms or simply a feeling that the heart is turning over or “flipflopping.” These occasional dysrhythmias are common in healthy people, but they also can be an indication of heart disease. The varied sources of dysrhythmias provide a wide range of alterations in the form of the electrocardiogram. Ectopic beats, which begin in the ventricle, display an abnormal QRS complex. This can indicate disease associated with insufficient blood supply to the heart muscle (myocardial ischemia). Multiple ectopic sites lead to rapid and uncoordinated contractions of the atria or ventricles. This condition is known as fibrillation. In atrial fibrillation, P waves are absent and the QRS complex appears at erratic intervals, or “irregularly irregular.” When the atrial impulse fails to reach the ventricle, a condition known as heart block results. If this is partial, the P-R interval (the time for the impulse to reach the ventricle) is prolonged. If complete, the ventricles beat

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the heart’s electrical activity and records it as a graphic tracing.

Purpose Health care team roles The electrocardiograph is conducted by a fully trained technologist and may be done in the cardiologist’s office, a testing facility, or at a hospital patient’s bedside. The technologist, or perhaps a nurse or nurse practitioner, will take the patients’ medical history, educate them about the procedure they are about to undergo, and help them relax. The results of the electrocardiograph will be interpreted by a qualified physician, usually a cardiologist. Resources BOOKS

Conover, Mary Boudreau. Understanding Electrocardiography. St Louis, MO: Mosby, 1996. PERIODICALS

Crawford, Michael H. “Practice Guidelines for Ambulatory Electrocardiography” Journal of The American College of Cardiology 34, no. 3 (1999). Article available at . Mangrum, J.M. “Tachyarrhythmias Associated With Acute Myocardial Infarction.” In Emergency Medicine Clinics of North America 19, no. 2 (May 2001): 385-95. Patel, R.J., G.M. Vilke, and T.C. Chan. “The Prehospital Electrocardiogram.” Journal of Emergency Medicine 21, no. 1 (July 2001): 35-9. ORGANIZATIONS

American Association of Critical-Care Nurses. 101 Columbia, Aliso Viejo, CA 92656-4109. (800) 899-2226. . The American College of Cardiology. Heart House, 9111 Old Georgetown Road, Bethesda, MD 20814-1699. (800) 253-4636. . American Heart Association. 7272 Greenville Ave., Dallas, TX 75231-4596. (800)242-1793. .

Maggie Boleyn, R.N., B.S.N.

Electrocardiography is used to detect heart-function abnormalities. It indirectly detects the heart’s electrical activity over time by measuring the electrical potential at the body’s surface. If the heart’s activity varies from normal, signs of this are seen in the surface electrical potentials. The electrocardiography unit produces a visual representation of the electrical potential, called an electrocardiogram (EKG or ECG), that is often recorded as a continuous line along a strip or special graph paper. When used to diagnose a heart ailment or check the effectiveness of a heart treatment, doctors, nurses, and other technicians read the strips, looking for telltale signs of various cardiac problems. Because the electrical activity of the heart is the basis for its workings, many heart problems show up in an EKG tracing. The machine can detect coronary artery disease, where the blood vessels carrying blood to the heart have hardened and no longer work effectively; a heart attack, either current or previous; and arrhythmias, a heart beating at an abnormal speed or rhythm.

Description The electrocardiography unit is a machine that transfers the very faint electrical signals of the heart into a visual representation of that activity. The unit commonly includes multiple electrodes and leads (often 12, but as few as three), a galvanometer to measure the electrical signal, an amplifier and filter to convert the faint electrical signal to one that can be seen, a computer screen or oscilloscope to display the output, and an ink-and-paper arrangement to produce hard copies of the signal. In the simplest arrangement, three pairs of bipolar electrodes, where one is positively charged and the other negatively charged, are placed on particular areas of the patient’s body. The electrodes are adhesive pads filled with conductive gel that are attached to the patient’s skin. Wires called leads connect the electrodes to the unit. The electrical signal measured by each group of electrodes is also called a Lead. When used to identify the signal, the term is often capitalized. Electrode placement

Electrocardiography unit Definition The electrocardiography unit, also called an electrocardiograph, is an apparatus that indirectly measures

The first pair of electrodes has the positive electrode placed on the left arm and the negative on the right arm; this produces Lead I. The second pair has the positive electrode placed on the left leg and the negative on the right arm; this produces Lead II. Lead III comes from the

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independently of the atria at about 40 beats per minute, and the QRS complex is mostly dissociated from the P wave.

Electrocardiography unit

third pair, where the positive electrode is placed on the left leg and the negative on the left arm. If an imaginary line is drawn between each pair of these electrodes it forms a triangle where the electrical difference (measured in volts) can be detected across each side of the figure. This arrangement is known as Einthoven’s triangle, after the inventor of the electrocardiograph. Finer measurements of electrical potential can be made if additional sets of electrodes are used. The first additional set of electrodes is known as the augmented connections because the signals are significantly weaker than Leads I–III and have to be additionally increased, or augmented, by the machine. These Leads are unipolar, meaning that they measure the electrical difference between that electrode and a group of others. Lead aVR measures the signal between the right arm (the positive electrode) and the average of the signals from the left arm and the left leg (two negative electrodes). Leads aVL and aVF are similarly arranged, with the left arm and the left leg having the positive electrode, respectively. All six of these limb leads measure electrical activity in the frontal plane of the heart, through the middle from top to bottom. A second additional set of electrodes are the unipolar chest Leads, also known collectively as the modified chest Lead (MCL). These Leads measure electrical potentials across the horizontal plane of the heart. They are unipolar, measuring the electrical difference between the positive electrode and the average of the collective signal from the right arm, left arm, and left leg. There are six leads placed across the chest, numbered V1–V6 from the patient’s right to left. V1 and V2 are put on either side of the sternum, in the fourth intercostal space (the space between the fourth and fifth rib). V4 is placed in the fifth intercostal space (between the fifth and sixth rib) on the line that divides the clavicle in half. V3 is placed halfway between V2 and V4. Both V5 and V6 are placed horizontal to V4, with V5 on the line that runs down the body from the inner armpit and V6 on the line that divides the armpit. Waveform production When the electrodes are placed as described, the electrical activity of the heart is printed in line patterns known as waves or waveforms. Waves come in two types—positive deflection (movement above the baseline or isoelectric line) and negative deflection (movement below the isoelectric line). Positive deflection is created when electrical activity flows toward the positive electrode; a negative deflection is produced when current flows away from the positive electrode (toward the negative). No heart activity produces a baseline or isoelectric 820

waveform. The isoelectric line is normally the beginning and ending of all waveforms. EKGs are recorded on strips of graph paper that are fed through the machine at a constant rate (25 mm/sec or 1 in/sec) to allow for easy estimates of beats per time period and for points of comparison between the isoelectric line and the wave. At this standard feed rate, each small block of the graph paper represents 0.04 seconds, each larger dark box (having a 5  5 group of small boxes within it) is 0.2 seconds. The normal heartbeat begins with an electrical impulse in the part of the heart with the fastest innate beat, the sinoatrial (SA) node. The electrical activity travels through the heart tissue, in a process known as depolarization, from the upper right of the organ to the lower left. Five major waves are produced: the P wave; the Q, R, and S waves (known as the QRS complex); and the T wave. The P wave results from the depolarization of both atria and is a rounded, upward deflection that usually lasts about 0.10 seconds (about two small blocks of graph paper). The PR interval (PRI) is the time needed for the electrical impulse to travel from the atria to the ventricles. Normally, this lasts about three to five small squares (or 0.12 to 0.20 seconds). The QRS complex has three recognized events and is the conduction of the impulse through the bundle of His and throughout the ventricles and atrial repolarization. The first downward deflection after PRI is the Q wave. It is followed by the largest deflection seen, the upward deflection of the R wave. Immediately after the R wave is a downward deflection called the S wave. The QRS complex generally happens in less than 0.12 seconds (three small squares) and all three waves are not always present, even in people with normal heart function. The time interval between ventricular depolarization and repolarization is known as the ST segment and it is normally isoelectric (baseline). The full cycle is completed with the T wave, which is the result of the ventricles repolarizing. This wave is often a slightly asymmetrical, rounded positive deflection that finishes at the baseline.

Operation To perform a resting EKG, the patient is placed on a table and the 12 electrodes are attached as described above. Sometimes, to improve connection, the areas of the skin where the electrodes will be placed are shaved or have conductive gel applied. Because some types of heart conditions are only evident when the heart is under stress, EKG analysis can also be performed with the patient on a treadmill.

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Electrocardiography unit

An electrocardiography unit uses electrodes to measure the electrical activity of the heart and translates it into a line on paper and a computer screen. Doctors, technicians, and others can use the line tracing to look for a number of cardiac problems. (Custom Medical Stock Photo. Reproduced by permission.)

Sometimes a patient’s symptoms occur at unpredictable intervals and are not exercise related. Heart activity can then be followed by a special portable EKG machine known as a Holter monitor. This EKG has three electrodes and stores the information for the monitoring period (generally from 24 hours to five days). Diagnosing heart problems In general, there are five aspects of the EKG that can reveal potential or present heart abnormalities: the heart rate, the heart rhythm, the P wave, the PR interval, and the QRS complex. The heart rate is determined by counting the number of QRS complexes (for ventricular rate) or P waves (for atrial rate) over six seconds (30 large boxes on the graph paper). Normal is between 60 to 100 beats per minute (bpm). Less than 60 bpm is considered a slow or bradycardic rate and greater than 100 bpm is considered a fast, or tachycardic rate. The heart rhythm, as revealed by the waveform pattern, can be classified either regular or irregular. To determine whether the ventricular rhythm is regular, a meas-

urement is made from R-to-R wave. A measurement from P-to-P wave determines the regularity of the atrial rhythm. If the interval is the same between waves, the rhythm is regular, if different, the rhythm is irregular. Numerous changes in the P wave, PR interval, and QRS complex are possible. They depend on the actual damage to the heart, such as those that accompany a heart attack (myocardial infarction or MI). First, as the heart becomes ischemic, or starved for oxygenated blood, repolarization of the ventricles becomes abnormal; this depresses the ST segment more than 1 mm below baseline and the T wave becomes inverted. Next, if there is no treatment of the ischemia, actual damage to the heart tissue will occur. This can be seen through an elevation of the ST segment of more than 1 mm above baseline. If the heart attack actually occurs (one or more coronary arteries becomes completely blocked), at least three possible indications can appear on the EKG. First, if it hasn’t already happened, the ST segment will become elevated and the T wave will invert. Changes in the ST segment will remain for up to four weeks after the attack and the T wave could remain inverted for a year. If all

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changing graph paper and ink, maintaining the electrodes and leads, and monitoring the machine for malfunction.

KEY TERMS Bipolar—A type of lead having one positive and one negative electrode Bradycardia—An abnormally slow heartbeat. Bundle of His—A group of special heart muscle fibers that transmit electrical impluses to the ventricles, beginning the contractions that pump blood into the aorta and pulmonary artery. Depolarization—The movement of an electrical charge through nerve or muscle tissue, changing its voltage. Einthoven’s triangle—The triangular arrangement of EKG electrodes on a patient, generally including the right arm, the left arm, and the left leg. Electrode—The point of connection between the EKG unit and the patient. Isoelectric—The baseline electrical level of the body. Lead—A conductive connector between the electrode and the EKG unit or the signal derived from a group of electrodes. Repolarization—The process in which a nerve or muscle cell returns to its normal electrical state after depolarization. Tachycardia—An abnormally fast heartbeat. Unipolar—A type of lead having one positive and multiple negative electrodes.

three of the layers of the heart have been affected by the attack, the Q wave will deflect more negatively. To be considered abnormal, the Q wave must be at least 0.04 seconds long (one small box) and be at least 25% of the height of the R wave. The Q wave will start large and shrink some over time, but will always be present after a so-called “Q-Wave” MI. It is important to rule out artifacts as the cause of a patient’s abnormal EKG. Common artifacts are patient movement, loose or defective electrodes, clammy skin, excessive chest hair, or improper grounding. The rule of thumb is to look to the patient and treat their distress, not what is showing on the monitor.

Maintenance

Specially trained assistants known as electrocardiograph technicians often operate and maintain EKG machines in larger hospital and cardiology group practice settings. In small settings, nurses and medical assistants perform the test. A doctor usually does the final interpretation of the tracing.

Training Many persons learn how to use an EKG machine through on the job training. However, training programs are available through outsourcing companies or in vocational and community colleges. The usual length of these college-based programs is 465 hours (four months). Program content includes classroom instruction in anatomy and physiology with an emphasis on the cardiac and vascular system, medical terminology, cardiovascular medications, patient care techniques, interpretation of cardiac rhythm, medical ethics, and a clinical practicum. Resources BOOKS

Beasley, Brenda M. Understanding EKGs: A Practical Approach. Upper Saddle River, NJ: Prentice Hall, 1999. Dubin, Dale. Rapid Interpretation of EKGs: An Interactive Course. Tampa, FL: Cover Publishing Company, 2000. PERIODICALS

Miracle, Vickie A. “Making Sense of the 12 Lead ECG.” Nursing 99 (July 1999): 34. ORGANIZATIONS

Alliance for Cardiovascular Professionals. 910 Charles Street, Fredericksburg, Virginia 22401. 540-370-0102. OTHER

Yanowitz, Frank G. “The Standard 12 Lead ECG.” The Alan E. Lindsay ECG Learning Center in Cyberspace. (April 5, 2001).

Michelle L. Johnson, M.S., J.D.

Electroencephalography Definition

Electrocardiograph technicians are in charge of maintenance of EKG machines. Their tasks include 822

Health care team roles

Electroencephalography, or EEG, is a neurological test that involves attaching electrodes to the head of a

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Purpose The EEG, also known as a brain wave test, is a key tool in the diagnosis and management of epilepsy and other seizure disorders. It is also used to assist in the diagnosis of brain damage and diseases such as strokes, tumors, encephalitis, mental retardation, and sleep disorders. The results of the test can distinguish psychiatric conditions (schizophrenia, paranoia, depression) from degenerative mental disorders such as Alzheimer’s and Parkinson’s diseases. An EEG may also be used to monitor brain activity during surgery to assess the effects of anesthesia, and also to determine brain death.

Precautions An EEG is generally performed as one test in a series of neurological evaluations. Rarely does the EEG form the sole basis for a particular diagnosis.

Description Before the EEG begins, a nurse or technologist attaches approximately 16 to 21 electrodes to the patient’s scalp with a conductive, washable paste. The electrodes are placed on the head in a standard pattern based on head circumference measurements. Depending on the purpose for the EEG, implantable, or invasive, electrodes are occasionally used. Implantable electrodes include sphenoidal electrodes, which are fine wires inserted under the zygomatic arch, or cheekbone; Depth electrodes, or subdural strip electrodes, are surgically implanted into the brain and are used to localize a seizure focus in preparation for epilepsy surgery. Once in place, even implantable electrodes do not cause pain. The electrodes are used to measure the electrical activity in various regions of the brain over the course of the test period. For the test, the patient lies on a bed, padded table, or comfortable chair and is asked to relax and remain still while measurements are being taken. An EEG usually takes no more than one hour, although long-term monitoring is often used for diagnosis of seizure disorders. During the test procedure, the patient may be asked to breathe slowly or quickly. Visual stimuli such as flashing lights or a patterned board may be used to stimulate certain types of brain activity. Throughout the procedure, the electroencephalography unit makes a continuous graphic record of the patient’s brain activity, or brainwaves, on a long strip of recording paper or computer screen. This graphic record is called an electroen-

cephalogram. If the display is computerized, the test may be called a digital EEG, or dEEG. The sleep EEG uses the same equipment and procedures as a regular EEG. Patients undergoing a sleep EEG are encouraged to fall asleep completely rather than just relax. They are typically provided a bed and a quiet room conducive to sleep. A sleep EEG lasts up to three hours, or up to eight or nine hours if it is a night sleep. In an ambulatory EEG, patients are hooked up to a portable cassette recorder. They then go about normal activities and take normal rest and sleep for a period of up to 24 hours. During this period, the patient and patient’s family record any symptoms or abnormal behaviors, which can later be correlated with the EEG to see if they represent seizures. An extension of the EEG technique, called quantitative EEG (qEEG), involves manipulating the EEG signals with a computer using the fast Fourier transform algorithm. The result is then best displayed using a colored gray scale transposed onto a schematic map of the head to form a topographic image. The brain map produced in this technique is a vivid illustration of electrical activity of the brain. This technique also has the ability to compare the similarity of the signals between different electrodes, a measurement known as spectral coherence. Studies have shown the value of this measurement in diagnosis of Alzheimer’s and mild closed head injuries. The technique can also identify areas of the brain having abnormally slow activity when the data are both mapped and compared to known normal values. The result is then known as a statistical or significance probability map (SPM). This allows differentiation between early dementia (increased slowing) or otherwise uncomplicated depression (no slowing).

Preparation Full instructions should be given to EEG patients when they schedule their test. Typically, individuals on medications that affect the central nervous system, such as anticonvulsants, stimulants, or antidepressants, are told to discontinue their prescription for a short time prior to the test (usually one to two days). However, such requests should be cleared with the treating physician. Patients may be asked to avoid food and beverages that contain caffeine, a central nervous system stimulant. Patients may also be asked to arrive for the test with clean hair free of spray or other styling products to make attachment of the electrodes easier. Patients undergoing a sleep EEG may be asked to remain awake the night before their test. They may be given a sedative prior to the test to induce sleep.

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patient to measure and record electrical activity in the brain over time.

Electroencephalography This woman is undergoing an electroencephalogram (EEG) to diagnose Alzheimer’s disease. On the computer screen at the right are the colored scans of the electrical activity in her brain. Alzheimer’s patients show a specific abnormality in their EEGs. (Photograph by Catherine Pouedras, Photo Researchers, Inc. Reproduced by permission.)

Aftercare If the patient has suspended regular medication for the test, the EEG nurse or technician should advise the patient when to begin taking it again.

Complications Being off medication for one to two days may trigger seizures. Certain procedures used during EEG may trigger seizures in patients with epilepsy. Those procedures include flashing lights and deep breathing. If the EEG is being used as a diagnostic for epilepsy (i.e., to determine the type of seizures an individual is experiencing) this may be a desired effect, although the patient needs to be monitored closely so that the seizure can be aborted if necessary. This type of test is known as an ictal EEG.

Results In reading and interpreting brainwave patterns, a neurologist or other physician will evaluate the type of brainwaves and the symmetry, location, and consistency 824

of brainwave patterns. Brainwave response to certain stimuli presented during the EEG test (such as flashing lights or noise) will also be evaluated. The four basic types of brainwaves are alpha, beta, theta, and delta, with the type distinguished by frequency. Alpha waves fall between 8 and 13 Hertz (Hz), beta are above 13 Hz, theta between 4 and 7 Hz, and delta are less than 4 Hz. Alpha waves are usually the dominant posterior rhythm in older children and adults when awake and relaxed. Beta waves are normal in sleep, particularly for infants and young children. Theta waves are normally found during drowsiness and sleep and are normal in wakefulness in children, while delta waves are the most prominent feature of the sleeping EEG. Spikes and sharp waves are generally abnormal; however, they are common in the EEG of normal newborns. Different types of brain waves are seen as abnormal only in the context of the location of the waves, the patient’s age, and the patient’s conscious state. Overall, pathology typically increases slow activity, such as theta or delta waves, but decreases fast activity, such as alpha and beta waves.

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Some abnormal beta rhythms include frontal beta waves that are induced by sedative drugs. Marked asymmetry in beta rhythms suggests a structural lesion on the side lacking the beta waves. Beta waves are also commonly measured over skull lesions, such as fractures or burr holes, activity known as a breach rhythm. Usually seen only during sleep in adults, the presence of theta waves in the temporal region of awake, older adults has been tentatively correlated with vascular disease. Another rhythm normal in sleep, delta rhythms, may be recorded in the awake state over localized regions of cerebral damage. Intermittent delta rhythms are also an indication of damage of the relays between the deep gray matter and the cortex of the brain. In adults, this intermittent activity is found in the frontal region while in children it is in the occipital region. The EEG readings of patients with epilepsy or other seizure disorders display bursts, or spikes, of electrical activity. In focal epilepsy, spikes are restricted to one hemisphere of the brain. If spikes are generalized to both hemispheres of the brain, multifocal epilepsy may be present. The EEG can be used to localize the region of the brain where the abnormal electrical activity is occurring. This is most easily done using a recording method, or montage, called an average reference montage. With this type of recording, the signal from each electrode is compared to the average signal from all the electrodes. The negative amplitude (upward movement, by convention) of the spike is observed for the different channels, or inputs, from the various electrodes. The negative deflection will be greatest as recorded by the electrode that is closest in location to the origin of the abnormal activity. The spike will be present but of reduced amplitude as the electrodes move farther away from the site producing the spike. Electrodes distant from the site will not record the spike occurrence. A final kind of abnormal result is the presence of slower-than-normal wave activity, which can either be a slow background rhythm or slow waves superimposed on a normal background. A posterior dominant rhythm of 7 Hz or less in an adult is abnormal and consistent with encephalopathy. In contrast, localized theta or delta

KEY TERMS Encephalitis—Inflammation of the brain. Fast Fourier transfer—A digital processing of the recorded signal resulting in a decomposition of its frequency components. Ictal EEG—An EEG done to determine the type of seizure characteristic of a person’s disorder. During this EEG, seizure medicine may be discontinued in an attempt to induce as seizure during the testing period. Sphenoidal electrodes—Fine wire electrodes that are implanted under the cheek bones, used to measure temporal seizures. Subdural electrodes—Strip electrodes that are placed under dura mater (the outermost, toughest, and most fibrous of the three membranes (meninges) covering the brain and spinal cord); used to locate foci of epileptic seizures prior to epilepsy surgery. Zygomatic arch—Cheekbone; a quadrilateral bone forming the prominence of the cheek; articulates with the frontal, sphenoid, and maxillary, and temporal bone.

rhythms found in conjunction with normal background rhythms suggest a structural lesion.

Health care team roles Electroencephalograpy is often performed by specially trained electrodiagnostic technologists. Training for such a position can be on the job but often involves study at a one to two-year college or vocational program. A typical program would include: • human anatomy and physiology • neurology and neuroanatomy • neurophysiology • medical terminology • computer technology and instrumentation Certification of electrodiagnostic technologists specializing in electroencephalography and the related area of evoked potentials is available through the American Board of Registration of Electroencephalographic and Evoked Potential Technologists. A physician such as neurologist, neurosurgeon, or internist does the final review and diagnosis based on the

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Not all decrease in wave activity is abnormal, however. The normal alpha waves seen in the posterior region of the brain are suppressed merely if the patient is tense. Sometimes the addition of a wave is abnormal. For example, alpha rhythms seen in a newborn can signify seizure activity. Finally, the area where the rhythm is seen can be telling. The alpha coma is characterized by alpha rhythms produced diffusely, that is, by all regions of the brain.

Electroencephalography unit

results of the EEG. The doctor can be present for the testing or may review saved tracings. Other health care professionals, such as nurses, aid in patient education concerning this procedure. Resources BOOKS

Misulis, Karl E. “Electroencephalography Basics.” In Essentials of Clinical Neurophysiology Boston: Butterworth-Heinemann. 1997. U.S. Department of Labor, Bureau of Labor Statistics. “Electroneurodiagnostic Technologist” In Occupational Outlook Handbook 2000-01 Edition. Washington, DC: The Bureau. 2000. PERIODICALS

Shpritz, D.W. “Neurodiagnostic Studies.” Nursing Clinics of North America 34 (September 1999): 593-606. Wallace, Brian, et al. “A History and Review of Quantitative Electroencephalograpy in Traumatic Brain Injury.” Journal of Head Trauma Rehabilitation 16 (April 2001): 165. ORGANIZATIONS

The EEG unit includes a set of electrodes, amplifiers and filters, and a recording unit. Generally, surface electrodes are used for EEG recording, using 21 electrodes placed according to standard positions on the subject’s scalp. However, implantable electrodes are also used for particular applications. For example, sphenoidal electrodes, which are fine wires inserted under the zygomatic arch, or cheekbone, are used when a patient is suspected of having temporal seizures. Depth electrodes, or subdural strip electrodes, are surgically implanted into the brain and are used to localize a seizure focus in preparation for epilepsy surgery. The electrical signals from the brain are very weak, typically on the order of 10 to 100 microvolts. As a result, the amplifiers are used to increase the signal for display or recording, and the filters are used to eliminate artifacts and electrical noise produced by other sources such as muscles. The recording unit can be a paper and pen arrangement, although digital display is now standard.

Operation

American Board of Registration of Electroencephalographic and Evoked Potential Technologists. P.O. Box 916633, Longwood, FL 32791-6633. (407) 788-6308. . OTHER

Duffy, Frank H. “Introduction to EEG and qEEG.” Clinical Neurophysiology Laboratory. Boston Children’s Hospital. (June 17, 2001).

Michelle L. Johnson, M.S., J.D.

Electroencephalography unit Definition The electroencephalography (EEG) unit is used to record the electrical output of the brain to produce a record called an electroencephalogram.

Purpose Measurements taken by an electroencephalography unit are used to diagnose and classify disorders of the brain including seizures, encephalopathy, encephalitis, some psychiatric diseases, and brain death. 826

Description

The first step in performing an EEG is correct placement of the electrodes. The International Federation of Societies for EEG and Clinical Neurophysiology (IFSECN) has established a system of placement called the 10-20 Electrode Placement System. This system places the 21 electrodes at scalp positions that are at 10% and 20% of the head circumference, thus taking into account differing head size. Each electrode position is identified with a key letter that specifies the region of the brain and a positioning number. For example, prefrontal electrodes are labeled Fp, while central electrodes are C and occipital are O. Even numbers are on the right side of the head and odd numbers are on the left, with lower numbers anterior and higher numbers posterior. Midline electrodes are labeled with a “z” rather than a number. Finding the exact point of placement of the electrodes involves measuring distances from various head landmarks, such as the nasion (the midpoint of the frontonasal suture) and the inion (the posterior occipital protuberance), and from one preauricular point (in front of the ear) to another. The electrodes are placed either at the intersection of these lines or at 10% or 20% of these various measurements about the head. For example, Cz is placed at the intersection of the nasion-inion line and the line that connects the preauricular points, while Fpz is 10% above the nasion and Oz is 10% above the inion. Standardized placement ensures that the results will be consistent and more easily compared to normal tracings.

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Electroencephalography unit

The electrodes taped to this boy’s scalp monitor his brain activity (brain waves) by detecting the electric impulses generated by the brain’s activity. (Science Source/Photo Researchers. Reproduced by permission.)

Electrodes are applied to the head using electrode gel, which acts as a malleable extension of the electrode. Often, precleaning the scalp electrode site with a waterbased, conductive agent is suggested for good contact. For long-term recordings, electrodes can be even more securely anchored using collodion (a mixture of pyroxylin, ether, and alcohol). This mixture quickly dries to a clear, tenacious film using compressed air.

Biological calibration involves sending one channel (the signal from a pair of electrodes) through all the amplifier inputs and comparing the signal with the displayed response; the two are adjusted until they are identical. Other adjustments that may be needed are damping the pen and setting sensitivity, which is usually started at 7 microvolts per millimeter and adjusted depending on the amplitude of the signal.

Once the electrodes are attached, the machine is calibrated in two phases, through square-wave calibration and biological calibration. Square-wave calibration involves sending a standard pulse and altering the time constants of the low-frequency filters (LFF) and high-frequency filters (HFF) such that the resulting wave has the desired square-wave shape. Standard settings for LFF is 1 Hertz (Hz) and for HFF is 70 Hz. (Frequencies below 1 Hz can be artifacts due to sweat or other sources. The EEG typically does not have components above 70 Hz.)

Generally, recordings are taken for at least 20 minutes to obtain an artifact-free result. The EEG unit records a series of waveforms that are not intrinsically normal or abnormal but must be interpreted based on the patient’s age, awake-sleep state, and topographical location of the wave. Information can also be determined by looking for missing right-to-left symmetry. Further tests include the response of the subject to stimulation (such as visual flash or hyperventilation) or state changes (drowsiness or sleep). Although not always abnormal, the

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Training

KEY TERMS Collodion—A syrupy liquid used to attach EEG electrodes to the scalp for long-term monitoring. Inion—The bump of bone located on the back lower part of the head, a landmark used for measurements in the placement of EEG electrodes. Nasion—The midpoint of where the frontal and nasal bones of the skull meet, a landmark used for measurements in the placement of EEG electrodes. Sphenoidal electrodes—Fine wire electrodes that are implanted under the cheek bones, used to measure temporal seizures.

Training to run an EEG unit can be on the job but often involves study at a one- to two-year college or vocational program. The formal postsecondary school training in this area is offered by hospitals and two-year community colleges. As of 2001, there were 12 formal programs approved by the Joint Review Committee on Education in Electroneurodiagnostic Technology of the Commission on Accreditation of Allied Health Programs (CAAHP). The programs usually last from one to two years with laboratory training, and often include the following classroom courses: • human anatomy and physiology • neurology and neuroanatomy

Subdural electrodes—Strip electrodes that are placed under dura mater (the outermost, toughest, and most fibrous of the three membranes [meninges] covering the brain and spinal cord); used to locate foci of epileptic seizures prior to epilepsy surgery.

• neurophysiology

Zygomatic arch—Cheekbone; a quadrilateral bone forming the prominence of the cheek; articulates with the frontal, sphenoid, and maxillary, and temporal bone.

BOOKS

presence of spikes and sharp waves can also aid in the diagnosis of the patient.

• medical terminology • computer technology and instrumentation Resources Misulis, Karl E. “Technical Requirements for Electroencephalography” In Essentials of Clinical Neurophysiology Boston: Butterworth-Heinemann. 1997. U.S. Department of Labor, Bureau of Labor Statistics. “Electroneurodiagnostic Technologist” In Occupational Outlook Handbook 2000-01 Edition. Washington, DC: The Bureau. 2000. PERIODICALS

Maintenance Electrodiagnostic technologists are in charge of daily maintenance of EEG machines. The tasks include changing graph paper and ink (if necessary), maintaining the electrodes and leads, and monitoring the machine for malfunction. Repair often involves outsource contracts or the use of personnel from the hospital engineering department.

Health care team roles The EEG unit is often run by specially trained electrodiagnostic technologists, although sometimes it is done by nurses or other allied health professionals. Nurses are often used to supervise patients during extended EEG monitoring for seizure study. Neurologists and other physicians make the final diagnosis based on the results of EEG studies. 828

Shpritz, D.W. “Neurodiagnostic Studies” Nursing Clinics of North America 34 (September 1999): 593-606. Wallace, Brian, et al. “A History and Review of Quantitative Electroencephalograpy in Traumatic Brain Injury.” Journal of Head Trauma Rehabilitation 16 (April 2001): 165. ORGANIZATIONS

The American Society of Electroneurodiagnostic Technologists. 204 West 7th Street, Carroll, IA 514012317. (712) 792-2978. . American Society of Neurophysical Monitoring. 7510 Clairemont Mesa Blvd., Suite 100, San Diego, CA 92111. (800) 479-7979. . OTHER

Bates, Timothy “Electroencephalography and Event Related Potentials.” In Brain Imaging Macquarie University. Sydney, Australia. 2001. (June 16, 2001).

Michelle L. Johnson, M.S., J.D.

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Definition Electrolytes are positively or negatively charged particles that readily dissolve in water. The predominant positively charged electrolytes in the body are sodium, potassium, calcium, and magnesium, while negatively charged electrolytes include chloride, phosphates, and bicarbonate.

Description Salts are chemical compounds composed of atoms that carry electrical charges. Dissolved in water, the components in a salt exist as ions. Collectively, these ions are called electrolytes. Electrolytes are dissolved in different compartments of body water including: the serum portion of the blood, inside the cells (intracellular), and outside the cells (extracellular). The concentration of these electrolytes varies considerably from one area to the other. However, there is a narrow concentration limit of these electrolytes that the body must maintain within each of these compartments. The body transfers electrolytes intracellularly and extracellularly as required to maintain electrolyte balance. Electrolyte concentrations of extracellular fluid can be measured in a blood sample.

Function The kidney filters electrolytes in blood and maintains a balance by excreting the proper amount in the urine. An electrolyte’s concentration in a solution of dissolved salts can be measured as the amount in milliequivalents (mEq) per volume of solution (i.e. per liter). Electrolytes have many functions and roles in the body. The concentration of electrolytes must be maintained within a narrow range within the blood, otherwise deleterious physiological effects may occur. Several of the most important electrolytes will be discussed individually in the following sections.

Role in human health Sodium balance The largest portion of the body’s sodium reserves is in the extracellular fluid, which includes the blood plasma. The kidneys function to control the sodium excreted in the urine; thus the level of sodium in the body is relatively constant on a daily basis. An upset between intake of sodium (through dietary consumption) and output (in urine and sweat) creates an imbalance, affecting the total amount of sodium in the body. Variations in the total

amount of sodium are related to the volume of water found in the blood. A decrease in the overall amount of sodium does not necessarily cause the concentration of blood sodium to fall, but may decrease blood volume. Low blood volume, such as occurs with hemorrhage, signals the kidneys to conserve both water and sodium through stimulation of aldosteone. This helps to return blood volume toward normal, by increasing the amount of extracellular fluid sodium. With an excess of sodium in the body, blood volume may rise. This increase in blood volume initiates an accumulation of extracellular fluid, often in the feet, ankles, and lower legs, resulting in a condition known as edema. The body maintains extracellular fluid sodium concentration homeostasis through the thirst mechanism and regulation of kidney water excretion by antidiuretic hormone (ADH). When sodium concentration—as opposed to too much total sodium—is too high, thirst prompts water intake and, at the same time, the ADH signals to the kidneys to conserve water, by increasing water absorption by the organs and passing less water into the excretory system.

Common disorders The electrolytes involved in disorders of salt balance are most often sodium, potassium, calcium, phosphate, and magnesium. The concentration of blood chloride is usually similar to the blood sodium concentration, while bicarbonate is related to acid-base balance. Sodium balance HYPONATREMIA. The most common electrolyte disorder is hyponatremia, it occurs in almost 1% of all patients hospital admissions. Hyponatremia is a condition characterized by low sodium in the blood, below 136 mEq per liter of blood. In hyponatremia, the sodium concentration has been overdiluted by an excess of water or a loss of sodium in the body. Hyponatremia may result from intraveous administration of water to hospitalized patients or can also occur with small amounts of water consumption in those who have impaired kidney function and several other conditions such as liver cirrhosis, heart failure, underactive adrenal glands as with Addison’s disease, and various antidiuretic hormone disorders. Over 50% of hospitalized patients with AIDS have been reported to suffer from hyponatremia. Lethargy and confusion are typically the first signs of hyponatremia. Muscle twitching and seizures may occur as hyponatremia progresses with risk of stupor, coma, and death in the most severe cases. Due to the effects on the central nervous system, mortality risk is considerably greater in

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acute hyponatremia than in chronic hyponatremia. Other factors that reduce survival are the presence of debilitating illnesses such as alcoholism, hepatic cirrhosis, heart failure, or malignancy. HYPERNATREMIA. Hypernatremia is a condition

characterized by a high concentration of sodium in the blood, above 145 mEq per liter of blood. There is too little water compared to the amount of sodium in the blood, often resulting from a low intake of water. Profuse sweating, vomiting, fever, diarrhea, or abnormal kidney function may result in hypernatremia. With age, there is a decreased thirst sensation; therefore, hypernatremia is more common in the elderly. Aging reduces the kidney’s ability to concentrate urine; therefore, taking diuretics may further exacerbate hypernatremia. Hypernatremia is very serious, particularly in the elderly. Almost half of individuals hospitalized for this condition will die, although it is often secondary to other illnesses.

Parathyroid hormone and calcitonin regulate the amount of calcium in the blood. There are four parathyroid glands located in the neck that increase secretion of parathyroid hormone when the calcium concentration falls too low. Consequently, the gastrointestinal tract is stimulated to absorb more calcium from the blood, release a greater amount of calcium from the bones, and to excrete less in the urine. At the same time, parathyroid hormone induces the kidneys to activate vitamin D which increases uptake of calcium from the gastrointestinal tract. Calcitonin is a hormone produced by the parathyroid, thyroid, and thymus glands. It acts to lower the calcium concentration in blood by enhancing uptake of calcium into the bones.

Common disorders

Major causes of high sodium levels include: • limited water access, particularly when combined with any other cause • excess water loss due to profuse sweating, vomiting, fever, diarrhea • disorders of other electrolytes • head trauma or neurosurgery involving the pituitary gland • use of drugs including lithium, diuretics, demeclocycline • diabetes insipidus • sickle cell disease As with hyponatremia, the major symptoms of hypernatremia result from brain dysfunction. Severe hypernatremia can lead to confusion, muscle twitching, seizures, coma, and death. The effects on central nervous system hyperosmolality and the seriousness of the underlying illness lead to greater mortality in acute hypernatremia compared to chronic hypernatremia.

Calcium balance HYPOCALCEMIA. A low calcium blood level is referred to as hypocalcemia. Calcium is measured in extracellular fluid in two forms: total calcium concentration and ionized calcium concentration. About 50% of the total calcium concentration in the plasma exists in ionized form, which is the form that has biological activity at cell membranes. The remainder is either bound to the plasma proteins (about 40%) or complexed in the non-ionized form (about 10%) with anions such as phosphate. In hypocalcemia the total calcium concentration falls below 2.4 mEq/l in the extracellular fluid. Hypocalcemia can result from a number of problems. The most common reason is an inability to mobilize calcium from the bones or a chronic loss of calcium in the urine.

Other causes of hypocalcemia include: • low blood albumin concentration • hypoparathyroidism

Calcium balance The body’s calcium reserves are predominately stored in bones, although the blood and cells also contain calcium. Calcium is necessary for proper functioning in many areas of the body including nerve conduction, muscle contraction, and enzyme functions. Like other electrolytes, the body controls calcium levels both in blood and cells. Calcium from the diet is absorbed in the gastrointestinal tract while the excess is excreted in the urine. A minimum of 500-1000 mg of calcium is required daily in order to maintain a normal calcium concentration. Normally, the body transfers calcium to the blood from the bones to maintain calcium homeostasis. If cal830

cium intake falls short of the requirement, too much calcium will be mobilized from the bones, weakening the bones and contributing to osteoporosis.

• vitamin D deficiency • renal failure • magnesium depletion • acute pancreatitis • hypoproteinemia • septic shock • hyperphosphatemia • drugs such as those used to treat hypercalcemia; anticonvulsants • excessive secretion of calcitonin

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HYPERCALCEMIA. A high calcium blood level is

referred to as hypercalcemia. The blood calcium concentration rises above 10.5 mg per deciliter of blood. Increased gastrointestinal tract absorption or increased intake of calcium may lead to hypercalcemia. Individuals who consume large amounts of calcium or who take calcium containing antacids can develop hypercalcemia. Absorption of calcium can be increased in the gastrointestinal tract with an overdose of vitamin D. The condition is usually first discovered during routine blood tests because hypercalcemia often doesn’t have any symptoms at all. If symptoms occur, typically the earliest are: • constipation • loss of appetite • nausea and vomiting • abdominal pain Large amounts of urine may be produced by the kidneys. Due to excess urine production, fluid levels in the body decrease and may lead to dehydration. Severe hypercalcemia may induce brain dysfunction symptoms such as weakness, confusion, emotional disturbances, delirium, hallucinations, and coma. Additionally, abnormal heart rhythms and death may follow. In chronic conditions, kidney stones or calcium-containing crystals that can cause permanent damage may form. Potassium balance Potassium plays a major part in cell metabolism and in nerve and muscle cell function. Most of the body’s potassium is located intracellularly, not extracellularly or in the blood. Too high or low concentrations of blood potassium can have serious effects such as an abnormal heart rhythm or cardiac arrest. The potassium concentration in the blood is maintained with the assistance of intracellular potassium. Like other electrolytes, potassium balance is regulated through gastrointestinal tract absorption of potassium in food, and by excretion of potassium by the kidneys. Some potassium is lost in the gastrointestinal tract, but most is lost through urine.

Some conditions and drugs influence potassium balance intracellularly, also affecting blood concentrations. High sources of dietary potassium are: • bananas • melons • tomatoes • oranges • potatoes and sweet potatoes • green leafy vegetables such as spinach, turnip greens, collard greens, kale etc. • most peas and beans • potassium supplements • salt substitutes (potassium chloride)

Common disorders Potassium balance HYPOKALEMIA. A low potassium blood level is

referred to as hypokalemia. It occurs when the blood potassium concentration falls below 3.8 mEq per liter of blood. Hypokalemia is common in the elderly. Common causes include decreased intake of potassium during acute illness, nausea and vomiting, and treatment with thiazide or loop diuretics. About 20% of patients receiving thiazide diuretics develop hypokalemia, which is dose-dependent but usually mild. Since several foods contain potassium, hypokalemia is not typically due to a low intake. It is usually due to malfunction of the kidneys or abnormal loss through the gastrointestinal tract. People with heart disease have to be especially cautious regarding hypokalemia (particularly when taking digoxin), because they are prone to developing abnormal heart rhythms. Potassium usually can be replaced relatively easily by eating foods rich in potassium or by taking potassium salts (potassium chloride) orally. HYPERKALEMIA. A high level of potassium in the

blood is referred to as hyperkalemia. It occurs when the blood potassium concentration rises above 5.0 mEq per liter of blood. Hyperkalemia typically results when the kidneys excrete too little potassium. Some common causes are due to: • drugs which block potassium excretion (angiotensin converting enzyme [ACE] inhibitors, triamterene, and spironolactone) • Addison’s disease • kidney failure

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An abnormally low blood calcium concentration may not produce any symptoms. However, over time the lack of calcium in the blood can affect brain function causing neurologic symptoms such as memory loss, depression, confusion, delirium, and hallucinations. Once calcium levels return to normal, these symptoms are reversible. Very severe cases of hypocalcemia can lead to seizures, tetany, and muscle spasms in the throat, affecting breathing. The condition is usually first discovered during routine blood tests because often there are no symptoms evident.

Electrolyte balance

deficiencies may lead to muscular weakness, twitches, and paralysis.

KEY TERMS Antidiuretic hormone (ADH)—A hormone that encourages the kidney to retain water when body stores are low. Bicarbonate—A salt of carbonic acid produced by neutralizing a hydrogen ion. Dehydration—A deficit of body water that results when the output of water exceeds intake. Diuretic—An agent or drug that eliminates excessive water in the body by increasing the flow of urine. Edema—An increase in blood volume instigates an accumulation of extracellular fluid resulting in swelling of the feet, ankles, and lower legs. Electrolyte—A substance such as an acid, bases, or salt. An electrolyte’s water solution will conduct an electric current and ionizes. Acids, bases, and salts are electrolytes.

Magnesium balance Magnesium influences the function of many enzymes. Dietary intake is essential to maintain normal levels. The body’s magnesium stores are predominately found in bone with little appearing in the blood. Excess is excreted in the urine or stool.

Common disorders Magnesium balance HYPOMAGNESEMIA. A low level of magnesium in the blood is known as hypomagnesemia. The level of magnesium in the blood decreases below 1.6 mEq per liter of blood. Metabolic and nutritional disorders are usually the culprit of hypomagnesemia, most often when intake of magnesium is decreased during starvation or intestinal malabsorption compounded with greater kidney excretion.

Symptoms of hypomagnesemia may include:

Homeostasis—An organism’s regulation of body processes to maintain internal equilibrium in temperature and fluid content.

• loss of appetite

Hypoparathyroidism—A condition resulting from an absence or deficiency in parathyroid hormone. It is characterized by hypocalcemia and hyperphosphatemia.

• sleepiness

Tetany—A general stiffening and spasms of the muscles that can occur in severe cases of hypocalcemia.

• a sudden release of potassium from the cell reservoir in such cases as when a large amount of muscle tissue is destroyed (crush injury) or severe burn injuries, or an overdose on crack cocaine The kidney’s ability to excrete potassium is overwhelmed due to a rapid influx into the blood, resulting in life-threatening hyperkalemia. Generally, hyperkalemia is more dangerous than hypokalemia. A blood potassium concentration above 5.5 mEq/liter starts to affect the electrical conducting system in the heart. If the concentration continues to increase, the heart rhythm becomes irregular which may cause the heart to eventually stop. Mild hyperkalemia often may not produce any symptoms. Symptoms may include an irregular heartbeat that could be experienced as palpitations. Hyperkalemia is typically first diagnosed during a routine blood test or by examining changes in an electrocardiogram. Severe 832

• nausea and vomiting • weakness • personality changes • muscle spasms • tremors When hypomagnesemia occurs along with hypocalcemia, the magnesium must be replaced before successful treatment of the calcium disorder. HYPERMAGNESEMIA. A high level of magnesium in the blood is referred to as hypermagnesemia. The blood magnesium concentration rises above 2.1 mEq per liter of blood. Hypermagnesemia is quite rare unless people with kidney failure are given magnesium salts or consume magnesium-containing drugs such as antacids. Weakness, low blood pressure, and impaired breathing can result and the heart may stop if the concentration increases above 12 to 15 mEq per liter.

Phosphate regulation Phosphorus occurs in the body almost solely in the form of phosphate, which is composed of one phosphorus and four oxygen atoms. Phosphate is found mostly in bones, although a significant amount is found intracellularly. It plays a role in energy metabolism and acid-base regulation, and it is used as a building block for DNA. Phosphate is excreted in the urine and stool.

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• spinach, turnip greens, collard greens, kale, and other green leafy vegetables • milk and dairy products • nuts • chocolate • many peas and beans • dark-colored soft drinks Resources BOOKS

Shaw, Patricia, ed. Fluids & Electrolytes Made Incredibly Easy! Springhouse, PA: Springhouse Publishing Co., 1997. Speakman, Elizabeth and Weldy, Norma Jean. Body Fluids and Electrolytes 8th ed. London: Mosby Incorporated, 2001. Workman, M. Linda Introduction to Fluids, Electrolytes and Acid-Base Balance London: W B Saunders Co., 2001. PERIODICALS

Beck, L.H. “The aging kidney. Defending a delicate balance of fluid and electrolytes.” Geriatrics 55, no. 4 (2000): 2628, 31-32. Sawka, M. N., and S. J. Montain. “Fluid and electrolyte supplementation for exercise heat stress.” American Journal of Clinical Nutrition 72, 2 suppl., (2000): 564S-572S. OTHER

Nr-Space, et al. Fluids & Electrolytes CD-ROM. Delmar Publishers, 2001.

Crystal Heather Kaczkowski, MSc.

Electrolyte tests Definition Electrolytes are positively and negatively charged ions that are found within the cells and extracellular fluids, including blood plasma. A test for electrolytes includes the measurement of sodium, potassium, chloride, and bicarbonate. These ions are needed to assess renal, endocrine, and acid-base function, and are components of both renal function and comprehensive metabolic biochemistry profiles. Other important electrolytes routinely measured in serum or plasma include calcium and phosphorus. These are measured together because they are both affected by bone and parathyroid diseases, and often move in opposing directions. Magnesium is another electrolyte that is routinely measured. Like calci-

um, it will cause tetany (uncontrolled muscle contractions) when levels are too low in the extracellular fluids.

Purpose Tests that measure the concentration of electrolytes are needed for both the diagnosis and management of renal, endocrine, acid-base, water balance, and many other conditions. Their importance lies in part with the serious consequences that relatively small changes that diseases or abnormal conditions may cause. For example, the reference range for potassium is 3.6-5.0 mmol/L. Potassium is often a STAT test because values below 3.0 mmol/L are associated with arrhythmia, tachycardia, and cardiac arrest, and values above 6.0 mmol/L are associated with bradycardia and heart failure. Abnormal potassium cannot be treated without reference to bicarbonate, which is a measure of the buffering capacity of the plasma. Sodium bicarbonate and dissolved carbon dioxide act together to resist changes in blood pH. For example, an increased plasma bicarbonate indicates a condition called metabolic alkalosis, which results in too high a blood pH. This may cause hydrogen ions to shift from the cells into the extracellular fluid in exchange for potassium. As potassium moves into the cells, the plasma concentration falls. The low plasma potassium, called hypokalemia, should not be treated by administration of potassium, but by identifying and eliminating the cause of the alkalosis. Administration of potassium would result in hyperkalemia when the acid-base disturbance is corrected. Sodium measurements are very useful in differentiating the cause of an abnormal potassium. Conditions such as the overuse of diuretics (drugs that promote lower blood pressure) often result in low levels of both sodium and potassium. On the other hand, Cushing’s disease (adrenocortical hyperfunction) and Addison’s disease (adrenocortical insufficiency) drive the sodium and potassium in opposing directions. Chloride levels will follow sodium levels with the exception of acid-base imbalances, in which chloride may move in the opposing direction of bicarbonate. In essence, diagnosis and management of a patient with an electrolyte disturbance is best served by measuring all four electrolytes.

Description Sodium is the principal extracellular cation and potassium the principal intracellular cation. Sodium levels are directly related to the osmotic pressure of the plasma. In fact, since an anion is always associated with sodium (usually chloride or bicarbonate), the plasma osmolality (total dissolved solute concentration) can be estimated using the following formula: Osmolality in

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Sources of phosphate include:

Electrolyte tests

milliosmoles per killigram water = serum sodium x 2 + Glucose/18 + BUN/2.8 where BUN is the blood urea nitrogen concentration. Since water will often follow sodium by diffusion, loss of sodium leads to dehydration and retention of sodium leads to edema. Conditions that promote increased sodium, called hypernatremia, do so without promoting an equivalent gain in water. Such conditons include diabetes insipidus (water loss by the kidneys), Cushing’s disease, and hyperaldosteronism (increased sodium reabsorption). Many other conditions, such as congestive heart failure, cirrhosis of the liver, and renal disease result in renal retention of sodium, but an equivalent amount of water is retained as well. This results in a condition called total body sodium excess, which causes hypertension and edema, but not an elevated serum sodium concentration. Low serum sodium, called hyponatremia, may result from Addison’s disease, excessive diuretic therapy, the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), burns, diarrhea, vomiting, and cystic fibrosis. In fact, the diagnosis of cystic fibrosis is made by demonstrating an elevated chloride concentration (greater than 60 mmol/L) in sweat. Potassium is the electrolyte used as a hallmark sign of renal failure. Like sodium, potassium is freely filtered by the kidney. However, in the distal tubule sodium is reabsorbed and potassium is secreted. In renal failure, the combination of decreased filtration and decreased secretion combine to cause increased plasma potassium. Hyperkalemia is the most significant and life-threatening complication of renal failure. Hyperkalemia is also commonly caused by hemolytic anemia (release from hemolysed red blood cells), diabetes insipidus, Addison’s disease, and digitalis toxicity. Frequent causes of low serum potassium include alkalosis, diarrhea and vomiting, excessive use of thiazide diuretics, Cushing’s disease, intravenous fluid administration, and SIADH. Calcium and phosphorus are measured together because they are both likely to be abnormal in bone and parathyroid disease states. Parathyroid hormone causes resorption of these minerals from bone. However, it promotes intestinal absorption and renal reabsorption of calcium and renal excretion of phosphorus. In hyperparathyroidism, serum calcium will be increased and phosphorus will be decreased. In hypoparathyroidism and renal disease, serum calcium will be low but phosphorus will be high. In vitamin D dependent rickets (VDDR), both calcium and phosphorus will be low; however, calcium is normal while phosphorus is low in vitamin D resistant rickets (VDRR). Differential diagnosis of an abnormal serum calcium is aided by the measurement of ionized calcium (i.e., calcium not bound by protein). Approximately 45% of the calcium in blood is bound to protein, 45% is ionized, and 10% is complexed to anions 834

in the form of undissociated salts. Only the ionized calcium is physiologically active, and the level of ionized calcium is regulated by parathyroid hormone (PTH) via negative feedback (high ionized calcium inhibits secretion of PTH). While hypoparathyroidism, VDDR, renal failure, hypoalbuminemia, hypovitaminosis D, and other conditions may cause low total calcium, only hypoparathyroidism (and alkalosis) will result in low ionized calcium. Conversely, while hyperparathyroidism, malignancies (those that secrete parathyroid hormone-related protein), multiple myeloma, antacids, hyperproteinemia, dehydration, and hypervitaminosis D cause an elevated total calcium, only hyperparathyroidism, malignancy, and acidosis cause an elevated ionized calcium. Serum magnesium levels may be increased by hemolytic anemia, renal failure, Addison’s disease, hyperparathyroidism, and magnesium based antacids. Chronic alcoholism is the most common cause of a low serum magnesium owing to poor nutrition. Serum magnesium is also decreased in diarrhea, hypoparathyroidism, pancreatitis, Cushing’s disease, and with excessive diuretic use. Low magnesium can be caused by a number of antibiotics and other drugs and by administration of intravenous solutions. Magnesium is needed for secretion of parathyroid hormone, and therefore, a low serum magnesium can induce hypocalcemia. Magnesium deficiency is very common in regions where the water supply does not contain sufficient magnesium salts. Magnesium acts as a calcium channel blocker, and when cellular magnesium is low, high intracellular calcium results. This leads to hypertension, tachycardia, and tetany. Unfortunately serum total magnesium levels do not correlate well with intracellular magnesium levels, and serum measurement is not very sensitive for detecting chronic deficiency because of compensatory contributions from bone. Ionized magnesium levels are better correlated with intracellular levels because the ionized form can move freely between the cells and extracellular fluids.

Measurement of electrolytes Electrolytes are measured by a process known as potentiometry. This method measures the voltage that develops between the inner and outer surfaces of an ion selective electrode. The electrode (membrane) is made of a material that is selectively permeable to the ion being measured. For example, sodium electrodes are made from a special glass formula that selectively binds sodium ions. The inside of the electrode is filled with a fluid containing sodium ions, and the outside of the glass membrane is immersed in the sample. A potential difference develops across the glass membrane that is dependent upon the difference in sodium concentration (activity) on the inside

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Total calcium and magnesium are usually measured by colorimetric procedures called dye binding assays. Calcium is displaced from protein by dilute acid or alkali and reacts with a dye (arsenazo III or cresolphthalein complexone) to form a colored product. When crosolphthalein complexone is used, 8-hydroxyquinoline is added to bind magnesium which also reacts with this dye. Magnesium is commonly measured by its reaction with a dye called Calmagite. A calcium chelator such as EGTA is added to prevent interference from calcium. Both calcium and magnesium may be measured by atomic absorption spectrophotometry. This procedure is more complex than colorimetric methods, but is also more accurate. Phosphorus is measured by reacting it with ammonium molybdate at an acid pH. The rate of ammonium phosphomolybdate formation is measured at 340 nm and is proportional to the inorganic phosphorus concentration (mono- and dihydrogen phosphate) of the sample.

Precautions Electrolyte tests are performed on heparinized whole blood, heparinized plasma, or serum, usually collected from a vein or capillary. Venipuncture is performed observing universal precautions for the prevention of transmission of bloodborne pathogens. In order to prevent hemoconcentration, the tourniquet must be removed from the arm as soon as the blood starts to flow. The needle gauge must be sufficient in width to prevent mechanical damage to the red blood cells that will result in hemolysis (rupture of the membrane of the red blood cells). Because the concentration of potassium, magne-

sium, and phosphorus within red blood cells is much higher than in the plasma, hemolysis will cause falsely elevated results for these analytes. Plasma is often preferred over serum for measuring potassium, as the process of blood clotting can release potassium from platelets. Heparin is the only anticoagulant acceptable for electrolyte testing, as all other anticoagulants act by chelating calcium. Samples for ionized calcium should be collected using balanced (low) heparin which has a concentration of 20 U/mL. Higher concentrations bind calcium. Ionized calcium samples should be transported and stored on ice under anaerobic conditions and measured within 30 minutes of sample collection as pH changes in the blood will affect the ionized calcium. Special procedures are followed when collecting a sweat sample for electrolyte analysis. This procedure, called pilocarpine iontophoresis, uses electric current applied to the arm of the patient (usually an infant) in order to convey the pilocarpine to the sweat glands where it will stimulate sweating. Care must be taken to ensure that the collection device (macroduct tubing or gauze) does not become contaminated and that the patient’s parent or guardian understands the need for the electrical equipment employed.

Preparation Usually no special preparation is necessary by the patient. Samples for calcium and phosphorus and for magnesium should be collected following an eight-hour fast.

Aftercare Discomfort or bruising may occur at the puncture site, or the person may feel dizzy or faint. Pressure to the puncture site until the bleeding stops reduces bruising. Applying warm packs to the puncture site relieves discomfort.

Complications Minor temporary discomfort may occur with any blood test, but there are no complications specific to electrolyte testing.

Results Electrolyte concentrations are similar whether measured in serum or plasma. Values are expressed as mmol/L for sodium, potassium, chloride, and bicarbonate. Magnesium results are often reported as milliequivalents per liter (meq/L) or in mg/dL. Total calcium is usually reported in mg/dL and ionized calcium in mmol/L. Since

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and outside of the glass membrane. This potential is measured by comparing it to the potential of a reference electrode. Since the potential of the reference electrode is held constant, the difference in voltage between the two electrodes is attributed to the concentration of sodium in the sample. Ion selective membranes can be made from materials other than glass. For example, the antibiotic valinomycin is used to make potassium-measuring electrodes. Neutral carrier ionophores selective for lithium, calcium, and magnesium are also used for measurement of these substances in laboratory medicine. Ion selective electrodes can be used to measure whole blood, serum, or plasma since they respond to the electrolyte activity in the water phase of the sample only. One important aspect of electrolyte measurement is an artifact (erroneous result) called pseudohyponatremia that may occur when sodium is measured using a diluted blood sample. This happens when the plasma contains excessively high lipids or protein. These solids displace plasma water from the specimen, resulting in a low measurement of sodium that does not occur with an undiluted sample.

Electromyography

Resources

KEY TERMS Tetany—Inappropriately spasms.

sustained

BOOKS

muscle

severe electrolyte disturbances can be associated with life-threatening consequences such as heart failure, shock, coma, or tetany alert values are used to warn physicians of impending crisis. Typical reference ranges and alert values are cited below.

Fishbach, Frances Talaska. A Manual of Laboratory and Diagnostic Tests, 6th ed. Philadelphia: Lippincott, 2000 pp. 338-355. Tierney, Lawrence M., Stephen J. McPhee, and Maxine A. Papadakis. Current Medical Diagnosis and Treatment 2001. 40th ed. New York: Lange Medical Books/McGraw-Hill, 2001. pp.869-884. OTHER

MedLine Plus. “Electrolytes.” 2001. .

• Serum or plasma sodium: 135-145 mmol/L Alert levels: less than 120 mmol/L and greater than 160 mmol/L. • Serum potassium: 3.6-5.4 mmol/L (plasma, 3.65.0mmol/L); Alert levels: less than 3.0 mmol/L and greater than 6.0 mmol/L. • Serum or plasma chloride: 98 - 108 mmol/L.

Electromyography Definition

• Sweat chloride: 4-60 mmol/L. • Serum or plasma bicarbonate: 18-24 mmol/L (as total carbon dioxide, 22-26 mmol/L); Alert levels: less than 10 mmol/L and greater than 40 mmol/L. • Serum calcium: 8.5-10.5 mg/dL (2.0-2.5 mmol/L); Alert levels: less than 6.0 mg/dL and greater than 13.0 mg/dL. • Ionized calcium: 1.0-1.3 mmol/L. • Serum inorganic phosphorus: 2.3-4.7 mg/dL (children, 4.0 - 7.0 mg/dL); Alert level: less than 1.0 mg/dL. • Serum magnesium: 1.8-3.0 mg/dL (1.2-2.0 meq/L or 0.5-1.0 mmol/L). • Iionized magnesium: 0.53-0.67 mmol/L. • Osmolality (calculated) 280-300 mosm/Kg.

Health care team roles A physician orders electrolyte tests and interprets the results. A nurse or phlebotomist usually collects the blood sample by venipuncture. In some instances the nurse performs the electrolyte test using a point-of-care instrument consisting of a single use cartridge of ionselective electrodes and a battery operated analyzer. In the laboratory setting electrolyte tests are performed by clinical laboratory scientists/medical technologists or clinical laboratory technicians/medical laboratory technicians. Nurses, nurse practitioners, and physician assistants may find themselves involved in explaining results to patients and advising them regarding treatment or dietary correction of any problems identified. 836

Erika J. Norris

Electromyography (EMG) is used to detect, process, and record electrical muscle activity in order to aid in the diagnosis of neuromuscular disease.

Purpose EMG is performed most often to help diagnose different neuromuscular diseases causing weakness. EMG can determine whether a particular muscle is responding appropriately to stimulation, and whether a muscle remains inactive when not stimulated. Although EMG is a test of the motor system, it may help identify abnormalities of nerves or spinal nerve roots that may be associated with pain or numbness. EMG may also be useful in determining the cause of certain symptoms, including numbness, atrophy, stiffness, fasciculation, cramps, deformity, and spasticity. EMG results can help determine whether symptoms are due to a muscle disease or a neurological disorder, and, when combined with clinical findings, usually allow a confident diagnosis. EMG can help diagnose many muscle and nerve disorders, including: • muscular dystrophy • congenital, mitochondrial, and metabolic myopathies • myotonias • compression neuropathies, such as carpal tunnel syndrome • peripheral neuropathies • radiculopathies

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Electromyography

• nerve lesions • amyotrophic lateral sclerosis (Lou Gehrig’s disease) • polio • spinal muscular atrophy • Guillain-Barré syndrome • ataxias • myasthenias EMG is also used in gait and motion analysis. EMG is performed dynamically (while the patient executes certain movements) to evaluate gait and movement problems. Clinical applications include assessment of patients with cerebral palsy, traumatic brain injury, spinal cord injury, motor neuron lesions, evaluation of athletic injuries, examination of gait abnormalities associated with stroke, and preoperative assessment of patients having corrective orthopedic surgery. EMG is one of the tests administered during polysomnography studies. EMG is used to measure neuromuscular activity during sleep to aid in the diagnosis of sleep disorders, such as restless legs syndrome.

Precautions No special precautions are needed for this test. Patients with a history of bleeding disorders should consult with their treating physician before the test. If a muscle biopsy is planned as part of the diagnostic workup, EMG should not be performed at the same site, as it may affect the microscopic appearance of the muscle.

Description EMG is performed using an electromyography unit consisting of electrodes and a computer-based recording unit. Electrodes are used to detect electrical activity generated by stimulating the muscles. Muscles are stimulated by signals from nerve cells called motor neurons. This stimulation causes electrical activity in the muscle, which in turn causes contraction. This electrical activity is detected by the EMG electrode and recorded by the electromyography unit computer. During an EMG test, the electrode is applied or inserted into the muscle to be tested. Surface, needle, and fine-wire electrodes may be used, depending on the type of stimulation required. Needle electrodes may cause some discomfort, similar to that of an injection. Recordings are made while the muscle is at rest, and then during the contraction. The person performing the test may move the limb being tested, and direct the patient to move it with various levels of force. The electrode may be

Electromyography is often used in biofeedback therapy and in diagnosing neuromuscular disorders. (Custom Medical Stock Photo. Reproduced by permission.)

repositioned for further recording. Other muscles may be tested as well. A typical session lasts from 30–60 minutes. A slightly different test, the nerve conduction velocity test, is often performed at the same time with the same equipment. In this test, stimulating and recording electrodes are used, and small electrical shocks are applied to measure the ability of the nerve to conduct electrical signals. This test may cause mild tingling and discomfort similar to a mild shock from static electricity. Evoked potentials may also be performed for additional diagnostic information. Nerve conduction velocity and evoked potential testing are especially helpful when pain or sensory complaints are more prominent than weakness.

Preparation No special preparation is needed. The doctor supervising and interpreting the test should be given information about the symptoms, medical conditions, suspected diagnosis, neuroimaging studies, and other test results.

Aftercare Minor pain and bleeding may continue for several hours after the test. The muscle may be tender for a day or two. Pain-relieving medications may be prescribed to relieve muscle soreness.

Complications There are no significant risks to this test, other than those associated with any needle insertion (pain, bleeding, bruising, or infection).

Results The end result of an EMG test is an electromyogram, a computer display or printout of EMG waveforms.

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KEY TERMS Fasciculation—Small involuntary muscle contractions visible under the skin. Motor neurons—Nerve cells that transmit signals from the brain or spinal cord to the muscles. Motor unit action potentials—Spikes of electrical activity recorded during an EMG that reflect the number of motor units (motor neurons and the muscle fibers they transmit signals to) activated when the patient voluntarily contracts a muscle. Nerve conduction velocity testing (NCV)—A type of test that uses an electromyography unit to evaluate electrical potentials from peripheral nerves by measuring how long it takes for a nerve impulse to reach a muscle after stimulation with an electrical current. Polysomnography—A group of studies (that includes EMG) performed while a patient is sleeping to diagnosis sleep disorders.

rologist or physiatrist conducts the EMG study. Some physical therapists trained in EMG may also administer the test. A trained electroneurodiagnostic technologist prepares patients for EMG testing, obtains medical histories, maintains equipment, records and calculates test results, and assists with testing. Resources PERIODICALS

American Association of Electrodiagnostic Medicine. “Who is Qualified to Practice Electrodiagnostic Medicine?” Position Statement. Muscle Nerve 22, Supplement 8 (May 1999): S263-S265. . Haig, Andrew J., Jeffery B. Gelblum, James J. Rechtien, and Andrew J. Gitter. “Technology Review: The Use of Surface EMG in the Diagnosis and Treatment of Nerve and Muscle Disorders.” Muscle Nerve 22, Supplement 8 (May 1999): S239-S242. Rechtien, James J., Jeffery B. Gelblum, Andrew J. Haig, and Andrew J. Gitter. “Technology Review: Dynamic Electromyography in Gait and Motion Analysis.” Muscle Nerve 22, Supplement 8 (May 1999): S233-S238. ORGANIZATIONS

There should be some brief EMG activity during needle insertion. This activity may be increased in diseases of the nerve and decreased in long-standing muscle disorders where muscle tissue is replaced by fibrous tissue or fat. Muscle tissue normally shows no EMG activity when at rest or when moved passively by the examiner. When the patient actively contracts the muscle, spikes (motor unit action potentials) should appear on the recording screen, reflecting the electrical activity within. As the muscle is contracted more forcefully, more groups of muscle fibers are recruited or activated, causing more EMG activity. The interpretation of EMG results is not a simple matter, requiring analysis of the onset, duration, amplitude, and other characteristics of the spike patterns.

American Academy of Neurology. 1080 Montreal Avenue, St. Paul, MN 55116. (651) 695-1940. . American Association of Electrodiagnostic Medicine. 421 First Avenue SW, Suite 300, East Rochester, MN 55902. (507) 288-0100. . American Society of Electroneurodiagnostic Technologists. 204 West 7th Street, Carroll, IA 51401-2317. (712) 7922978. . OTHER

Jabre, Joe F. “Needle Examination.” EMG Manual: The Electronic Version. . Jabre, Joe F. “Nerve Conduction Studies.” EMG Manual: The Electronic Version. .

Electrical activity at rest is abnormal; the particular pattern of firing may indicate denervation (for example, a nerve lesion, radiculopathy, or lower motor neuron degeneration), myotonia, or inflammatory myopathy. Decreases in the amplitude and duration of spikes are associated with muscle diseases, which also show faster recruitment of other muscle fibers to compensate for weakness. Recruitment is reduced in nerve disorders.

Jennifer E. Sisk, M.A.

Electroneurodiagnostic technology Definition

Health care team roles EMG is performed by clinicians with special training in electroneurodiagnostic medicine. Usually, a neu838

The practice of electroneurodiagnostic (END) technology involves the use of devices such as an electroencephalograph (EEG) unit to evaluate the function of a

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Description END technologists use various devices to aid in the evaluation and examination of the nervous system. These devices receive and record the electrical impulses produced by the brain or other parts of the nervous system. Characteristic changes in the nerve impulses can determine whether a patient has an organic basis for a mental or behavioral problem, such as a tumor or Alzheimer’s disease. The devices can also diagnose particular diseases such as neuropathies (disease of the nerves), myopathies (diseases of the muscles), epilepsy, or stroke. These tests can evaluate the condition of critically ill patients, to determine the presence of cerebral death, and help assess the probability of a patient recovering from a coma. One test commonly performed by END technologists is electroencephalography. This test monitors the electrical output of the brain, displays it on a monitor, and records it on a strip of paper for review by a neurologist or other physician. The technologist is often responsible for taking the patient’s medical history, helping the patient relax by explaining the procedure of the test, and applying the electrodes to the designated sites on the person’s head. To get medically useful results, the technologist must use the appropriate machine settings and correct for interference coming from sources other than the patient’s brain. EEG studies can be done within the hospital or clinic, or on an ambulatory basis (typically over a 24hour period) while the patient continues everyday activities. For ambulatory monitoring, the technologist is responsible for patient education and answering questions, correctly attaching the electrodes, and upon completion of the monitoring, removing the recorder and obtaining a read-out. Technologists review the entire read-out and select specific areas for examination by the neurologist. Another specialized form of EEG is long term monitoring for epilepsy (LTME). This procedure is used to accurately diagnose the type of seizure occurring in patients who are not responding to medication. In many cases, the patient is admitted to the hospital for 24-houra-day monitoring so that seizures can be captured on videotape and EEG recording. Monitoring is performed to diagnose seizure type or to localize seizure onset within the brain for possible epilepsy surgery. Technologists place electrodes on the patient’s head, as in a standard EEG, and behavior is recorded by closed circuit camera

onto videotape. Additional wire electrodes are sometimes inserted near the ear by the neurologist; these electrodes provide better information about temporal lobe seizures than scalp electrodes alone. Antiepileptic drugs are generally reduced or tapered off before or during the admission, which can last from one to several days. Often a family member is asked to stay with the patient, so that a seizure alarm can be triggered. A second group of procedures commonly performed by END technologists are evoked potential tests. These tests separate the response of the patient’s nervous system to various specific stimuli from background activity and record the results. The technologist is responsible for attaching electrodes to the patient and setting the machine to deliver the desired type and intensity of stimulus. Often the technologist performs a step-wise increase in the intensity of the stimulus and records the response of the patient’s brain, spinal nerves, or sensory receptors to the input. Commonly, the stimulus is magnetic or electrical in origin, although visual and auditory stimuli are also used. Technologists also perform nerve conduction studies (NCS), in which an electrode is placed over a peripheral nerve and a muscle, and a record is made of the response of the muscle to stimulation of the nerve. Various nerve and muscular problems have characteristic responses to repeated or increased intensity of stimuli, and the results from these tests can aid in differential diagnosis. NCS is often performed in conjunction with an electromyogram. That test is performed by a physician, although the END technologist can help with the process. Another test often performed by END technologists is electronystagmography (ENG). ENG records the electrical potentials of the eyes. This test is used to document induced or spontaneous nystagmus, involuntary rapid movements of the eyeballs. An ENG can differentiate between inner ear and central nervous system causation for complaints of dizziness. A subset of END technologists specialize in administering sleep disorder studies and are called polysomnographic technologists. During these testing procedures, called polysomnography, technologists monitor brain waves, respiration, and heart activity. They must understand the usual effect upon each of these systems with the different stages of sleep. Often a detailed report of each evening’s readings is required for review by the supervising physician, separating the recorded results into the various sleep stages. As the primary medical personnel present for overnight monitoring, they may also have additional responsibilities in overseeing the well-being of patients staying at the sleep center.

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patient’s brain or other component of the nervous system in order to diagnose tumors, strokes, epilepsy, sleep problems, and other nervous disorders.

Electroneurodiagnostic technology

KEY TERMS Electroencephalography—The recording of changes in electric output in various areas of the brain using electrodes commonly placed on the scalp. Electronystagmography—The electronic recording of eye movements that can document induced or spontaneous nystagmus. Evoked potential testing—The electronic measurement of sensory and physical responses to specific stimuli. Nerve conduction studies—The electronic measurement of the muscular response to the stimulation of a particular nerve. Polysomnography—The recording of changes in electric output of the brain, in respiration, and in heartbeat during sleep.

Technologists’ duties may also include clerical and technical work such as scheduling appointments, ordering supplies, and maintaining equipment. More senior END technologists may have administrative duties such as supervising and training less experienced technicians, managing the END laboratory, arranging work schedules, and keeping records. Additionally, some more senior personnel can perform research or have teaching duties.

Work settings END technology is practiced in general hospitals, psychiatric hospitals, health maintenance organizations (HMOs), and in private clinic or office practice settings. In the hospital, technologists may work within a dedicated room in the neurology department, may push portable equipment to the patient’s bedside, or may do both kinds of monitoring. One area of rapid growth is the performance of intraoperative neurodiagnostic tests by END technologists. These tests require an understanding of the effects of anesthesia on brain activity and involve working in the operating room with general and neurosurgeons.

Education and training

The formal postsecondary school training in this area is offered by hospitals and two-year community colleges. As of 2001, there were 12 formal programs approved by the Joint Review Committee on Education in Electroneurodiagnostic Technology of the Commission on Accreditation of Allied Health Programs (CAAHP). The programs usually last from one to two years with laboratory training, and often include the following classroom courses: • human anatomy and physiology • neurology and neuroanatomy • neurophysiology • medical terminology • computer technology and instrumentation Training to perform polysonograms may require a full year of additional study.

Advanced education and training The American Board of Registration of Electroencephalographic and Evoked Potential Technologists awards the credentials of Registered EEG Technologist, Registered Evoked Potential Technologist, and Certification in Neurophysiologic Intraoperative Monitoring (CNIM). These certifications are based on the successful completion of both an oral and a written exam. On-the-job training is required to sit for the exam. Continuing education hours are required every two years for certificate renewal and the certificates are good for 10 years. The Board of Registered Polysomnographic Technologists certifies polysomnographic technologists as Registered Polysomnographic Technologists, which involves on-the-job training and a passing score on a written examination. Continuing education opportunities are available through various organizations including the American Society of Electroneuordiagnostic Technologists and the American Association of Electrodiagnostic Medicine.

Future outlook

Although many current END technologists were trained on the job, employers are now favoring candidates who have completed formal training in the area. Some hospitals require applicants for trainee positions to have postsecondary training, whereas others only expect 840

a high school diploma. Employers will look for courses taken in health, biology, anatomy, and mathematics in applicants for training positions. Often those who do not have formal training are transfers from other allied health professions, such as licensed practical nurses.

The 2000-01 Occupational Outlook Handbook of the U.S. Department of Labor states that demand for this occupation will grow more slowly than average through the year 2008. Reasons for the slower growth include more sophisticated equipment and cross-training of other

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Resources BOOKS

U.S. Department of Labor, Bureau of Labor Statistics. “Electroneurodiagnostic Technologist.” In Occupational Outlook Handbook 2000-01 Edition. Washington, D.C.: The Bureau. 2000. ORGANIZATIONS

American Board of Registration of Electroencephalographic and Evoked Potential Technologists, P.O. Box 916633, Longwood, FL 32791-6633. (407) 788-6308. . The American Society of Electroneurodiagnostic Technologists, 204 West 7th Street, Carroll, IA 514012317. (712) 792-2978. . American Society of Neurophysical Monitoring, 7510 Clairemont Mesa Blvd., Suite 100, San Diego, CA, 92111. (800) 479-7979. . Association of Polysomnographic Technologists, c/o Applied Measurement Professionals, P.O. Box 14861, Lenexa, KS, 66285-4861. (913) 541-1991 ext. 474, . Board of Registered Polysomnographic Technologists, 475n Riverside Drive, Seventh Floor, New York, NY, 10115. (212) 367-4370. .

Michelle L. Johnson, M.S., J.D.

Electroneurography Definition Electroneurography is the measurement of the speed of conduction of impulses down a peripheral nerve. The test is done to detect and roughly quantify the extent of nerve damage.

Purpose Electroneurography, also known as nerve conduction studies (NCS), nerve conduction velocity (NCV), or stimulation myelographic study (SMS), is used to detect the presence of a neuropathy in a particular nerve. Anatomically, there are three conditions that significantly decrease nerve conduction velocities: • demyelination (loss of myelin covering of the nerve)

• conduction blocks (damage that stops continued movement of nerve impulse) • axonal loss (nerve cell death) Electroneurography is used to detect and evaluate a wide variety of diseases or conditions involving nerve damage. It is a routine test after traumatic nerve damage such as carpal tunnel syndrome or to investigate suspected peripheral nerve dysfunctions or neuropathies. Nerve problems caused by viral infections such as HIV-1 or HSV-1 are also common indications for this procedure. Electroneurography can detect nerve damage that occurs as a side effect of systemic problems, including diabetes mellitus, B vitamin deficiency, multiple nutrient deficiency due to malabsorption of digested food, kidney failure, amyloidosis, and alcoholism. Electroneurography can also evaluate nerve damage caused by several bacterial infections or toxicities such as diphtheria, leprosy, and botulism poisoning. This test is also used to diagnose and follow the progression of many diseases of the nervous and muscular systems such as amyotrophic lateral sclerosis (ALS), myasthenia gravis, muscular dystrophies, and multiple sclerosis (MS).

Precautions There are no contraindications for this test. It is noninvasive and very low risk.

Description Electroneurography is based on the observation that when a nerve is electrically stimulated, a reaction will occur somewhere down the nerve or in the muscle served by the nerve. By using appropriate electrode placement, the reaction to the electrical stimulus is recorded. Examining the characteristics of the reaction and the timing of the reaction reveals both the velocity of conduction and the latency (time between stimulus and response) of the tested nerve. This test requires that the nerve being tested is relatively close to the skin surface, although needle electrodes can be used to test deep nerves. Two sets of electrodes are used to perform the test, stimulating and recording. Normally, the stimulating electrodes are metal or felt pads placed on the surface of the skin, about 0.6 to 1.1 inches (1.5 to 3 cm) apart. Correct placement requires a strong understanding of neurological anatomy and varies from nerve to nerve. Conduction cream can be applied to maximize the effectiveness of the connection. Usually, the cathode (typically the black-colored electrode) is placed down the nerve from the anode (typically the red-colored electrode) in the direction of conduction.

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allied health professionals to perform these procedures. However, states with high concentrations of older patients, such as Florida, anticipate a better than average growth in this allied health area.

Electroneurography

The test works most effectively if maximal stimulation of the nerve is achieved. This is determined through step-wise increases in the stimulus output, and setting the stimulus 25–50% above this level. However, the greater the stimulation, the greater the chance of the stimulus being perceived as painful by the patient. Nevertheless, the duration of the discomfort is relatively short, and less than maximal stimulation produces results that cannot be interpreted and are therefore not medically useful. Stimulation is most difficult in patients who are obese, edemic (retaining water), or have unusually thick or calloused skin. Increasing stimulus duration, altering the placement of the cathode, or using needle electrodes can overcome stimulation problems. Recording electrodes are placed according to the type of response that is being sought. If muscular reaction is the goal, the active recording electrode is placed over the belly (thickest area) of the muscle being tested, while the second recording electrode, called a reference electrode, is place on a tendon. Placement is correct if the graphic representation of the response shows an initial negative deflection (upwards) in the graph of the response. If a nerve is being tested, the active electrode is placed directly over the nerve. The reference electrode is placed distally (pointing away from the electrode). Recording electrodes that test motor response are often metal, circular discs, while sensory recording electrodes come in many shapes such as buttons, rings, clips, discs, or bare wire. The test will run from about 20 minutes to about two hours, depending on the number of nerves being tested and if electromyography, a test commonly performed in conjunction with electroneurography, is being done. The cost of the test is about $500 and is usually covered by insurance.

Preparation Low body temperature can greatly distort the results of electroneurography. Particularly in cold weather, it is important to warm the muscles being tested and to maintain normal body temperature throughout the testing procedure.

Aftercare There are no aftercare procedures for this test. Patients may immediately resume normal activities.

Complications There are no complications resulting from this test. 842

Results Among the possible results from this test are measurements of motor response, sensory nerve response, and nerve conduction velocities. Motor response The motor (muscular) response is characterized by its waveform, amplitude, duration, and distal latency. The waveform is relatively simple, with a large negative deflection (upwards) followed by a large positive deflection (downward), producing a peak, although the exact shape depends on the placement and type of electrode. The amplitude (expressed in millivolts) is the value from the baseline to the peak of the negative response. Amplitude value depends on the number and synchronization of the muscle fibers that are being stimulated. The use of a maximal stimulation of the nerve ensures all possible fibers will be recruited. The duration of the motor response is the time from the beginning of the negative deflection to the completion of the positive deflection. In disease states, along with decreased amplitude, the duration of the response will be increased if the muscle fibers do not fire together. The distal latency is the time it takes from stimulus to the beginning of the negative deflection, and is measured in milliseconds. If bilateral measurements are taken, this value will be increased on the side having damage to the nerve or neuromuscular junction. Each motor response characteristic is more difficult to read if electrode placement covers more than one muscle, emphasizing the need to isolate one muscle whenever possible. Sensory nerve response Like motor response, sensory nerve responses, or action potentials, are characterized by a particular waveform, amplitude, duration, and distal latency. The normal waveform includes a negative deflection (upward), a larger positive deflection (downward), followed by a negative rebound back to baseline, forming an S-shaped wave, although the exact shape differs with the type of electrodes, placement, or the use of three electrodes. Amplitude is measured from the peak of the negative response to baseline and is measured in microvolts. Like motor responses, high amplitude and short duration in a sensory nerve response indicate large numbers of axons firing simultaneously. Disease states can reduce amplitude and increase duration. Distal latency is measured from stimulus to negative peak and is expressed in milliseconds. When taking sensory nerve

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Nerve conduction velocity Nerve conduction velocities to a muscle can be calculated if it is possible to stimulate a nerve in two places along its length. Two latency measurements are made, a distal latency and a proximal latency (in milliseconds, msec). The distance between the two stimulation points is then measured (in millimeters, mm) and divided by the difference between the two latency values. This value is the conduction velocity of the nerve in meters per second. For sensory nerves, only one stimulation point is used, and the velocity is calculated by dividing the distance between the active and reference electrodes (in mm) by the latency (in msec).

KEY TERMS Amplitude—The distance from the baseline to the peak of the motor or sensory response represents the approximate number of healthy muscle fibers or nerves available. Demyelination—Loss of the insulating cover of the nerve cell. Demyelination significantly reduces measured nerve conduction velocity. Latency—The amount of time between stimulus and motor or sensory nerve response. Waveform—The shape of the electrical response recorded by the active recording electrode.

• computer technology and instrumentation

Once results have been calculated, these are compared to a table of standard values. Tables have been devised that sort results by different characteristics such as the patient’s age, sex, height, nerve length, or a combination of these factors. An example of a commonly used table is one published by the Cleveland Clinic Foundation. This table sorts results by patient age and is based on standard electrode distances for the measurement of different nerve velocities. In general, demyelination is indicated if conduction velocities have fallen below 50% of normal. Even significant loss of axons commonly reduces conduction velocities by only about 30%, based on a loss of the fastest conducting fibers.

Certification of electrodiagnostic technologists specializing in electroneurography and the related area of evoked potentials is available through the American Board of Registration of Electroencephalographic and Evoked Potential Technologists.

When analyzing the results of this test, it should be taken into consideration that electroneurography tests the best surviving nerve tissue. This characteristic means that results can be normal despite extensive nerve damage. Nevertheless, abnormal results can provide extremely useful information, including distinguishing between demyelination and loss of axons and pinpointing the exact location of a nerve injury.

Resources

Health care team roles Electroneurography is often performed by specially trained electrodiagnostic technologists. Training for such a position can be on the job but often involves study at a one- to two-year college or vocational program. A typical program would include:

A physician such as a neurologist, neurosurgeon, or internist does the final review and diagnosis based on the results of electroneurography. The physician can be present for the testing or may review saved tracings. Other health care professionals such as nurses aid in patient education concerning this procedure.

BOOKS

Kimura, Jun and Nobuo Kohara. “Electrodiagnosis of Neuromuscular Disorders.” In Neurology in Clinical Practice, ed. Walter G. Bradley et al. Boston: Butterworth Heinemann, 2000. ORGANIZATIONS

American Board of Registration of Electroencephalographic and Evoked Potential Technologists. P.O. Box 916633, Longwood, FL, 32791-6633. (407) 788-6308. . The American Society of Electroneurodiagnostic Technologists. 204 West 7th Street, Carroll, IA 514012317. (712) 792-2978. .

• human anatomy and physiology

OTHER

• neurology and neuroanatomy

Jabre, Joe F. “The Electronic EMG Manual.” January 20, 2001. .

• neurophysiology • medical terminology

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responses, it is important to isolate the recording electrodes away from innervated muscles, as the motor response will swamp the much smaller sensory nerve response.

Electronic fetal monitoring

Electronic fetal monitoring Definition The electronic fetal monitor (EFM) is a device that records an unborn baby’s heart rate and the presence or absence of the mother’s uterine contractions.

Purpose The EFM is used to assess fetal well being during routine prenatal visits. It is also used during labor and delivery when high-risk factors exist or when a clinical condition develops beforehand that places the fetus at risk. High risk factors for EFM during labor include: • low gestational age • high maternal age • placenta or cord problems • meconium in the aminotic fluid • hypertension • proteinuria • facial nerve palsy A fetus having trouble in labor often exhibits characteristic changes in heart rate after a contraction (late decelerations). Trouble is also indicated by significant slowing of the heart rate during a contraction (variable deceleration). If the fetus is not receiving enough oxygen to withstand the stress of labor, and delivery is many hours away, a cesarean section (C-section) may be necessary.

Two contraction stress tests, which measure the placenta’s ability to provide enough oxygen to the fetus during pressure, are also used with electronic fetal monitoring. The nipple stimulation contractions stress test involves the mother self-stimulating her nipple while contractions and FHR are monitored. Another test, called oxytocin stimulation, involves the administration of the hormone oxytocin intravenously until three uterine contractions are observed within ten minutes, during which time the FHR is monitored. Sometimes, it is difficult to hear the baby’s heartbeat with the monitoring device. Other times, the monitor may show subtle signs of a developing problem. In either case, the physician may recommend the use of an internal monitor, which provides a more accurate record of the baby’s heart rate. The internal monitor (or fetal scalp electrode) uses an electrode attached to the baby’s scalp through the cervix during an internal vaginal exam. The internal monitor can only be used when the cervix is dilated. In 1995, a technical bulletin issued by the American College of Obstetricians and Gynecologists (ACOG) reported that the prudent use of intermittent auscultation (listening) of fetal heart rate is equivalent to continuous electronic fetal monitoring in a low-risk pregnancy. Intermittent auscultation involves listening to the FHR every 15 minutes during active labor until complete cervical dilation. From complete dilation to delivery, the FHR should be obtained every five minutes and timed to obtain the FHR during a contractions and for 30 seconds afterwards. In complicated pregnancies, however, continuous EFM is recommended during labor. EFM is used in most deliveries directed by physicians.

Description The monitor produces a continuous paper record of the fetal heart rate (FHR) and records uterine contractions. FHR is captured on the top part of the paper printout; uterine activity, when monitored, appears on the lower part of the tracing. Electronic fetal monitoring can be performed externally or internally. The external ultrasound approach is non-invasive and uses sensors (electrodes) placed on the mother’s abdomen with an elastic belt. Another belt holds the contraction monitor. External electronic fetal monitoring includes a nonstress test, which measures FHR accelerations with normal movement of the fetus. Sometimes the fetal movement is encouraged by giving the mother a small meal or something to drink. Fetal acoustic stimulation and moving the fetus by rubbing the abdomen gently may also be used. 844

Preparation There are no special preparations required for external fetal monitoring. Preparation for placement of an internal scalp lead (ISL) is the same as for a routine vaginal exam.

Complications In general, no risks are associated with external fetal monitoring. However, the test can initiate labor and is generally not given to mothers at risk for preterm labor or with a condition that requires a cesarean section. Internal monitoring poses risks associated with improper placement of the electrodes. Some data indicate that EFM leads to unnecessary C-sections. Another drawback includes loss of maternal mobility when used during labor, which may slow labor.

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Electronic fetal monitoring A fetal monitoring belt can be used to monitor a fetus through the abdominal wall and uterus. (Custom Medical Stock Photo. Reproduced by permission.)

Results The normal fetal heart rate (FHR) ranges from 120 to 160 beats per minute (bpm). Just as an adult’s heart rate rises with movement, FHR rises when the baby moves. A reactive heart rate tracing (also known as a reactive non-stress test, or NST) is considered a positive sign of fetal well being. A non-reactive NST may or may not imply fetal well being. The monitor strip is considered to be reactive when the FHR rises at least 15 to 20 bpm above the baseline heart rate for at least 20 seconds. This must occur at least twice in a 20-minute period. Results are considered abnormal if the FHR drops below 120 or rises above 160 for sustained periods. In either of these cases the baby may be exhibiting fetal distress. A mean FHR of less than 110 bpm may indicate bradycardia (slow heart beat). A mean FHR of over 160 bpm may indicate a tachycardia (rapid beating of the heart). However, some babies who are having problems may not exhibit such clear signs. During a contraction, the flow of oxygen from the mother through the placenta to the baby is temporarily stopped. It is as if the baby has to hold its breath during

each contraction. Both the placenta and the baby are designed to withstand this condition. Between contractions, the baby should be receiving more than enough oxygen to do well during the contraction. One sign that a baby is not getting enough oxygen between contractions is a drop in the baby’s heart rate after the contraction (late deceleration). The heart rate recovers to a normal level between contractions, only to drop again after the next contraction. This is a more subtle sign of distress. Trouble is also indicated by significant slowing during a contraction (variable decelerations). Fetal monitoring is not a perfect test. Fetal assessment in labor is subject to differences in interpretation and consequent intervention; therefore, institutional policies and procedures should be followed.

Health care team roles Electronic fetal monitoring is primarily conducted by specialists in obstetrics and gynecology. Qualified registered nurses and advanced practice nurses may assist in or conduct electronic fetal monitoring.

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Electrophysiology study of the heart

Society for Maternal-Fetal Medicine. 409 12th Street, SW, Washington, DC 20024(202). 863-2476. .

KEY TERMS Auscultation—Listening to sounds within organs to help in diagnosis in treatment. C-section—A cesarean section; delivery of a baby through an incision in the mother’s abdomen instead of through the vagina.

OTHER

American College of Obstetricians and Gynecologists. “Fetal Heart Rate Patterns: Monitoring, Interpretation, and Management” In ACOG Technical Bulletin Number 207, (1995) Washington, DC.

Late deceleration—Transient fetal brachycardia exceeding 100 beats per minute which reaches its height more than 30 seconds after the peak of the uterine contraction. Non-stress test—A record of the fetal heart rate in the absence of contractions (stress). Reactive stress test—A positive sign of fetal well being. The FHR rises at least 20 beats per minute above the baseline heart rate for at least 20 seconds, occurring at least twice in a 20-minute period. Variable deceleration—Fetal bradycardia below 100 beats per minute denoting compression of the umbilical cord at the height of a uterine contraction.

Electrophysiology study of the heart Definition An electrophysiology study (EPS) of the heart is a nonsurgical analysis of the electrical conduction system (normal or abnormal) of the heart. The test employs cardiac catheters and sophisticated computers to generate electrocardiogram (EKG) tracings and electrical measurements with exquisite precision from within the heart chambers.

Purpose

Training Applying the external monitor is simple, but requires practice in the proper placement of the monitoring devices. The interpretation of the tracings, however, requires continued vigilance in education and clinical practice. Training should include instruction in auscultation, electronic FHR monitoring, and evaluation of uterine activity. Resources BOOKS

Cunningham, Gary, et al. “Antepartum Assessment.” In Williams Obstetrics, 20th ed. Stamford: Appleton & Lange, 1997, 1009-1022. Jackson, David. “Fetal Distress in the Intrapartum Period.” In Current Therapy in Obstetrics and Gynecology, 5th ed. Philadelphia: W.B. Saunders, 2000, 398-401. ORGANIZATIONS

The American College of Nurse-Midwives. 818 Connecticut Ave. NW, Suite 900, Washington, DC 20006. (202) 7289860. . American College of Obstetricians and Gynecologists. 409 12th St., S.W., PO Box 96920, Washington, DC 200906920. (202) 638-5577. . The Association of Women’s Health, Obstetric and Neonatal Nurses (AWHONN). 2000 L Street, NW, Suite 740, Washington, DC 20036. (202) 261-1200. . 846

Maggie Boleyn, R.N., B.S.N.

An EPS can be performed solely for diagnostic purposes or to pinpoint the exact location of electrical signals (cardiac mapping) in conjunction with a therapeutic procedure called catheter ablation. A cardiologist may recommend an EPS when the standard EKG, Holter monitor, event recorder, stress test, echocardiogram, or angiogram cannot provide enough information to evaluate an abnormal heart rhythm, called an arrhythmia. An EPS offers more detailed information about the heart’s electrical activity than many other noninvasive tests because electrodes are placed directly on heart tissue. This placement allows the electrophysiologist to determine the specific location of an arrhythmia and, oftentimes, correct it during the same procedure. This corrective treatment is considered a permanent cure; in many cases, the patient may not need to take heart medications. EPS may be helpful in assessing: • certain tachycardias or bradycardias of unknown cause • patients who have been resuscitated after experiencing sudden cardiac death • various symptoms of unknown cause, such as chest pain, shortness of breath, fatigue, or syncope (dizziness/fainting) • response to anti-arrhythmic therapy

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Pregnant patients should not undergo EPS because of the exposure to radiation during the study, which may harm the growing baby. Patients who have coronary artery disease may need to be treated prior to EPS. EPS is contraindicated in patients with an acute myocardial infarction, as the infarct may be extended with rapid pacing. The test is also contraindicated for patients who are uncooperative.

Description The rhythmic pumping action of the heart, which is essentially a muscle, is the result of electrical impulses traveling throughout the walls of the four heart chambers. These impulses originate in the sinoatrial (SA) node (specialized cells situated in the right atrium, or top right chamber of the heart). Normally, the SA node, acting like a spark plug, spontaneously generates the impulses, which travel through specific pathways throughout the atria to the atrioventricular (AV) node. The AV node is a relay station sending the impulses to more specialized muscle fibers throughout the ventricles (the bottom chambers of the heart). If these pathways become damaged or blocked or if extra (abnormal) pathways exist, the heart’s rhythm may be altered (too slow, too fast, or irregular), which can seriously affect the heart’s pumping ability. The patient is transported to the x-ray table in the EPS lab and connected to various monitors. Sterile technique is maintained. A minimum of two catheters is inserted into the right femoral (thigh) vein in the groin area. Depending on the type of arrhythmia, the number of catheters used and their route to the heart may vary. For certain tachycardias, two more catheters may be inserted in the left groin and one in the internal jugular (neck) vein or in the subclavian (below the clavicle) vein. The catheters are about 2 mm in diameter, about the size of a spaghetti noodle. The catheters used in catheter ablation are slightly larger. With the help of fluoroscopy (x rays on a television screen), all the catheters are guided to several specific locations in the heart. Typically, four to 10 electrodes are located on the end of the catheters, which have the ability to send electrical signals to stimulate the heart (called pacing) and to receive electrical signals from the heart; but not at the same time (just as a walkie-talkie cannot send and receive messages at the same time). First, the electrodes are positioned to receive signals from inside the heart chambers, which allows the doctor to measure how fast the electrical impulses travel in the patient’s heart at that time. These measurements are

called the patient’s baseline measurements. Next, the electrodes are positioned to pace. That is, the EPS team tries to induce (sometimes in combination with various heart drugs) the arrhythmia that the patient has previously experienced so the team can observe it in a controlled environment, compare it to the patient’s clinical or spontaneous arrhythmia, and decide how to treat it. Once the arrhythmia is induced and the team determines it can be treated with catheter ablation, cardiac mapping is performed to locate the precise origin and route of the abnormal pathway. When this is accomplished, the ablating electrode catheter is positioned directly against the abnormal pathway, and high radiofrequency energy is delivered through the electrode to destroy (burn) the tissue in this area. Pediatric patients present challenges in EPS. In 2001, an analysis of 45 pediatric patients who underwent electrophysiologic study was conducted. The researchers concluded that success rates and the prevention of complications in children may be increased by using ultrasound guidance for access of the internal jugular vein for coronary sinus cannulation (insertion of a tube for the transport of fluid) during EPS. Access was successfully obtained in all 45 of the patients without major complications using this technique.

Preparation The following preparations are made for an EPS: • The patient may be advised to stop taking certain medications, especially cardiac medications, that may interfere with the test results. • The patient is kept fasting for six to eight hours prior to the procedure. Fluids may be permitted until three hours before the test. • Blood tests usually are ordered one week prior to the test. • The patient undergoes conscious sedation (awake but relaxed) during the test. • A local anesthetic is injected at the site of catheter insertion. • Peripheral pulses are marked with a pen prior to catheterization. This permits rapid assessment of pulses after the procedure.

Aftercare The patient needs to rest flat in bed for several hours after the procedure to allow healing at the catheter inser-

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Electrophysiology study of the heart

Precautions

Electrophysiology study of the heart

Complications

KEY TERMS Ablation—Removal or destruction of tissue, such as by burning or cutting. Angiogram—X ray of a blood vessel after special x-ray dye has been injected into it. Bradycardia—Relatively slow heart action, usually considered as a rate under 60 beats per minute. Cardiac catheter—Long, thin, flexible tube, which is threaded into the heart through a blood vessel. Cardiologist—Doctor who specializes in diagnosing and treating heart diseases. Echocardiogram—Ultrasound image of the heart. Electrocardiogram—Tracing of the electrical activity of the heart.

EPS and catheter ablation are considered low-risk procedures. There is a risk of bleeding and/or infection at the site of catheter insertion. Blood clot formation may occur and is minimized with anti-coagulant medications administered during the procedure. Vascular injuries causing hemorrhage or thrombophlebitis are possible. Cardiac perforations are possible. If the right internal jugular vein is accessed, the potential for puncturing the lung with the catheter exists and could lead to a collapsed lung. Because ventricular tachycardia or fibrillation (lethal arrhythmias) may be induced in the patient, the EPS lab personnel must be prepared to defibrillate the patient as necessary. Patients should notify their health care provider if they develop any of these symptoms: • numbness or tingling in the extremities

Electrode—A medium, such as platinum wires, for conducting an electrical current.

• heavy bleeding

Electrophysiology—Study of how electrical signals in the body relate to physiologic function.

• loss of function in extremities

Event recorder—A small machine, worn by a patient usually for several days or weeks, that is activated by the patient to record his or her EKG when a symptom is detected. Fibrillation—Rapid, random contraction (quivering). Holter monitor—A small machine, worn by a patient usually for 24 hours, that continuously records the patient’s EKG during usual daily activity.

• change in color and/or temperature of extremities

Results Normal findings indicate that the heart initiates and conducts electrical impulses within normal limits. Abnormal findings include confirmation of arrhythmias, such as: • supraventricular tachycardias

Stress test—Recording a patient’s EKG during exercise.

• ventricular arrhythmias

Supraventricular tachycardia—A fast heart beat that originates above the ventricles.

• bradycardias

Health care team roles

Tachycardia—Fast heartbeat. Thrombophlebitis—Venous inflammation with the formation of thrombus (a clot in the cardiovascular system).

tion sites. The patient often returns home either the same day of the test or the next day. Someone should drive the patient home. Patient education To minimize bleeding and pain, instruct the patient to keep the extremity in which the catheter was placed immobilized and straight for several hours after the test. 848

• accessory pathways

The relatively simple EPS is performed in a special laboratory under controlled clinical circumstances by cardiologists, nurses, and technicians with special training in electrophysiology. Resources BOOKS

Grubb, Blair P., and Brian Olshansky. Syncope: Mechanisms and Management. Armonk, NY: Futura Publishing, 1997. Pagana, Kathleen D., and Timothy J. Pagana. Diagnostic Testing and Nursing Implications, 5th ed. St. Louis: Mosby, 1999. Singer, Igor. Interventional Electrophysiology Baltimore, MD: Williams & Wilkins, 1997.

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Liberman L, Hordof AJ, Hsu DT, Pass RH. “UltrasoundAssisted Cannulation of the Right Internal Jugular Vein during Electrophysiologic Studies in Children.” Journal of Interventional Cardiology and Electrophysiology 5, no 2 (June 2001): 177-9. ORGANIZATIONS

American Association of Critical-Care Nurses. 101 Columbia, Aliso Viejo, CA 92656-4109. (800) 899-2226. . The American College of Cardiology Heart House, 9111 Old Georgetown Road, Bethesda, MD 20814-1699. (800) 253-4636 . American Heart Association. 7272 Greenville Ave., Dallas TX 75231-4596. (800) 242-1793. . Cardiac Arrhythmia Research and Education Foundation (C.A.R.E.). 2082 Michelson Dr. #301 Irvine, CA 92612. (800) 404-9500. . Medtronics Manufacturer of Therapeutic Devices. 7000 Central Ave. NE Minneapolis, MN 55432-3576. (800) 328-2518. United States Catheter Instruments (USCI). 129 Concord Road Billerica, MA 01821. (800) 826-BARD.

Maggie Boleyn, R.N., B.S.N.

Electrosurgery machines Definition The electrosurgery machine produces high radiofrequency energy sufficient to induce cutting and/or coagulation in body tissues by an electrode during (electro)surgery.

• the electrosurgical unit (ESU), which generates the radiofrequency current • dispersive pads/electrodes for electrical current dispersion and foot pedals for operation in cut or coagulation mode A complete circuit must be connected for current to flow, as in any circuit. In the case of electrosurgery, the circuit comprises the electrosurgical power unit, the active electrode (where cutting or coagulation transpire), the dispersive electrode (also known as the “return electrode,” for return of current), and the path of least resistance through the patient’s own body from the active electrode to the return electrode. When the circuit is complete and current can flow through it without too great of a resistance, the electricity that causes coagulation and cutting is readily applied to appropriate sites at the surgeon’s discretion. The low frequency power input of the wall (i.e. 60 Hz in the United States) is converted by the ESU to a highfrequency (on the order of 400,000 to 1,000,000 Hz) alternating current output that yields the therapeutic effects of electrosurgery. Safety is important with all electrical equipment; consequently the ESU should be grounded to a true earth ground that is electrically isolated from other grounds in the operating room, so that neither the surgeon nor the patient are shocked or electrocuted. The high-frequency current is transmitted to the patient via the active electrode, which is insulated along its length until the electricity-emitting tip is reached, and which may take the form of: • a one-piece electrode • a pencil handpiece • forceps • suction tips

Purpose The instrument is designed to provide the correct electrical waveforms to deliver to the site of surgery in order to coagulate blood vessels and to cut tissues smoothly. Surgeons may use the electrosurgery tool instead of, or in conjunction with, a conventional scalpel. When used properly, the electrosurgery unit damages tissue considerably less than the scalpel, with the added ability to stem bleeding safely.

Description Commercial electrosurgery machines may differ significantly, but comprise multiple components, which include: • the electrode(s)

The complete circuit discussed above may be achieved through either bipolar or monopolar modalities. Bipolar surgery is as the title implies, involving the use of two poles, or electrodes. The electrodes (active and return) are fixed upon a forceps-shaped tool. When pinched, the surgeon may apply current that traverses only the tissue in between the two electrodes, thereby coagulating it (unless the tissue is completely desiccated, in which case some current may leak into surrounding tissue). Carrying low-voltage current and affecting little tissue, the bipolar instrument is considerably safer than the monopolar device. Neurosurgeons usually opt for the bipolar tool over monopolar for this reason and for its inherent delicacy, among others. The monopolar instrument is often used in place of the bipolar for three main reasons: it is easier to use, it

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PERIODICALS

Electrosurgery machines

KEY TERMS Coagulate—To clot or cause hemostasis; in electrosurgery, to cause tissue dehydration without cutting. Hemostasis—Stoppage of bleeding.

possesses the added capability of cutting tissue, and it is able to coagulate larger blood vessels. The active electrode, which may be in shape of a blade, loop, ball, needle, or pencil, can be disposable or reusable. Current emitted from this electrode is dispersed over a large area of padding by one of two types of dispersive electrode: conductive or capacitive. This can prove difficult, and is one reason why bipolar is the safer choice. Any erroneous selection or misuse of dispersive pads can result in a dangerous predicament for both the patient and the surgeon. While systems in use as of 2001 generally retain a number of alarms and warning systems built in, health care personnel must remain aware of the dangers implicit in using the equipment.

Operation Three modes of operation are available, and can be produced on command, dependent upon the waveform issued by the ESU: • Cutting: A high-frequency alternating current yields smooth, rapid cuts that evoke little to no hemostasis. The current stimulates cells to swell and explode. • Fulguration: Sparking the tissue to lead to coagulation. There is no tissue-electrode contact; rather, voltage is raised in order to incite a spark between electrodes in order to coagulate the tissue in between. • Desiccation: The drying out of cells leading to coagulation. Stems from direct contact with the active electrode and leaves a soft brown eschar, or scab. It is key for all health care personnel involved in electrosurgery to be educated about the specific ESU and electrodes used by physicians at their location. The power settings on the ESU unit do not necessarily correspond to the quantity of power delivered. Thus, personnel must know not to equate numerical power settings with specific units unless explicitly labeled that way, i.e. one must not equate a power setting of “1” with 1 watt (or 100 watts) of power. Even if the amount of power is not known in watts, medical personnel must have an intuitive idea of what the different power settings mean in terms of the ability to cut, to coagulate, and for safety. 850

Most machines make it easier with the ability to pre-program cutting and coagulation settings so that the surgeon and staff can move swiftly and accurately between settings during surgery. Smoke can also be an issue with electrosurgery, so many units as of 2001 come equipped with smoke evacuation and filtration systems, which the staff must also learn how to operate through reading manufacturers’ manuals.

Maintenance Most maintenance on the electrosurgery power unit is generally performed by trained biomedical equipment technicians or biomedical engineers unless nursing staffers are adequately trained. The electrodes, however, must be cleansed and sterilized by the staff immediately following each surgery if they are not disposable.

Health care team roles Most of the electrosurgical machine configuration and settings are handled by nursing staff and technicians. Often the operating room (O.R.) personnel know more about setting up the machine, its safety controls, and its handling than the surgeons using the equipment. This is because surgical residents are not formally trained in electrosurgical use; thus, since O.R. nursing personnel are usually trained by the manufacturer’s sales representatives, the surgeons tend to rely on nursing staff to set up and manage the equipment. It is therefore very much an integral aspect of the staff’s responsibility to alert surgeons to possible dangers, especially electrical, inherent in using the electrosurgical machine. The electrode insulation mentioned above is a key element in electrosurgical safety, so staff should remain alert for inadequate or defective insulation.

Training Health care personnel are generally trained by the sales representatives of the electrosurgery unit’s manufacturer to set up and properly maintain the equipment. Without care and knowledge of the electrosurgery apparatus, great harm can be caused to patients undergoing surgery. Special attention should be paid to the manual since each ESU model is unique. Resources PERIODICALS

Van Way, C. W., III. “Electrosurgery 101.” Current Surgery 57, no. 2 (March-April, 2000): 172-177.

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OTHER

Electrosurgical Devices and Principles. . Solid State Coagulation. .

Bryan Ronain Smith

Electrotherapy Definition Electrotherapy is the use of electrical stimulation for therapeutic purposes. Specifically, electrotherapy uses energy waves that are part of the electromagnetic spectrum to produce desired physiological and chemical effects in the body.

Purpose Electrotherapy is used for three therapeutic purposes: (1) to relieve pain; (2) to stimulate physiochemical changes; and (3) to stimulate muscle contraction. Pain relief Electrotherapy is used to manage both acute and chronic pain. In the gate model of pain, the neural fibers that carry the signal for pain and those that carry the signal for proprioception (body position) are mediated through the same central junction. Because signal transmission along pain fibers is slower than transmission along proprioception fibers, the gate model suggests that intense stimulation of proprioception fibers can block the slower-moving pain signals. Some forms of electrotherapy attempt to stimulate these proprioception fibers to reduce the sensation of pain. Other forms of electrotherapy alleviate pain by introducing analgesics and antiinflammatory medications via electric current to the painful area. Various types of pain are indications for electrotherapy, including: • post-operative incision pain • fracture pain • pain associated with labor and delivery • foot pain

• pain associated with tendinitis • pain associated with certain types of arthritic inflammation • back and neck pain Stimulation of physiochemical changes Electrotherapy is also used to induce physiological and chemical changes. Some forms of electrotherapy induce these changes by introducing heat into the deep tissues; this deep heating increases blood flow to and from the problematic region and improves drainage. Other forms of electrotherapy are thought to stimulate the body’s production of corticosteroids and vitamin D. Still others are believed to promote wound healing by stimulating intracellular activity. Indications for the forms of electrotherapy that induce physiochemical changes include: • inflammatory orthopedic conditions • bronchitis • otitis media • sinusitis • prostatitis • certain immunoregulated dermatologic conditions such as psoriasis • open lesions and certain types of skin ulcers Stimulation of muscle contraction Electrotherapy is used to stimulate the contraction of muscles during rehabilitation. This type of electrical stimulation is used to prevent muscle atrophy and to reeducate muscles after trauma or surgery. This form of electrotherapy can also be used to relieve muscle spasms. Indications for electrotherapy to stimulate muscle contraction include: • healthy innervated muscle at risk of atrophy from immobilization or injury • denervated (lacking natural neural connection) muscle that might atrophy or degenerate • low back spasm

Precautions Although each modality of electrotherapy has its specific set of contraindications, cardiac pacemakers are a general contraindication for electrotherapy. Electrical signals from electrotherapy devices can interact with the electrical signals from pacemakers and interfere with pacemaker functioning. Pacemaker disruption is particu-

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Van Way, C. W., III, and C. S. Hinrichs. “Electrosurgery 201: Basic electrical principles.” Current Surgery 57, no. 3 (May-June, 2000): 261-264.

Electrotherapy

larly acute with such modalities as diathermy and electrical nerve stimulation. However, less interference may occur with such radiation modalities as infrared, ultraviolet, and cold laser treatments (these modalities are discussed in detail below in the Description section). Contraindications for pain relief electrotherapy include: • undiagnosed pain (pain is a symptom that might signal a serious condition that may need to be treated directly) • current use of narcotic medications that can desensitize patients to stimuli • patient hyposensitivity in particular areas of the body • pregnancy, except when electrotherapy is used to relieve pain of labor and delivery For the use of electrotherapy to stimulate physiochemical changes, contraindications include: • acute inflammation • hemorrhage • foreign bodies or metallic implants • patient hyposensitivity in particular areas of the body • recent treatment with ionizing radiation therapies • pulmonary tuberculosis • severe diabetes • lupus erythematosus • photosensitivity or current use of photosensitizing drugs For the use of electrotherapy to stimulate muscle contraction, contraindications include: • new fracture • hemorrhage • phlebitis

Description Pain relief For pain management, the two commonly used modalities of electrotherapy are transcutaneous electrical nerve stimulation (TENS) and iontophoresis. TENS relieves pain by stimulating proprioception nerve fibers to block the transmission of competing pain signals. Although both proprioception and pain receptors respond to electrical stimulation, there is some evidence that the proprioreceptive nerves respond to different kinds of waveforms from the forms that stimulate pain receptors; TENS uses the electrical waveforms that target proprioreceptors. 852

Electrodes are generally placed at points of pain, trigger points, acupuncture points, or over nerve roots. Parameters determining the character of the TENS stimuli are selected; these parameters include the waveform, frequency, duration, and amplitude of the wave. The duration of each TENS session is usually one hour. A typical patient is prescribed TENS four times daily for initial pain control. With continued use and as pain decreases, the frequency of TENS sessions can gradually be reduced to two sessions or one session daily. The use of TENS for pain management is covered by insurance, but only for specific types of pain for limited time periods. TENS is typically well-covered for acute postoperative pain management, but TENS use for chronic pain complaints varies by insurer. Although the use of TENS to relieve labor and delivery pain has been documented overseas, this application of TENS is generally not approved by insurers in the United States. A second form of electrotherapy used for pain relief is iontophoresis. Iontophoresis refers to the transdermal (through the skin) introduction of ionic compounds using direct current. This method of pain management is sometimes covered by insurance. In the United States, iontophoresis is almost always administered using dedicated iontophoresis devices. These machines allow for the finetuning of treatment parameters such as the amplitude of the current, the duration of treatment, and the automated ramping up and down of current at the start and end, respectively, of each treatment session. Iontophoresis units also come equipped with electrodes embedded in fiber pads or gel that carry the desired drug. For pain management, the drugs used in iontophoresis are analgesics and anti-inflammatory compounds, and include such medications as dexomethasone, lidocaine, and salicylate. To begin iontophoresis, the delivery electrode containing the drug is placed in the area where pain is reported. Whether a drug is placed at the site of a negative or a positive electrode depends on the drug’s ionic charge. Lidocaine has a positive charge and is placed with a positive delivery electrode, while the negatively-charged compounds of dexomethasone and salicylate are used with a negative delivery electrode. After securing the delivery electrode, a second electrode, of opposite polarity, is placed on the body at a fixed distance (determined by the particular iontophoresis unit) away from the first electrode. Lead wires are attached to the electrodes, with the positive lead attached to the positive electrode and the negative lead to the negative electrode. The intensity of the electric current is then slowly increased until the predetermined level is reached, and this level is maintained throughout the main treatment session.

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Stimulation of physiochemical changes Diathermy and radiation are two forms of electrotherapy that are used to induce physiological and chemical changes in the body. Diathermy refers to the use of high-frequency electromagnetic waves (greater than 10 MHz) as therapeutic stimuli. Shortwave diathermy uses waves of 13, 27, or 45 MHz, while microthermy uses waves of up to 2450 MHz in frequency. Both forms of diathermy generate heat in deep muscle tissue, although microthermy is believed to be absorbed more by superficial fatty issue. The patient is placed between the electrodes, and the power level is adjusted until the patient reaches resonance (as determined by automated measurement systems) with a pre-established heating level. Each diathermy session lasts 10–30 minutes, depending on the size of the target area. The heat generated by diathermy is believed to improve blood circulation, relax muscular tension, and promote drainage in the target areas. Because of the lack of large controlled studies of diathermy, it may not be covered by insurance. Radiation therapies in the context of electrotherapy include infrared, ultraviolet, and cold laser therapies. Infrared therapies—heat lamps, moist heat packs, and chemical heat packs—are used to apply superficial heat to improve circulation in target areas. Ultraviolet lamps are thought to stimulate the body’s production of corticosteroids and vitamin D. For some therapies, ultraviolet radiation is used in conjunction with photosensitive or photoactivated medications. Cold laser treatments—most commonly, the directing of a low-powered helium-neon laser beam over the target area—are used to facilitate wound healing. Cold laser may also be used for pain relief, with the laser directed at acupuncture points, trigger points, and nerve roots. Typically, ultraviolet and cold laser treatments do not exceed two minutes, while infrared treatments can last between 10 and 30 minutes. Infrared or heat therapies are viewed as conventional treatments and are covered by insurers as part of a short-term physical therapy regimen. Ultraviolet thera-

pies, however, are only covered for very specific dermatological conditions such as disabling psoriasis. Cold laser treatments are categorized as investigational, or experimental, therapy and are not covered. Large uncontrolled trials have shown some benefits of cold lasers in promoting wound healing, but smaller controlled trials have shown little or no benefit. Studies of the pain-relieving effects of cold laser suggest no benefit beyond that which can be obtained through conventional treatments. Stimulation of muscle contraction The use of electrical stimulation to stimulate muscle contraction is known as neuromuscular electrical stimulation (NMES) or functional electrical stimulation (FES). NMES/FES therapies apply pulses of electrical current to target muscle groups to stimulate active motion, strengthen muscles, and prevent muscle atrophy. In NMES/FES, electrodes are placed initially on the belly of the muscle that is to be stimulated. AC electrical stimulation is then applied at low levels (threshold levels for muscle movement). Based on muscle responses to the threshold stimulation, electrode positions are adjusted until the motor points of the muscle (optimal positions for generating muscle movement) are found. Electrodes are then secured at these optimal positions. After the electrodes have been placed, parameters for NMES/FES are programmed into the electrical stimulator unit. Parameters include the amplitude of the electrical pulse, the duration of each pulse, the frequency of pulses, the duration of on/off (activation/rest) periods during the treatment session, ramping modulation (gradual increases and decreases) in stimulation, and duration of the treatment session. The maximum pulse amplitude recommended for NMES/FES is generally the maximum amplitude that can be tolerated by a given patient. Regarding pulse duration, there remains some ambiguity about the optimal duration time of each pulse; current practices suggest that pulse duration be set between 50 and 1000 microseconds. Pulse frequency tends to range from 30 pulses per second to 100 pulses per second. Since continuous electrical stimulation leads to early muscle fatigue, treatment sessions include rest periods between activation periods. The duration of “on” (activation) periods is typically 10–15 seconds; “off” (rest) periods can last up to one or two minutes. Treatment sessions may last between 10 and 20 minutes, and usually do not exceed one hour. Electrical stimulation can begin after parameters are set. In general, the intensity of the stimulation is increased from contraction to contraction within a given session, and is also increased from session to session, depending on how well the patient tolerates the increases.

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Electrotherapy

Treatment “dosages” are given in terms of milliampere-minutes—that is, the product of the amplitude of the current (in milliamperes, mA) and the duration of treatment (in minutes). For example, a treatment consisting of two mA for 30 minutes would be a dose of 60 mAmin. Note that such a recommended dose would also allow the therapist to administer a treatment session of three mA for 20 minutes. In general, dosages range from 40 to 80 mA-min, with current intensity ranging from one to four mA, and treatment duration ranging from 20 to 40 minutes.

Electrotherapy

Complications

KEY TERMS Denervation—A lack of nerve input into a muscle, organ, or other body part that normally receives neural input. Innervation—The presence of nerve input into a muscle, organ, or other body part. Osteogenesis—New bone growth.

NMES/FES is usually approved by insurers for postsurgical rehabilitation and rehabilitation after immobilization (after a limb has been in a cast or splint). This form of electrotherapy is typically not approved for spinal cord injuries or for muscles that have been denervated.

Preparation Preparation for electrotherapy requires first that the physical therapist clarify the problem area and condition with the patient. The physical therapist then selects the appropriate therapeutic modality for the complaint and determines the relevant parameters for each electrotherapeutic modality. The skin of the target area must be clean. For modalities requiring electrodes, the skin of the target area must also be free of lesions. For TENS therapy, conduction gels are used on the surface of the skin; otherwise, moisture on the tips of the electrodes is sufficient. For ultraviolet therapies, a small area of the skin should be tested to determine the minimal erythema (reddening of the skin) dosage prior to treatment. For some ultraviolet therapies, a photosensitizing medication is given prior to treatment. If pain relief is the goal, the patient should discontinue the use of pain medications that might obscure the effect of electrotherapy. For iontophoresis, the patient must be queried on possible sensitivities; for example, an allergy to dexamethasone would rule out the use of dexamethasone as an anti-inflammatory ionic substance.

After treatment, the patient should be checked for burns from electrodes or poorly placed wires. Heat burns are possible with almost all electrotherapy modalities. These types of burns occur when there is a buildup of heat in regions where electrical resistance is high. Causes of these high-resistance burns include electrodes being placed in sclerotic (scarred) areas; electrodes being placed in areas with wrinkled or folded skin or other areas where electrode contact is poor; or electrodes being poorly moistened. A complication of iontophoresis is chemical burn. Chemical burns occur when too much sodium hydroxide accumulates at the negative electrode. A pink lesion is apparent immediately after treatment, which becomes an oozing wound two to three hours later. This type of burn can be treated with antibiotics and a dressing, but tends to heal slowly. This complication can be prevented by decreasing the intensity of the current or by increasing the area of the negative electrode so that the current is dispersed over a larger area. Complications arising from cold laser treatment include dehydration, protein coagulation (clumping), and thermolysis (melting). While dehydration is reversible, protein coagulation and thermolysis are not. The typical cause of these complications is the use of cold laser at excessively high power.

Results TENS and iontophoresis should result is a reduction of pain and/or reduced symptoms of inflammation. There may be a concomitant increase in range of motion. If diathermy and radiation are used, improved drainage may be reported. In addition, depending on the specific therapy, improvement in skin conditions and wound healing are expected. The reduction of pain and inflammation may also be reported. NMES/FES should maintain or improve muscle strength. If the electrical stimulation is used to alleviate muscle spasm, relief from spasm is an expected result.

Aftercare Patient comfort should be monitored throughout the therapeutic session. After treatment, the patient should be queried about excessive levels of discomfort. Excessive discomfort should serve as a guide for modulating electrotherapy parameter settings in the future. In the case of such direct electrical stimulation as NMES/FES, the skin under the probes should be massaged with a neutral cream after treatment. 854

Health care team roles Because the physical therapist has typically received training in electrotherapy during his/her course of studies, he/she is the primary care provider during electrotherapy. The physical therapist delivers the therapeutic care and monitors the patient during electrotherapy. If the patient has been referred by a physician or other health care provider and the provider requests briefings, the

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Resources BOOKS

Kahn, Joseph. Principles and Practice of Electrotherapy. 4th ed. New York: Churchill Livingstone, 2000. Low, John, and Ann Reed. Electrotherapy Explained. Boston: Butterworth Heinemann, 2000. Nelson, Roger M., Karen W. Hayes, and Dean P. Currier, eds. Clinical Electrotherapy. 3rd ed. Stamford, CT: Appleton & Lange, 1999.

Genevieve Pham-Kanter

Element deficiencies see Mineral deficiency

Elimination diet Definition An elimination diet functions as a test, determining whether patients may have a sensitivity to certain foods. Initially, patients stop eating foods suspected of causing illness. Then, after a suitable period of time (often 10–14 days), they review their symptoms. If significant improvement has occurred, it is assumed that an allergy or intolerance to certain foods may be involved. These suspect foods are then reintroduced to the diet, one by one. When symptoms return (usually within three days), the problematic food is identified and removed from the diet.

Benefits Elimination diets are potentially useful in identifying hard-to-detect food intolerances that proponents believe are responsible for a wide range of ailments. These include constipation, headaches, migraine, infections of the ear or sinuses, frequent colds, post-nasal drip, chronic nasal congestion, sore throats, chronic cough, eczema, hives, acne, asthma, pain or stiffness in the muscles or joints, heart palpitations, indigestion, ulcers of the mouth, stomach, or duodenum, Crohn’s disease, diarrhea, yeast infections, urticaria, edema, depression, anxiety, hyperactivity, weight change, and generalized fatigue.

Description The following lists of appropriate and inappropriate foods for an elimination diet represent general guidelines. Elimination diets vary according to practitioner and the specific symptoms or allergy. Foods that may be prohibited in an elimination diet include those containing: • Additives: monosodium glutamate, artificial preservatives, sweeteners, flavors, or colors. • Alcohol: beer, ale, stout, porter, malt liquors, wine, coolers, vodka, gin, rum, whiskey, brandy, liqueurs, and cordials. • Citrus fruits: oranges, calamondins, tangerines, clementines, tangelos, satsumas, owaris, lemons, limes, kumquats, limequats, and grapefruit. • Commonly eaten foods: anything consumed more than three times weekly, as well as foods that are craved or that cause a feeling of weakness. • Corn: as well as corn syrup or sweetener, corn oil, vegetable oil. popcorn, corn chips, corn tortillas. • Dairy products: milk, milk solids, cheese, butter, sour cream, yogurt, cottage cheese, whey, and ice cream. • Eggs: both yolks and whites. • Gluten: any pasta, breads, cakes, flour, or gravies containing wheat. • Honey. • Maple syrup. • Sugar: candy, soft drinks, fruit juices with added sugar or sweetener, cakes, cookies, sucrose, fructose, dextrose, or maltose. Foods that may be allowed include: • Cereals: puffed rice or millet, oatmeal, or oat bran. • Daily multivitamin: this is especially important during extended dieting to replace missing nutrients. • Fats and oils: soy, soy milk, soy cheese, sunflower oil, safflower oil, flaxseed oil, olive oil, and sesame oil. • Fruits and vegetables: typically, anything except corn and citrus fruits. Some practitioners suggest fruit be consumed in moderation, and preferably whole as opposed to juices. • Grain and flour products: rice cakes or crackers, rye or spelt bread (both must be 100% with no added wheat), kasha, rice, amaranth, quinoa, millet, oriental noodles, other exotic grains. • Legumes: soybeans, string beans, black beans, navy beans, kidney beans, peas, chickpeas, lentils, tofu.

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therapist reports on the effects of the therapy and on the patient’s progress.

Elimination diet

KEY TERMS Anaphylactic shock—An extreme allergic reaction characterized by swelling, constriction of the bronchi, circulatory collapse, heart failure, and even death. Urticaria—Itchy pustules that may be caused by a hypersensitivity to food, drugs, or other substances.

Canned beans should be avoided unless they are free of preservatives and sugar. • Seeds and nuts: must not contain sugar or salt. Nut butters are allowed if they meet this requirement and are organic. • Water: two quarts daily. Preferably bottled, as tap water contains potential allergens including fluoride and chlorine. • Other: honey, white vinegar, salt, pepper, garlic, onions, ginger, herbal teas, coffee substitutes, spices or condiments (mustard, ketchup) that are free from sugar, preservatives, and citrus. These products can commonly be found at health food stores. An important complement to any elimination diet is a food diary, in which all dietary consumption is recorded, along with any subsequent symptoms. Patterns should be evident after about one month of record keeping.

Precautions As with all therapies, anyone considering an elimination diet should weigh the potential benefits against the risks. The decision, according to some, is comparable to deciding to take a prescribed medication, and should be done only under the supervision of a competent medical practitioner. Elimination diets should never be used by individuals with severe food allergies, as reintroducing a suspect food may provoke an asthma attack, anaphylactic shock, or other dangerous reaction. Generally, an elimination diet will be used only when symptoms are believed to be related to just one or two suspect foods. Patients need to know that following a strict elimination diet is not an easy matter. It is extremely important to read packaged-food labels carefully, because many processed foods contain monosodium glutamate, sugar, and other substances that may be prohibited. It is almost impossible for elimination-diet patients to eat in restaurants, at school, or at the homes of friends. The resulting 856

isolation must be considered as part of the decision to undertake an elimination diet. Patients should also consider whether they have sufficient time for the extra planning, shopping, and food preparation involved. Elimination-diet patients should be vigilant to replace any nutrients missing from their restricted diet. For example, calcium supplements may be advisable for someone eliminating dairy products from the diet. Needless to say, any prescribed medications should be continued during any diet. Putting a very young child on an elimination diet may endanger the child’s nutrition and normal growth. A breastfeeding mother may harm both her own health and that of her infant if she undertakes an elimination diet during lactation.

Side effects The most significant side effects of an elimination diet are nutritional disorders resulting from a prolonged, highly restrictive diet, and the risk of a serious reaction as suspect foods are re-introduced to the diet. Some proponents also caution that patients consuming a very limited variety of foods risk becoming allergic to those very foods. For these reasons, professional supervision and substitution of missing nutrients are both essential.

Research and general acceptance Elimination diets are widely used by medical doctors, but considerable differences of opinion exist over the range of illnesses that may be caused by food allergies or intolerances. Many physicians and researchers question the role of allergies in migraine, rheumatoid arthritis, osteoarthritis, and other conditions. Some doctors suggest that elimination diets should be used only after other diagnostic methods have been tried, including history-taking, skin tests, blind food challenges, and radioallergosorbent testing.

Training and certification Because of the risks involved, elimination diets should be undertaken only under competent medical supervision. Some patients may wish to consult an allergy specialist. Resources BOOKS

Brostoff, Jonathan, and Linda Gamlin. Food Allergies and Food Intolerance: The Complete Guide to Their Identification and Treatment. Rochester, VT.: Inner Traditions Intl. Ltd, 2000.

David Helwig

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Definition An emergency medical technician-paramedic is a licensed and/or certified out-of-hospital health-care provider. EMTs represent the uppermost level of prehospital health care providers and serve as managers of prehospital treatment teams. They work under the direction of a physician—often by two-way radio—to evaluate and manage acutely ill or injured patients in ambulance services or other life-support units.

Description The emergency medical system is a complex emergency response structure that has strict guidelines for its certification levels of health professionals. Emergency medical technicians are classified under four levels of prehospital certification: First Responder; Emergency Medical Technician-Basic (EMT-B); Emergency Medical Technician-Intermediate (EMT-I), and Emergency Medical Technician-Paramedic (EMT-P). Education and training varies across the four levels, with the emergency medical technician-paramedic having the highest level of training. An emergency medical technician has developed independent reasoning and training to make rapid assessments and interventions that can save people’s lives. The EMT-P is considered an extension of the emergency room physician to the patient in the field and has the greatest amount of responsibility. Provision of initial treatment The responsibilities of an emergency medical technician are numerous, demanding, and extremely stressful. The EMT’s most common responsibilities are related to provision of initial treatment: • Organization and preparation for emergency calls: Besides having all of the equipment stocked, ambulance maintained and cleaned, and communication devices checked, the emergency medical technician must be psychologically and emotionally prepared to care for distressed patients and family members. • Immediate and safe response to the emergency scene by knowing the proper location and road systems while maneuvering a heavy and bulky ambulance through traffic. • Assessment of the safety hazards at the emergency scene, including the safety of the crew, the victims, and the bystanders—as well as understanding the nature of the injuries or illnesses that may be encountered.

• Rapid and efficient evaluation of victims of trauma or illness, using advanced patient assessment skills while recognizing and assigning priority to the most critical injury or illness. • Delivery of high-quality patient care while utilizing protocols for procedures and interventions established by the emergency medical technician agency, as well as recognizing the need for back-up by an emergency physician. • Transportation of patients to appropriate institutions if the patients are unstable or needing specialty care (i.e. neurological trauma, cardiovascular intervention). The emergency medical technician makes the decision regarding the best facility for managing the patient’s injury or illness. • Keeping records of all assessment findings and interventions completed on the patient from the field to the receiving facility. Other responsibilities Over the years, the scope of the EMTs responsibilities has widened to include educating the public about health issues and participating in injury and disease prevention programs. EMTs are also playing an increasingly important role in medical and public health research programs.

Work settings Emergency medical technicians can work in a variety of settings. Many EMTs work for ambulance agencies. On the other hand, emergency centers, sports facilities, long-term care facilities, and large industries are also employing emergency medical technicians to deliver health care.

Education and training Prerequisites Educational requirements for emergency medical technicians differ slightly from state to state. Some EMT programs are designed to accommodate part-time students; others are structured as full-time college-level courses of study. The average length of training for EMTs is 1000 hours, but upgraded standards will probably add a small increase to the number of training hours over the next few years. Persons considering an EMT-P program must be high school graduates and demonstrate their ability to meet the physical and psychological demands of emergency work. The physical demands are considerable, since EMTs must frequently lift and move patients away

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Emergency medical technicians Emergency medical technicians are trained to respond to emergency situations ranging from car accidents to chemical spills. (M. Kowal/Custom Medical Stock Photo. Reproduced by permission.)

from danger zones or into emergency vehicles, without time to call for assistance. Likewise, the sheer number of potential on-the-job hazards, ranging from toxic chemical spills or fire to collapsing buildings or human violence adds to the emotional stress of EMT work. In addition to demonstrating their physical stamina and emotional stability, persons entering an EMT-P program must be certified at the EMT-ambulance level. Some programs, however, offer a combination of EMT-ambulance and EMT-P training. Students who have acquired basic EMT training in the armed forces within the past 12 months and have had their work approved by a state agency may be permitted to enroll in an EMT-P program. Course work In some states, students enrolled in EMT-P programs are eligible to earn an associate’s degree. On the national level, the United States Department of Transportation (U.S. DOT) determines the minimum requirements that must be met for the education of emergency medical technicians. Accredited EMT-P programs include didactic instruction, in-hospital clinical experience, and a supervised field internship in an advanced life-support 858

unit. The course work should also acquaint students with an understanding of their legal and ethical responsibilities as emergency medical personnel. The education of a emergency medical technician focuses on three dimensions of human experience and activity: • The affective domain: assignment of various feelings, morals, and thoughts to information, situations, and scenarios. • The cognitive domain: recall of information and comprehension of facts, figures, and statistics. • The psychomotor domain: skill attainment through practice in clinical and controlled laboratory settings. Advanced skills and knowledge of medical management of patients in the field is a central component of EMT training. Common areas of training are: • advanced airway management techniques, including endotracheal intubation • intravenous fluid management, including the initiation of intravenous lines and administration of proper fluid replacement

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KEY TERMS

• cardiac monitoring, interpretation, and intervention • advanced patient assessment and evaluation • management of trauma patients • administration of established advanced cardiac life support, including defibrillation (delivering an electrical shock) for abnormal heart rhythms • administration of advanced first aid • complex immobilization techniques used in acute fractures, dislocations, and strains • proper physical restraining of violent patients, with training focused on safety and de-escalation techniques Continuing education and specialized training

Defibrillation—A procedure to stop the fibrillation (irregular contraction) of heart muscle by using electric shock. Emergency medical technician—A licensed and/or certified out-of-hospital health care provider who serves as the manager of the prehospital treatment team. Intubation—Inserting a tube in a patient’s mouth or nose to assist delivery of oxygen or air.

Practice: Introduction to Advanced Prehospital Care. Upper Saddle River, NJ: Prentice-Hall, 2000.

The education of EMTs does not end with course completion and certification or licensure. The importance of keeping one’s skills current is equally important. Every two years, emergency medical technicians must acquire a specific number of continuing education credits in order to maintain certification or licensure in their respective states. Most employers will provide classes for the emergency medical technicians to obtain the necessary continuing education credits.

Bledsoe, Bryan E., Robert S. Porter, and Richard S. Cherry. Emergency Medical Technician Care: Principles & Practice: Patient Assessment. Upper Saddle River, NJ: Prentice-Hall, 2000.

Specialized certifications are important for the emergency medical technician to complete and update every two years. These certifications include: Advanced Cardiac Life Support (ACLS), Pediatric Advanced Life Support (PALS), Basic Trauma Life Support (BTLS), and Prehospital Trauma Life Support (PHTLS).

Wilson, Landice. “On Call: Emergency Medical Technicians.”Career World 27 (February 1999): 21-23.

Future outlook The role of emergency medical technicians is expanding because of their ability to independently manage various types of patients. The emergency medical technician has become instrumental in transport of critical care patients from one facility to another via ground transport, helicopter, or larger aircraft. In order for a emergency medical technician to function on an acute care transport vehicle, additional training in critical care medications, ventilators, various advanced monitoring systems, and fluid management must be completed.

PERIODICALS

Miller, Danny. “When You Really Are the First Responder at the Scene.”Ocupational Health & Safety 70 (April 2001): 40-46.

OTHER

Lavonas, Eric. “Medical Control from Emergency Medicine/Emergency Medical Systems.”emedicine.comMay, 200l. . (May 11, 2001). National Association of Emergency Medical Technicians. 408 Monroe Street, Clinton, MS 39056. (601) 924-7744. [email protected].

Lori Beck, RN, MSN, FNP-C

EMG see Electromyography

Resources BOOKS

American Medical Association. Health Professions Career and Education Directory, 29th ed. Chicago, IL: AMA Press, 2001. Bledsoe, Bryan E., Robert S. Porter, and Richard S. Cherry. Emergency Medical Technician Care: Principles &

Emphysema Definition Emphysema is a chronic respiratory disease in which overinflation of the alveoli or air sacs causes a decrease in respiratory function and often dyspnea.

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• administration of emergency medications

Emphysema

Description Emphysema is the most common cause of death from respiratory disease in the United States, and is the fourth most common cause of death overall. There are 1.8 million Americans with the disease, which ranks fifteenth among chronic conditions that cause limitations of activity. Around 44% of those with emphysema state that their activities of daily living have been affected by the disease. Normally functioning lungs are elastic, efficiently expanding and recoiling as air passes freely through the bronchus to the alveoli, where oxygen is moved into the blood and carbon dioxide is filtered out. When a person inhales cigarette smoke, his or her immune system responds by releasing substances that are meant to defend the lungs against the smoke. These substances can also attack the cells of the lungs. Normally, the body inhibits such action by releasing other substances. In smokers and those with the inherited emphysema defect, however, no such prevention occurs, and the lung tissue is damaged in such a way that it loses its elasticity. The small passageways leading to the alveoli collapse, trapping air within the alveoli. The alveoli, unable to recoil efficiently and move the air out, overexpand and rupture. The smaller areas of alveoli destruction are known as blebs and the larger ones are called bullae. As the disease progresses coughing and dyspnea occur. In the later stages the lungs cannot supply sufficient oxygen to the blood. Emphysema often occurs with other respiratory diseases, particularly chronic bronchitis. These two diseases are often referred to as one—chronic obstructive pulmonary disease (COPD). Emphysema is most common among people aged 50 years and older. Those with inherited emphysema may experience the onset as early as their 30s or 40s. Men are more likely than women to develop emphysema, but female cases are increasing as the number of female smokers rises.

Causes and symptoms Heavy cigarette smoking causes about 80–90% of all emphysema cases. However, a few cases are the result of an inherited deficiency of alpha-1-antitrypsin (AAT). The number of Americans with this deficiency is relatively small, probably no greater than 70,000. Pipe, cigar, and marijuana smoking can also damage the lungs. While a person may be less likely to inhale cigar and pipe smoke, these types of smoke can also impair lung function. Marijuana smoke is even more damaging because it is inhaled deeply and held in the lungs longer by the smoker. 860

The symptoms of emphysema develop gradually over many years. It is a common occurrence for many emphysema patients to have lost 50–70% of their functional lung tissue before they become aware that something is wrong. Dyspnea, a chronic mild cough (which may be productive of large amounts of dark, thick sputum, and often dismissed as “smoker’s cough”), and sometimes weight loss are associated with emphysema. Initially, a patient may notice shortness of breath only when he or she is exercising. However, as the disease progresses, it will occur during less exertion, and ultimately with no exertion at all. Emphysema patients may also develop an enlarged, or “barrel,” chest. Other symptoms may include skipped breaths, insomnia, morning headaches, nasal flaring, increased difficulties breathing while lying down, chronic fatigue, and swelling of the feet, ankles, or legs. Those with chronic emphysema are at risk for other complications resulting from weakened lung function. These include pneumonia, pulmonary hypertension, cor pulmonale, and chronic respiratory failure.

Diagnosis A history of heavy smoking alone is not enough for a physician to differentiate emphysema from other respiratory diseases. A physician will combine information on symptoms, medical history, physical examination, lung function tests, and chest x ray results to make a diagnosis of emphysema. One of the first clues may be a hollow sound heard through a stethoscope as the patient’s chest is being tapped. The hollow sound is the result of the enlargement or rupture of the lungs’ alveoli. A variety of pulmonary function tests may be ordered. In the early stages of emphysema, the only result may be dysfunction of the small airways. Patients with emphysema may show an increase in the total amount of air that is in the lungs (total lung capacity), but a decrease in vital capacity. With severe emphysema, vital capacity is substantially below normal. Spirometry, a procedure that measures respiratory gases and resulting pulmonary function, aids in the diagnosis of emphysema. A chest x ray is often ordered to aid in the diagnosis of emphysema, though patients in the early stages of the disease may have normal findings. Abnormal findings on the chest x ray include excessive inflation of the lungs and an abnormally increased chest diameter. The diaphragm may appear depressed or flattened. In addition, patients with advanced emphysema may show an enlargement of the heart. The physician may observe blisters in the lungs and bulging of the accessory muscles of the respiratory system. Late in the disease an EKG will show signs of right ventricular failure in the heart

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and increased hemoglobin due to lower oxygen in the patient’s blood. Other tests that may be performed include peak flow measurements, arterial blood gases, and pulse oximetry.

Treatment Treatment methods for emphysema do not cure or reverse the damage to the lungs. However, they can slow the progression of the disease, relieve symptoms, and help control possibly fatal complications. The first step in treatment for smokers is to quit smoking to prevent any further deterioration of breathing ability. Smoking cessation programs may be effective. Consistent encouragement, along with the help of health care professionals as well as family and friends, can help increase the quit rate. If the patient and the health team develop and maintain a complete program of respiratory care, disability can be decreased, acute episodes of illness may be prevented, and the number of hospitalizations reduced. However, only smoking cessation has been shown to slow down the progression of the disease; and among all other treatments, only oxygen therapy has exhibited an increase in survival rate. Home oxygen therapy may improve the survival times in those patients with advanced emphysema who also have hypoxemia, or low blood oxygen levels. It may improve the patient’s tolerance of exercise, as well as improve their performance in certain aspects of brain function and muscle coordination. The functioning of the heart may also improve with an increased concentration of oxygen in the blood. Oxygen may also decrease insomnia and headaches. Some patients may receive oxygen only at night, but studies have illustrated that it is most effective when administered for at least 18, but preferably, 24 hours per day. Those patients just beginning the therapy may wish to postpone continuous oxygen administration until it becomes absolutely necessary because of inconvenience and decreased mobility. Portable oxygen tanks prescribed to patients carry a limited supply and must be refilled on a regular basis by a home health care provider. Medicare and most insurance companies cover a large proportion of the cost of home oxygen therapy. Patients should be instructed regarding special safety issues involving the transport and presence of oxygen in the home. A variety of medications may be used in the treatment of emphysema. Usually the patient responds best to a combination of medicines rather than one single drug. Bronchodilators are sometimes used to help alleviate the patient’s symptoms by relaxing and opening the airways. There are three primary categories of bronchodilators:

A scanning electron microscopy (SEM) of lung tissue showing the ruptured alveoli (air sacs) that characterize emphysema. (Photograph by Hossler, Custom Medical Stock Photo. Reproduced by permission.)

sympathomimetics (isoproterenol, metaproterenol, terbutaline, albuterol), which can be inhaled, taken by mouth, or injected; parasympathomimetics (atropine); and methylxanthines (theophylline), which may be administered intravenously, orally, or rectally. Another category of medication often used is corticosteroids or steroids (beclomethasone, dexamethasone, triamcinolone, flunisolide). These help to decrease the inflammation of the airway walls. They are occasionally used if bronchodilators are ineffective in preventing airway obstruction. Some patients’ lung function improves with corticosteroids, and inhaled steroids may be beneficial to patients with few side effects. A variety of antibiotics are frequently given at the first sign of a respiratory infection, such as increased amounts of sputum or a change in the color of the sputum. Expectorants can help loosen respiratory secretions, enabling the patient to more easily expel them from the airways. Many of the medications prescribed involve the use of a metered dose inhaler (MDI) that may require special instruction to be used correctly. MDIs are a convenient and safe method of delivering medication to the lungs. However, if they are used incorrectly the medication will not get to the right place. Proper technique is essential for the medication to be effective. For some patients, surgical treatment may be the best option. Lung volume reduction surgery is a surgical pro-

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KEY TERMS Alveoli—Small cells or cavities. In the lungs, these are air sacs in which oxygen enters the blood and carbon dioxide is filtered out. Arterial blood gases—A test to analyze blood for oxygen, carbon dioxide, and bicarbonate content, as well as blood pH. Used to test the effectiveness of respiration. Cor pulmonale—A disease characterized by an increase in bulk of the right ventricle of the heart that can lead to heart failure.

• Aerosol treatments. These treatments may involve solutions of saline, often mixed with a bronchodilator, which are then inhaled as an aerosol. The aerosols thin and loosen secretions. A treatment normally takes 10–15 minutes and is given three or four times a day. Patients with COPD can be instructed to perform a variety of self-help measures that can help improve their symptoms and ability to participate in activities of daily living. These measures include: • Avoiding any exposure to dust and fumes. • Avoiding air pollution, including secondhand cigarette smoke.

Hypoxemia—A condition characterized by deficient oxygen supply in the blood.

• Avoiding other people who have infections like the cold or flu, and getting a pneumonia vaccination and a yearly flu shot.

Peak flow measurement—Measurement of the maximum rate of airflow attained during a forced vital capacity determination.

• Drinking plenty of fluids to help loosen respiratory secretions so they can be coughed up more easily.

Pulmonary—Related to or associated with the lungs.

• Avoiding extreme heat or cold and high altitudes (special precautions can be taken that may enable the emphysema patient to fly on a plane).

Pulse oximetry—The noninvasive monitoring or determination of oxygen-hemoglobin saturation of the blood.

• Maintaining adequate nutritional intake; normally, a high-protein diet taken in many small feedings, is recommended.

cedure in which the most diseased parts of the lung are removed to enable the remaining lung and breathing muscles to work more efficiently. Preliminary studies suggest improved survival rates and better functioning with the surgery. Another surgical procedure used for emphysema patients is lung transplantation. Transplantation may involve one or both lungs. However, it is a risky and expensive procedure and donor organs may not be available. For those patients with advanced emphysema, keeping the air passages reasonably clear of secretions can prove difficult. Some common methods for mobilizing and removing secretions include: • Postural drainage. This technique helps to remove secretions from the airways. The patient lies in a position that allows gravity to aid in draining different parts of the lung. This is often done after the patient inhales and aerosol medication. The basic position involves the patient lying on the bed with chest and head over the side and forearms resting on the floor. • Chest percussion. This technique involves a caregiver lightly clapping the back and chest of the patient. It may help to loosen thick secretions. • Coughing and deep breathing. These techniques may aid the patient in bringing up secretions. 862

Many patients are interested in whether any alternative treatments for emphysema are available. Some practitioners recommend supplements of antioxidant nutrients. There have also been some studies indicating a correlation between a low vitamin A status and COPD, with suggestions that supplements of vitamin A might be beneficial. Aromatherapists have used essential oils like eucalyptus, lavender, pine, and rosemary, to help relieve nasal congestion and make breathing easier. The herb elecampane may act as an expectorant to help patients clear mucus from the lungs. The patient should discuss these remedies with their health care practitioner prior to trying them, as some may interact with the more traditional treatments already being given.

Prognosis Emphysema is a serious and chronic disease that cannot be reversed. If detected early effects and progression can be slowed, particularly if the patient ceases smoking immediately. Complications of emphysema include higher risks for pneumonia and acute bronchitis. Overall, the prognosis for patients with emphysema is poor, with a medical survival rate for all COPD patients of four years, and even less for emphysema patients. However, individual cases vary, and many patients can live much longer with supplemental oxygen and other treatment measures.

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Many members of the health care team may treat the patient with emphysema. The patient usually seeks help from a physician first, who will make the diagnosis. In the course of the diagnostic workup, x-ray technicians and respiratory therapists may treat the patient. The nurse plays an important role in assessing the patient, administering medications, in teaching the patient how best to cope with and understand the disease, and—in some cases—provides home care. The physical therapist may assist the patient to find ways of increasing their strength and activity tolerance.

Prevention The best way to prevent emphysema is to avoid smoking. Even patients with inherited emphysema should avoid smoking, as it hastens onset and worsens severity of the disease. If patients quit smoking as soon as evidence of small airway obstruction begins, they can significantly improve their prognosis. Resources

aged endocardium is more likely to become infected when bacteria enter the bloodstream. When this happens, during surgical or dental procedures, for example, a condition called bacteremia results. The circulating bacteria can then enter the heart, where damaged tissue or other abnormalities allow them to multiply and cause an infection. Endocarditis is a life-threatening disease that interferes with the heart’s ability to pump blood. Untreated, it is always fatal.

Description Endocarditis most commonly occurs in people whose hearts have damaged valves. This may be the result of acquired valvular disease from rheumatic fever or other diseases. Patients with mitral valve prolapse, in which a poorly functioning mitral valve regurgitates blood back into the heart, allowing bacteria to multiply, are also at risk for endocarditis. Prosthetic (artificial) heart valves are more likely to become infected as well. Bacteremia that causes endocarditis can occur in several ways:

BOOKS

• from a localized infection such as a urinary tract infection, pneumonia, skin infection, or dental infection

Beers, Mark H., and Robert Berkow. The Merck Manual of Diagnosis and Therapy, 17th ed. Whitehouse Station, NJ: Merck and Company, Inc., 1999.

• as a result of certain medical conditions, such as severe periodontal disease, colon cancer, or inflammatory bowel disease

PERIODICALS

• during dental or surgical procedures, such as dental cleaning, tooth extractions, tonsil removal, or endoscopic examinations

“Data Mounting on Merits of Lung Volume Reduction Surgery.” Family Practice News (February 15, 2001): 5. Lewis, Laurie. “Optimal Treatment for COPD.” Patient Care (May 30, 2000): 60. ORGANIZATIONS

American Lung Association. 1740 Broadway, New York, NY 10019. (212) 315-8700. . The National Emphysema Foundation. 15 Stevens St., Norwalk, CT 06856. . National Heart, Lung and Blood Institute. .

Deanna M. Swartout-Corbeil, R.N.

Endocarditis Definition Endocarditis is an infection of the endocardium, the inner lining of the heart muscle and its four valves (tricuspid, pulmonary, mitral, and aortic). Abnormal or dam-

• through in-dwelling catheters used for intravenous medications, intravenous feeding, or dialysis • intravenous drug use using unsterilized, contaminated needles and syringes The bacteria that cause most endocarditis are grampositive cocci, such as Staphylococcus or Streptococcus. Staphylococcal endocarditis occurs most often among intravenous drug users and patients with in-dwelling venous catheters. Gram-negative bacterial endocarditis or fungal endocarditis is much less common; patients are usually intravenous drug users or those with prosthetic heart valves. Endocarditis patients who appear critically ill are usually suffering from acute bacterial endocarditis, while those with subacute bacterial endocarditis have less severe but persistent symptoms such as weight loss, fatigue, and low-grade fever. If not discovered and treated, endocarditis can permanently damage the heart valves. If a valve is damaged, it may allow blood to flow backward—a condition known as regurgitation. As a result of a poorly function-

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Health care team roles

Endocarditis

vessels of the lungs, they may cause coughing or shortness of breath. Emboli lodged in the brain may cause a stroke, with such symptoms as numbness, weakness, or paralysis on one side of the body or sudden blindness or double vision. Emboli may also damage the kidneys, causing nephritis. Sometimes the capillaries on the surface of the spleen rupture, causing it to become enlarged and tender. Patients with any of these symptoms require immediate medical attention.

Diagnosis

ing valve, the heart muscle has to work harder to pump blood and may become weakened, leading to congestive heart failure.

Clinicians diagnose endocarditis by taking a history and performing a physical examination, during which they may observe such signs as fever, an enlarged spleen, signs of kidney disease, or hemorrhaging. The clinician may also detect a heart murmur. A heart murmur may indicate abnormal flow of blood through one of the heart chambers or valves. Laboratory analysis of the patient’s blood identifies the bacteria or other microorganisms that may be causing the infection.

Another danger associated with endocarditis is that the overgrowth of bacteria colonizing heart valves may break off and form emboli that can become lodged in arteries. An embolism to an artery supplying the brain can cause a stroke; an embolus lodged in the blood vessels of the lungs may cause pneumonia.

The diagnostic workup also involves echocardiography to check for abnormalities in the structure of the heart wall or valves. Conventional echocardiography uses ultrasound to view the structures of the heart. This diagnostic procedure is transthoracic; the ultrasound transducer is placed on the chest wall.

This echocardiogram shows an aortic regurgitation due to endocarditis, an infection of the lining membrane of the cardiac chambers. (Custom Medical Stock Photo. Reproduced by permission.)

Causes and symptoms Most cases of infective endocarditis occur in patients between the ages of 15 and 60, with a median age at onset of about 50 years. Men are affected about twice as often as women. Other risk factors for endocarditis are congenital heart problems, heart surgery, past history of endocarditis, and intravenous drug use. Patients with acute bacterial endocarditis are generally critically ill. Patients with subacute bacterial endocarditis tend to have a low-grade fever, which rarely rises above 102°F (38.9°C), chills, weakness, cough, difficulty breathing, headaches, arthralgias (aching joints), and loss of appetite, although these symptoms vary with individual patients. Emboli may also cause a variety of symptoms, depending on their location. Emboli throughout the body may cause Osler’s nodes, which are small, reddish, painful bumps most commonly found on the inside of fingers and toes. Emboli may also cause petechiae, which are tiny purple or red spots on the skin resulting from hemorrhages under the skin’s surface. Tiny hemorrhages resembling splinters may also appear under the fingernails or toenails. If emboli become lodged in the blood 864

One of the hallmarks of endocarditis that may be observed during echocardiography is vegetation, which is the abnormal growth of tissue, composed of blood platelets, bacteria, and a clotting protein called fibrin, that grows around a valve. Another indicator is regurgitation, or the backward flow of blood, through one of the heart valves. A normal echocardiogram does not exclude the possibility of endocarditis, but an abnormal echocardiogram can confirm its presence. If an echocardiogram cannot be performed or its results are inconclusive, a modified technique called transesophageal echocardiography is sometimes performed. This technique involves passing an ultrasound device into the esophagus to get a clearer image of the heart.

Treatment When infective endocarditis is suspected, the patient is admitted to the hospital and antibiotic treatment is started before the results of the blood culture are available. The choice of antibiotics depends on which infecting microorganism is suspected. Once the results of the blood culture become available, the physician will prescribe specific antibiotics known to be effective against the specific microorganism involved.

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Once the fever and acute symptoms have resolved, most patients are able to continue antibiotic therapy at home. During this time, patients make regular visits to the health care team to ensure that the antibiotic therapy is working, that it is not causing adverse side effects, and that there are no complications such as emboli or congestive heart failure. Patients must be advised to alert the health care team to any symptoms that could indicate serious complications. For instance, difficulty breathing or edema (swelling) in the legs could indicate congestive heart failure. Headache, joint pain, blood in the urine, or stroke symptoms could indicate an embolus; and fever and chills could indicate that the treatment is not working and the infection is worsening. Finally, diarrhea, rash, itching, or joint pain may suggest an adverse reaction to the antibiotics. Patients experiencing any of these symptoms should be advised to seek immediate medical attention. In some cases surgical intervention may be needed to treat congestive heart failure, recurring emboli, infection that does not respond to treatment, poorly functioning heart valves, and endocarditis involving prosthetic (artificial) valves. The most common surgical treatment involves debriding (cutting away) damaged tissue and replacing the damaged valve.

Prognosis Untreated infective endocarditis progresses and is always fatal. However, when diagnosed and properly treated within the first six weeks of infection, the infection can be completely cured in about 90% of the cases. The prognosis depends on a number of factors, such as the patient’s age and overall physical condition; the severity of the diseases involved; the exact site of the infection; how vulnerable the microorganisms are to antibiotics; and the nature of the complications.

KEY TERMS Aortic valve—The valve between the left ventricle of the heart and the aorta. Congestive heart failure—A condition in which the heart muscle cannot pump blood as efficiently as it should. Echocardiography—A diagnostic test using reflected sound waves to study the structure and motion of the heart muscle. Embolus—A bit of foreign material, such as gas, a piece of tissue, or tiny clot, that circulates in the bloodstream until it becomes lodged in a blood vessel. Endocardium—The inner wall of the heart muscle, which also covers the heart valves. Mitral valve—The valve between the left atrium and the left ventricle of the heart. Osler’s nodes—Small, raised, reddish, tender areas associated with endocarditis, commonly found inside the fingers or toes. Petechiae—Tiny purple or red spots on the skin associated with endocarditis, resulting from hemorrhages under the skin’s surface. Pulmonary valve—The valve between the right ventricle of the heart and the pulmonary artery. Transducer—A device that converts electrical signals into ultrasound waves and ultrasound waves back into electrical impulses. Transesophageal echocardiography—A diagnostic test using an ultrasound device passed into the esophagus of the patient to create a clear image of the heart muscle. Tricuspid valve—The valve between the right atrium and the right ventricle of the heart. Vegetation—An abnormal growth of tissue around a valve that can develop following a bacteremia. Vegetation is composed of blood platelets, the infecting bacteria, a few white blood cells, and fibrin, a protein involved in clotting.

Health care team roles Endocarditis is generally diagnosed by a primary care physician, emergency medicine physician, or cardiologist. Nurses, ECG technicians, laboratory technologists and other allied health professionals have important roles in the diagnosis of endocarditis as well as institution

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Today the treatment of endocarditis is more complicated as a result of antibiotic resistance. Over the past few years, especially as antibiotics have been overprescribed, more and more strains of bacteria have become increasingly resistant to a wider range of antibiotics. For this reason, a few different types of antibiotics—or even a combination of antibiotics—may be necessary to treat the infection successfully. Antibiotics are usually prescribed for about six weeks but may be given for an even longer period of time if the infection is resistant to treatment.

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of timely treatment. Nurses and other practitioners involved in triage or screening in the emergency department, clinic, office, or other treatment setting must accurately assess patients with indications of endocarditis. ECG technicians and laboratory technologists are responsible for performing the diagnostic tests, ECG, and blood cultures to confirm the diagnosis and causative microorganism. In the hospital, nurses and allied health professionals are responsible for closely monitoring patients for complications.

Prevention Some individuals are especially prone to endocarditis. These include patients with past history of endocarditis, those with congenital heart problems or heart damage from rheumatic fever, and patients with prosthetic heart valves. Intravenous drug users are also at increased risk. Patients at high risk for endocarditis need to take a dose of prophylactic antibiotics before undergoing procedures likely to cause bacteria to enter the bloodstream, such as most dental procedures. The American Heart Association recommends two grams of amoxicillin (children: 50 mg/kg) taken by mouth one hour before dental appointments. Patients who are allergic to penicillin can take clindamycin, cephalexin, or azithromycin instead. Resources

Endocrine system Definition The endocrine system is a widespread group of glands and organs that acts as the body’s control system for producing, storing, and secreting chemical substances called hormones.

Description The primary glands that compose the endocrine system are the hypothalamus, pituitary, thyroid, parathyroid, adrenal, pineal, ovary, and testes. The pancreas, considered both an organ and a gland, is also part of the system. The thymus is sometimes considered an endocrine-system organ. Although not part of the endocrine system, other organs that secrete hormones are the heart, brain, lungs, kidneys, liver, skin, and placenta. The word “endocrine” means that in response to specific stimuli, the hormones produced by the glands are released into the bloodstream.

Function Hormones are compounds produced by the endocrine glands. They generally control the growth, development, and metabolism of the body; the electrolyte composition of body fluids; and reproduction. The specific functions of the endocrine glands and pancreas are unique.

BOOKS

Ahya, Shubhada N., Kellie Flood, and Subramanian Paranjothi. The Washington Manual of Medical Therapeutics, 30th Edition. Philadelphia: Lippincott Williams & Wilkins, 2001. Faculty Members of the Yale University School of Medicine. The Patient’s Book of Medical Tests. Boston, New York: Houghton Mifflin Company, 1997. ORGANIZATIONS

American Heart Association. 7272 Greenville Avenue, Dallas, TX 75231. (214) 373-6300. . National Heart, Lung, and Blood Institute. Information Center, P.O. Box 30105, Bethesda, MD 20824-0105. (301) 9513260. . OTHER

“Infective Endocarditis.” The Merck Manual. . “Medical and Dental Perspectives on Infective Endocarditis: A Tale of Two Professions.” .

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Pituitary gland The pituitary is the master gland of the endocrine system. Located at the base of the brain, the gland, which is about the size of a marble, consists of two parts: anterior and posterior. The anterior pituitary produces hormones that either stimulate other glands (such as adrenal, testis, ovary, and thyroid) to produce target-gland hormones, or directly affect the target organs. Three of these hormones—adrenocorticotropic hormone (ACTH), gonadotropins, and thyroid-stimulating hormone (TSH)—act on other glands. ACTH stimulates the adrenal cortex to produce corticosteroid hormones and small amounts of male and female sex hormones. Gonadotropins are two hormones that regulate the production of male and female sex hormones and the egg (ova) and sperm (spermatozoa) cells. TSH stimulates the thyroid gland to produce and release thyroid hormone. Another pituitary hormone, growth hormone (GH), has a central role in controlling the growth and development of the body and its components, including organs, tissue, and muscle. It also affects the metabolism of car-

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Pineal

Pituitary

Hypothalamus

Thyroid parathyroids

Thymus

Adrenal gland (suprarenal gland)

Pancreas (islets of Langerhans)

Ovary (female) 2

Testis (male) 2

The structures of the endocrine system. (Delmar Publishers, Inc. Reproduced by permission.)

bohydrates, protein, and fat. For example, GH increases glucose levels in the blood by reducing the amount of glucose used by muscle cells and adipose tissue and by promoting glucose production from certain liver molecules. Other functions of GH include increasing the amount of amino acids that cells take from the blood and stimulating the breakdown of lipids (fats) in adipose tissue. The pituitary hormone prolactin acts with other hormones in female breast development and helps regulate breast-milk production (lactation). Two hormones, vasopressin and oxytocin, are stored but not produced in the posterior pituitary. Vasopressin, also called arginine vasopressin (AVP), helps the body to conserve water by increasing reabsorption of water from the kidneys. Oxytocin stimulates contractions in the uterus during childbirth and activates milk injection caused by an infant sucking on the breast.

Adrenal glands The adrenals are small glands on top of the kidneys. The adrenals have two parts: an outer layer called the cortex, and an inner layer called the medulla. The adrenal cortex produces a variety of hormones called corticosteroids, including hydrocortisone (cortisol), which helps increase blood glucose levels. It also reduces the amount of glucose absorbed by muscles and adipose tissue. Another function of cortisol is to protect the body from the adverse affects of stress, including emotional and physical trauma. The adrenal medulla produces adrenaline and noradrenaline, substances that increase the heart rate and blood pressure during times of stress. Their action is referred to as the “fight-or-flight” response.

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Thyroid gland The thyroid gland is composed of two sections in front of the windpipe and below the voice box. It produces two hormones, thyroxine (T4) and tri-iodothyronine (T3), which together are called the thyroid hormones. They help regulate growth and development and help in childhood brain development. The thyroid also contains cells that produce the hormone calcitonin, which helps to maintain normal calcium levels in the blood. Parathyroid glands The parathyroid complex is composed of four small glands, each the size of a pea, and each located on the four corners of the thyroid gland. They secrete parathyroid hormone, which regulates calcium levels in the blood. Pancreas The pancreas is located in the upper abdomen, just behind and below the stomach. It has two functions: to produce various enzymes that aid in digestion; and to produce insulin and glucagon, hormones that are key to the body’s management of glucose (sugar) in the blood. The primary purpose of insulin is to lower bloodglucose levels in the body. It helps form glycogen, proteins, and lipids, which are stored in the body (usually in the liver, muscles, and adipose tissue) to be used for energy. Glucagon increases blood-glucose levels, an action opposite to that of insulin. A strict balance between the glucagon and insulin is required to maintain proper blood-sugar levels. Hypothalamus Located deep inside the brain, the hypothalamus maintains direct control of the pituitary gland. It acts as the central “control room” of the endocrine system, directing the activities of the other parts of the system. These activities include regulating eating and drinking, sexual behavior, blood pressure, heart rate, body temperature, emotions, and the sleeping/waking cycle. When the brain receives information indicating that hormonal changes are needed somewhere in the body, the hypothalamus secretes chemicals that stimulate or suppress hormone production in the pituitary gland. Pineal and thymus The pineal is located in the center of the brain. This gland secretes melatonin, a hormone that helps regulate the sleeping/waking cycle. Disturbances in the production of melatonin causes jet lag, experienced by many long-distance travelers. Melatonin also influences devel868

opment of the male and female sex glands. The thymus processes lymphocytes in infants and is partly responsible for immune-system development. Ovaries and testes The ovaries and testes, also called the sex glands, produce cells and hormones essential to reproduction and development of the body, including male and female sex characteristics. The three types of sex hormones are estrogens, progestogens, and androgens (including testosterone). The main role of estrogens is to coordinate development and function of the female genitalia and breasts. Estrogens are also associated with the start of the menstrual bleeding cycle. Estrogen production in the ovary ceases during menopause. Estrogen is also produced in men (by the testes), though at lower levels than occur in women. Progestogens are produced in the ovaries during part of the menstrual cycle, and in the placenta during pregnancy. They cause changes in the lining of the uterus to prepare it for pregnancy, and they act with estrogens to stimulate mammary-gland development in the breasts to prepare for lactation. Progesterone is the main progestogen hormone. The primary androgen produced in the testes is the steroid testosterone. While mainly associated with male development, testosterone is produced in small amounts in women by the ovaries. During pregnancy, testosterone helps to develop the internal and external male sex organs. In males, testosterone promotes the growth of the sex organs and develops or stimulates male characteristics, such as deepening voice; growth of facial, pubic, and other body hair; and muscle growth and strength. In adult males, testosterone maintains the masculine characteristics and sexual potency and regulates sperm production.

Role in human health A wide variety and dozens of symptoms can indicate a hormonal imbalance in the body. However, a specific group of symptoms give an initial indication of a problem in the endocrine system. For example, excessive thirst, frequent urination, and unexplained weight loss are classic signs of diabetes mellitus, the most common endocrine disorder. Many primary-care physicians still treat endocrine problems, especially diabetes, themselves. However, the primary care doctor often makes a preliminary diagnosis and then refers the patient to an endocrine-system specialist, called an endocrinologist. Disorders of the endocrine system often, but not always, result from an over- or underproduction of a par-

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Common diseases and disorders There are two basic classes of endocrine disorders: problems associated with hormone-production levels, and problems caused by tissues that are unable to respond to hormones. Hormone-production disorders are broken into two groups: insufficient hormone production, called hypofunction; and too much hormone production, called hyperproduction. Endocrine-system disorders include the following: • Diabetes mellitus is a disease that includes type 1 and type 2 diabetes. Type 1 is an autoimmune disease caused when the immune system destroys certain insulin-producing cells in the pancreas. This causes the pancreas to produce little or no insulin. Type 1 diabetes usually develops in children and young adults, but it can appear at any age. Symptoms include increased thirst and urination, unexplained weight loss, blurred vision, and extreme fatigue. There is no cure; insulin, first used in 1921, remains the only treatment. Type 2 diabetes accounts for 90% to 95% of diabetes cases. It usually develops in adults over age 40 and is usually associated with obesity. In type 2, the pancreas produces insulin, but the hormone is not used effectively by the body, a condition called insulin resistance. Several years after onset, insulin production decreases below the level needed to maintain glucose homeostasis. The result is the same as for type 1 diabetes: glucose builds up in the blood because the body cannot use it efficiently. Symptoms develop gradually and include increased thirst and urination, weight loss, fatigue, nausea, blurred vision, frequent infections, and wounds or sores that heal slowly. Insulin resistance is treated with drugs such as thiazolidinedions (rosiglitazone and pioglitazone) and biguanides (metformen). When insufficient insulin is produced, type 2 diabetes appears. However, research indicates progression of insulin resistance to type 2 diabetes can usually be halted or slowed with the insulin-resistance medications, or by lifestyle changes that result in weight loss.

• Hypothyroidism is caused by the thyroid gland producing too little thyroid hormone. It can lead to severe hypothyroidism, a disorder that usually develops after age 40. Symptoms include intolerance to cold, lethargy, fatigue, weight gain, and mental sluggishness. Congenital hypothyroidism is present at birth and has the same symptoms. If left untreated, it can lead to mental retardation. The standard treatment for both hypothyroid disorders is thyroid hormone-replacement medications such as levothyroxine (Synthroid, Unithroid, Levoxyl, and Levothroid) and triiodothyrine. • Hyperthyroidism is due to an excess of thyroid hormones and affects women more frequently than men. Symptoms include nervousness, weight loss, intolerance to heat, diarrhea, heart palpitations, and insomnia. Some patients experience protruding eyes and trembling. Treatments include medications to inhibit thyroid-hormone production, and removal or destruction of the thyroid gland with radioactive iodine. The most common cause of the excessive thyroid production is Graves’ disease, an autoimmune disorder of the thyroid gland. • Addison’s disease is caused by underactivity or immune-system destruction of the adrenal gland. It can be life-threatening if left untreated. Symptoms include weakness, fatigue, nausea, dehydration, fever, and hyperpigmentation (darkening of the skin without sun exposure.) The standard treatment is with corticosteroid hormones and adequate dietary salt. • Cushing’s syndrome and Cushing’s disease are different disorders with similar symptoms: obesity, weakness, easily bruised skin, acne, and hypertension (high blood pressure.) Cushing’s syndrome is usually caused by excessive production of glucocorticoid hormones in the adrenal gland. However, it can sometimes be caused by benign or cancerous tumors of the adrenal gland. Cushing’s disease usually results from the overproduction of the adrenocoticotropic hormone in the pituitary gland, due to a benign tumor. Treatment for both disorders can include surgery, radiation therapy, chemotherapy, and blocking production of the glucorticoid hormones with drugs. • Less common endocrine disorders include acromegaly, gigantism, and hypogonadism. Acromegaly occurs in adults and gigantism in children. Both are caused by a pituitary tumor that spurs overproduction of growth hormone. Hypogonadism causes delayed sexual maturity in children and infertility in adults. It is caused by underproduction of follicle-stimulating hormone (FSH) in the pituitary gland.

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ticular hormone. Too much or too little of a hormone can be harmful. The endocrine organs use a feedback mechanism to regulate hormone levels. It acts much like a household thermostat, increasing production of a specific hormone when it detects too little in the blood, or decreasing production when it detects too much or the right amount. Tight control of hormone levels is needed for the body to function properly. The endocrine organs secrete hormones directly into the bloodstream, where special proteins usually bind to them, helping to maintain them as they travel through the body.

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Wilson, J. D. “Prospects for Research for Disorders of the Endocrine System.” Journal of the American Medical Association (February 7, 2001): 624.

KEY TERMS Adipose tissue—Connective tissue in which fat is stored and that has the cells distended by droplets of fat. Autoimmune—A term that refers to a condition in which antibodies or T cells attack the molecules, cells, or tissue of the body organ or system producing them. Electrolyte—A nonmetallic electric conductor in which current is carried by ion movement. Lactation—The secretion of milk by the mammary gland in the breasts. Lymphocytes—Weak cells produced in the lymphoid tissue. Menopause—The period when natural menstruation stops, usually between ages of 45 and 50. Menstruation—The discharge of blood from the uterus that occurs in approximately monthly intervals in females, starting at puberty.

Resources

American Association of Clinical Endocrinologists. 1000 Riverside Avenue, Suite 205, Jacksonville, FL 32204. (904) 353-7878. . American Diabetes Association. 1701 North Beauregard Street, Alexandria, VA 22311. (800) 342-2383. . American Thyroid Association. Montefiore Medical Center, 111 East 210th Street, Room 311, Bronx, NY 10467. (718) 882-6085. . Endocrine Society. 4350 East West Highway, Suite 500, Bethesda, MD 20814. (301) 941-0200. .

Ken R. Wells

Endodontic therapy see Root canal therapy Endodontics see Dental specialties

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BOOKS

Constanti, A., et al. Basic Endocrinology for Students of Pharmacy and Allied Health Sciences. Newark, NJ: Harwood Academic, 1998. Hall, J. E., and L. Nieman, editors. Handbook of Diagnostic Endocrinology. Totowa, NJ: Humana Press, 2001. Krentz, A. Churchill’s Pocket Book of Diabetes. New York: Churchill Livingston, 2001. Matthew, N. J. How the Endocrine System Works. Malden, MA: Blackwell Science, 2001. Wilson, J. D., et al. Williams Textbook of Endocrinology. St. Louis, MO: W. B. Saunders, 1998. PERIODICALS

American Diabetes Association. “Implications of the Diabetes Control and Complications Study.” Diabetes Care (January 2001): 825. Elliott, B. “Diagnosing and Treating Hypothyroidism.” The Nurse Practitioner (March 2000): 92+. Emanuele, N. and M. A. “The Endocrine System: Alcohol Alters Critical Hormonal Balance.” Alcohol Health and Research World (Winter 1997): 53-64. Hiller-Sturmhofel, S., and A. Bartke. “The Endocrine System: An Overview.” Alcohol Health and Research World (Summer 1998): 153-154. Lamberts, S. W. J., et al. “The Endocrinology of Aging.” Science (October 17, 1997): 419-424.

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ORGANIZATIONS

Definition An endoscope is characterized by its often long, thin (sometimes flexible) lighted tube containing fiber-optical instrumentation attached to a viewing device through which one may closely observe, via the naked eye or an attached camera, the surface of a canal or hollow organ in the body.

Purpose The endoscope is often used as a form of less invasive monitoring of the body instead of, or in conjunction with, surgery. A key aspect of the device is that it is not only capable of traversing the body to allow direct observation, but may also be equipped with endoscopic accessories that allow manipulation and diagnostic/therapeutic procedures to be performed much less invasively than more conventional surgical operations. Endoscopic surgery minimizes pain, hospital stays, and recovery time, which is good for patients. Its use is also promoted by health insurance companies and hospital administrators inclined toward reduced costs as well as to offer the best treatment options technology can provide.

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The endoscope is a generalization of a broad variety of fiber-optical scopes used to elucidate diverse aspects of the body to medical practitioners for various purposes. Endoscopes come in two main categories: rigid and flexible. The rigid endoscope is designed with a rigid insertion tube and is preferred over flexible endoscopes when feasible because the rigidity allows use of optics that permit greater resolution and the absence of a visible lattice structure. However, it is more difficult to design and construct a rigid endoscope, which entails using lenses rather than fibers to transmit the image externally to the user or to a camera. The fiber-optical endoscope can in general be viewed as a simple input/output device that utilizes an objective lens system along with a fiber relay and an ocular for magnification. The objective component is inserted directly into the body with a lighting constituent and focuses an image onto the two-dimensional surface of the array of fibers. These fibers, on the order of 10 micrometers, are bundled in groups of hundreds of thousands. Each pixel of a picture can be associated with a fiber in a one-to-one fashion of input light that is transferred from the objective end through the optical fiber relay, and magnified by the ocular to an output image on camera or seen with the naked eye. The elegant aspect is that these fibers may be twisted and flexed without damaging the image, which proves to be an integral element in many types of endoscopy. The optical layout discussed above has been simplified considerably; for spherical, chromatic, and other optical aberrations must be dealt with in order to manufacture a functional endoscope. Not only must endoscopes be precisely organized optically, but great care must be taken to ensure their biocompatibility, since they come in close contact with extremely sensitive internal body surfaces. Accordingly, biocompatibility is of prime importance to the United States Food and Drug Administration (FDA), which considers endoscopes to be “short-term mucosal contacting, externally communicating devices and testing [for approval of use] should include, but is not limited to, mucosal irritation, sensitization, cytotoxicity, acute systemic toxicity, and short-term implantation.” Endoscopes may be used to observe and biopsy as well as to perform actual surgeries through tiny incisions in appropriate sites. The latter generally involves use of miniature video cameras and minute surgical instrumentation, often electrosurgical equipment, forceps, or biopsy attachments. While fiberoptic technology utilizes extremely thin strands of glass or plastic to transmit light through repeated internal reflection along the optical fiber lengths

for image formation and visualization, other forms of endoscopy have surfaced. Electronic endoscopes, which do not require fiber optics (yet possess a field-of-view identical to the fiber-optic endoscope as well as similar controls depressible by finger-tip, i.e. air insufflation, suction, and water injection) are also on the market. These devices boast a mounted computer chip (in reality three chips for red, blue, and green light) on the tip. They are lower-maintenance due to the lack of fiber optics, and images from them can easily be sent to a television monitor for the entire operating room to view. Even more recently (as of July 2001), technology has permitted the development of high-speed 3D endoscopic measurements. Forms of endoscopy The abundance of instruments falling under the designation “endoscope” includes the following, with brief descriptions of each: • Amnioscope: Used to examine the fetus through the cervical canal prior to membrane breakage. • Angioscope: Used to examine the interior of blood vessels. The scope must thus be very long, slender (generally on the order of 0.5 mm), and flexible to accomodate navigation of minute spaces and dynamic curvature. • Arthroscope: Used to examine intraarticular surfaces of joints. Arthroscopes are rigid and contain stacks of optical lenses while the eyepiece is generally attached to a video camera. Due to the frequency of knee injuries, the arthroscope is most often used to diagnose and help treat knee damage. • Bronchoscope: Aids in exploring the interior of the bronchi, their branches, and tracheal mucosa (the windpipe tissue lining). • Choledochoscope: Used to examine the bile duct (duct carrying bile from the liver to the gallbladder or from the gallbladder to the small intestine) during an open surgical procedure intraoperatively. Both rigid and flexible scopes are employed. • Colonoscope: Used to examine the lower section of the bowel, the large intestine, i.e. the colon. • Culdoscope: Used to examine the pelvis and its structures. The scope is normally introduced through a small incision in the posterior vaginal cul-de-sac. • Cystoscope: Used to examine the urinary tract and bladder; it employs similar optics to the arthroscope, yet possesses a longer depth of insertion. • Cystourethroscope: Used to examine the urethra, bladder, and distal ureter.

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Description

Endoscope Endoscope machinery. (Photograph by Christopher Springmann. The Stock Market. Reproduced by permission.)

• Encephaloscope: Used to examine brain cavities. • Endoscopic retrograde cholangiopancreatography: Used in diagnosis of pancreatic disease through injection of radio-opaque dye into biliary and pancreatic ducts while examining the duodenal area. • Enteroscope: Used to examine the esophagus, small intestine, and stomach. • Esophagogastroduodenoscope: Used to examine the esophagus, duodenum, and stomach.

• Laryngoscope: Used to examine the larynx (the sphincter at the entrance of the trachea). • Mediastinoscope: Used to examine the mediastinum (mass of tissues and organs separating the lungs, i.e. the heart, esophagus, trachea, etc). Often used for visualization of lymph nodes and tumors in the superior mediastinum. • Nephroscope: Used to examine the kidneys, i.e. the renal pelvis, calyces, and upper ureter. It is employed during open procedures intraoperatively.

• Esophagoscope: Used to examine the channel connecting the pharynx to the stomach.

• Proctoscope: Used to examine the rectum.

• Gastroscope: Used to examine the stomach lumen.

• Resectoscope: Used to perform resections of tissue as a part of a diagnostic or therapeutic procedure.

• Gonioscope: Used to examine and help determine the configuration of the angle between the iris and cornea.

• Rhinoscope: Used to examine the nasal cavity.

• Hysteroscope: Used to examine the passage of the uterine cervix and cavity.

• Sigmoidoscope: Used for direct examination of the sigmoid colon.

• Laparoscope: Used to examine the peritoneal cavity through the anterior abodominal wall and is commonly rigid. This scope is the most common type used by the general surgeon.

• Thoracoscope: Used to examine the pleural cavity through an intercostal space (space between adjacent ribs, filled by intercostals muscles).

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• Ureteroscope: Used to examine the ureter.

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Operation Endoscopic procedures are sometimes performed under local anesthesia, especially with regard to upper gastrointestinal endoscopy. However, the majority of patients are sedated entirely. After the appropriate anesthetic has been administered, the physician inserts the endoscope in the anatomically relevant position and views the patient. The anesthesiologist, meanwhile, remains busy watching for blood pressure drops and reductions in oxygen saturation; this concern has resulted in a mandate that elderly, cardiovascularly risky, and anemic patients receive extra oxygen during the procedure. Of paramount importance is the disinfection of used endoscopes. Endoscopic cross-infection is rare, but does occur. According to Davidson’s Principles and Practice of Medicine, cross-infection has occurred in three ways: • Transmission of pathogenic organisms from one patient to another, with salmonella the most frequent organism. • Transmission of infection, such as hepatitis B, to staff by needle-stick injury. • Introduction of opportunistic organisms that colonize the instruments in storage. These may cause serious infection in immunocompromised patients and can cause sever biliary or pancreatic sepsis if introduced during endoscopic retrograde cholangiopancreatography. To eliminate this possibility, many medical practices have become accustomed to disinfecting endoscopes again in the morning before the first patient arrives. To prevent the above from occurring, health personnel must abide by strict procedures. Endoscopes should be submerged in detergent and water immediately upon removal from a patient. Valves and other removable components (including such endoscopic accessories as biopsy forceps) must be meticulously cleansed with cotton tips and a soft toothbrush, while channels must be washed. Disinfection by immersion in 2% gluteraldehyde (or 10% succine dealdehyde) for at least 20 minutes is strongly recommended since the scrubbing does not wipe out bacteria entirely. Also, medical personnel should wear gloves and masks as well as eye protection for positive hepatitis B or HIV patients. The general guideline for endoscopic disinfection is fivefold: cleaning (by mechanical scrubbing); disinfecting (by immersion in guteraldehyde or some other high-level disinfectant); rinsing (using sterile water); drying (using forced air prior to storage); and storing (without recontaminating equipment, i.e. by hanging it vertically).

Maintenance Proper care of endoscopes and endoscopic instrumentation should result in: • enhanced life span of endoscopes and accessory instruments • reduced repair and replacement costs • low number of microorganisms, restricting infection possibilities As indicated above, disinfection is a chief concern in the field of endoscopy. Proper disassembly, cleansing, rinsing, drying, storage, and reassembly of the equipment, all according to the manufacturer’s instructions, can help it to remain viable and safe for a long while. Corrosion is a common cause of equipment failure; stainless steel can in fact spot and stain. According to the company Gamma Endoscopy, “when endoscopic instruments do spot or stain common causes are: • very acid or alkaline pH detergents • improperly dissolved detergent leaving residual powder • high mineral content of the water used for cleaning, rinsing, or in the steam autoclave • residual disinfection solution • disinfection solutions with an acidic pH • residual blood, organic matter, or irrigation solution (e.g. saline), especially if instruments are not completely disassembled or thoroughly cleaned • chemical change resulting from prolonged exposure of dissimilar metals to electrolytic solutions (e.g. normal saline, disinfection solutions) • scratches on instruments that allow corrosive agents to get below the passivation layer, a protective layer on the instrument surface All moving parts should be lubricated before [reassembly] to prevent ‘freezing’ of stopcocks and forceps jaws. It is necessary to check the instruction manual to determine which parts to lubricate, and a waterbased lubricant may be used when reassembling portions of instruments before sterilization/disinfection. Because sterilization/disinfection mediums may not penetrate tight-locking mechanisms, endoscopic instruments should not be reassembled before sterilization or disinfection.” If all other methods fail, endoscopes may be sent to instrument refurbishment companies that specialize in endoscopic repair.

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• Urethroscope: Used to examine the urethra.

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CO 80231-5711. (800) 755-2676 or (303) 755-6300. .

KEY TERMS

OTHER

Fiber optics—A technology using glass (or plastic) fibers to transmit data. A fiber optic cable is simply a bundle of these threads, each of which is capable of transmitting light wave data. Fiber optic cables can carry much more data in less space than conventional metal wires (i.e. they have greater bandwidth), are thinner and lighter, and are appropriate for transmission of digital data. It is possible to construct flexible fiber bundles that are spatially aligned for use in endoscopic procedures.

Endoscope Tutorial. .

Bryan Ronain Smith

Endotracheal tube management Definition

Health care team roles Physicians perform endoscopic procedures while nurses and other medical personnel aid them. Health personnel prepare the equipment prior to examination and play a critical role in disinfecting it after the procedure has culminated. Endoscopes and accessories should be examined by health care staff for structural integrity, proper function, and cleanliness before use; during the exam; immediately following disinfection procedures; and prior to disinfection/sterilization. It is also recommended that endoscopes and accessories be thoroughly tested before initial use and used in accordance with the manufacturer’s manual.

Endotracheal tube management consists of ensuring a patent (open and unblocked) airway, suctioning pulmonary and oral secretions, and providing frequent oral and/or nasal care.

Purpose The endotracheal tube is the most common artificial airway used for short-term airway management or mechanical ventilation. The tube may be inserted either orally or nasally. The patient with a endotracheal tube must be closely monitored to ensure that the tube remains patent, that skin breakdown does not occur from the tube, and that infection is prevented.

Precautions Training Training varies from procedure to procedure among the widely varying types of endoscopy; however, disinfection training is essentially similar, except that there are major differences in cleansing between rigid, flexible (the most difficult), and electronic endoscopes.

Description

Resources PERIODICALS

Dietze, B., H. Neuman, U. Mansmann, and H. Martiny. “Determination of Gluteraldehyde Residues on Flexible Endoscopes after Chemothermal Treatment in an Endoscope Washer-Disinfector.” Endoscopy 33, no. 6 (2001): 529-532. Hasegawa, K., and Y. Sato. “Endoscope system for high-speed 3D measurement.” Systems and Computers in Japan 32, no. 8 (July 2001): 30-39. ORGANIZATIONS

The Association of Perioperative Registered Nurses (AORN). AORN, Inc., 2170 South Parker Rd., Suite 300, Denver,

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If the patient is restless or agitated, any activities that involve loosening the straps that hold the endotracheal tube in place should be rescheduled for a time when the patient is calm or after a sedative has been given. Otherwise, the tube may be inadvertently removed and the airway lost.

A primary portion of endotracheal tube management is suctioning down the tube every two hours or as needed. This is a sterile procedure. The color and amount of any sputum return should be noted since the endotracheal tube provides a direct connection to the lungs, making these patients highly susceptible to infection. The oral cavity should also be suctioned as these patients often have difficulty swallowing saliva. The patient must also be monitored for skin breakdown in either the oral or nasal cavity (depending on where the tube is inserted). Thorough oral care should be provided every eight hours and as needed. If the patient

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The endotracheal tube has a cuff that is inflated with air to hold the tube in place in the trachea. The amount of air in the cuff should be checked every eight hours to ensure that the cuff is not exerting too much pressure on the trachea walls. This is often done by the respiratory therapist, but may also be done by the nurse.

Preparation Any needed supplies for endotracheal tube care should be at the bedside prior to beginning the procedure. This includes a sterile suction kit, a bottle of sterile 0.9% sodium chloride, sterile gloves, a clean bite block if necessary, and tape already torn into appropriately-sized pieces. It is recommended that another health care professional firmly hold the endotracheal tube in place during any activity that requires loosening the straps that hold the tube. The patient should also be preoxygenated with 100% oxygen prior to suctioning.

KEY TERMS Bite block—Plastic device inserted into the patient’s mouth to prevent him/her from biting on the endotracheal tube. Endotracheal tube—Flexible tube inserted into the trachea via either the oral or nasal cavity for the purpose of providing an airway and supplemental oxygen, as well as providing access for suctioning.

form sterile suctioning and both are responsible for assessing respiratory status. However, it is usually the nurse who repositions the tube and provides oral care. Resources BOOKS

“Providing Endotracheal Tube Care.” In Critical Care Skills: A Nurse’s PhotoGuide, edited by June Norris. Springhouse, PA: Springhouse Corporation, 1996, pp. 280-293. Thelan, Lynne, et al. Critical Care Nursing: Diagnosis and Management. St. Louis, MO: Mosby, 1998.

Abby Wojahn, RN, BSN, CCRN

Aftercare All waste should be properly disposed of, either in the garbage or a biohazard container. The respiratory status of the patient should be reassessed. The insertion point (in centimeters) of the endotracheal tube should be confirmed to be the same as prior to the procedure, unless the purpose of the procedure was to change the depth of the tube.

Complications The greatest risk of manipulating the endotracheal tube is that it may be inadvertently removed, causing the patient to experience respiratory distress.

Results The anticipated outcomes of endotracheal tube management include a continuously patent airway, control of oral and pulmonary secretions, and prevention of infection.

Health care team roles The nurse and respiratory therapist are equally responsible for endotracheal tube management. Both per-

Endurance testing Definition Endurance testing involves determining the amount of time a person can maintain an activity or perform a task or activity of daily living before becoming fatigued and needing to stop. The level of activity used to test endurance can be minimal to maximal.

Purpose Endurance testing is often used to assess a person’s cardiovascular fitness to determine if cardiovascular disease is present and to evaluate the patient before embarking on a physical fitness program. The goal of exercise testing is to produce a sufficient level of exercise stress without too much strain on an individual. Exercise tests measure heart rate, blood pressure, respiratory rate, and breathlessness. The patient also reports on a rating of perceived exertion (RPE), which is a 15-point scale that

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has a bite block to prevent them from biting the tube, it must be removed and cleaned or replaced every eight hours. The tube should be repositioned so that it is not continuously exerting pressure in the same area. If the tube is taped to the patient’s face, the tape must be removed and replaced on the opposite side of the face at least once per day and as needed.

Endurance testing

grades exertion from extremely light to extremely hard. Clinicians make note of any discomfort or pain. Maximal exercise testing can be used to determine the greatest amount of activity a person can endure and how rigorous the activity can be. Submaximal testing determines the best level for a person to safely engage in during a physical activity program. Other types of endurance testing are important in determining how independent an individual can be in performing work activities. Such testing is particularly important in work hardening programs. A person who is injured on the job may be referred to a rehabilitation therapist for work hardening treatment. The therapist ascertains whether the individual can perform job tasks, and if not, designs a relevant rehabilitation program. It is often a challenge to accurately duplicate work environments.

Precautions A person with poor balance or coordination should not undergo endurance testing that involves movements that could cause dizziness or fainting. Persons with cardiac disease, hypertension, or diabetes could experience distress during endurance testing and must be closely monitored.

Description Clients are generally referred to a therapist by a physician treating them for a disease or disability. The physician often includes specific instructions. Endurance testing can be conducted in a variety of ways. A device such as a dynamometer is used to measure strength, and physical endurance can subsequently be charted. A therapist can determine endurance by instructing a client to perform a particular task for a specific length of time or perform the task for a specific number of repetitions. A therapist also can instruct a client to perform a task until becoming fatigued. Exercise testing protocols TREADMILL TEST. The treadmill is one of most commonly used endurance tests. Although the Bruce Treadmill Test protocol has been the most widely used, its results have been considered to sometimes overestimate a person’s exercise capacity. Although it is best suited for younger and active patients, the Bruce protocol was designed to diagnose cardiovascular disease. During treadmill tests, individuals walk on various inclines at various speeds for increasing lengths of time. BICYCLE ERGOMETRY. Bicycle tests are a common alternative to treadmill testing. A bicycle ergometer

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measures the individual’s workload and increases workload in increments for eight to 12 minutes. For patients with lower limb limitations who cannot be tested on a treadmill or bicycle, the upper limb ergometer, a modified bicycle with hand-powered pedals, is used. For wheelchair-bound individuals, some clinicians have fabricated wheelchair ergometers. Such testing is not widely used because of lack of equipment. TWELVE-MINUTE RUN TEST. This test consists of various run-walk tests. It is typically used to evaluate cardiopulmonary fitness for functional individuals. The patient is asked to cover the longest distance possible in 12 minutes, preferably by running, but by walking if needed. TWENTY-METER SHUTTLE TEST. This test assesses maximal aerobic capacity and was designed for children, adults, and athletes. The subject runs between two lines spaced 20 meters apart. The examiner increases the pace at which the subject is required to run back and forth. The highest speed reached is the maximal aerobic speed. ONE-MILE TRACK WALK TEST. This test was designed for many age groups and fitness levels. The examiner records the time an individual can walk one mile. SELF-PACED WALKING TEST. This test was developed for the elderly and for those with low fitness levels. It involves walking at three speeds down a hallway while speed, time, stride frequency, and heart rate are measured. This protocol evaluates a person’s walking efficiency and cardiopulmonary capacity. It does not actually test endurance but can provide guidelines for activities of daily living.

Many people are affected by low endurance or loss of stamina for a variety of reasons. After age 50, muscle strength and endurance begin to decline. People with physical disabilities also typically have endurance problems. A typical treatment plan to build endurance includes such aerobic exercise as walking, jogging, swimming, and bicycling. Aerobic exercise improves cardiovascular health, which also increases endurance. Specific activity goals should be set for the client. In work-hardening programs, therapists use several assessment devices to determine a person’s capacity to return to work. The Baltimore Therapeutic Equipment (BTE) work simulator allows users to replicate most upper-limb motions and tasks involved in many job activities. For example, a client may be asked to repetitively lift a box weighing 40 pounds (18 kg) at any pace until becoming tired. How well the simulator measures endurance has only been analyzed recently. Clients were found to have

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A computer monitors this man’s cardiorespiratory system performance as he exerts himself on an exercise bike. (Photograph by James King-Holmes. Science Source/Photo Researchers. Reproduced by permission.)

an easier time completing tasks in the simulated environment than in the workplace. One occupational therapist who performs work-hardening programs for workers injured on off-shore oil rigs found that employees were able to perform the strenuous work in the air-conditioned clinical setting but did not last long after getting back to the humid conditions of the workplace. To improve the program, the therapist built a facility and duplicated the humid conditions, then tested clients for a full work day.

Preparation A thorough medical history is taken and all surgeries documented prior to administering an exercise test. Practitioners should inquire about current medications and any physical or cognitive limitations the individual may have. This alerts medical professionals to any underlying problems or possible complications. Other issues that should be considered when determining exercise testing protocol are the person’s age, weight, nutritional status, mobility, assistive device use, and work environment.

To conduct an aerobic test, clinicians should ensure that the risk of injury is minimized. The client should be instructed how to properly perform exercises to avoid injury. Practitioners should keep in mind that an exercise test can be too stressful depending on the person’s condition. Any medical professional involved in administering exercise testing should be certified in cardiopulmonary resuscitation (CPR). Proper monitoring depends on individual circumstances. Heart rate is typically measured before, during, and after any testing procedure. The 12-lead electrocardiogram (EKG) is monitored before the test and periodically throughout the test. Following the test, the EKG and blood pressure are measured again, and every one to two minutes subsequently until levels return to baseline.

Aftercare Following completion of a treatment program for building strength and endurance, a client should be educated on a continuing treatment program to be done at home. Strength and endurance will wane if activity is not maintained.

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Complications Occupational and physical therapists in return-towork programs must take into consideration that work simulation techniques don’t entirely duplicate working conditions. The type of activity performed may also affect endurance. A person may show less endurance when performing an activity that he or she finds unpleasant or perceives as useless. The most effective intervention and treatment programs are associated with clients performing tasks they enjoy or that reflect the individual’s self-worth.

Journal of Back and Musculoskeletal Rehabilitation 55 (March/April 2001): 184–190. Ting, W., J. Wessel, S. Brintnell, R. Maikala, and Y. Bhambhani. “Lifting Endurance in Healthy Men.” American Journal of Occupational Therapy 50 (May 1996): 338–346. ORGANIZATIONS

The American Occupational Therapy Association. 4720 Montgomery Lane, Bethesda, MD 20824-1220. (301) 652-2682. . The American Physical Therapy Association. 1111 North Fairfax Street, Alexandria, VA 22314-1488. (703) 6842782. .

Meghan M. Gourley

Health care team roles Collaboration among all caregivers plays a big part in any kind of rehabilitation intervention. Referring physicians should communicate with the therapist about the client and what treatment is recommended. Social workers or mental health professionals involved with the client should also be apprised of interventions, because emotional problems could affect test outcomes. Resources BOOKS

Frontera, Walter R., ed. Exercise in Rehabilitation Medicine. Champaign, IL: Walter R. Frontera, David M. Dawson, and David M. Slovik, 1999. Grabois, Martin, Susan J. Garrison, Karen A. Hart, and L. Don Lehmkuhl, eds. Physical Medicine & Rehabilitation, The Complete Approach. Houston, TX: Blackwell Science, Inc., 2000. Reed, Kathlyn L., and Sharon Nelson Sanderson. Concepts of Occupational Therapy. Baltimore, MD: Lippincott Williams & Wilkins, 1999. Shankar, Kamala. Exercise Prescription. Philadelphia: Hanley & Belfus, Inc., 1999. PERIODICALS

Dean, Elizabeth, and Vanessa Noonan. “Submaximal Exercise Testing: Clinical Application and Interpretation.” Physical Therapy 80 (August 2000): 782-807. Dolecheck, Roy, Jesica and Janette K. Schkade. “The Extent Dynamic Standing Endurance is Effected [sic] When CVA Subjects Perform Personally Meaningful Activities Rather than Nonmeaningful Tasks.” The Occupational Therapy Journal of Research 19 (Winter 1999): 40–54. Lan, Ching, Jin-Shin Lai, Ssu-Yuan Chen, and May-Kuen Wong. “Tai Chi Chuan to Improve Muscular Strength and Endurance in Elderly Individuals: A Pilot Study.” Archives of Physical Medicine and Rehabilitation 81(May 2000): 604–607. Schramm, Donna Marie. “Applications of Physical and Occupational Therapy in Chronic Pain Syndrome.”

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Enema administration Definition The term enema is used to refer to the process of instilling fluid through the anal sphincter into the rectum and lower intestine for a therapeutic purpose. An enema administration is performed using a flexible plastic rectal tube with several large holes in the tip. This is connected to the tubing from a solution bag or container. An enema can also be performed using a prepackaged solution that comes in a soft plastic bottle with a pre-lubricated rectal tip attached. Enema solutions are prepared using plain tap water or saline, soapsuds solutions, oil solutions, or various medication solutions.

Purpose The most common purpose for administering an enema is to stimulate peristalsis (involuntary contraction) and to evacuate stool from the rectum. A tap water or soapsuds enema dilates the bowel, stimulates peristalsis, and lubricates the stool to encourge a bowel movement. These types of enemas are instilled and held for five to 10 minutes, as tolerated. They are used to treat constipation, to cleanse the bowel before a bowel exam, and to cleanse the bowel before bowel surgery. Another type of enema, the oil retention enema, is prepared in a smaller volume and is retained in the bowel for 30–60 minutes. The purpose of the oil retention enema is to soften the hardened stool and allow normal elimination. Enemas are also used to deliver medication directly onto the rectal mucous membranes to be absorbed into the bloodstream. Steroid enema solutions can be administered to alleviate bowel inflammation in patients with ulcerative colitis.

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Precautions Enemas should not be used as a first-line treatment for constipation. Frequent use of enemas can lead to fluid overload, bowel irritation, and loss of muscle tone of the bowel and anal sphincter. Never deliver more than three consecutive enemas to treat a patient. A patient with diarrhea may not be able to hold an enema. Enema administration must be used with caution in cardiac patients who have arrhythmias or have had a recent myocardial infarction. Insertion of the enema tube and solution can stimulate the vagus nerve which may trigger an arrhythmia such as bradycardia. Enemas should not be given to patients with undiagnosed abdominal pain because the peristalsis of the bowel can cause an inflamed appendix to rupture. Enemas should be used cautiously in patients who have had recent surgery on the rectum, bowel, or prostate gland. If the patient has rectal bleeding or prolapse of rectal tissue from the rectal opening, cancel the enema and consult with the physician before proceeding. Do not force the enema catheter into the rectum against resistance. This can cause trauma to the rectal tissue. Use only mild castile soap for soapsuds enemas because other soap preparations are too harsh and irritate the rectal tissue.

Description To administer an enema solution, the clinician should have the patient lie down on the left side, knees bent. Lift the upper buttock so that the rectal opening can be visualized. Place the lubricated tip of the enema catheter at the anal opening, and gently advance the catheter through the anal sphincter into the rectum toward the umbilicus (navel), 3–4 in (7.5–10 cm) for an adult. Insert the tubing 2 in (5 cm) for a child less than six years and 1 in (2.5 cm) for an infant. After alerting the patient, open the enema tubing to allow the solution to flow or squeeze premixed enema solutions slowly into the rectum. If the patient complains of cramping, slow or stop the enema flow and have the patient breathe slowly through the mouth to encourage relaxation. When giving fluid through an enema bag, start with the bag suspended from an IV pole at the patient’s hip level. As the tubing is opened, slowly raise the IV pole to promote fluid flow until the bag is 12 inches (30.5 cm) above the hip for an adult. Continue to hold the rectal tube in place throughout the procedure or it will be expelled from the rectum.

If the fluid will not flow in, gently rotate the tubing within the rectum to clear the holes of the tubing from the wall of the bowel or the impacted stool that may be occluding the flow. If ordered to give a high enema, slowly raise the bag no more than 18 inches (46 cm) above the adult patient’s hip (12 inches (30.5 cm) above a child’s hip and six inches (15 cm) above an infant’s hip). This will increase the water pressure to deliver the fluid higher into the bowel. When all of the solution has been administered, clamp the tubing, remove the enema catheter, and release the buttock.

Preparation Before administering an enema, ensure the patient’s privacy by closing the room door. The patient should be encouraged to empty both bladder and bowels before the procedure. Have the patient undress completely from the waist down. Position the patient on the bed on his or her left side with the top knee bent and pulled slightly upward toward the chin. Place a waterproof pad under the patient’s hips to protect the bedding and drape a sheet over the patient covering the entire body except the buttocks. Place a bedpan and toilet paper within quick access. Explain the procedure to the patient. Emphasize the importance of breathing slowly through the mouth to encourage relaxation of the rectal sphincter and to avoid oppositional pressure. Let the patient know that while he or she may feel the urge to defecate, most enemas need time to work and he or she should try to hold the fluid for at least five to 10 minutes after instillation (30–60 minutes for retention enemas and longer for some medicated enema solutions). Check the medication label if it is a medicated solution to avoid medication errors. Be sure it is the right medicine, the right dose (strength), the right time, the right person, and the right method. Verify the expiration date on the label. Do not use outdated medicine. Wash hands thoroughly and put on gloves. To prepare for premixed disposable enema instillations, follow the directions on the package. Most premixed disposable enemas come with the tip already lubricated. Shake the solution bottle. Remove the cap from the tip and expel excess air from the apparatus before use. To prepare solutions to be administered using an enema bag, heat the solution to 105°F. Adult solutions are generally 750–1000cc of solution for a non-retention enema and 150–200cc of fluid for a retention enema. Children’s solutions are 250–500cc of solution for a non-retention enema and 75–150cc of solution for a retention enema. Infants’ solutions are 150–250cc of solution for a nonretention enema. If preparing a medicated solution, follow the physician’s orders. Select a rectal tube appropri-

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Antibiotic enema solutions can be administered to treat localized bacterial infections. Medicated hypertonic enema solutions can be used to pull excessive potassium or ammonia from the bloodstream through the rectal wall. These substances are then eliminated with the stool.

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Complications

KEY TERMS Anal sphincter—A ring-shaped muscle located at the bottom of the anal canal that maintains constriction to keep the anal canal closed to the outside of the body. The anal sphincter relaxes and opens during defecation. Defecation—The process of eliminating stool from the body. Hypertonic—A solution that has a higher osmotic pressure than a comparative solution.

ate to the patient’s size (#14–30 French rectal tube for an adult, #12–18 for a child, #12 for an infant) and connect it to the tubing from the bag. Fill the enema bag with the solution and open the tubing. Run the solution through the tubing to the tip of the rectal tube to clear air from the line. Clamp the tubing and adjust the bag on an IV pole so that it will hang at the patient’s hipline. Put water-soluble lubricant on a clean 4x4 gauze pad and roll the tip of the rectal tube in the lubricant. Coat all of the rectal tube that will be inserted into the rectum to avoid traumatizing the rectal tissue [3–4 inches (7.3–10 cm) for an adult, 2–3 inches (5–7.5 cm) for a child, 1–1 1/2 inches (2.5–4 cm) for an infant].

Aftercare After administering an enema, remain near the patient in case he or she needs assistance with the bedpan or to get to the bathroom. Medicated enemas that are expelled immediately may need to be repeated, using fresh solution. Follow the directions or consult with the physician. To assist the patient with retaining an enema after instillation, apply gentle pressure to the rectal opening using a 4x4 gauze pad or squeeze the buttocks together. Tuck a 4x4 gauze pad between the buttocks to collect seepage. This maneuver may help the patient feel more secure. Cover the patient after the procedure and instruct him or her to lie still for five to 10 minutes or longer if a medicated solution or retention enema is administered. This will allow time for the solution to take effect. Wash items that might be reused, such as non-disposable enema bags and tubing, in warm soapy water. Rinse and allow them to air dry. Place disposable items, gauze pads, and gloves in a trash bag, then seal and discard it. Assist the patient to the bathroom or with the bedpan after he or she has held the enema solution for the correct amount of time. Hands should be washed after performing the procedure. Note the results of the enema. 880

Complications of enema administration are not common but can include irritation, swelling, redness, bleeding, or prolapse of the rectal tissue. If any of these symptoms are apparent, or if the patient complains of pain or burning during enema instillation, stop the procedure and notify the physician.

Results Most enemas, because of their liquid state, are absorbed quickly and work rapidly. Retention enemas will take 30–60 minutes to achieve full therapeutic effect. Cleansing enemas usually work within 10–15 minutes to cleanse the bowel and relieve constipation. They may, however, need to be repeated one or two times to thoroughly cleanse the bowel in preparation for a bowel exam or bowel surgery. Medicated enemas, such as antibiotic or anti-inflammatory solutions, may need to be repeated daily over a period of a week or more for full therapeutic effect.

Health care team roles Enemas are administered by a licensed nurse (R.N. or L.P.N.) in the health care setting. Unlicensed staff, however, may be trained to administer non-medicated enemas under the direction of a registered nurse in some settings. An alert and cooperative patient may also be allowed to self-administer non-medicated enemas in some health care settings under the direction of a nurse. The nurse should, however, assess the patient and the effectiveness of the enema. The patient, or members of the patient’s family, can be taught to administer an enema in the home setting. Resources BOOKS

“Giving a Medicated Enema.” In Nurse’s Clinical Guide to Medication Administration. Springhouse, PA: Springhouse Corporation, 2000. OTHER

“Administering an Enema.” Mosby Online . “The Enema.” McKinley Health Center Online . “Enemas. My Life Path.” Blue Shield of California Online https://www.mylifepath.com/article/gale/100272742. “Fecal Elimination Notes.” Phillips Community College of the University of Arkansas Online . “Fleet Enema Mineral Oil.” WebMD Online . “Predsol Retention Enema.” E-Doc Online .

Enemas

KEY TERMS Carminative—An agent that will remove gases from the gastrointestinal tract. Electrolyte—A substance that conducts electric current within the body and is essential for sustaining life. Intestine—Also called the bowels. Divided into large and small intestine, they extend from the stomach to the anus, where waste products exit the body. The small intestine is about 20 ft (6 m) long and the large intestine, about 5 ft (1.5 m) long. Rectum—The portion of bowel just before the anus. The prefix recto is used with a variety of words in relation to conditions that affect the rectum.

Some health care workers differentiate between high and low enemas. A high enema, given to cleanse as much of the large bowel as possible, is usually administered at higher pressure and with larger volume (1,000 cc), and the individual changes position several times in order for the fluid to flow up into the bowel. A low enema, intended to cleanse only the lower bowel, is administered at lower pressure, using about 500 cc of fluid. Oil retention enemas serve to lubricate the rectum and lower bowel, and soften the stool. For adults, about 150 to 200 cc (approximately two-thirds, to three-quarters of a cup) of oil is instilled, while in small children, 75 to 150 cc (one-third to two-thirds of a cup) of oil is considered adequate. Salad oil or liquid petrolatum are commonly used at a temperature of 91°F (32.8°C). There are also commercially prepared oil retention enemas. The oil is usually retained for one to three hours before it is expelled.

12 in (30 cm) above the level of the bed; for a high cleansing enema, the container may be 12–18 in (30–45 cm) above the bed level, because the fluid is to be instilled higher into the bowel.

Preparation The solution used in the procedure is measured, mixed, and warmed before administration of the enema.

Aftercare If necessary, a stool specimen will be collected for diagnostic evaluation. If the enema was given to alleviate constipation, good nutritional education is necessary to prevent the recurrence of constipation in the future. The recommendation is normally with a high fiber diet (between five and six servings per day of whole grain foods) and adequate fluid intake (between seven and eight glasses of water per day). A study reported in the Canadian Nurse sought to evaluate whether the use of laxatives, enemas, and suppositories could be reduced by using more bran in the diet. It was found that the subjects given bran with their breakfasts each day reduced use of laxatives, enemas, and suppositories by nearly 50%. Regular exercise and going to the bathroom when necessary will also help. If constipation is a chronic problem, medical help should be consulted to determine if there is an underlying disorder.

Complications Habitual use of enemas as a means to combat constipation can make the problem even more severe when their use is discontinued. Enemas should be used only as a last resort for treatment of constipation and with a doctor’s recommendation. The use of enemas can cause an irregular heartbeat in some patients.

Results

The rectal tube used for infusion of the solution, usually made of rubber or plastic, has two or more openings at the end through which the solution can flow into the bowel. The distance to which the tube must be inserted is dependent upon the age and size of the patient. For adults, insertion is usually 3–4 in (7.5–10 cm); for children, approximately 2–3 in (5–7.5 cm); and for infants, only 1–1.5 in (2.5–3.75 cm). The rectal tube is lubricated before insertion with a water-soluble lubricant to ease insertion and decrease irritation to the rectal tissues.

Optimum results are thorough and appropriate cleansing of the lower bowel when necessary, and the introduction of proper diet and exercise to prevent chronic constipation.

The higher the container of solution is placed, the greater the force with which the fluid flows into the patient. Routinely, the container should be no higher than

• Primary care physicians (PCPs) will commonly order enemas for the relief of constipation, or for patients at risk for fecal impaction, to prevent more serious com-

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Health care team roles Healthcare providers will typically become involved in the treatment of constipation or fecal impaction as a side effect of other, debilitating illnesses.

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• Registered nurses (RNs) or licensed practical nurses (LPNs) will often be responsible for either administering the enema or assuring that the patient knows how to administer it to themselves. Nurses will monitor the results of the enema to see if it has been effective in cleansing the lower bowel. Nursing staff involved in the administration of enemas need to be aware that this is an intrusive procedure that can be upsetting to patients. Professionalism and understanding are essential. Nurses should educate the patient about the procedure and should also be involved in teaching patients about the importance of diet and exercise in the prevention of chronic constipation. Resources BOOKS

Frank, L, J Schmier, L Kleinman, R. Siddique, A. Bhattacharjya, M Rothman. “Cost of Nursing-Based Constipation Care in Nursing Homes.” The Gerontologist (Oct 15, 2000): 345. Kozier, Barbara, RN, MN, Erb, Glenora, RN, BSN, Blais, Kathleen, RN, EdD, Wilkinson, Judith M., RNC, MA, MS. Fundamentals of Nursing, Concepts, Process and Practice. 5th ed. Redwood City, CA: Addison-Wesley, 1995. Nettina, Sandra. Lippincott Manual of Nursing Practice. 7th ed. Philadelphia: Lippincott, 2001, p. 579.

Joan M. Schonbeck

Enteral nutrition see Nasogastric intubation and feeding

called a jejunostomy. Some people use the word “ostomy” as a word that covers all types of enterostomies.

Purpose Enterostomies are performed to create a new opening for the passage of fecal matter when normal intestinal functioning is interrupted or when diseases of the intestines cannot be treated by medications or less radical surgery. Some situations that may require enterostomies include: • Healing of inflamed bowel segments. Enterostomies performed for this reason are usually temporary. • Emergency treatment of gunshot or other penetrating wounds of the abdomen. An enterostomy may be required to prevent the contents of the intestine from causing a serious inflammation of the inside of the abdominal cavity (peritonitis). These enterostomies are also usually temporary. • Placement of a tube for enteral feeding. Enteral feeding is a method for conveying nutritional solutions directly into the stomach or jejunum through a tube. Tube enterostomies may be long-term, but are not permanent. • Removal of diseased sections of the intestines. Ileostomies performed for this reason are permanent. The most common disorders requiring permanent ileostomy are Crohn’s disease, familial polyposis, and ulcerative colitis. Familial polyposis and ulcerative colitis are serious health risks because they can develop into cancer. • Treatment of advanced cancer or other causes of intestinal obstruction.

Precautions

Enterostomy Definition An enterostomy is a procedure in which the surgeon makes a passage into the patient’s small intestine through an incision in the abdomen, leaving an opening to allow for drainage or to insert a feeding tube. The opening is called a stoma from the Greek word meaning mouth. Enterostomies may be either temporary or permanent. They are classified according to the part of the intestine that is used to create the stoma. If the ileum, which is the lowest of the three sections of the small intestine, is used to make the stoma, the operation is called an ileostomy. If the jejunum, which is the middle section of the small intestine, is used, the operation is

Enterostomies are usually performed only as emergency treatments for traumatic injuries in the abdomen or as final measures for serious disorders of the intestines. Most patients do not refuse the procedure once the need for it is explained. A small minority, however, refuse enterostomies because of strong psychological reactions to personal disfigurement and the need to relearn bowel habits.

Description Ileostomy Ileostomies represent about 25% of enterostomies. They are performed after the surgeon removes a diseased colon and sometimes the rectum as well. The most com-

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plications such as intestinal obstruction, or as a means of cleansing the bowel prior to tests or surgery.

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mon ileostomy is called a Brooke ileostomy after the English surgeon who developed it. In a Brooke ileostomy, the surgeon makes the stoma in the lower right section of the abdomen. The ileum is pulled through an opening (incision) in the muscle layer. The surgeon then turns the cut end of the intestine inside out and sews it to the edges of the hole. He or she then positions an appliance for collecting the fecal material. The appliance consists of a plastic bag that fits over the stoma and lies flat against the abdomen. The patient is taught to drain the bag from time to time during the day. The bag needs to be emptied frequently because the digested food contains large amounts of water. Shortly after the operation, the ileostomy produces one to two quarts of fluid per day. However, after a month or two of adjustment, the volume decreases to one or two pints per day. Nearly 30% of patients receiving the Brooke ileostomy for inflammatory bowel disease develop at least a limited infection. Another 20%–25% require at least a minor surgical revision. KOCK POUCH (CONTINENT ILEOSTOMY). The Kock pouch is a variation of the basic ileostomy and is named for its Swedish inventor. In the Kock technique the surgeon forms a pouch inside the abdominal cavity behind the stoma to collect fecal material. The stoma is shaped into a valve to prevent fluid from leaking onto the patient’s abdomen. The patient then empties the pouch several times daily by inserting a tube (catheter) through the valve. The Kock technique is sometimes called a continent ileostomy because the fluid is contained inside the abdomen. It is successful in 70%–90% of cases. Patients with chronic ulcerative colitis usually have all of the diseased tissue removed during the Kock method. The primary benefit of the Kock approach compared with the Brooke method is that discharge is captured without an external appliance. Unfortunately, the complication rate following the Kock technique is much higher than with the Brooke method. Patients receiving both techniques have problems with perineal wound healing in about onethird of cases.

enterostomies are performed in patients who need tube feeding for longer than six weeks, or who have had recent mouth or nose surgery. Jejunostomies require a continuous infusion of nutrients whereas tube feeding through the stomach can be given in large single feedings (boluses). As long as the patient’s intestinal tract can function, tube feedings are considered preferable to intravenous feeding because it is safer and helps keep the patient’s digestive tract functioning.

Preparation Preoperative preparation includes both patient education and physical preparation. Patient education If the patient requires a permanent ileostomy, the doctor will explain what will happen during the procedure and why it is necessary. Most patients are willing to accept an ostomy as an alternative to the chronic pain and diarrhea of ulcerative colitis or the risk of cancer from other intestinal disorders. The patient also can meet with an enterostomal therapist (ET) or a member of the United Ostomy Association, which is a support group for people with ostomies. Medical preparation The patient is prepared for surgery with an evaluation of his or her nutritional status, possible need for blood transfusions, and antibiotics if necessary. If the patient does not have an intestinal obstruction or severe inflammation, he or she may be given a large quantity of a polyethylene glycol (PEG) solution to cleanse the intestines before surgery.

Aftercare Aftercare of an enterostomy is both psychological and medical. Patient education

Jejunostomy A jejunostomy is similar to an ileostomy except that the stoma is placed in the second section of the small intestine rather than the third. Jejunostomies are performed less frequently than ileostomies and are almost always temporary procedures. Tube enterostomies Tube enterostomies are procedures in which the surgeon makes a stoma into either the stomach itself or the jejunum in order to insert a tube for liquid nutrients. Tube 884

Ileostomy patients must learn to watch their fluid and salt intake. They are at greater risk of becoming dehydrated in hot weather, from exercise, or from diarrhea. In some cases they may need extra bananas or orange juice in the diet to keep up the level of potassium in the blood. Poorly digested foods, such as lightly cooked vegetables, certain types of fruit, nuts, and corn can lead to stromal obstruction if the food is not thoroughly chewed. Patient education includes social concerns as well as physical self care. Many ileostomy patients are worried

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In some instances the appliance is poorly fitted. This can lead to problems with the skin near the stoma. Certain foods, such as onions and beans, can produce bad odors in the ileostomy bag. The odor primarily develops from bacteria working on these digested foods. Frequent bag emptying and the addition of chlorine or sodium benzoate tablets to the bag can significantly reduce odor. Medical aftercare If the enterostomy is temporary, aftercare consists of the usual monitoring of surgical wounds for infection or bleeding. If it is a permanent ileostomy, aftercare includes teaching the patient to use the appliance or empty the Kock pouch, to keep the stoma clean, and to readjust bathroom habits. Recovery takes a significant amount of time because major surgery is a shock to the system and the intestines take several days to resume normal functioning. The patient’s fluid intake and output will be checked frequently to minimize the risk of dehydration.

Complications Enterostomies are not considered high-risk operations by themselves. Possible complications include:

KEY TERMS Crohn’s disease—A disease of the intestines that causes inflammation leading to scarring, thickening of the walls of the intestine, and eventual obstruction. Duodenum—The first of the three segments of the small intestine. The duodenum connects the stomach and the jejunum. Enteral nutrition—A technique for feeding patients with liquid formulas conveyed directly into the stomach or jejunum through tubes. Enterostomal therapist (ET)—A specialized counselor, usually a registered nurse, who provides ostomy patients with education and counseling before the operation. After surgery the ET helps the patient learn to take care of the stoma and appliance, and offers long-term emotional support. Familial polyposis—A disease that runs in families in which lumps of tissue (polyps) form inside the colon. Familial polyposis may develop into cancer. Ileum—The third segment of the small intestine, connecting the jejunum and the large intestine. Jejunum—The second of the three segments of the small intestine, connecting the duodenum and the ileum.

• Skin irritation caused by leakage of digestive fluids onto the skin around the stoma is the most common complication.

Kock pouch—A type of ileostomy in which the surgeon forms an artificial rectum from a section of the ileum. A Kock pouch is sometimes called a continent ileostomy because it is drained with a tube.

• Diarrhea, both severe and chronic, needs to be brought to the attention of the physician.

Ostomy—A common term for all types of enterostomies.

• Gallstones or stones in the urinary tract may develop. • Inflammation of the ileum can occur. • Odors from an ileostomy can often be prevented by a change in diet. • Intestinal obstruction may develop. • Prolapse can occur in which a section of the bowel pushes out of the body. • Leakage from the ileostomy pouch can occur if the stoma is not at least 2 inches above the level of the skin. • Variceal bleeding—bleeding from blood vessels around the stoma—can occur in patients with portal hypertension and other conditions.

Stoma—The surgically constructed mouth or passage between the intestine and the outside of the patient’s body. Tube enterostomy—An enterostomy performed to allow the insertion of a feeding tube into the jejunum or stomach. Ulcerative colitis—A disease of the colon characterized by inflammation of the mucous lining, ulcerated areas of tissue, and bloody diarrhea.

• Ileal abscess and fistula can occur, in which the ileum becomes punctured by sutures, recurrent disease, or the effects of a poorly-fitted appliance.

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about the effects of the operation on their close relationships and employment. If the patient has not seen an ET before the operation, the aftercare period is a good time to find out about self-help and support groups. The ET can also evaluate the patient’s emotional reactions to the ostomy.

Epidural therapy

Results

Resources

Normal results include recovery from the surgery with few or no complications. About 95% of people with ostomies recover completely, are able to return to work, and consider themselves to be in good health. Many ileostomy patients enjoy being able to eat a full range of foods rather than living on a restricted diet. Some patients, however, need to be referred to psychotherapists to deal with depression or other emotional problems after the operation.

BOOKS

Baron, Robert B. “Nutrition.” In Current Medical Diagnosis & Treatment 2001. Ed. Lawrence M. Tierney, Jr., et al. Stamford, CT: Appleton & Lange, 2001. Goldman, Lee, and J. Claude Bennett. Cecil Textbook of Medicine. Philadelphia: WB Saunders, 1999. “Large Intestine.” In Current Surgical Diagnosis & Treatment. Ed. Lawrence W. Way. Stamford, CT: Appleton & Lange, 1994. ORGANIZATIONS

United Ostomy Association (UOA). 19772 MacArthur Blvd., Ste 200, Irvine, CA 92612-2405. (800) 826-0826. .

Health care team roles A variety of allied health personnel will be involved in the care of individuals who require a enterostomy. A surgeon will perform the actual procedure. A nurse will likely be involved in aftercare instructions, and an important member of the allied health care team is the ET. The ET is generally a registered nurse who has received specialized training in the area of enterostomy and is typically certified in the field. The ET generally performs the following activities: • presurgical counseling and education of the patient and family • care of the stoma immediately following the operation • training of the patient in the proper use of the appliance and overall long-term self-care

Mark A. Mitchell

Enzyme immmunoassay see Immunoassay tests Epidural anesthetic see Anesthesia, local

Epidural therapy Definition An epidural is a local (regional) anesthetic delivered through a small tube into a vacant space outside the spinal cord, the epidural space.

• proper fitting of the appliance • educating the patient on the daily management of the stoma • advising the patient on how to cope with skin complications and odor problems • identifying stomal problems associated with the surgery • supporting the patient emotionally, physically, and morally • providing information about the national organization for those who have received an ostomy—the United Ostomy Association Nutritional therapists may also consult the patient about various nutritional factors and how they might affect the patient who has undergone an enterostomy. In particular, this information will include how various foods lead to diarrhea, or bad odors in the bag. Wound care nursing specialists also may be called in when wound healing is not progressing at an appropriate rate. 886

Purpose The anesthetic agents that are infused through the small catheter block spinal nerve roots in the epidural space and the sympathetic nerve fibers adjacent to them. Epidural anesthesia can block most of the pain of labor and birth for vaginal and surgical deliveries. Epidural analgesia is also used after cesarean sections to help control post-operative pain.

Precautions The primary problem associated with receiving epidural anesthesia is low blood pressure, otherwise known as hypotension, because of the blocking of sympathetic fibers in the epidural space. The decreased peripheral resistance that results in the circulatory system causes dilation of peripheral blood vessels. Fluid collects in the peripheral vasculature (vessels), simulating a condition that the body interprets as low fluid volume. A simple measure that prevents most hypotension is the

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infusion of 500-1000 cc of fluid intravenously into the patient prior to the procedure. Ringer’s lactate, as opposed to a solution containing dextrose, is preferable because the elevated maternal glucose that accompanies the rapid infusion of solutions containing dextrose can result in hyperglycemia in the newborn with rebound hypoglycemia. It is important not to place a woman flat on her back after receiving an epidural because the supine position can bring on hypotension. If a woman’s blood pressure does drop, then the proper treatment is to turn her on her side, administer oxygen, increase the flow of intravenous fluids and possibly administer a medication such as ephedrine if the hypotension is severe. Very rarely, convulsions can result from severe reactions. Seizure activity would be treated with short-acting barbiturates or diazepam (Valium).

Description Epidural anesthesia, because it virtually blocks all pain of labor and birth, is particularly helpful to women with such underlying medical problems as pregnancyinduced hypertension, heart disease, and pulmonary disease. Epidural anesthesia for labor is usually initiated at the woman’s request, providing the labor is progressing well, or if the mother feels severe pain during early labor.

Preparation To prepare for the administration of epidural anesthesia, the woman should have the procedure explained fully and sign consent forms if required. An intravenous line is inserted if not already in place. She is positioned on her side or in a sitting position and connected to a blood pressure monitoring device. The nurse/assistant has the following equipment available: oxygen, epidural insertion equipment, fetal monitor, and additional intravenous fluid. The health care provider cleans the area with an antiseptic solution, injects a local anesthetic to create a small wheal at the L 3-4 area (between the third and fourth lumbar vertebrae) and inserts a needle into the epidural space. Once it is ascertained that the needle is in the correct place, a polyethylene catheter is threaded through the needle. The needle is removed and a test dose of the anesthetic agent is administered. The catheter is taped in place along the patient’s back with the end over her shoulder for easy retrieval when further doses are required. If the patient responds well to the test dose a complete dose is administered. Pain relief should be to the

Epidural anesthesia may be administered to a woman in labor to ease the pain of labor and birth. (M. English, MD/Custom Medical Stock Photo. Reproduced by permission.)

level of the umbilicus. The epidural anesthesia lasts approximately 40 minutes to two hours, or longer as required. If necessary, additional doses of anesthetic, or top-up, are injected through the catheter or a continuous infusion on a special pump. Epidural anesthesia can be given in labor in a “segmented” manner. In this instance, the laboring woman receives a small dose of anesthesia so that the perineal muscles do not fully relax. The baby’s head is more apt to undergo internal rotation when the perineal muscles are not lax thus facilitating delivery. At the time of delivery, an additional dose can be administered for perineal relief. Women who have cesarean deliveries may have additional medication injected into the epidural to control intra-operative pain. Medications used generally are narcotics such as fentanyl or morphine (Duramorph). Side effects include severe itching, nausea, and vomiting. Treatment of these side effects with the appropriate med-

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KEY TERMS Analgesia—A medication that decreases the awareness of pain. Anesthesia—Loss of sensation through the administration of substances that block the transmission of nerve impulses signaling the feeling of pain and pressure. Regional anesthesia—Blocking of specific nerve pathways through the injection of an anesthetic agent into a specific area of the body.

ication can be helpful. Despite these problems, epidural analgesia is an effective method to relieve pain after cesarean delivery, allowing the woman to move well, thereby facilitating rapid recovery.

Aftercare It is important to carefully monitor vital signs after the administration of epidural anesthesia. Hypotension can result in fetal death and can also have grave consequences for the mother. The nurse should monitor the patient constantly and use a continuous blood pressure machine to obtain regular blood pressure readings for 2030 minutes after each administration of anesthesia. The systolic blood pressure should not fall below 100 mm Hg or be 20 mm Hg less than a baseline systolic blood pressure for a hypertensive patient. It is important to remind the woman to empty her bladder at least every two hours. With epidural anesthesia there is loss of sensation of the need to void. Sometimes, if the bladder fills excessively it could actually block the descent of the baby’s head. A catheter can be inserted into the bladder to drain the urine. The nurse needs to closely monitor intake and output and assess the bladder for signs of distension.

Occasionally, slow absorption of the medication from the epidural space into the circulation can result in toxic reactions evident by decreased level of consciousness, slurred speech, loss of coordination, drowsiness, nervousness, and anxiety. The health care provider should look out for these signs, and also report any elevation in temperature, before a top-up dose is administered.

Results Epidural anesthesia is a safe and effective method of giving pain relief to women during labor and delivery and also can be used for cesarean births. It is believed that very little of the anesthetic is absorbed throughout the body (systemically), therefore epidural anesthesia is ideal because it does not pass medication on to the baby.

Health care team roles Epidurals are administered by anesthesiologists and certified nurse anesthetists. Undergoing the insertion of an epidural can be a frightening experience for the patient because of the injection technique. It is important to offer ample encouragement and support during the entire process. Resources BOOKS

Pillitteri, Adele. Maternal & Child Health Nursing. 3rd ed. Philadelphia: Lippincott, 1999. ORGANIZATIONS

Complications Side effects and complications are rare but sometimes the patient will experience a “spinal headache” due to leakage of cerebrospinal fluid (CSF). When a woman receives epidural anesthesia for labor pains, at times the labor can be prolonged because of excessive relaxation of the muscles. Also, the baby’s head may not rotate—especially if it is in the occiputposterior position (the back of the head is facing toward the woman’s back). The woman may not have the sensation that results in the desire to push during contractions 888

when she is fully dilated. These complications may result in an increased incidence of births with the use of vacuum extraction, forceps, or even cesarean deliveries. Administering a Pitocin (oxytocin) drip intravenously can counter this problem. Pitocin is a medication that causes the uterus to contract. Allowing the epidural to wear off in the second stage of labor, when the woman is pushing, may avoid this problem, but the return of the labor pains may be overwhelming to the woman.

American Association of Nurse Anesthetists (AANA). 222 S. Prospect Avenue, Park Ridge, IL 60068. (847) 692-7050. . OTHER

Anesthesia Options for Labor and Delivery: What Every Expectant Mother Should Know. AANA, 2001. .

Nadine M. Jacobson, RN

Epilepsy see Seizure disorder

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Epstein-Barr virus test see Infectious mononucleosis test

patients with heartburn or gastroesophageal reflux disease (GERD). • X-ray studies investigate dysphagias, either by using a fluoroscope to follow the progress of barium during the process of swallowing, or by using radioactive scanning techniques.

Precautions

Esophageal function tests Definition The esophagus is the muscular tube through which food passes on its way from the mouth to the stomach. The main function of the esophagus is to propel food into the stomach. In order to ensure material does not go the wrong way (reflux), sphincters at either end of the esophagus close when material is not passing through them in the correct direction. Esophageal function tests are used to determine if these processes are normal or abnormal.

Purpose The esophagus has two sets of constricting muscles (or sphincters) at the top and bottom. Each of these muscular areas must contract in an exact sequence for swallowing to proceed normally. The upper esophageal sphincter normally stops the backflow of stomach contents into the pharynx and larynx. The lower esophageal sphincter guards against stomach acid moving up into the esophagus. The lower sphincter should be tightly closed, except to allow food and fluids to enter the stomach. The three major symptoms occurring with abnormal esophageal function are difficulty with swallowing (dysphagia), heartburn, and chest pain. Doctors perform a variety of tests to evaluate these symptoms. Endoscopy, which is not a test of esophageal function, is often used to determine if the lining of the esophagus has any ulcers, tumors, or areas of narrowing (strictures). Many times, however, endoscopy only shows the doctor if there is an injury to the esophageal lining, and the procedure gives no information regarding the cause of the problem. Therefore, in addition to endoscopy, several studies are available that measure esophageal function. There are three basic types of tests used to assess esophageal function:

Since sedatives may alter test values, they are not administered prior to esophageal function testing. Eating prior to the test will also alter the results. Pregnant patients undergoing x-ray exams should carefully review the risks and benefits of any proposed tests with their doctors. Additionally, patients with bowel obstruction should not participate in any test using barium. Also, esophageal function tests are contraindicated in those patients who are unable to cooperate with the test.

Description Manometry This study is designed to measure the pressure changes produced by contraction of the muscular portions of the esophagus. An abnormality in the function of any one of the segments of the esophagus can cause difficulty in swallowing (dysphagia). This exam is most useful in evaluating patients whose endoscopy yields normal results. During manometry, the patient swallows a thin tube carrying a device that senses changes in pressures in the esophagus. Readings are taken at rest and during the process of swallowing. Medications are sometimes given during the study to aid in the diagnosis. The results are then transmitted to recording equipment. Manometry is most useful in identifying diseases that produce disturbances of motility or contractions of the esophagus. In 2001, a solution containing five drops of peppermint oil in 10 mL of water was found to improve the manometric features of diffuse esophageal spasm (DES). The peppermint oil solution eliminated simultaneous esophageal contractions in all patients in the study.

• Manometry is used to study the way the muscles of the esophagus contract, and is most useful for the investigation of difficulty with swallowing.

ESOPHAGEAL PH MONITORING. This procedure measures the esophagus’ exposure to acid reflux from the stomach. The test is ideal for evaluating recurring heartburn or gastroesophageal reflux disease (GERD). Excessive acid reflux may produce ulcers, or strictures resulting from healed ulcers, in addition to the symptom of heartburn.

• Esophageal pH monitoring measures changes in esophageal acidity, and is valuable for evaluating

Normally, acid refluxes into the esophagus in small amounts for short periods of time. The lower esophageal

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EPS see Electrophysiology study of the heart

Esophageal function tests

sphincter usually prevents excessive reflux (in patients without disease). Spontaneous contractions that increase esophageal emptying and production of saliva also act to prevent damage to the esophagus. Researchers have shown that in the esophagus, the presence of acid is damaging only if it persists for prolonged periods. Therefore, esophageal pH monitoring has been designed to monitor the level of acidity over 24 hours, usually in the home. In this way, patients are able to maintain their daily routine, document their symptoms, and correlate symptoms with specific activities. During this period, a thin tube with a pH monitor remains in the esophagus to record changes. After the study, a computer is used to compare changes in acidity with symptoms reported by the patient. Additional tests, the Bernstein test (also known as the acid perfusion test) and the acid clearing test, may be performed. In the Bernstein test, hydrochloric acid (HCl) is directed into the esophagus. If the patient experiences pain with the administration of the HCl, the test is positive for reflux esophagitis. If there is no discomfort, another cause must be found to explain the patient’s symptoms. In the acid clearing test, HCl is also directed into the esophagus. However, in this test, the patient’s ability to quickly swallow the HCl is examined. If the patient needs more than 10 swallows, it indicates the patient has problems with esophageal motility. pH monitoring is usually performed before surgery to confirm the diagnosis and to judge the effects of drug therapy. In 2001, studies showed that integrated esophageal and gastric acidity provided better quantitative measures of GERD pathophysiology than conventional pH parameters. This finding has implications for the evaluation of therapeutic interventions. X-RAY TESTS. X-ray tests fall into two categories: (1) those performed using barium and a fluoroscope; and (2) those performed with radioactive materials. Studies performed with fluoroscopy are especially useful in identifying structural abnormalities of the esophagus. Oftentimes a sandwich or marshmallow coated with barium is used to identify the site of an obstruction. However, fluoroscopy can diagnose or provide important information about a number of disorders involving esophageal function, including craniopharyngeal achalasia (a swallowing disorder of the throat), decreased or reverse peristalsis, and hiatal hernia.

During fluoroscopy, the radiologist can observe the passage of material through the esophagus in real time, and video recordings may also be made. This is particularly useful when the swallowing symptoms appear to occur mostly in the upper region of the esophagus. The most common cause of difficulty swallowing is a previ890

ous stroke, although other diseases of the neuromuscular system (like myasthenia gravis) can produce similar symptoms. Scans using low-dose radioactive materials are useful because they may demonstrate that food passes more slowly than normal through the esophagus, and how slowly the bolus may be passing. These studies involve swallowing food coated with radioactive material, followed by a nuclear medicine scan. Scans are often used when other methods have failed to make a diagnosis, or if it is necessary to determine the degree of the abnormality.

Preparation Patients should not eat or drink anything after midnight before the exam. Many medications affect the esophagus; doses may need to be adjusted or even discontinued prior to testing. Patients must inform their physician of any and all medications they take, including over-the-counter medications, and any known allergies.

Aftercare For most of these studies, no special care is needed after the procedure. Patients can often engage in normal daily activities following almost all of these tests. One exception is that patients who undergo a x-ray exam with the use of barium may experience constipation. A cathartic may be given to those patients.

Complications Exposure of a fetus to x-rays, especially in the first three months, can be extremely harmful to the fetus. Barium swallows may also cause impaction (hardening) of fecal matter. Additionally, although the tubes passed through the esophagus during some of the esophageal function tests are small, and most patients adjust to them quite well, some patients may gag and aspirate (breathe in) some gastric juices.

Results Normal findings include: • lower esophageal sphincter pressure ranging from 10–20 mm Hg • normal peristaltic waves • normal size, shape, position, patency and filling of the esophagus • negative acid reflux • acid clearing in less than 10 swallows

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Manometry is used to diagnose abnormalities related to contraction or relaxation of the various muscular regions of the esophagus. These studies cannot distinguish whether injury to either the muscle or nerves of the esophagus is producing the abnormal results—only the final effect on esophageal muscle is identified. Results should be interpreted in light of the patient’s entire medical history. For example, there are many diseases that cause poor relaxation of the lower esophageal sphincter. When no cause is found, the condition is called achalasia. Achalasia is a frequent finding in individuals with Down’s syndrome. Abnormal results of pH tests can confirm symptoms of heartburn or indicate a cause of chest pain (or rarely, swallowing difficulties). Doctors may want to initiate or change medications based on these results, or even repeat the test using different doses of medication. As noted above, these studies are indicated before surgical treatment of GERD. X-ray tests can serve to document an abnormality, and they are far from perfect. If they are negative, then other studies are often needed.

Health care team roles The health care team may consist of the physician, the nurse, and others. A radiologist will be required if the procedure involves scans, x-rays, or nuclear medicine studies. Unlicensed assistive personnel (UAPs), such as GI assistants, GI technicians or medical technicians may have direct patient care responsibility. They are supervised by a registered nurse (RN). UAPs can assist the physician and RN during diagnostic and therapeutic procedures. The RN is responsible for the assessment of patient care needs and for determining the capability of assistive personnel to whom a task is delegated. An advanced practice nurse (APN) specializing in gastroenterology may perform a comprehensive history and physical assessment. Depending on the practice, the APN may also order and/or perform diagnostic studies. Otherwise, these tasks are performed by the physician. Training An APN is a nurse who has completed an advanced degree in nursing (master’s or doctorate). An APN may be a nurse practitioner or a clinical nurse specialist. UAPs may receive on-the-job training in their duties.

KEY TERMS Achalasia—Failure to relax. Often applied to sphincter muscles, the normal function of which is persistent contractions with periods of relaxation. Bolus—“A lump.” May describe a mass of food ready to be swallowed, or a preparation of medicine via the oral or intravenous (IV) route. Cathartic—An active agent which produces bowel movements. Craniopharyngeal achalasia—A a swallowing disorder of the throat. Diffuse esophageal spasm (DES)—An uncommon condition that results in simultaneous contractions of the esophagus. Esophagus—The muscular canal between the throat and the stomach. Heartburn—Acid liquid raised from the stomach, causing a burning sensation in the esophagus. Hiatal hernia—A condition in which part of the stomach pushes up through the same hole in the diaphragm that the esophagus passes through. Peristalsis—The contraction of muscles which passes food from the mouth to the stomach and out the anus.

Patient education If barium is used in the testing, the patient should understand that all of the barium needs to be excreted. At first, the patient’s stools will be white, but once the barium has been completely excreted, the stools will return to normal. Advise the patient that a sore throat is common after tests requiring tube placement. Explain to the patient that sedatives are not given prior to testing involving tube placement, due to the interference with the test results and test administration. Resources BOOKS

Castell, June A., and R. Matthew Gideon. “Esophageal Manometry.” In The Esophagus, 3rd edition, edited by Donald O. Castell and Joel E. Richter. Philadelphia: Lippincott, 1999, pp. 101-117. Pagana, Kathleen D., and Timothy J. Pagana. Diagnostic Testing and Nursing Implications, 5th ed. St. Louis, MO: Mosby, 1999, pp. 62-64 and 69-70.

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• negative Bernstein test

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Smout, Andre. “Ambulatory Monitoring of Esophageal pH and Pressure.” In The Esophagus, 3rd edition, edited by Donald O. Castell and Joel E. Richter. Philadelphia: Lippincott, 1999, pp. 119-133. PERIODICALS

Gardner JD, Rodriguez-Stanley S, Robinson M. “Integrated acidity and the pathophysiology of gastroesophageal reflux disease.” American Journal of Gastroenterology 96, no. 5 (May 2001):1363-70. Mujica VR, Mudipalli RS, Rao SS. “Pathophysiology of chest pain in patients with nutcracker esophagus.” American Journal of Gastroenterology 96, no. 5 (May 2001):1371-7. Pimentel M, Bonorris GG, Chow EJ, Lin HC. “Peppermint oil improves the manometric findings in diffuse esophageal spasm.” Journal of Clinical Gastroenterology 33, no.1 (July 2001): 27-31. On line at: . Zarate N, Mearin F, Hidalgo A, Malagelada JR. “Prospective evaluation of esophageal motor dysfunction in Down’s syndrome.” American Journal of Gastroenterology 96, no. 6 (June 2001):1718-24. ORGANIZATIONS

The American Society for Gastrointestinal Endoscopy (ASGE). Thirteen Elm Street, Manchester, MA 019441314. (978) 526-8330. . Illinois Nurses Association—Advanced Practices Registered Nurses (APRNs) statistics. 105 W. Adams Suite 2101. Chicago, IL 60603. . The Society for Gastroenterology Nurses and Associates (SGNA). 401 North Michigan Avenue, Chicago, IL 60611-4267. (800) 245-7462. .

Maggie Boleyn, RN, BSN

Ergonomic assessment Definition Ergonomic assessment is a physical therapist’s or other specialist’s evaluation of a workplace and its furnishings, tools, and tasks in relation to the physical abilities of the worker. It is also known as work activities evaluation and treatment.

Purpose The professional evaluation is used to identify and report any risk factors that the worker may encounter while employed. By identifying those risks for injury and physical stress, the evaluator provides recommendations 892

for modified design and practice. The ergonomic assessment and its implementation can help make the work environment safer and more physically efficient. It will also help reduce injuries and related expenses while improving the well-being, productivity, and morale of employees. A job analysis (a written description of tasks according to their physical functions and requirements) may be provided, to match the capabilities of the worker to the job’s physical requirements. Ergonomic assessment reports and subsequent modifications help the employer to meet insurance company, Occupational Safety and Health Administration (OSHA), or other organizational standards. The physical therapist may be called in to treat an injured worker or make general preventative recommendations. The therapist helps the worker return to work more quickly and safely by advising revisions in the work tasks and environment. The employer receives advice in how to accommodate the abilities of a disabled or recently injured employee in compliance with the Americans with Disabilities Act (ADA) requirements.

Precautions Ergonomic assessments are used to prevent further or recurring injuries. If a worker returns to work while still in recovery or returns to the same dangerous environment, the injury is liable to happen again, perhaps with a worse outcome.

Description Ergonomic assessment is provided to an employer or employee to identify risk factors in the workplace; provide recommendations of ways to reduce them; and to prevent or treat injuries and accommodate disabilities. The evaluation helps employees perform their jobs in a safe, healthy, and efficient manner, spending less time off due to work-related disorders. The term ergonomics is derived from the Greek roots erg, meaning work and nomos, meaning natural laws. OSHA defines ergonomics as “the science of fitting the jobs to the people who work in them,” stating that “work-related musculoskeletal disorders (MSDs) result when there is a mismatch between the physical capacity of workers and the physical demands of their jobs.” Some job-related MSDs include carpal tunnel syndrome, tendinitis, and back injuries. Many industries and work environments expose workers to hazardous conditions and constant physical stress resulting in accident, injury, and such chronic conditions as work-related musculoskeletal disorders (WMSDs), cumulative trauma disorders (CTDs), and repetitive motion injuries (RMIs). Some high-risk groups

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Once these risks are identified, the recommendations may be in the form of a work risk analysis report that includes a biomechanical description of the job, a description of observed risks, and steps to correct them. Ergonomic assessment and intervention includes the “Five E’s” of correction and injury prevention: • Ergonomic-engineering: Redesigning the job or workspace to reduce stress. For example, the height or angle of a counter, chair or keyboard may be adjusted. • Exposure reduction: Reducing the amount of time workers are exposed to unavoidable stress by rotating tasks; increasing the variety of tasks performed and how they are performed; and changing physical positions and movements. • Exercise: Stretching the muscles relieves stress and helps to prevent injury. This proves especially important when certain physically stressful tasks must be repeatedly performed. • Enforcement of preventative procedures or policies: Teaching such procedures as proper lifting techniques, are necessary if they are to benefit the employees. • Education: Knowing the proper procedures and the physical reasons for use.

Preparation A physical therapist may either be employed by a company to treat workers on-site or act as a consultant with various companies. If the treatment is in response to an employee injury, the employer’s insurance company generally pays for the physical therapist’s services. If the therapist is providing general injury prevention consultation the employer usually pays for the service, which is cost-effective because it reduces injury-related expenses. Physical therapists are by the nature of their training well educated in anatomy, posture, body mechanics, and ergonomics, but the physical therapist who provides ergonomic assessment and treatment in the workplace may also have additional training or education in ergonomics and occupational health. Physical therapists are generally used more outside the United States, but

KEY TERMS ADA—Americans with Disabilities Act. Biomechanics—The study of biological and muscular activity. CTD—Cumulative trauma disorder. Ergonomics—Arranging and studying things people use to derive efficient and safe conditions that produce the best results. OSHA—Occupational Administration.

Health

and

Safety

RMI—Repetitive motion injury. WMSD—Work-related musculoskeletal disorders.

would prove beneficial given their expertise in the human body and its activities.

Aftercare After the ergonomic assessment for each employee’s job assignment and work station has been conducted and the employees have been instructed in proper work place ergonomics and safety, beneficial results depend on application. The employer needs to actually apply recommendations for changes in the work station or job description. Employees also have to continue to put the new techniques they have learned into practice.

Complications Whle complications resulting from the ergonomic assessment itself are not likely, there may possibly be complications resulting from an injured employee’s early return to work, even with a modified job description. If the resumed or modified activity causes irritation or risk of reinjury, the employee may need to cease the resumed activities and return to the physical therapist or physician for further treatment. Care should be taken to screen employees for any conditions contraindicating exercise before preventative stretches or other new physical activities are recommended.

Results The desired outcomes of ergonomic assessment and intervention are quicker return to work by injured employees, a safer and more efficient work environment, prevention of future injuries, and increased understanding of safe work and postural practices. By reducing

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are assembly line workers, manufacturing employees, health care workers, and office workers. Jobs requiring continual heavy lifting or constant repetition of the same motion can be especially stressful. Office work—especially that involving constant computer use—can lead to various physical problems. These include eye strain from artificial lighting and computer screens; back problems related to incorrect posture and chairs or work stations; and hand, wrist, or arm injuries due to excessive or incorrect keyboard use.

Esophagogastroduodenoscopy

injuries, Workers’ Compensation claims, and employee absenteeism, adjustments made to the work environment and related activities can lead to reductions in cost to the employer.

Health care team roles

a small flexible tube is used to view the esophagus, stomach, and duodenum (part of the small intestine). Small instruments may also be passed through the tube to treat disorders or biopsy lesions.

Purpose

A company doctor, Workers’ Compensation doctor, or other physician may refer the patient to a physical therapist for treatment and workplace ergonomic evaluation. The employer also has the option of directly requesting the physical therapist’s services. Educational specialists and others with special training in ergonomics and occupational health may be involved in addition to or in place of the physical therapist. Often the physical therapist will be the sole consultant for the employer and employees.

An EGD is performed to evaluate (or treat) symptoms relating to the upper gastrointestinal tract, such as: • upper abdominal or chest pain • nausea or vomiting • gastroesophageal reflux disease (GERD) • difficulty swallowing (dysphagia) • anemia • bleeding from the upper intestinal tract

Resources ORGANIZATIONS

American Physical Therapy Association (APTA). 1111 North Fairfax Street. Alexandria, VA 22314. (703) 684-2782. . Center for Industrial Ergonomics. Lutz Hall, Room 445, University of Louisville, Louisville, Kentucky 40292. (502) 852-7173. . Occupational Safety and Health Administration (OSHA). U.S. Department of Labor, Occupational Health and Safety Administration, Office of Public Affairs, Room N3647, Washington, D.C. 20210. (202) 693-1999. . OTHER

Ergonomics.org. 2001. . Smart Care PT. 2001. . “Workplace Assessment & Management.” Australian Physiotherapy Association (APA). . World Medicus Page. 2001. .

Diane Fanucchi, B.A., C.C.R.A.

Esophageal radiography see Upper GI exam

In addition, an EGD may be used to confirm abnormalities indicated by other exams, such as an upper GI series or a CT scan, or may be used to treat certain conditions, such as an area of narrowing (stricture) or bleeding in the upper gastrointestinal tract. Upper endoscopy is more accurate than x rays for detecting inflammation, ulcers, or tumors. It is used to diagnose early cancer and can frequently determine whether a growth is benign or malignant. Biopsies (small tissue samples) of inflamed or “suspicious” areas can be obtained and examined by a pathologist. Cell scrapings can also be taken by the introduction of a small brush; this helps in the diagnosis of cancer or infections. Small instruments can be passed through the endoscope and can stretch narrowed areas or remove swallowed objects (such as coins, pins or other foreign bodies). In addition, bleeding from ulcers or vessels can also be treated by endoscopic techniques.

Precautions An EGD is contraindicated in patients with: • severe upper gastrointestinal (UGI) bleeding • history of bleeding disorders such as platelet dysfunction or hemophilia • esophageal diverticula

Esophagogastroduodenoscopy Definition

• recent UGI surgery

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• suspected perforation

An EGD is also contraindicated for those patients who are unable to cooperate fully with the procedure.

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First, patients either gargle a local anesthetic or have one sprayed into their mouth (onto the throat) to numb the gag reflex. Patients are also usually sedated for the procedure by injection of medications into a vein. The endoscopist then has the patient swallow the scope, which is passed through the upper gastrointestinal tract. The lens or camera at the end of the instrument allows the endoscopist to examine each portion of the upper gastrointestinal tract; photos can be taken for reference. Air is pumped in through the instrument to allow proper observation. Biopsies and other procedures can also be performed.

Preparation The upper intestinal tract must be empty for the procedure, so patients must not eat or drink anything for at least six to 12 hours before the exam.

Aftercare Someone should be available to take the person home after the procedure and stay with them for a while; patients will not be able to drive themselves due to sedation. Pain or any other unusual symptoms should be reported immediately. It is important to recognize early signs of any possible complication. The doctor should be notified if the patient has: • fever • trouble swallowing (dysphagia) • difficulty breathing (dyspnea) • increasing throat, chest, or abdominal pain

Complications The overall complication rate of EGD is less than 2%, and many of these complications are minor (such as inflammation of the vein through which medication is given). However, serious complications can and do occur. Almost half of them are related to the heart or lungs. Bleeding or perforations are also reported, especially when tumors or narrowed areas are treated or biopsied. Infections have also been transmitted (rarely); careful attention to cleaning procedures should prevent this complication.

Results Normal results show the esophagus, stomach and duodenum without any strictures, ulcers or erosions,

KEY TERMS Duodenum—The first portion of the small intestine. Endoscope—A surgical tool used to view areas that can’t be directly observed (like the esophagus or the colon). Esophagus—The muscular canal between the throat and the stomach. Pathologist—A doctor who specializes in the anatomic (structural) and chemical changes that occur with diseases. These doctors function in the laboratory, examining biopsy specimens, and regulating studies performed by the hospital laboratories (blood tests, urine tests, etc). Pathologists also perform autopsies.

diverticula, masses, or bleeding. Other abnormal results include esophageal infections, fissures and tears. An increasingly common finding is medication-induced esophageal injury, caused by tablets and capsules that have lodged in the esophagus.

Health care team roles The health care team may consist of the physician, the nurse, and others. Unlicensed assistive personnel (UAPs), such as GI assistants, GI technicians or medical technicians may have direct patient care responsibility. They are supervised by a registered nurse (RN). UAPs can assist the physician and RN during diagnostic and therapeutic procedures. The RN is responsible for the assessment of patient care needs and for determining the capability of assistive personnel to whom a task is delegated. An advanced practice nurse (APN) specializing in gastroenterology may perform a comprehensive history and physical assessment. Depending on the practice, the APN may also order and/or perform diagnostic studies. Otherwise, these tasks are performed by the physician. Training An APN is a nurse who has completed an advanced degree in nursing (master’s or doctorate). An APN may be a nurse practitioner or a clinical nurse specialist. UAPs may receive on-the-job training in their duties. Patient education Instruct the patient not to eat or drink anything until the gag reflex has returned. Normally, the gag reflex will

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return in two to four hours after the procedure. To test if the gag reflex has returned, place a spoon on the back of the tongue for a few seconds with light pressure. If the patient does not gag, wait 15 minutes and attempt the maneuver again. Do not use small or sharp objects. Advise the patient that hoarseness and a mild sore throat are normal after the procedure. Encourage cool fluids and gargling to relieve the soreness. Because of the introduction of air during the procedure, it is normal to have some bloating, belching and flatulence after an EGD. To prevent pill-induced esophageal injury, advise patients to drink at least 4 ounces of liquid with any pill, and at least 8 ounces of liquid with pills that can cause injury. Patients should remain sitting upright for 30 minutes after taking pills that are likely to cause injury. Resources BOOKS

Edmundowicz, Steven.”Endoscopy.” In The Esophagus, 3rd edition, edited by Donald O. Castell and Joel E. Richter. Philadelphia: Lippincott, 1999, 89-99. Pagana, Kathleen D., and Timothy J. Pagana. Diagnostic Testing and Nursing Implications, 5th ed. St. Louis, MO: Mosby, 1999, 71-72. Young, Harvey S., and Emmet B. Keeffe, “Complications of Gastrointestinal Endoscopy.” In Sleisenger and Fordtran’s Gastrointestinal and Liver Disease, edited by Mark Feldman, et al. Philadelphia: W.B. Saunders Company, 1997, 301-309. PERIODICALS

Macedo, G., Riberio, T., “Esophageal obstruction and endoscopic removal of a cocaine packet.” American Journal of Gastroenterology 96, no. 5 (May 2001):1656-7. OTHER

Olympus America. 2 Corporate Center Drive, Mellville, NY 11747, (800) 848-9024. ORGANIZATIONS

The American Society for Gastrointestinal Endoscopy (ASGE). Thirteen Elm Street, Manchester, MA 019441314. (978) 526-8330. . Olympus America. 2 Corporate Center Drive, Mellville, NY 11747, (800) 848-9024. The Society for Gastroenterology Nurses and Associates (SGNA). 401 North Michigan Avenue, Chicago, IL 60611-4267. (800) 245-7462. .

Maggie Boleyn, RN, BSN

Estradiol test see Sex hormones tests Estriol test see Triple marker screen test Estrogen fractions test see Sex hormones tests 896

Ethical codes and oaths Definition Ethical codes and oaths are statements of the moral principles and values that govern the conduct of a group, profession, or individual. In the health professions, ethical codes embody the ideals of compassion for the suffering and respect for the dignity of all human beings, as well as the highest standards of clinical research and practice. Ethics as a discipline is the study of moral values and moral reasoning. There are two major approaches to ethics, normative and non-normative. Non-normative ethics describes and studies moral beliefs without making value judgments about right and wrong. Normative ethics tries to define and distinguish between right and wrong.

Description Ethical codes and oaths are formal statements that serve to remind practitioners of their obligations to their patients and to the larger society. In the United States and Canada, the ethical codes that have been drafted by the various health professions are also regarded as the foundation of the legal obligations of health care professionals—including disciplinary standards. For example, a patient who files a complaint with the ethics committee of a physician’s medical society or hospital can take the complaint to the state licensing board as well. Ethics committees in the health professions have the power to suspend or expel members who have violated the ethical code that governs the profession. The ethical standard set by the professional organization may be simple and forthright like the Hippocratic Oath for physicians, or more thorough and specific as is the code of conduct for nurses. Modern medical codes and oaths are patterned after the Hippocratic Oath and contain the same basic concepts: to work for the good of one’s patients; to cause them no harm; to honor the profession of medicine and protect it from corruption; to give no drugs or perform no operation that would cause harm to the patient; and to keep medical information confidential.Whether the code is an ancient or a contemporary version, it gives the health care professional a high standard of conduct for which to strive.

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Historical background The earliest statement of ethical standards for physicians is the so-called Hippocratic Oath, attributed to the “father of medicine” in the fifth century B.C. In the West, both Judaism and Christianity gave extensive consideration to the importance of the physician’s moral character as well as his clinical duties to patients. In Judaism, medical ethics is rooted in the study of specific case histories interpreted in the light of Jewish law. In medieval Christianity, ethical reflection took the form of an emphasis on duty, moral obligation, and right action. In both faiths, the relationship between the medical professional and the patient was regarded as a covenant or sacred bond of trust rather than an economic transaction or a business contract. Since the eighteenth century, several developments have led to increased concern about the ethical standards of the health professions. These changes include: • A philosophical emphasis on individual freedom and personal rights rather than on obligations to family or society. • Advances in scientific knowledge and technology that raise new questions about the nature of human personhood, life, and death. • Recognition of the vulnerability of the health professions to abuse by government authority. Specific examples include medical experiments on concentration camp inmates in Nazi Germany and the abuse of psychiatry in Stalinist Russia. • The increased role of economic considerations in health care decisions on the individual as well as the communal level. • The loss of a universal moral framework accepted by all or most people. Although there are a number of religious and philosophical perspectives on ethical questions that many people accept, none of these perspectives is accepted by everyone. Present models for making ethical decisions in medicine Models are outlines or patterns that can be used in ethical decision-making to help the care provider organize his or her thoughts and bring in all relevant considerations. One widely used model for decision-making in medicine holds that any ethical decision must consider four factors: • Medical indications. These include the diagnosis and treatment of the patient’s condition.

• Patient preferences. This factor assumes that health professionals should respect the patient’s wishes, and wherever possible provide care that does not violate them. • Quality of life. This factor is to be evaluated from the patient’s point of view, not the medical professional’s perspective. • The wider context. This factor includes all the other features that may be involved in a specific decision, such as the family’s feelings, legal considerations, socioeconomic issues, religious practices, and others. Another model that is sometimes used in clinical practice proposes three rules to be followed in ethical decision-making: • Impartiality. This rule requires the health professional to place him- or herself in the patient’s position and ask whether they would be willing to have the action performed if they were the patient. • Universality. This rule asks whether the health professional would be willing to apply the same solution to the patient’s situation in all similar cases. • Justifiability. This rule asks the health professional to consider whether he or she could defend the decision to other people or discuss it in public. Other considerations Although there are many medical codes and guidelines within individual medical associations, some observers have proposed a universal code of ethics binding on all health care professions. It has been suggested that a universal code of ethics would unify the medical community and restore society’s trust in its professional care givers. Another dimension of ethical decision-making in medicine that has received greater attention in recent years is the role of empathy and compassion. The ethical codes that govern health professionals do not specify these characteristics in health care providers, but both care givers and patients increasingly recognize that ethical integrity can be cold and lifeless without emotional rapport. Human beings have feelings as well as capacities for intellectual reflection and analysis. Empathy and compassion help to build trust between care giver and patient, improve communication, and often contribute to healing.

Professional implications One implication for health professionals is the importance of studying ethical issues during one’s professional education. Many medical, dental, and nursing

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the Tavistock Group.” British Medical Journal 318 (January 23, 1999): 248-251.

KEY TERMS

ORGANIZATIONS

Empathy—The ability to identify with the feelings or thoughts of another person. Ethics—A system or set of moral principles; also, the study of values relating to human conduct. Hippocratic Oath—The ethical oath attributed to Hippocrates that is used as a standard for care by physicians worldwide. Non-normative ethics—An approach to ethics that emphasizes analysis of moral decisions without making judgments of right or wrong. Normative ethics—An approach to ethics that attempts to define right and wrong and distinguish between them.

American Medical Association, Council on Ethical and Judicial Affairs. 535 North Dearborn St., Chicago, IL 60610. (312) 645-5000. Canadian Medical Association. 1867 Alta Vista Drive, Ottawa ON K1G 3Y6. (613) 731-8610x2307 or (888) 855-2555. Fax (613) 236-8864. [email protected]. Society for Academic Emergency Medicine. 901 North Washington Avenue, Lansing, MI 48906-5137. (517) 485-5484. Fax: (517) 485-0801. [email protected]. OTHER

Canadian Medical Association. Code of Ethics of the Canadian Medical Association. Policy statement approved by the CMA Board of Directors, October 15, 1996.

Rapport—A relation between two people that is harmonious and sympathetic.

Peggy Elaine Browning

Ethics, medical see Medical ethics schools now include courses in their curricula that deal with such topics as moral decision-making, definitions of life and death, the ethical complexities of professionalpatient relationships, and the moral safeguards of medical research. A second implication is recognizing the necessity of interdisciplinary conversation and cooperation. Health professionals can benefit from the insights of scholars in the social sciences, philosophy, theology, law, and history. At the same time, health professionals have much to offer to scholars in other fields gained from their clinical experience. Resources BOOKS

Brody, Baruch A., et al. Medical Ethics: Codes, Opinions, and Statements. New York: BNA Books, 2000. This book is a collection of the ethical statements and positions of the twenty-six leading medical societies in the United States. Jonsen, Albert R. A Short History of Medical Ethics. New York: Oxford University Press, 2000. PERIODICALS

Hughes, James J., and Damien Keown. “Buddhism and Medical Ethics: A Bibliographic Introduction.” Journal of Buddhist Ethics 7 (2000): 1-12. Levine, Carol. “Hands on/hands off: Why health care professionals depend on families but keep them at arm’s length.” Journal of Law, Medicine, and Ethics (Spring, 2000). Smith, Richard. “Education and debate: Shared ethical principles for everybody in health care: A working draft from

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Ethics, nursing see Code of ethics for nurses

Euthanasia Definition Euthanasia is the act of putting a person (or animal) to death painlessly, or allowing a person (or animal) to die by withholding medical treatment in cases of incurable (and usually painful) disease. The word “euthanasia” comes from two Greek words that mean “good death.” Euthanasia is sometimes called “mercy killing.”

Description Terms and categories It is important to distinguish euthanasia from “assisted suicide,” which is sometimes used loosely as a synonym for euthanasia. Assisted suicide, which is often called “self-deliverance” in Britain, refers to a person’s bringing about his or her own death with the help of another person. Because the other person is often a physician, the act is often called “doctor-assisted suicide.” Assisted suicide is illegal everywhere in the United States except the state of Oregon, while euthanasia is illegal in all fifty states. Euthanasia strictly speaking means that the physician or other person is the one who per-

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Euthanasia is usually categorized as either active or passive, and as either voluntary or involuntary. The first set of categories refers to the means of ending life, and the second set of categories refers to the agent of the decision. Active euthanasia involves putting a patient to death for merciful reasons; passive euthanasia involves withholding medical care, or not doing something to prevent death. In voluntary euthanasia, the patient is the one who wishes to die and has usually requested either active or passive euthanasia. In involuntary euthanasia, someone else makes the decision to terminate the patient’s life, usually because the patient is in a coma or otherwise unable to make an informed request to die. Another important term to understand is the socalled doctrine of double effect. This is a legal term that has been underscored by the United States Supreme Court in one of its decisions. The doctrine of double effect states that a medical treatment intended to relieve pain but that incidentally hastens the patient’s death is still appropriate and legally acceptable. In other words, a doctor who gives a dying patient high doses of morphine to prevent pain, knowing that such high doses may shorten the patient’s life by a few days, is protected by the doctrine of double effect. Historical overview Although euthanasia has been practiced in various human societies for centuries, it has become a major social issue only in the twentieth century. Some ancient societies allowed infants born with serious birth defects to die, and some allowed the elderly to starve themselves to death as a form of voluntary euthanasia. In addition, it was not unusual for soldiers on the battlefield to give a death blow, or coup de grâce, to a mortally wounded comrade to prevent him from being captured by the enemy as well as to end his suffering. The French phrase literally means “stroke of mercy.” In the nineteenth century, euthanasia became a topic of ethical discussion partly because the discovery of reliable anesthetics and analgesic (pain-killing) medications meant that painless death was now easier to bring about. Prior to this period, the methods of suicide that were available to people were either violent, painful, or uncertain—and sometimes all three. For example, when the heroine of one mid-nineteenth-century French novel commits suicide by taking arsenic, the author describes

her agonizing death in clinical detail. But after the discovery of chloroform, ether, nitrous oxide, and similar anesthetics, people began to consider using them to relieve the suffering of the dying as well as the pain involved in surgical operations. In the twentieth century, a number of social and technological changes made euthanasia a morally acceptable choice to growing numbers of people. The Euthanasia Society of America (which changed its name to the Society for the Right to Die in 1975) was founded as early as 1938. One important change was the increasing size of the elderly population, a development that resulted from the lengthening of the life span brought about by advances in medical science. A second was the invention of respirators, intravenous feeding, dialysis machines, and other means of prolonging a patient’s life even in cases of terminal illness. Discomfort at the thought of ending one’s life at the mercy of machinery is frequently mentioned in public opinion polls as a justification for euthanasia or assisted suicide. Another important transition was a change in social attitudes in favor of individual freedom and autonomy, rather than emphasizing a person’s membership in a family or community. Many people today feel strongly that they are the best judges of their own well-being, and that they should have the “right to die” if necessary.

Viewpoints Medical professionals As of 2001, most North American professional societies in the health care professions have stated their opposition to active euthanasia. The American Medical Association (AMA) sponsored the establishment of an Institute for Ethics in the late 1990s, intended to educate American doctors about pain relief, palliative care at the end of life, and alleviation of patients’ fears. The AMA has expressed its concern about the expansion of doctorassisted suicide in the Netherlands—which became legal in April 2001—to include euthanasia without the patient’s knowledge or consent. The American Nurses Association (ANA) signed on to the amicus curiae (friend of the court) brief submitted by the AMA to the United States Supreme Court in 1997 opposing doctorassisted suicide. The ANA also stated that the health care professions should emphasize respectful, compassionate, and ethically responsible care at the end of life, including palliative care, so that patients do not seek assisted suicide as an alternative.

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forms the last act that causes death. For example, if a physician injects a patient with a lethal overdose of a pain-killing medication, he or she is performing euthanasia. If the physician leaves the patient with a loaded syringe and the patient injects himself or herself with it, the act is an assisted suicide.

Euthanasia

Professional implications

KEY TERMS

The goals of medicine and health care

Active euthanasia—Putting a person to death as an act of mercy, as when a physician gives a patient a lethal dose of a medication. Assisted suicide—A form of self-inflicted death in which a person voluntarily brings about his or her own death with the help of another, usually a physician, relative, or friend. Doctrine of double effect—A legal principle that protects physicians treating patients to relieve pain even though the palliative treatment may shorten the patient’s life. Mercy killing—Another term for euthanasia. Palliative care—A form of health care intended to relieve pain without attempting to cure the disease or condition. Passive euthanasia—The withholding of medical care, or not taking some other action to prevent death; allowing a person to die. Self-deliverance—Another term for assisted suicide. Voluntary euthanasia—A form of euthanasia in which a person asks to die, either by active or by passive euthanasia.

Religious groups In the United States and Canada, most mainstream Christian and Jewish groups remain opposed to active and involuntary euthanasia, though some permit carefully regulated forms of passive euthanasia. Christian and Jewish bodies emphasize not only God’s ultimate power over death and life, and the value of human beings as creatures made in God’s image, but also the relationships that bind humans to one another and to God. From this perspective, these religious traditions stand in contrast to the individualism of much of secular culture. Contemporary Buddhist thought is divided on the issue of euthanasia. Some Buddhist ethicists believe that euthanasia and assisted suicide are both consistent with Buddhist principles, but others disagree. One reason for the disagreement is the fact that Buddhism encountered Western medicine and its ethical dilemmas only relatively recently. 900

Euthanasia and assisted suicide compel medical professionals to reexamine their understanding of the purposes and goals of medical treatment. Those who maintain that preserving life and doing no harm are central to the ethical practice of medicine will have a different view of euthanasia from those who regard the relief of suffering as central. Professional-patient relationships The brief that the AMA submitted to the Supreme Court in 1997 included physician-patient relationships among its reasons for rejecting doctor-assisted suicide. Many American and Canadian physicians believe that acceptance of doctor-assisted suicide would undermine the credibility of the health care professions, and destroy trust between doctors and patients. In addition, others have pointed to the potential abuse of a physician’s power to end a patient’s life. Interprofessional consultation and cooperation Euthanasia and assisted suicide are questions that involve public policy, the legal system, and religious institutions as well as the health care professions. The complexity of the social and political considerations, together with the moral concerns, requires better communication among these different groups. One promising development has been the introduction of graduate-level ethics courses that bring together students from law, medical, nursing, and theological schools. Another has been the establishment of research centers and “think tanks” devoted to end-of-life issues. Resources BOOKS

Dubler, Nancy N. “Legal and Ethical Issues.” Chapter 14 in The Merck Manual of Geriatrics, 2nd ed. Whitehouse Station, NJ: Merck Research Laboratories, 2000. Leone, Daniel A. (Editor). The Ethics of Euthanasia (At Issue). San Diego, CA: Greenhaven Press, 1999. Manning, Michael. Euthanasia and Physician-Assisted Suicide: Killing or Caring? Mahwah, NJ: Paulist Press, 1998. Pool, Robert. Negotiating a Good Death: Euthanasia in the Netherlands. Binghamton, NY: Haworth Press, 2000. Somerville, Margaret A. Death Talk: The Case Against Euthanasia and Physician-Assisted Suicide. Montreal: McGill-Queen’s University Press, 2001. PERIODICALS

Haddad, Amy M. “Where Do You Stand on Euthanasia?” RN (April 1991): 38-42.

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ORGANIZATIONS

American Medical Association, Council on Ethical and Judicial Affairs. 535 North Dearborn St., Chicago, IL 60610. (312) 645-5000. American Nurses Association. 600 Maryland Ave. SW, Ste. 100 West, Washington, DC 20024. (800) 274-4262. . Canadian Medical Association. 1867 Alta Vista Drive, Ottawa ON K1G 3Y6. (613) 731-8610x2307 or (888) 855-2555. Fax (613) 236-8864. [email protected]. Citizens United Resisting Euthanasia. 812 Stephen St., Berkeley Springs, WV 25411. (304) 258-5433. . The Hemlock Society USA. P.O. Box 101810, Denver, CO 80250. (800) 247-7421. Web site: . OTHER

Administrative Committee, National Conference of Catholic Bishops. Statement on Euthanasia. Adopted in committee, September 1993. Commission on Theology and Church Relations of the Lutheran Church-Missouri Synod (LC-MS). Christian Care at Life’s End. Report adopted, February 1993. Evangelical Lutheran Church in America (ELCA), Division for Church in Society. End of Life Decisions. Statement adopted by the ELCA Church Council, November 1992. National Association of Evangelicals (NAE). Euthanasia: Termination of Medical Treatment. Resolution adopted at the NAE Annual Conference, 1994. Union of Orthodox Jewish Congregations. Testimony before the United States Senate Judiciary Committee in a hearing on the Pain Relief Promotion Act, May 2, 2000.

Ken R. Wells Rebecca Frey

Purpose EP studies, also known as evoked responses, measure the very faint electrical response of the brain, brainstem, or peripheral nerves to a mild stimulus, displaying it as a wave on a paper strip or computer monitor. Because the response is of such low amplitude, the responses to many stimuli must be averaged to distinguish the potentials from the background brain activity. The general purpose of this group of tests is to diagnose nerve disorders and to distinguish nonorganic loss of sensation from nerve damage. The tests can locate the site of the lesion and serve to evaluate the condition of a patient’s nervous response after treatment or during surgery. Auditory EP studies are often used to assess the cause of a hearing loss or balance problems, especially in children. They are the most common way hearing loss is evaluated in premature infants. Most auditory EPs record activity from the brainstem, and are therefore called brainstem auditory evoked potentials. This test is also particularly useful in screening for acoustic neuroma (a benign tumor of the nerves of the auditory canal). Visual EP studies are used to assess eyesight in infants and children, as well as to diagnose disorders of the optic nerve and muscles. They can also distinguish hysterical blindness, a psychiatric disorder, from blindness caused by nerve damage. Somatosensory EP studies are commonly used in the diagnosis of multiple sclerosis and transverse myelitis, although magnetic resonance imaging (MRI) has made this test less useful for these purposes. After trauma, somatosensory EP can determine whether loss of sensation in an arm or leg is due to injury in the brain or spinal cord. Auditory, visual, or somatosensory testing can detect tumors and other abnormalities affecting the brain and spinal cord, assess brain stem function in coma, and assist in the determination of brain death. Perhaps the most prominent future role of this group of tests is the monitoring of brain activity and signals from the nerves during surgery on the brain, spine, or carotid region, and during general anesthesia.

Precautions

Evoked potential studies Definition Sensory evoked potential (EP) studies are the measurement of the electrical response of nervous tissue to auditory, visual, and somatosensory stimulation.

There are several benign conditions that can affect the results of evoked potential studies. Visual EP tests should not be performed on persons having severe nearsightedness. Auditory EP studies are contradicted for persons having excessive earwax or severe inflammation of the middle ear. All three types of tests can be adversely affected by muscle spasms in the head or neck of the patient.

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Hughes, James J., and Damien Keown. “Buddhism and Medical Ethics: A Bibliographic Introduction.” Journal of Buddhist Ethics 7 (2000): 1-12. Pfettscher, Susan. “Nephrology Nurses, Euthanasia, and Assisted Suicide.” ANNA Journal (Oct. 1996): 524-526. Singer, Peter A. “Medical ethics (Clinical review).” British Medical Journal 321 (July 29, 2000): 282-285. Sullivan, Molly. “Ethics of Assisted Suicide and Euthanasia.” Nursing Management (March 1999): 31-32.

Evoked potential studies

Preparation

KEY TERMS Amplitude—The distance from the baseline to the peak of the sensory response; represents the approximate number of healthy nerves available. Latency—The amount of time between stimulus and sensory nerve response. Waveform—The shape of the electrical response of the brain, brainstem, or peripheral nerve as recorded by the active electrode.

The patient’s hair should be clean, with no gels, sprays, or other preparations applied. Jewelry should be removed.

Aftercare After the tests, the electrodes are removed with acetone and the scalp is cleaned. The patient can resume normal activities.

Complications There are no complications that result from this group of tests.

Description The test is often performed by an electrodiagnostic technologist, a nurse, or another allied health professional. It begins with the location and marking of specific spots on the patient’s head for placement of electrodes. These spots are cleaned, and an adhesive conducting paste is applied. Cup electrodes are attached. For somatosensory EP, spots on the arm or leg are also marked and cleaned; electrodes may be taped in place. The patient sits or reclines in a chair throughout the tests. For a visual EP, electrodes are attached to the scalp over the brain region responsible for vision. The patient focuses on a TV screen that displays a checkerboard pattern. The eye not being tested is covered with a patch. For children or others whose attention may wander, goggles are used which show the pattern to one eye at a time. Each eye is usually put through two series of tests where hundreds of sample recordings are collected for averaging. The entire procedure takes approximately one hour.

Results Results are recorded as waveforms, either on paper or a digital display. For somatosensory or visual EPs, the traces are displayed so a negative potential at the active electrode produces an upward deflection in the wave. Brainstem auditory EPs, in contrast, are recorded such that a positive potential at the active electrode produces an upward deflection. By using these conventions, the waves of interest are always recorded as upward deflections. In general, EP tests produce both latency (speed of conduction) and amplitude (electrical strength of response) results, with the latency measurements more often clinically significant. Results are often compared to age-specific normal values that are established at each laboratory, with a value of 2.5 to 3.0 standard deviations from the mean interpreted as abnormal. Comparisons between data collected from the left and right sides of an individual patient are also informative.

Health care team roles

For auditory EP, electrodes are placed on the top of the head and on the earlobe of the ear being tested. Headphones are used to deliver a series of clicks to one ear at a time. A masking or static sound is played into the other ear. Each ear is usually put through two trials, and the entire procedure takes approximately one hour.

Evoked potential studies are often performed by specially trained electrodiagnostic technologists. Training for such a position can be on the job but often involves study at a one- to two-year college or vocational program. A typical program would include:

For somatosensory EP, electrodes for recording are placed on the scalp and along the spinal cord, while electrodes for delivering a mild electrical shocks are placed on either the arm or the leg. The shock is not painful, but may cause some twitching and tingling. Multiple trials are done for each nerve tested, and the entire procedure can take up to three hours, if both arm and leg nerves are evaluated.

• neurology and neuroanatomy

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• human anatomy and physiology • neurophysiology • medical terminology • computer technology and instrumentation Certification of electrodiagnostic technologists specializing in evoked potentials and the related area of electroencephalography is available through the

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A physician such as neurologist, neurosurgeon, or internist does the final review and diagnosis based on the results of EP studies. The doctor can be present for the testing or may review saved tracings. Other health care professionals, such as nurses, aid in patient education concerning this procedure. Resources BOOKS

Emerson, Ronald G. “Somatosensory Evoked Potentials.” In Comprehensive Clinical Neurophysiology, Eds. Levin, Kerry H. & Hans O. Lüders. Philadelphia: W. B. Saunders Company, 2000. Epstein, Charles M. “Visual Evoked Potentials.” In Comprehensive Clinical Neurophysiology, Eds. Levin, Kerry H. & Hans O. Lüders. Philadelphia: W. B. Saunders Company, 2000. Lüders, Hans O., and Kiyohito Terada. “Auditory Evoked Potentials” In Comprehensive Clincial Neurophysiology, Eds. Levin, Kerry H. & Hans O. Lüders. Philadelphia: W.B. Saunders Company, 2000. Misulis, Karl E. “Evoked Potential Basics.” In Essentials of Clinical Neurophysiology. Boston: ButterworthHeinemann, 1997. PERIODICALS

Shpritz, D.W. “Neurodiagnostic Studies.” Nursing Clinics of North America 34 (September 1999): 593-606. ORGANIZATIONS

American Board of Registration of Electroencephalographic and Evoked Potential Technologists, P.O. Box 916633, Longwood, FL 32791-6633. (407) 788-6308. .

Michelle L. Johnson, M.S., J.D.

Evoked responses see Evoked potential studies Ewing’s sarcoma see Sarcomas

tain fitness, and is important as a means of physical rehabilitation.

Purpose Exercise is used in preventing or treating coronary heart disease, osteoporosis, weakness, diabetes, obesity, and depression. Range of motion is one aspect of exercise important for increasing or maintaining joint function. Strengthening exercises provide appropriate resistance to the muscles and increase endurance and strength. Cardiac rehabilitation exercises are developed and individualized to improve the cardiovascular system for prevention of and rehabilitation from cardiac disorders and diseases. A well-structured exercise program can improve general health by increasing strength, endurance, balance, and confidence. Furthermore, an exercise program may delay or minimize the effects of disease and aging. The benefits of exercise not only extend into the areas of physical health, but also enhance emotional well-being.

Precautions Before beginning any exercise program, evaluation by a physician is recommended to rule out any potential health risks. Once health and fitness are determined and any or all physical restrictions identified, the exercise program should be under the supervision of a health care professional, especially when used as a form of rehabilitation. If symptoms of dizziness, nausea, excessive shortness of breath, or chest pain are present during any exercise program, the individual should stop the activity and inform the physician before resuming activity. Exercise equipment must be checked often for wear and durability.

Description There are two types of rehabilitation to restore or improve function: cardiac and physical rehabilitation. Cardiac rehabilitation

Exercise Definition Exercise is physical activity that is planned, structured, and repetitive for the purpose of conditioning any part of the body or to improve performance in a specific task. Exercise is utilized to improve health, main-

Exercise is very helpful in prevention of and rehabilitation from cardiac disorders and disease. With an individually designed exercise program set at a safe level, heart failure patients can improve their fitness levels substantially. Endurance or aerobic routines, such as running, brisk walking, cycling, or swimming, increase the strength and efficiency of the muscles of the heart. The increase in endurance should also translate into a generally more active lifestyle.

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American Board of Registration of Electroencephalographic and Evoked Potential Technologists.

Exercise Exercise can be used to restore muscle strength after an illness or injury. A computer monitors this man’s performance and provides a visual display of his progress. (Photograph by Geoff Tompkinson. Science Source/Photo Researchers. Reproduced by permission.)

Physical rehabilitation Physical rehabilitation deals with improving function in specific individuals who have functional impairments secondary to disease, injury, or disuse. This is accomplished by therapeutic exercise that focuses on strengthening, coordination, balance, and endurance training. Both types of rehabilitation can incorporate range of motion exercises and strengthening exercises. RANGE OF MOTION EXERCISE. Range of motion exer-

cise refers to activity aimed at improving movement of a specific joint. This motion is influenced by several structures: configuration of bone surfaces within the joint; joint capsule; ligaments; and muscles and tendons acting on the joint. There are three types of range of motion exercises: passive, active, and active assistive. Passive range of motion is movement applied to the joint solely by anoth904

er person or persons or by a passive motion machine. When passive range of motion is applied, the joint of the individual receiving exercise is completely relaxed while the outside force takes the body part, such as a leg or arm, throughout the available range. Injury, surgery, or immobilization of a joint may affect the normal joint range of motion. Active range of motion is movement of the joint provided entirely by the individual performing the exercise. In this case, there is no outside force aiding in the movement. Active assistive range of motion is described as the joint receiving partial assistance from an outside force. This range of motion may result from the majority of motion applied by the exerciser or by the person or persons assisting the individual. It may also be a half-andhalf effort on the joint from each source. STRENGTHENING EXERCISE. Strengthening exercise increases muscle strength and mass, bone strength, and

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Strengthening exercises can be further categorized in terms of the mode of resistive training, such as isometric, isotonic, or isokinetic. ISOMETRIC EXERCISE. During isometric exercises muscles contract; however, there is no motion in the affected joints. The muscle fibers maintain a constant length throughout the entire contraction. The exercises are usually performed against an immovable surface or object, such as pressing the hand against the wall. The muscles of the arm are contracting but the wall is not moving as a result of the physical effort. Isometric training is effective for developing total strength of a particular muscle or group of muscles. It is often used for rehabilitation, since the exact area of muscle weakness can be isolated and strengthening can be administered at the proper joint angle. This kind of training can provide a relatively quick and convenient method for overloading and strengthening muscles without any special equipment and with little chance of injury. ISOTONIC EXERCISE. Isotonic exercise differs from isometric exercise in that there is movement of the joint during the muscle contraction. It is exercise with a fixed resistance and variable speed. A classic example of an isotonic exercise is weight training with dumbbells and barbells. As the weight is lifted throughout the range of motion, the muscle shortens and lengthens. Calisthenics are also an example of isotonic exercise. These would include chin-ups, push-ups, and sit-ups, all of which use body weight as the resistance force. ISOKINETIC EXERCISE. Isokinetic exercise utilizes machines that control the speed of movement within the range of motion. Isokinetic exercise attempts to combine the best features of both isometrics and weight training. It is resistive exercise utilizing a fixed speed and variable resistance. It provides muscular overload at a constant preset speed while the muscle mobilizes its force through the full range of motion. For example, an isokinetic stationary bicycle set at 90 revolutions per minute means

that no matter how hard and fast the exerciser works, the isokinetic properties of the bicycle will allow the exerciser to pedal only as fast as 90 revolutions per minute. Machines known by such brand names as Cybex and Biodex provide isokinetic resistance; they are generally used by physical therapists and are not readily available to the general population.

Preparation A physical examination by a physician is important to determine if strenuous exercise is appropriate or detrimental for the individual. Prior to the exercise program, proper stretching is important to prevent the possibility of soft tissue injury resulting from tight muscles, tendons, ligaments, and other joint-related structures.

Aftercare Proper cool-down after exercise is important in reducing the occurrence of painful muscle spasms. It has been documented that proper cool-down may also decrease frequency and intensity of muscle stiffness the day following any exercise program.

Complications Improper warm-up can lead to muscle strains. Furthermore, overexertion with insufficient rest time between exercise sessions may lead to musculoskeletal injury. Stress fractures are also a possibility if activities are strenuous over long periods of time. Although exercise is safe for the majority of children and adults, there is still a need for further research to evaluate potential risks of strength training in children. There is a possibility of exercise “burnout,” or over-training, if the exercise program is not varied and adequate rest periods are not taken between exercise sessions.

Health care team roles Significant health benefits are obtained by including a moderate amount of physical exercise in the form of an exercise prescription. Physical activity plays a positive role in preventing disease and improving overall health status. People of all ages, both male and female, benefit from regular physical activity. Regular exercise also provides significant psychological benefits and improves quality of life. Patient education Nurses and other allied health professionals can educate their patients by using videotapes, manuals, and Web-based literature. However, it would be recommended that instructional workshops or classes be set up in an

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the body’s metabolism. It can help attain and maintain proper weight and improve body image and self-esteem. A certain level of muscle strength is needed to do daily activities, such as walking, running, and climbing stairs. Strengthening exercises increase muscle strength by putting more strain on a muscle than it is normally accustomed to receiving. This increased load stimulates the production of proteins inside each muscle cell that allow the muscle as a whole to contract with greater force. There is evidence indicating that strength training may be better than aerobic exercise alone for improving selfesteem and body image. Weight training allows immediate feedback through observation of progress in muscle growth and improved muscle tone.

Eye examination

Exercise electrocardiogram see Stress test

KEY TERMS

Exercise stress test see Stress test

Aerobic—Exercise training that is geared to provide a sufficient cardiovascular overload to stimulate increases in cardiac output. Calisthenics—Exercise involving free movement without the aid of equipment. Endurance—The time limit of a person’s ability to maintain either a specific force or power involving muscular contractions. Osteoporosis—A disorder characterized by loss of calcium in the bone, leading to thinning of the bones. It occurs most frequently in postmenopausal women.

effort to appropriately evaluate patient safety and mechanics during exercise. Physical therapists often work with patients who are recovering from cardiac diseases or strokes. Training For nurses and allied health professionals, certifications are available to qualified candidates. Usually a period of study and testing is required in becoming certified. The American College of Sports Medicine provides well established certification programs. Resources BOOKS

Hall, C. M., L. T. Brody. Therapeutic Exercise Moving Toward Function. Philadelphia: Lippincott, Williams & Wilkins, 1999. Magee, D. J. Orthopedic Physical Assessment. Philadelphia: W.B. Saunders Co., 1997. McArdie, William D., Frank I. Katch, and Victor L. Katch. Exercise Physiology: Energy, Nutrition, and Human Performance. Philadelphia: Lea and Febiger, 1991. PERIODICALS

Colan, Bernard J. “Exercise for Those Who Are Overweight: Just the Start in Fitness Plan.” Advance For Physical Therapy 8, no. 25 (June 1997). ORGANIZATIONS

American College of Sports Medicine. P.O. Box 1440, Indianapolis, IN 46206-1440. (317) 637-9200. American Physical Therapy Association. 1111 North Fairfax St., Alexandria, VA 22314-1488. (703) 684-ATPA. .

Mark Damian Rossi, Ph.D, P.T., C.S.C.S. 906

Exercise thallium test see Thallium heart scan External fetal monitoring see Electronic fetal monitoring Extracorporeal shock-wave lithotripsy (ESWL) see Lithotripsy Eye and orbit ultrasounds see Ophthalmologic ultrasounds

Eye examination Definition An eye examination is a series of tests performed by an ophthalmologist or an optometrist to determine if there are any pre-existing or potential problems with a patient’s vision.

Purpose Eye examinations measure a person’s ocular health and visual status, in order to detect abnormalities in the components of the visual system, and to determine how well the person can see. Eye exams may also reveal the presence of non-eye diseases such as high blood pressure or diabetes. Infants should be examined to detect any physical abnormalities. If a problem is noted the infant can be further examined, generally by a pediatric ophthalmologist. A child without symptoms should have an eye exam before age three. Early exams are important because some conditions may result in permanent problems with vision. For example, amblyopia, more commonly known as a lazy eye, should be corrected before permanent damage occurs, usually between the ages of six and nine. If a child continues to be symptom-free, the second exam should take place before first grade. After first grade, the American Optometric Association recommends an eye exam every two years until age 19. From ages 19–40, an examination every two to three years is recommended, and from ages 41–60, an exam every two years is recommended. After that, healthy persons without risk factors are recommended to have annual examinations. Doctors should advise patients at risk for eye disease that they

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may need more frequent checkups. Persons with visual problems should seek medical attention right away.

Precautions The examiner, who may be an O.D., D.O., M.D., ophthalmic nurse, ophthalmic assistant, or ophthalmic technician, should log any medications the patient is taking and any existing health conditions. Some medications can affect vision or interfere with the eyedrops used during the exam. Certain types of eyedrops should not be prescribed if the patient has asthma, heart problems, or other conditions. The patient may need transportation if the eyes are dilated. Physicians may advise patients to wear dark glasses to decrease the glare from strong light until the effects of the medication are sufficiently diminished.

Description An eye examination is performed by an optometrist (who has an O.D. degree) or an ophthalmologist. Ophthamologists either have an M.D. or a D.O. (doctor of osteopathy) degree. An eye examination, given by an ophthalmologist or optometrist with assistance from ophthalmic nurses, assistants and technicians, costs about $100 and may or may not be covered by insurance. It begins with a patient history and continues with a series of primary tests. Additional specialized tests are administered as needed. The primary tests can be divided into two groups: those that evaluate the physical state of the eyes and surrounding areas; and those that measure the ability to see. Some variation exists, but most eye examiners and their assistants take a patient history and perform a standard set of primary tests. Patient history and initial observations The ophthalmic nurse, assistant, or technician will take eye and medical histories that include the patient’s chief complaint, any past eye disorders, current medications, any family history of eye disorders, and any systemic disorders the patient may have. Sample questions may include “How is your vision?” or “Do you have any allergies?” Examiners also should ask about the patient’s lifestyle. This information may modify prescriptions. For example, a construction worker needs protective eyewear. Patients should be encouraged to bring all of their currently used corrective lenses to the exam (contacts and glasses). This allows the ophthalmic staff to determine the prescription using a lensometer, and allows the examiner to determine the efficacy of the current prescription.

A doctor examines a patient’s eyes using an ophthalmoscope. (Photograph by Andy Levin. Science Source/Photo Researchers. Reproduced by permission.)

Visual acuity tests Visual acuity measures how clearly the patient can see. The examiner measures each eye separately, with and without the current prescription. Examiners use a Snellen eye chart with lines of different-sized letters. Each line has a number at the side denoting the distance from which a person with normal vision can read that line. Other charts are available for children or anyone unfamiliar with the Roman alphabet. Charts should be placed at the recommended distance (usually 20 feet, or 6 m) from the patient. At that distance, persons with normal vision can read the line marked 20/20, and are said to have 20/20 vision. Patients who cannot read that line are assigned a ratio based on the smallest line they can read. The first number (numerator) of the ratio is the distance between the chart and the patient, and the second number (denominator) is the distance where a person with normal vision would be able to read that line. The ratio 20/40 means the patient sees at 20 feet what people with normal vision can see at 40 feet. When a patient is unable to read any of the lines, the patient is moved closer until the line with the largest letters is readable. A ratio of 5/200 means the person being tested can see at five feet (1.8.m) what a normal person can see at 200 feet (60 m). If a patient can’t read the chart at all, the examiner may hold up fingers and ask the patient to count them at various distances. The examiner records the result as “counting fingers” at the distance of recognition. If the patient cannot count the fingers at any distance, the examiner determines if the patient can see hand movements. If so, the result is recorded as “hand movements.” If not, the examiner determines if the patient can detect light from a penlight. Detection of light and its direction is recorded as “light projection.” If the patient can detect

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Refraction examination If a patient has visual acuity less than 20/20, the examiner will determine the refractive error and prescribe corrective lenses. To determine refractive error, the examiner utilizes a phoropter. A phoropter is an instrument equipped with many lenses. The examiner uses them to test many combinations of corrections in order to learn which correction allows the patient to see the eye chart most clearly. The phoropter also contains prisms, and sometimes the examiner will intentionally make the patient see double. This maneuver may help in determining a slight eye turn, as well as comparing the acuity of the right and left eye. The exam assesses far (distance) vision and near (reading) vision. Examiners can also determine a lens prescription by utilizing an automated refracting device. The device measures the necessary refraction by shining a light into the eye and scanning the reflected light. Another way to obtain a prescription is using a hand-held retinoscope. As in the automated method just mentioned, the doctor shines a light in the patient’s eyes and can determine an objective prescription. This is helpful in young children or infants. Eye examiner using an ophthalmoscope. (Phototake, NYC. Reproduced by permission.)

the light but not its direction, the result is recorded as “light perception.” If the patient cannot detect the light at all, the result is recorded as “no light perception.” Eye movement examination The examiner asks the patient to follow an object (often the examiner’s finger) left, right, up, down, and in all four diagonal directions in order to ensure that the eyes are capable of the full range of motion and that the motions are smooth. Next is a peripheral visual field test. The examiner asks the patient to stare at an object, then quickly covers one eye and notes any movement in the eye that remains uncovered. This procedure is repeated with the other eye. This, and another similar test, helps detect an eye turn or problem with fixation. The examiner may also have the patient look at a pen and follow it as it is moved close to the eyes to check convergence. Iris and pupil examination The doctor or assistant checks the pupil’s response to light and accommodation (whether it dilates and constricts appropriately). The iris is viewed for symmetry and overall physical appearance. The iris is checked more thoroughly during the slit lamp examination. 908

Physicians or assistants may instill eyedrops in the patient’s eyes before refraction. The drops relax accommodation so that the refraction is more accurate. This is helpful in children and people who are farsighted. Ophthalmoscopic examination These observations are best accomplished after dilating the pupils and require an ophthalmoscope. The ophthalmoscope most frequently used is a called a direct ophthalmoscope. It is a hand-held illuminated 15X multilens magnifier that allows the examiner to view the back of the inside area of the eye (the fundus). The retina, blood vessels, optic nerve, and other structures are examined. Slit lamp examination The slit lamp (biomicroscope) is a microscope with an adjustable light source. This instrument magnifies and illuminates the external structures of the eyes. The lid and lid margin, cornea, iris, pupil, conjunctiva, sclera, and lens are examined. The slit lamp is also used in contact lens evaluations. With the use of a condensing lens, the biomicroscope provides an excellent view of the internal structures of the eye. Visual field measurement A perimeter, an instrument for measuring visual fields, is a hollow hemisphere equipped with a light

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Intraocular pressure (IOP) measurement Small probes called tonometers are used to measure IOP. Contact tonometers contact the eyeball directly. A colored anesthetic eyedrop is usually instilled immediately before this test. Other tonometers (noncontact tonometers) measure pressure by expelling a puff of air toward the eyeball from a very short distance. The noncontact tonometers are often not as accurate as the contact tonometers. Additional tests In addition to the primary tests already described, the examiner should observe the general health of the eye and structures around it. Depending upon the results of all the primary tests, other tests may also be necessary. These can include, but are not limited to, binocular indirect ophthalmoscopy, gonioscopy, color vision tests, and contrast sensitivity. The patient may have to return for additional visits.

Aftercare Seeing clearly does not necessarily mean the eyes are healthy. Patients should be advised that regular checkups can detect abnormalities. Patients also should be examined if they notice a change in vision, eyestrain, blur, flashes of light, a sudden onset of floaters, distortion, double vision, redness, pain or discharge. External observations INITIAL OBSERVATIONS AND SLIT LAMP EXAM. Some general observations the doctor may be looking for include: head tilt; drooping eyelids; eye turns; red eyes; eye movement; the iris size, shape, and color; clarity of the cornea, anterior chamber, and lens. The anterior chamber lies behind the cornea and in front of the iris. If it appears cloudy or if cells can be seen in it during the slit lamp exam, an inflammation may be present. A narrow anterior chamber may place the patient at risk for glaucoma. Any abnormality indicates a need for medical care.

Internal observations OPHTHALMOSCOPIC EXAM. The observations include, but are not limited to, the retina, blood vessels, optic nerve, macula, and fovea. The macula is a 3–5 mm area of the central retina and is responsible for central vision. The fovea is a small area located within the macula and is responsible for sharp vision. When a person looks at something, they are directing the fovea at the object. Changes in the macular area can be observed with the ophthalmoscope. Retinal tears or detachments can also be seen. An abnormality may indicate a need for medical care.

Visual ability VISUAL ACUITY. The refraction will determine the refractive status for each eye. Different materials for glasses or contact lenses may be suggested. VISUAL FIELDS. A normal visual field extends about 60° upward, about 75° downward, about 65° toward the nose, and about 100° toward the ear. There is one blind spot close to the center, which corresponds to the area of the optic nerve, which has no light-sensing cells. Defects in the visual field signify damage to the retina, optic nerve, or the neurological visual pathway. An abnormality may indicate a need for medical care.

Results An eye examination can help maintain or restore clear, comfortable vision. It also aids in disease prevention. After an examination, patients should be more aware of their ocular health and general health.

Health care team roles Nursing and allied health professionals play an important role in the eye examination and follow-up. Ophthalmic assistants and technicians facilitate the examination by logging the pertinent patient history. Depending on skill level, ophthalmic assistants may perform measurement of visual acuity under both low and high illumination; assessment of ocular motility and binocularity; and assessment of visual fields and measurement of IOPs with tonometers. Advanced and intermediate level ophthalmic technicians perform refractions and determine the patient’s depth perception. These professionals may also perform corneal topography (mapping). Some of these professionals seek certification through the American Board of Opticianry/National Contact Lens Examiners and other organizations. These organizations offer seminars and testing that inform pro-

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source that projects dots of light over the inside surface of the hemisphere. The patient’s head is positioned so that the eye being tested is at the center of the sphere and 33 cm. (about 13 in.) from all points on the hemisphere’s inside surface. The patient stares straight ahead at an image on the center of the surface of the perimeter, and signals whenever they detect a light with their peripheral, or side, vision. The perimeter records whether flashes are seen or missed and maps the patient’s field of vision.

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fessionals of technological advances in refraction and eyeglass manufacturing.

KEY TERMS

Resources

Amblyopia—Decreased visual acuity, usually in one eye, in the absence of any structural abnormality in the eye. Conjunctiva—The mucous membrane that covers the white part of the eyes (sclera) and lines the eyelids. Cornea—Clear outer covering of the front of the eye. Floaters—Translucent specks that float across the visual field, due to small objects floating in the vitreous humor. Fundus—In the eye, fundus refers to the back area that can be seen with the ophthalmoscope. Glaucoma—Glaucoma results in optic nerve damage and a decreased visual field and blindness if not treated. It is usually associated with increased IOP, but that is not always the case. The three factors associated with glaucoma are increased IOP, a change in the optic nerve head, and changes in the visual field. Gonioscope—An instrument used to inspect the eye (e.g., the anterior chamber). It consists of a magnifier and a lens equipped with mirrors; it’s placed on the patient’s cornea. Iris—The colored ring just behind the cornea and in front of the lens that controls the amount of light sent to the retina. Macula—The central part of the retina where the rods and cones are densest. Ophthalmoscope—An instrument designed to view structures in the back of the eye. Optic nerve—The nerve that carries visual messages from the retina to the brain. Pupil—The circular opening that looks like a black hole in the middle of the iris. Retina—The inner, light-sensitive layer of the eye containing rods and cones; it transforms the image it receives into electrical messages which are then sent to the brain via the optic nerve. Sclera—The tough, fibrous, white outer protective covering that surrounds the eye. Slit lamp—A microscope that projects a linear slit beam of light onto the eye; it allows viewing of the conjunctiva, cornea, iris, aqueous humor, lens, and eyelid. Tonometer—An instrument that measures intraocular pressure (IOP).

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BOOKS

Chang, David F. “Ophthalmologic Examination.” In General Ophthalmology, 14th ed., edited by Vaughan, D., T. Asbury, and P. Riordan-Eva. Stamford, CT: AppletonLange, 1995. ORGANIZATIONS

American Academy of Ophthalmology. PO Box 7424, San Francisco, CA 94120-7424. (415) 561-8500. . American Optometric Association. 2420 North Lindbergh Boulevard, St. Louis, MO 63141. (800) 365-2219. . Joint Commission on Allied Health Personnel in Ophthalmology. 2025 Woodlane Drive St. Paul, MN 55125-2995. (888) 284-3937. . OTHER

“Optometric Clinical Practice Guideline: Comprehensive Adult Eye and Vision Examination.” American Optometric Association Online .

Mary Bekker

Eye glasses Definition Eye glasses are devices that correct refractive errors in vision. Eye-glass lenses are mounted in frames that position the lenses in front of the eyes.

Purpose Eye glasses are used to correct or improve the vision of patients with nearsightedness (myopia), farsightedness (hyperopia), presbyopia, and astigmatism. They are also utilized to correct refractive errors after cataract surgery.

Precautions Ophthalmic assistants, technicians, and nurses take a careful patient history to determine patient sensitivities to certain frame materials. Patients allergic to certain plastics should avoid frames or lenses manufactured from that type of plastic. Patients allergic to nickel should not wear Flexon frames. Ophthalmic personnel also address

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Description Eyes are examined by optometrists (O.D.s) or ophthalmologists (M.D.s), with assistance from ophthalmic assistants, technicians, or nurses. If necessary, prescriptions are given to patients for glasses. An optician generally makes the glasses. Eye glasses can be created in an in-office laboratory or an off-site manufacturing lab. Patients whose eyes have refractive errors do not see clearly without glasses. This is due to the fact that the light emitted by the objects they see does not come into focus on their retinas. For farsighted (hyperopic) patients, images come into focus behind the retina; for nearsighted (myopic) patients, images come into focus in front of the retina. Lenses Lenses work by changing the direction of light so that images come into focus on the retina. The greater the index of refraction of the lens material and the greater the difference in the curvature between the two surfaces of the lens, the greater the change in direction of light that passes through it, and the greater the correction. Lenses can be unifocal, with one correction for all distances, or they can correct for more than one distance (multifocal). One type of multifocal lens, the bifocal, has an area of the lens (usually at the bottom) that corrects for near objects (about 14 in [35.5 cm] from the eyes); the remainder of the lens corrects for distant objects (about 20 ft [6 m] from the eyes). Another type of multifocal lens, a trifocal, has an area in-between that allows correct viewing of intermediate objects (usually about 28 in [71 cm]), such as computer screens or automobile dashboards. The greater the index of refraction, the thinner the lens can be. Lenses are made from either glass or plastic (hard resin). Plastic is lightweight and more impactresistant than glass. Glass is scratch-resistant and provides the best visual acuity. In recent years, however, glass that is thinner and more impact-resistant has been developed. A plastic called CR-39, introduced in the 1960s, is the plastic of choice of most opticians. Today, eyeglass wearers can also choose between polycarbonate, which is the most impact-resistant material available for eyewear, and polyurethane, which has exceptional optical qualities

and an index of refraction of up to 1.66, much higher than the conventional plastics. Polycarbonate is the most easily scratched of the plastics used for lenses, so an anti-scratch coating is always applied to the lenses. In addition, an improvement in the polycarbonate manufacturing process now produces clear lenses—previously all polycarbonate lenses had a bluish cast. Patients with high prescriptions should consider high index materials. Aspheric lenses also are useful for high prescriptions. They are flatter and lighter than conventional lenses. These lenses make it possible for patients with higher prescriptions and thick lenses to wear metal and titanium frames, when formerly they could wear only plastic frames. There are many lenses and lens-coating options for individual needs, including coatings that block harmful ultraviolet (UV) light or UV and blue light. Such coatings are not needed on polycarbonate lenses, which already have UV protection. There are anti-scratch coatings that increase the surface hardness of lenses and anti-reflective (AR) coatings that eliminate almost all glare. AR coatings may be particularly helpful to people who use computers or drive at night. Polarized lenses that block reflected light also allow better vision in sunny weather. Photosensitive (photochromic) lenses that darken in bright light are handy for people who do not want to carry an extra pair of sunglasses. Photochromic lenses are available in glass, plastic, and polycarbonate. Frames Frames can be made from metal or plastic, and they can be rimless. There is an almost unlimited variety of shapes, colors, and sizes. The type and degree of refractive correction in the lens determine to some extent the type of frame most suitable. Some lenses are too thick to fit into metal rims, and some large-correction prescriptions are best suited to frames with small-area lenses, since a smaller lens area minimizes the thickness of a lens with a large correction for myopia. Rimless frames are the least noticeable type, and they are lightweight because they have only an upper rim to which the nosepiece and temples are attached. The lenses are held in place in the frames by nylon string that encircles the bottom of the lenses and attaches to the upper rim. Metal frames are less noticeable than plastic and are lightweight. They are available in solid gold, gold-filled, anodized aluminum, nickel, silver, stainless steel, titanium, and titanium alloy. Until the late 1980s, when titanium-nickel alloy and titanium frames were introduced,

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the patient’s lifestyle. People at risk for accidents due to professions, sports, or hobbies are advised to choose plastic lenses, preferably polycarbonate. Also, people at risk of receiving electric shocks should avoid metal frames.

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metal frames were, in general, more fragile than plastic frames. The titanium frames, however, are very strong and lightweight. An alloy of titanium and nickel, called Flexon, is strong and lightweight and returns to its original shape after being twisted or dented. It is not perfect for everyone, though, because some patients are sensitive to nickel. Plastic frames are durable, can accommodate just about any lens prescription, and are available in a wide range of prices. They are also offered in a variety of plastics (including acrylic, epoxy, cellulose acetate, cellulose propionate, polyamide, and nylon) and in different colors, shapes, and levels of resistance to breakage. Epoxy frames are resilient and return to their original shape after being deformed, so they do not need to be adjusted as frequently as other types. Nylon frames are almost unbreakable. They revert to their original shape after extreme trauma and distortion; because of this property, though, they cannot be readjusted after they are manufactured.

Preparation Before eye glasses are prescribed, an optometrist or an ophthalmologist examines the patient’s eyes. The exam begins with the physician or ophthalmic assistant taking a detailed medical history from the patient. Then the physician, or in some cases a highly trained ophthalmic assistant, begins the ocular examination by measuring visual acuity and refracting. During the exam, the physician or ophthalmic assistant also determines ocular motility and alignment, nearpoint of convergence, near fusional vergence amplitudes, relative accommodation measurements, and accommodative amplitude and facility. Corrective lens prescriptions, if necessary, are then given to patients. To be correctly fitted for eye glasses, the distance between the patient’s eyes (PD) is measured, so that the optical centers of the lenses correlate with the pupillary axis. Bifocal heights also are measured with the chosen frame in place and adjusted on the patient. If not positioned correctly, the patient may experience eyestrain or will not have the optimal visual results. After the eye glasses are ready for the patient, the dispensing optician, physician, or ophthalmic assistant ascertains the proper fit to ensure the best vision and comfort. Patients may sometimes need up to two weeks to adjust to a new prescription. However, if problems persist the glasses should be rechecked. Presbyopic patients may choose over-the-counter reading glasses instead of professionally prescribed eye 912

glasses. These patients should be advised that the distance between the lenses in these glasses is for a “standard” person. If a patient is sensitive or has more closely set eyes, for example, blurred vision and headaches may result from the use of these glasses. In addition, the prescriptions are equal for both eyes, these glasses do not correct for astigmatism, and they are made with cheaper lens and frame materials. As a result, these over-thecounter reading glasses may not be a patient’s best option.

Aftercare Patients are advised to return to the physician’s office if they experience headaches or blurred vision. If these symptoms do not occur, they are instructed to return to the office for a regular eye examination in one or two years.

Complications Matching an individual with the correct frames and lenses usually avoids complications. Ensuring that the lenses are positioned properly will greatly reduce the likelihood of headaches and blurred vision. A thorough patient history minimizes the chance that the patient will select a frame that causes sensitivities or lenses that could harm his or her eyes.

Results It is normally expected that people will achieve 20/20 vision while wearing corrective lenses.

Health care team roles Nursing and allied health professionals assist with eyeglass examination and fitting, and with patient education. With advances in refracting technology, technicians now have duties that previously were performed only by optometrists or ophthalmologists. Ophthalmic assistants and technicians facilitate the fitting process by recording the pertinent patient history and measuring the eye for the proper lens fit. Advancedand intermediate-level ophthalmic technicians perform refractions and determine the patient’s depth perception. These professionals also may perform corneal topography (mapping). Some of these professionals seek certification through the American Board of Opticianry and the National Contact Lens Examiners or other organizations. These organizations offer seminars and testing that help professionals keep current with technological advances in refracting and eyeglass manufacturing.

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Patients are told that it may take up to two weeks to adjust to new eye glasses. They also are advised to return to the physician’s office if they experience blurry vision and headaches. AR-coating and other specialized lens coatings need special care to maintain the coat and prevent scratching. Patients are told to carefully clean their lenses with special cloths and cleaners obtained from the physician or optician, never to use paper towels or harsh soap. Training Optometrists and ophthalmologists receive training in optometry or during a medical residency for these procedures. In some practices, ophthalmic personnel complete part of the eye exam. Ophthalmic assistants, technicians, and nurses can complete specialized training from certified programs to learn how to refract and complete other parts of the eye exam. Opticians receive training in creating lenses. Resources BOOKS

Zinn, Walter J., and Herbert Solomon. Complete Guide to Eyecare, Eyeglasses & Contact Lenses. 4th ed. Hollywood, FL: Lifetime Books, 1997. PERIODICALS

Pustareri, Thomas J., M.D. “Contact Lenses for Today’s Lifestyles.” Ophthalmology Management 5 (January 2001).

KEY TERMS Astigmatism—A vision condition that occurs when the cornea is slightly irregular in shape. This irregularity prevents light from focusing properly on the retina. Cornea—The clear outer covering of the front of the eye. Index of refraction—A constant number for any material that is an indicator of the degree of the bending of the light caused by that material. Lens—A device that bends light waves. Polycarbonate—A very strong type of plastic often used in safety glasses, sport glasses, and children’s eye glasses. Polycarbonate lenses have approximately 50 times the impact resistance of glass lenses. Presbyopia—A condition affecting people over the age of 40 where the system of accommodation that allows focusing of near objects fails to work because of age-related hardening of the lens of the eye. Retina—The inner, light-sensitive layer of the eye containing rods and cones; it transforms the image it receives into electrical messages sent to the brain via the optic nerve. Ultraviolet (UV) light—Part of the electromagnetic spectrum with a wavelength just below that of visible light. It is damaging to living material, especially eyes and DNA.

ORGANIZATIONS

American Academy of Ophthalmology. PO Box 7424, San Francisco, CA 94120-7424. (415) 561-8500. . American Board of Opticianry and the National Contact Lens Examiners. 6506 Loisdale Rd., Suite 209, Springfield, VA 22150. (703) 719-5800. . American Optometric Association. 2420 North Lindbergh Boulevard, St. Louis, MO 63141. (800) 365-2219. . Contact Lens Association of Ophthalmologists, 721 Papworth Avenue, Suite 206, Metairie, LA 70005. (504) 835-3937. . Optician Association of America. 10341 Democracy Lane, Fairfax, VA 22030-2521. (800) 443-8997. <www.opticians.org>. Opticians Association of America. 7023 Little River Turnpike, Suite 207, Annandale, VA 22003. (703) 916-8856. .

OTHER

Hirsch, Dahlia, M.D. “The Fine Art of the Efficient Patient Visit.” Review of Ophthalmology Online. . Kattouf, Richard S., O.D. “Achieving Maximum Efficiency (Without Sacrificing Quality of Care).” Optometric Management Online. . “Lenses Through Time: A Fascinating Historical Look at Eyeglass Trivia.” . Polycarbonate Lens Council. “New Developments in Polycarbonate.” . “Polymer Scientists Engineer Better Remedies.” Journal of the American Medical Association. .

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Eyedrop instillation

drops to body temperature by holding the bottle in his or her hand for about two minutes.

Eyedrop instillation Definition Eyedrop instillation is the dispensation of a sterile ophthalmic medication into a patient’s eye.

Purpose Eyedrops may be instilled to treat a number of eye disorders or to anesthetize an eye before treatment. An ophthalmic assistant, technician, nurse or physician instills eyedrops during a routine eye examination or during treatment for ocular disease. Anesthetic eyedrops are instilled before surgery on the eye. Sometimes ophthalmic professionals instill dyes to help diagnose ocular disease, either by traditional methods, or by intravenous administration, or by the use of strips. Eyedrops or ophthalmic solutions are used to treat glaucoma, uveitis, allergic reactions and infections. Dilatory eyedrops may be instilled during an examination to achieve a better view of the retina.

Precautions Health care professionals need to ensure that the proper drug is being instilled and that it has not passed its expiration date. Some ophthalmic solutions may be contraindicated or can cause allergic reactions. Eyedrop containers should be clearly labeled and checked before instillation. The eyedrops should also be monitored for discoloration or sedimentation, which indicate that the ophthalmic solution is decomposing. In that case, a new dose of medicine should be obtained and the affected bottle discarded. Moreover, the ophthalmic staff member dispensing the drops should double-check the patient’s identification and chart to ensure the correct dose is being instilled into the correct eye. The dispensing ophthalmic professional should never touch the tip of the eyedropper to the patient’s eye. Touching will contaminate the remaining medication. In case of direct eye contact, the medication should be thrown away.

Description Sterilization is an important part of eyedrop instillation. Before eyedrops are instilled, the ophthalmic assistant, technician, nurse, optometrist, or ophthalmologist should wash his or her hands thoroughly. The ophthalmic staff member then should gather all necessary supplies. For some eyedrops, the dispenser may want to warm the 914

Next, the dispenser should position the patient correctly. The patient should sit back in the examination chair with their head slightly hyperextended. Once the patient is correctly positioned, the dispenser should clean the eyelids from the inner canthus outward with a sterile saline solution to remove any eye secretions or previously instilled medications. The dispenser should wash their hands after these preparations are completed. Immediately before instillation, the dispenser should depress the patient’s lower lid with the finger of one hand and lightly pinch the patient’s lower lid to make a pouch for the medication. The upper lid should also be held open to prevent blinking during instillation. The dispenser should tell the patient to look up. Using the other hand, the dispenser should instill the drop into the everted lower lid. The drops should not be instilled on the cornea. This precaution is necessary to avoid startling the patient, or causing unnecessary pain. After the appropriate amount of medication is instilled, the ophthalmic professional should release the lid and remove any excess fluid. The patient should be told to gently close their eyes so as to not release any medication. If another medication is to be instilled, a delay of at least 30 seconds is required between instillations.

Preparation Patients should have the procedure explained to them before instillation to ensure best results. If patients are treated for certain eye ailments such as conjunctivitis, they should be warned in advance not to wear contact lenses or eye makeup. Before instillation, the ophthalmic staff should double-check the dosage and type of medication. They should also wash their hands thoroughly.

Aftercare Patients who will be dispensing their own eyedrops after the initial treatment need careful instructions on proper instillation. Allied health professionals should guide patients step by step through the procedure to ensure maximum benefit from the medication. If patients are treated for infections or conjunctivitis, they should be advised to wash their hands regularly; avoid touching their eyes; avoid wearing eye makeup or contact lenses; and to discard any eye drops or eye makeup used before treatment for the infection began. Follow-up appointments for further treatment may also be necessary.

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Complications Eyedrops cause irritation in some patients that might result in eye redness or burning. Stronger medications can cause more extreme allergic symptoms, such as dizziness and disorientation. Some cycloplegic drops can cause such severe reactions as delirium, a rapid pulse, and difficulty swallowing. Patients should be monitored after instillation, and health care professionals should record any side effects.

Results Properly instilled eyedrops should effectively treat a number of eye disorders. Dilatory drops facilitate eye refraction and retinal examination.

Health care team roles Nursing and allied health professionals are usually responsible for eyedrop instillation. Ophthalmic assistants, technicians and nurses ensure that the proper dosage is administered to the correct patient, the medication is fresh, the medication and eyedropper are sterile and in good condition, and the patient is told step-by-step how the procedure is performed. The allied health professional may also need to repatch an affected eye, monitor patients for side effects, chart medications for each patient, and dispose of (used) equipment. Resources BOOKS

“General Management Modalities.” In Brenner & Suddath’s Textbook of Medical and Surgical Nursing. 7th ed. Philadelphia, PA: J.B. Lippincott Company, 1992. Stedman’s Medical Dictionary. 26th ed. Baltimore, MD: William & Wilkins, 1995. ORGANIZATIONS

American Academy of Ophthalmology. PO Box 7424, San Francisco, CA 94120-7424. (415) 561-8500. .

KEY TERMS Canthus—Either of the angles formed by the meeting of an eye’s upper and lower eyelids. Conjunctivitis—Inflammation of the thin membrane covering the eye. It is caused by bacteria, virus, allergies, etc. Cornea—The clear outer covering of the front of the eye. Cycloplegic drops—Drops used to dilate the pupil and paralyze the eye’s powers of accommodation. Drops—A term for a liquid medicine taken in specific doses and usually applied by a dropper. Glaucoma—An eye disease in which increased pressure within the eyeball can result in damage to the optic disk and a loss of vision. Ophthalmic solutions—Sterile solutions for instillation in the eye. Uveitis—Inflammation of the uvea. The uvea is a continuous layer of tissue that consists of the iris, the ciliary body, and the choroid. The uvea lies between the retina and sclera.

American Optometric Association. 2420 North Lindbergh Boulevard, St. Louis, MO 63141. (800) 365-2219. . Joint Commission on Allied Health Personnel in Ophthalmology. 2025 Woodlane Drive, St. Paul, MN 55125-2995. (888) 284-3937. . OTHER

“Conjunctivitis.” American University Online. . “Eye Care Tip of the Month: Use Eyedrops Correctly.” American Optometric Association Online. . “Guidelines for Administration of Eyedrops and Eye Ointment.” School of Nursing, The University of Texas at Austin Online. .

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Glaucoma patients using eyedrop medications should be monitored to determine if the drops are effective. Many times a combination of drops is necessary to treat glaucoma.

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F Factor XI deficiency see Hemophilia Factor IX deficiency see Hemophilia Factor V Leiden test see Thrombosis risk tests Factor VIII deficiency see Hemophilia

Fad diets Definition According to the United States Surgeon General’s Report on Nutrition and Health, fad diets include “the promotion for profit of special foods, products, processes, or appliances with false or misleading health or therapeutic claims.”

Purpose Fad diets are generally used by consumers to shed a great amount of weight in a short period of time. They are usually based on the erroneous belief that a particular food or food component can cause rapid weight loss or cure a disease. Another tenet of fad diets is that certain foods are harmful and therefore should be avoided completely.

Precautions Fad diets usually result in a short-term weight loss—but most people gain the weight back after discontinuing the diet. The American Dietetic Association (ADA) has established a few guidelines to help evaluate the reliability of fad diets. They suggest that consumers avoid diets that claim weight loss can be achieved in a very short period of time; that imply that weight can be

lost without any physical activity; or that rely on undocumented studies. The most reliable way to lose weight safely and maintain weight loss is by eating a variety of foods and exercising consistently. Dieters who follow the guidelines set by the ADA, which include eating a variety of foods, balancing food intake with exercise, choosing a variety of fruits and vegetables, limiting saturated fat and cholesterol, and keeping total fat intake to a moderate level will have a healthy lifestyle—which when adhered to will ultimately aid in weight management. Many fad diets, for example, counsel dieters to eliminate certain foods or to eat one specific food for a long period of time. This approach does not promote healthy eating habits, nor does it augur well for permanent weight loss.

Description Fad diets have been promoted and used for many years. Some of the most popular fad diets today include high-protein diets, liquid diets, the grapefruit diet, foodcombining diets, the cabbage diet, and a variety of diet pills. High-protein diets High-protein diets began in the 1970s, based on the theory that too many carbohydrates in the diet interfere with the body’s ability to burn fat. This diet encourages the consumption of large quantities of protein-rich foods such as meat, fish, shellfish, eggs, poultry, and cheese. Some popular high-protein diets include the Atkins diet, the Zone, and the protein-power diet. Liquid diets Liquid diets actually began in the early 1930s, but gained more popularity in the 1970s when commercial meal-replacement health shakes began to hit the market. SlimFast and Nestlé Sweet Success are two brands of health shakes that are usually consumed as a replacement

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KEY TERMS Ketones—Acidic by-products of fat breakdown that alter the acid-base balance of the blood. Nitrogen—A component of protein that is highly toxic when too much protein is consumed and the kidneys are unable to process and excrete it. Saturated fat—Type of fat that is usually solid at room temperature.

Diet pills and prescription drugs have become one of the most marketable tools against obesity, but their safety and effectiveness is questionable. Both diet pills and prescription drugs can reduce appetite and promote fullness by changing brain chemicals. Prescription drugs should be an option only for people who are significantly overweight.

Complications High-protein diet

for two meals and a snack during the day. Health shakes normally provide about 200 calories each, with the last meal of the day consisting of low-fat, nutrient-dense foods that offer another 600 calories. The grapefruit diet Grapefruit is essentially a fat-free, low-calorie, lowsodium food that is high in vitamin C, beta-carotene, and fiber. The grapefruit diet began in the 1930s, when the Hollywood diet made its debut. This regimen consisted of a few vegetables, a small amount of protein, and a grapefruit (which was thought to possess a fat-burning enzyme) at every meal. It is usually followed for a period of three weeks. The diet provides only 800 calories per day, which makes the possibility of weight loss very likely. Food-combining diets Food-combining diets are based on the mistaken idea that carbohydrates and proteins should not be consumed at the same time, and that fruit should not be eaten with proteins or carbohydrates. There are a variety of food-combining diets, but most recommend eating large portions of fruit for the first several days, which is thought to burn up calories before the body metabolizes them. A few carbohydrates and very little protein are then added during the last part of the diet. The cabbage soup diet The cabbage soup diet is a more recent fad that results in a significant amount of weight loss from shedding water. It consists of eating cabbage soup, which contains cabbage, onions, green peppers, tomatoes, celery, and water, for one week. Each day as much soup is eaten as desired, along with one specified food, which can also be eaten in unlimited amounts. The cabbage does not burn fat, but it does promote a sense of fullness. 918

This type of diet does slow the rate of carbohydrate absorption, which helps control blood sugar levels and promotes a feeling of fullness. However, high-protein diets also tend to be high in saturated fat and cholesterol, which can contribute to heart disease. When high-protein diets are followed for a very for a long time, they cause the body to burn excessive amounts of fat for fuel, This releases chemicals called ketones into the bloodstream, causing dizziness, headaches, nausea, and bad breath. Too much protein also places extra work on the kidneys, forcing them to work harder to excrete the nitrogen present in protein. They also create extra work for the liver, which must break the protein compounds into individual amino acids. Liquid diets While liquid diets are often convenient and easy to prepare, the transition back to solid foods can lead to weight gain. Grapefruit diet While this diet is very low in calories and almost guaranteed to result in some weight loos, limiting dieters to such a small amount of food is very restrictive and eliminates such vital nutrients as calcium, iron, folic acid, and other vitamins. Food-combining diet Since fruits are so low in calories, it is possible to lose a significant amount of weight in a short period of time. Due to the protein restriction, however, muscle and organ tissues may be broken down for energy. Cabbage-soup diet This diet can cause bloating, gas, nausea, and lightheadedness after a few days. It is not recommended by health professionals; but since soup is usually a low-calorie food, eating this soup in conjunction with a healthy diet consisting of a variety of foods can facilitate a healthy weight loss.

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Falls

Diet pills

Fainting see Syncope

These compounds may help start weight loss, but their benefit usually plateaus after a year, after which their effect declines. In addition, they can strain the heart by increasing blood pressure and heart rate.

Fallopian tube x rays see Hysterosalpingography

Results While each of these diets may result in a temporary weight loss, most are unhealthful and deprive the body of needed nutrients. Most dieters regain the weight after they stop following the diet.

Health care team roles The American Dietetic Association, the United States Surgeon General, the National Academy of Sciences, and the American Heart Association all employ qualified professionals who can educate consumers on the advantages and disadvantages of fad diets. While certain components of fad diets may aid in weight management when used in conjunction with a healthy lifestyle, it is not recommended that they be used alone. People must understand that behavior modification is the most effective way to lose weight and keep it off. Through physical exercise, eating a variety of nutritious foods, and consciously changing eating habits, weight loss can be achieved and maintained. Resources BOOKS

Mahan, Kathleen L., and Sylvia Escott-Stump. Krause’s Food, Nutrition, and Diet Therapy. Philadelphia: W.B. Saunders Company, 2000. PERIODICALS

Ashley, Judith M., and William T. Jarvis. “Position of the American Dietetic Association: Food and Nutrition Misinformation.” Journal of the American Dietetic Association (June 1995): 705-707. OTHER

Rhodes, Maura. “Nutrition and Diet: America’s Top 6 Fad Diets.” Good Housekeeping. (June 25, 2001). “Send Fad Diets Packing.” American Dietetic Association. (April 28, 2001). “Weight Loss in a Pill.” American Dietetic Association Online. (April 28, 2001).

Lisa M. Gourley

Falls Definition Falls are a common source of injury, particularly in the elderly population. They are more likely to occur if impairments in balance, strength, perception, joint range of motion, postural function or coordination are present. Serious injury from falls, such as fractures, occur commonly in people with osteoporosis, a common degenerative disease involving loss of bone mass. Hip fracture is one of the most serious potential consequences of a fall, with a mortality rate as high as 20%.

Description Falling is a serious health problem in the United States, especially for the elderly. According to the National Center for Injury Prevention and Control, one in every three adults 65 years of age and older falls each year, with an increasing incidence as a person ages. Falls can result in serious injury, not only posing a burden on the individual who falls, but also on family members and the health care system.

Causes and symptoms Falls can often be attributed to environmental hazards. Icy sidewalks and uneven terrain are common dangers. In the home, climbing on unstable step stools, sliding in wet showers, or slipping on throw rugs are frequent causes of falls. Medical factors can also make falls more likely to occur. Orthostatic hypotension, sensory loss, stroke, dementia, medications, and neuromuscular disease increase the risk of falling. Deficits in strength, joint range of motion, coordination, sensory perception, and vision may further impair balance. Osteoporosis, common in the elderly population, makes a fall more likely to result in serious injury.

Diagnosis Individuals who are at risk of falling because of a medical condition or medications need to be routinely

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Sensation Falls among people 65 years of age and older Falls are the leading cause of accidental deaths in persons over 65 years of age. Falls are the seventh leading cause of death among people older than 65 years. In the United States 75% of deaths from falls occur in the 12% of the population that is older than 65 years. From 75 years of age the rate of death from falls rises for both genders and all racial groups. Thirty-three percent of healthy community-dwelling elders (older than 65 years) fall annually. Sixty-seven percent of nursing home residents fall annually. Between 33% and 67% of older patients in hospital-like environments fall annually. Complications from falls or prolonged floor contact after falls include fear of falling, dehydration, pressure sores, hypothermia, pneumonia, and rhabdomyolysis. Whites who fall have twice the hip fracture rate as persons from other racial groups. Five percent of falls among older people will result in fractures. The most common fractures as a result of falls among the elderly are humeral, wrist, pelvis, and hip, with the presence of osteoporosis making fractures more likely. Ten to twenty percent of falls among older people will result in soft-tissue injuries, with 50% of these requiring medical care. Falls contribute to 40% of admissions to nursing homes. Seventy percent of emergency room visits by people older than 75 years are due to falls. SOURCE:

National Center for Health Statistics, 1980, 1984.

tested for instability during functional activities. The following characteristics should also be assessed: • balance • strength

Sensation testing of the lower extremities assesses light touch, pressure, and limb awareness. Vision Vision should be assessed by a licensed professional. If corrective lenses are indicated, they should be used during further testing, such as balance and gait assessment. Joint range of motion Joint motion assessment evaluates the loss of range of motion and its relationship to impairments in transfers and gait. Hearing If hearing loss is suspected, it should be tested and corrected, if possible, before rehabilitation is addressed. Postural awareness In a rehabilitation center, individuals can be put through a battery of tests that assess perception of the center of gravity with relation to the environment. Specific tests include postural sway tests and perturbation tests. Gait Walking can be evaluated by direct observation to assess for gait abnormalities. If a severe gait disturbance is present, further gait analysis using motion analysis, force platforms, and electromyography should be done.

• sensation

Treatment

• vision • joint range of motion • hearing • postural awareness • gait Balance Balance testing can be done in a rehabilitation facility to assess people’s ability to transfer weight and control their center of gravity. Numerous tests such as the Berg balance assessment, functional reach test, get-upand-go test, and Tinnetti tests are useful in a balance evaluation.

Someone who has fallen, once medically stable, needs to be evaluated for: • balance • strength

Strength Strength testing should be done to identify weakness, strength asymmetry between sides, and muscle strength imbalance within the same limb. 920

Individuals who have fallen may have such injuries as fractures, dislocations, bruising, cuts to the skin, and muscle tears that may require casting, surgery, or hospitalization, depending on the severity. Initiation of lifelong medications for osteoporosis to reduce the rate of further bone loss may be indicated. Most people, including the frailest elderly, can usually benefit from an exercise program that includes strengthening and balance components. Assistance in regaining confidence may also be needed.

• sensation • vision • joint range of motion

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KEY TERMS

• postural awareness • gait If deficits are noted and the reason for the fall is clear, a treatment plan can be developed that may include: • balance training • strength training • aerobic exercise • sensory integration • correction of vision • change in medication • flexibility exercises • hearing aids • postural exercises • patient education • family and caregiver education • analysis of environmental barriers • gait retraining Treatment may include the fabrication of an orthotic for lower limb dysfunction; prescription of an assistive device such as a cane or rolling walker; and education to the patient or caregiver regarding safety in the home.

Prognosis How quickly and completely a patient recovers after a fall depends on the extent of the injury, the patient’s medical condition prior to the fall, and the rehabilitation program. A positive attitude and adequate social support can be critical factors to a patient’s recovery. Regaining mobility is critical, especially for the elderly patient who rapidly loses strength and function when immobile. A severe injury such as hip fracture has high morbidity and mortality, partially due to the long bed rest required after the injury.

Health care team roles Nurses and other allied health professionals need to coordinate rehabilitation activities in an effort to integrate all facets of rehabilitation with functional activities. The rehabilitation team must take an active role in patient, caregiver, and family education, specifically related to restoring mobility and preventing falls in the home.

Falls

• hearing

Coordination—The ability to do activities with precision and proficiency. Electromyography—An evaluation tool that can detect electrical activity of muscles during an activity. Force platform—A large plate, usually mounted in the floor, that records forces when an individual stands or walks on it. Motion analysis—Use of an instrumented system to record whole-body and joint movement for later analysis. Perturbation tests—Tests in which the patient stands on a platform, and a small, rapid movement of the platform is used to disturb balance. Forces and sway are recorded as the individual loses balance and then recovers. Sensory perception—The ability to perceive touch, pressure, pain, and joint position in the limbs and trunk. Transfers—The movement from one position to another, such as sit-to-stand, supine-to-sit, wheelchair-to-toilet, etc.

Prevention Individuals, especially the elderly, should take the following steps to minimize their risk of falling: • Take someone’s arm when icy or slippery surfaces cannot be avoided. • Remove loose rugs from floors. • Use only steady stepstools with hand supports when additional height is needed. • Install hand rails on stairs. • Wear good walking shoes. • Assess the home for small objects and cords that can be tripped on as well as unstable pieces of furniture. • Install grab bars next to toilets and in showers. • Evaluate home lighting. Use night lights in bathrooms and between the bedroom and bathroom. • Have vision and hearing checked regularly. • Report dizziness, fainting, unusual sensations, or sudden loss of function to a physician at once.

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• Engage in daily exercise that incorporates aerobics, weight training, and balance and coordination exercises. Resources BOOKS

Bennett S.E., J.L. Karnes. Neurological disabilities, assessment and treatment. Philadelphia: Lippincott, 1998. Hertling D., R.M. Kessler. Management of Common Musculoskeletal Disorders. Baltimore, MD: Lippincott, Williams & Wilkins, 1996. PERIODICALS ORGANIZATIONS

“Falls and hip fractures among older adults.” Centers for Disease Control. National Center for Injury Prevention and Control. . 2001.

Mark Damian Rossi, Ph.D, P.T., C.S.C.S.

Farsightedness see Hyperopia FAS see Fetal alcohol syndrome

According to a U.S. Department of Agriculture (USDA) food consumption study, fat intake peaked to 70 lb (31.75 kg) per person between 1970 and 1993. Since then, levels have dropped slightly, to around 66 lb (29.9 kg); but one concern is the rising percentage provided by added fats and oils from fried food and snack foods. Current recommendations state that total fat intake should comprise less than 30% of total calories, and saturated fat less than 10%. For a 1500-calorie diet, this standard means less than 1.76 oz (50 g) total fat and 0.59 oz (17 g) saturated fat; for 2500-calorie diets, it is 2.92 oz (83 g) and 0.98 oz (28 g), respectively. People can refer to food labels, which list these amounts.

Precautions Research shows that two types of dietary fats in particular, saturated fats and trans fats, raise blood cholesterol, which increases CHD risk.

Description The major fats in foods are saturated, polyunsaturated, monounsaturated and trans fatty acids, which are discussed below.

Fats, dietary Definition Dietary fats are one of the three forms of energy-giving nutrients, providing a rich source of energy.

Purpose Fats or lipids carry unique properties; they are packed with calories (9 kcal per gram, more than double the amount in protein and carbohydrate), and because they are insoluble in water, they help with the absorption and transport of the fat-soluble vitamins A, D E, and K. Dietary fat not required immediately for energy is stored in layers of fatty tissue under the skin and around internal organs, where it can be called upon for energy. Fats contain about 95% triglycerides, which are lipids consisting of three fatty acid chains. Besides providing energy and essential fatty acids necessary for brain development and proper growth, dietary fats get considerable attention because of their association with coronary heart disease (CHD) and stroke, leading causes of death in the United States. Atherosclerosis, the underlying cause in both, involves changes in the innermost layer of the large arteries. Atherosclerosis often begins in childhood, and while many factors play roles, lesions called plaque form from fat deposits and such other materials as calcium and fibrin. 922

• Saturated fatty acids (SFA) or saturated fats get their name because they hold the maximum number of hydrogens possible in their chains. In general, the longer and more saturated the chain, the harder the fat is at room temperature. Coconut oil is an exception. Foods contain a mixture of fatty acids, but SFA are concentrated in certain animal and vegetable foods, such as beef, chicken, pork, dairy products, palm and coconut oil. Reducing dietary SFAs has the biggest effect on decreasing blood cholesterol. • Monounsaturated fatty acids (MFA) are getting good press in the fat world, with many experts advocating the Mediterranean eating style that is high in olive oil, fish, and vegetables. Mediterranean countries have low CHD incidence, but it is unknown how much other factors play a role. MFAs lower blood cholesterol when they replace SFAs. Aside from olive oil, other high MFA foods include canola oil, peanut and peanut oil, such nuts as pecans and almonds, and avocados. • Polyunsaturated fatty acids (PUFA), such as margarine and sunflower oil, were recommended during the 1980s for lowering blood cholesterol. However, research shows PUFAs can lead to toxic products that promote cardiovascular disease, so heavy intake is not recommended. High sources include vegetable seeds and their oils. Research on a type of PUFA called omega-3 fatty acid is demonstrating benefits in such

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• Trans fatty acids are the latest “bad guys,” with recent research showing they raise blood cholesterol. Trans fats are high in processed food products, in which manufacturers add hydrogen to liquid oils (hydrogenation) to increase stability. Major sources include stick margarine, commercial baked goods, and the frying fats used in most snack foods, restaurants and fast-food chains. Food labels will list trans fats as hydrogenated or partially hydrogenated fats. Healthy people should eat no more than 10% of total calories as saturated fats and trans fats. For those with CHD, diabetes or high LDL cholesterol, this percentage drops to 7%. • Other types of dietary fats exist, including lecithin and cholesterol. Cholesterol, an essential component in brain and nerve cells, is found in animal foods, but is also produced and stored in the liver. The role of dietary cholesterol in blood cholesterol levels and CHD is less clear than in the past. Meat, poultry, seafood, egg yolks and dairy products all contain cholesterol, while plant foods such as fruits, vegetables, grains, nuts and seeds do not. Americans should not exceed the recommended level of 0.1 oz (300 mg) per day. The average American woman eats 0.07 oz (217 mg) cholesterol daily, the average man 0.12 oz (337 mg).

KEY TERMS Atherosclerosis—Sclerosis or hardening and thickening of the arterial wall, causing a loss of elasticity. Coronary heart disease (CHD)—A disease involving the blood vessels surrounding the heart; also called coronary artery disease (CAD). High-density lipoprotein (HDL)—A plasma lipoprotein containing mostly protein and less cholesterol and triglyceride; high levels of HDL lower CHD risk. Low-density lipoprotein (LDL)—The major cholesterol carrier in the blood, with high levels associated with increased coronary heart disease risk. Fatty acid—Fatty acids are a group of carbon chains that make up fat. The body requires some, called essential fatty acids, to form membranes and synthesize important compounds. Lipids—A group of compounds that include fats, oils and related compounds found in foods and the human body. Omega-3 fatty acids—Named because their first double bond occurs at the third carbon from the methyl end, the three omega-3s (EPA, LNA and DHA) are believed to benefit inflammatory diseases. Monounsaturated fatty acid (MUFA)—A fatty acid containing one double bond, which lowers plasma cholesterol when replacing SFAs and is believed to be safer than polyunsaturated fats. Polyunsaturated fatty acid (PUFA)—A fatty acid that is liquid at room temperature, lowers plasma cholesterol when replacing SFAs, but too much can promote cardiovascular disease Saturated fatty acid (SFA)—A fatty acid that has no double bonds, is solid at room temperature, and raises blood cholesterol levels.

Complications Treating high lipids If a person’s blood lipid levels are high, dietary treatment is often initiated to lower the low density lipoprotein fraction and total blood cholesterol levels. Current American Heart Association recommendations include reducing saturated fat to less than 7% of calories; limiting cholesterol to < 200; losing weight if appropriate; and increasing soluble fiber to 0.35–0.88 oz (10–25 g) per day. High-density lipoprotein (HDL) levels, also

referred to as the good cholesterol, is related more to genetic and other factors than to diet, although moderate alcohol consumption raises HDL. Some people also have high plasma triglyceride (TG) levels, which accumulating evidence is showing may be an important heart disease risk factor. Dietary guidelines involve low simple sugars, low-saturated fat diets, restricted alcohol and weight loss if indicated. Drug therapy is often initiated.

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inflammatory disease as rheumatoid arthritis and atherosclerosis. Seafood contains the most omega-3s, although tofu, soybean, canola oil and nuts all contain one type of omega-3. Two PUFAs, linoleic acid and alinolenic acid, are called essential fatty acids because they cannot be synthesized in the body. If linoleic acid replaces other forms of fatty acid in the diet, then lowdensity lipoprotein (LDL) cholesterol decreases and high-density lipoprotein (HDL) cholesterol increases. If linoleic acid replaces saturated fat, total cholesterol decreases but HDL levels also decrease. Safflower oil has the most linoleic acid. A-linolenic acid comes mainly from fish oils. It results in decreased production of triglycerides but has little effect on total cholesterol levels.

Fecal impaction removal

Results A diet containing 30% or less fat is considered compatible with good health. Diets with dietary fat intakes below 15% can negatively affect blood lipids in some people. For people with high blood lipid levels, dietary fat management goals involve moving the total cholesterol and LDL levels to normal. However, because diet modification lowers serum cholesterol levels by about 10–15%, patients whose blood levels remain high often seek drug therapy.

Health care team roles • Registered dietitians are often sought out by patients and health professionals to assess fat intake and instruct on diet modifications, and for those seeking weight loss through dietary fat restriction. • Nursing and allied health professionals can provide health histories and check laboratory test results for potential treatment. The American Heart Association provides dietary guidelines and patient education materials. All health professionals can play important roles in educating the public about dietary fat.

extend up into the sigmoid colon, the loop of large bowel above the rectum. Impaction is most common in inactive elderly people, but there are other causes beside inactivity. Among the other causes are: • medications, including antacids that have aluminum as an ingredient; calcium and iron supplements; a category of anti-hypertensive drugs known as calcium channel blockers; allergy medicines (antihistamines); such psychotropic medications as antidepressants and tranquilizers; such hormones as estrogen and progestin; and medications to reduce spasms such as those used in treating Parkinson’s disease • poor bowel habits; not having a regular schedule for evacuating the bowel • inadequate fluid intake • a diet that is lacking in such fibers as bran, fruit, and vegetables • such rectal disorders as rectocele

ORGANIZATIONS

In addition to the discomfort this condition creates, untreated fecal impaction can also become a serious health problem, producing a chronically over-dilated bowel, or megacolon, that can require surgical correction. It is possible for rectal tissue to become damaged, ulcerated, or even necrotic (lose its blood supply due to the pressure of the stool). The most serious potential complication is that the lower bowel can become completely obstructed. Such intestinal obstruction is potentially fatal.

American Heart Association. National Center, 7272 Greenville Ave., Dallas, TX 75231. 1-800-AHA-USA1. <www.americanheart.org>.

The possibility that the patient has a fecal impaction should be considered if he or she shows any or all of the following symptoms:

Linda Richards, R.D., C.H.E.S.

• complaints of inability to have a bowel movement despite frequently feeling the urge to defecate

Resources BOOKS

Mahan, L. K., Escot-Stump, S. Krause’s Food, Nutrition, & Diet Therapy. Philadelphia: W. B. Saunders Company, 1996.

• upon defecation, the stool appears to be either diarrheic or thin and pencil-like • abdominal pain

Fecal impaction removal

• bloating and a swollen or hard abdomen • anorexia, or lack of appetite; nausea; and vomiting

Definition Fecal impaction removal is the digital (using the finger) means of breaking up and removing a fecal impaction, or mass of hardened, clay-like stool lodged in the rectum.

• the presence of hard stool in the rectum • increased restlessness in patients suffering from Alzheimer’s disease or other forms of dementia

Precautions

Purpose Fecal impaction is the result of extreme constipation. As the patient is unable to expel the stool, it further accumulates into a larger, harder mass that is impossible to pass by normal defecation. This accumulated stool can 924

• complaints of general malaise, or not feeling well

This digital breaking up and removal of impacted stool can potentially damage the mucous membrane linings in the bowel, and the stimulation to the vagus nerve that has endings in the rectum can cause heart irregular-

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Description As gently as possible, the nurse inserts a gloved, lubricated index finger and massages around the edges of the impaction, gradually working the gloved finger into the mass to break it up. The broken-up pieces of stool are dislodged by carefully working them downward toward the end of the rectum. During this procedure, the patient should be checked regularly to assure that there are no untoward effects such as weakness, diaphoresis or clamminess, or changes in pulse rate.

KEY TERMS Megacolon—A massively swollen colon, usually associated with severe and chronic constipation that can exist as a congenital condition or develop later in life. Sigmoid colon—The S-shaped part of the colon, part of the large intestine, positioned between the descending colon and the rectum. Vagus nerve—The tenth and longest cranial nerve, responsible for control of the heart and other internal organs.

Health care team roles Preparation The nurse positions the patient on his or her side, with knees flexed and back toward the nurse. A waterproof pad is placed under the patient’s buttocks, and a bedpan to hold any removed stool is kept nearby. Occasionally, a patient will request to stand in the bathroom near the toilet during this procedure, but that is not advisable due to possible adverse reactions and the fact that this can be an exhausting process. The nurse then puts on rubber gloves and applies lubricant to the index finger that will be inserted to break up the impaction. Explanation of what is to be done, and reassurance that if the procedure is causing discomfort it will be stopped immediately, should be given before beginning.

Aftercare After the disimpaction is completed, it may be necessary to administer an enema or give a suppository to complete the stool removal. The most important aspect of care is the prevention of the reoccurrence of problems with elimination.

Complications Vagus nerve stimulation, causing cardiac irregularities with possible fainting or weakness, is the most serious potential complication. However, rectal bleeding, the result of trauma to the bowel mucosa, can also occur.

Results Expected results will be the removal of the hardened stool from the patient’s rectum, making the patient much more comfortable.

This procedure is rarely undertaken, as normally health care staff try to prevent the occurrence of fecal impaction through medications, diet, and such treatment as enemas or suppositories. Such prevention is desirable due to the risks involved. However, if fecal impaction removal must be done, it should be done only by a physician or nurse, as they should be aware of the possible untoward effects. • A nurse will normally be the person who actually removes impacted stool. • Both registered nurses (RNs), or licensed practical nurses (LPNs) must complete a prescribed course in nursing and pass a state examination. RNs typically have a degree in nursing. If the physician does not disimpact the patient, usually it will be the job of a RN. However, in some situations, a LPN may be the person responsible for carrying out this procedure. Resources BOOKS

Kozier, Barbara, RN, MN, Erb, Glenora, RN, BSN, Blais, Kathleen, RN, EdD, Wilkinson, Judith M., RNC, MA, MS. Fundamentals of Nursing, Concepts, Process and Practice, 5th ed. Redwood City, CA: Addison-Wesley, 1995. OTHER

“Fecal Impaction.” Medline, U.S. Department of Health and Human Services, National Institutes of Health. . July 20, 1999. Toth, Peter P., MD, PhD. “Gastroenterology: Constipation and Fecal Impaction.” University of Iowa Family Practice, Virtual Hospital. Feb.12, 2001.

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ities. It is therefore a procedure that is undertaken only with extreme caution. Most often, nurses remove fecal impactions upon receiving a physician’s order, or under a physician’s supervision.

Fecal incontinence

Fecal incontinence Definition Fecal incontinence is the inability to control the passage of gas or stools (feces) through the anus. For some people, fecal incontinence is a relatively minor problem that is limited to a slight occasional soiling of underwear, but for others it involves a considerable loss of bowel control. This loss can have a devastating effect on a patient’s quality of life and psychological well-being. Fortunately, professional medical treatment is usually able to restore bowel control or at least substantially reduce the severity of the condition.

Description Fecal incontinence, also called bowel incontinence, can occur at any age, but is most common among people over the age of 65, who sometimes have to cope with urinary incontinence as well. The condition is more common among women than men. The problem affects as many as 6.5 million Americans. The wider public health impact of fecal incontinence is considerable. In the United States, more than $400 million is spent each year on disposable underwear and other incontinence aids. Fecal incontinence is the second most common reason for seeking a nursing home placement. One-third of the institutionalized elderly suffer from this condition. Incontinence sufferers, however, often hesitate to ask their doctors for help because they are embarrassed or ashamed.

Causes and symptoms Fecal incontinence can result from a wide variety of medical conditions, including childbirth-related anal injuries, other causes of damage to the anus or rectum, and nervous system problems. Vaginal-delivery childbirth is a major cause of fecal incontinence. In many cases, childbirth results in damage to the anal sphincter, which is the ring of muscle that closes the anus and keeps stools within the rectum until a person can find an appropriate opportunity to defecate. Nerve injuries during childbirth may also be a factor in some cases. A study in 2000 by the Brigham and Women’s Hospital in Boston, Massachusetts, found that women who had episiotomies were at higher risk for postpartum fecal incontinence. Childbirth-related incontinence is usually restricted to gas, but for some women it involves the passing of liquid or solid stools. The removal of hemorrhoids by surgery or other techniques (hemorrhoidectomies) can also cause anal 926

damage and fecal incontinence, as can more complex operations affecting the anus and surrounding areas. Anal and rectal infections, as well as Crohn’s disease, can lead to incontinence by damaging the muscles that control defecation. New-onset fecal incontinence can also be a sign of colorectal cancer. For some people, incontinence becomes a problem when the anal muscles begin to weaken in midlife or old age. Dementia, mental retardation, strokes, brain tumors, multiple sclerosis, and other conditions that affect the nervous system can cause fecal incontinence by interfering with muscle function or the normal rectal sensations that trigger sphincter contraction and are necessary for bowel control. One study of multiple sclerosis patients discovered that about half were incontinent. Nerve damage caused by long-lasting diabetes mellitus (diabetic neuropathy) is another condition that can give rise to incontinence.

Diagnosis Medical assessments in cases of fecal incontinence typically involve three steps: assessing the patient’s medical history; performing a physical examination of the anal region; and testing for objective information regarding anal and rectal function. Medical history The medical history relies on questions that allow an evaluation of the nature and severity of the problem and its effect on the patient’s life. The information obtained may include: how long the patient has been suffering from incontinence; how often and under what circumstances incontinence occurs; whether the patient has any control over defecation; and whether the patient has obstacles to defecation in his or her everyday surroundings, such as a toilet that can be reached only by climbing a long flight of stairs. For women who have given birth, a detailed obstetric history is also necessary. Physical examination The physical examination begins with a visual inspection of the anus and the perineum for hemorrhoids, infections, and other conditions that might explain the patient’s difficulties. During this phase of the examination the doctor asks the patient to bear down. Bearing down enables the physician to check whether rectal prolapse or certain other problems exist. Rectal prolapse means that the patient’s rectum has been weakened and drops down through the anus. Next, a pin or probe is used to stroke the perianal skin. Normally this touching causes the anal sphincter to contract and the anus to pucker

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Laboratory tests Information from the medical history and physical examination usually needs to be supplemented by tests that provide objective measurements of anal and rectal function. One of the most common tests is a colonoscopy, which can be included in the physical examination or can be performed in a laboratory setting. Anorectal manometry, another common procedure, involves inserting a small tube (catheter) or balloon device into the anal canal or rectum. Manometry measures, among other things, pressure levels in the anal canal, rectal sensation, and anal and rectal reflexes. Tests are also available for assessing nerve damage. An anal ultrasound probe can supply accurate images of the anal sphincter and reveal whether injury has occurred. Magnetic resonance imaging, which requires the insertion of a coil into the anal canal, is useful at times.

Treatment Fecal incontinence arising from an underlying condition such as diabetic neuropathy can sometimes be helped by treating the underlying condition. When that does not work, or when no underlying condition can be discovered, one approach is to have the patient use a suppository or enema to stimulate defecation at the same time every day or every other day. The goal is to restore regular bowel habits and keep the bowels free of stools. Medications such as loperamide (Imodium) and codeine phosphate are often effective in halting incontinence, but only in less severe cases involving liquid stools or urgency. Dietary changes and exercises done at home to strengthen the anal muscles may also help. Good results have been reported for biofeedback training. In successful cases, patients regain complete control over defecation, or at least improve their control, by learning to contract the external part of the anal sphincter whenever stools enter the rectum. All healthy people have this ability. Biofeedback training begins with the insertion into the rectum of a balloon manometry device hooked up to a pressure monitor. When the bal-

loon is inflated, it simulates the presence of stools in the rectum by causing pressure changes that are recorded on the monitor. The monitor also records sphincter contraction. By watching the monitor and following instructions from the equipment operator, the patient gradually learns to contract the sphincter automatically in response to fullness in the rectum. Sometimes one training session is enough, but often several are needed. Biofeedback is not an appropriate treatment in all cases, however. It is used only with patients who are highly motivated; who are able, to some extent, to sense the presence of stools in the rectum; and who have not lost all ability to contract the external anal sphincter. Some people may require surgery, and these procedures may themselves have complications. Sphincter damages caused by childbirth, as well as certain other kinds of incontinence-related sphincter injuries, are often effectively treated with surgery. Sometimes surgical treatment requires building an artificial sphincter using a thigh muscle (the gracilis muscle). At one time a colostomy was necessary for severe cases of incontinence, but this procedure is now rarely performed.

Prognosis Fecal incontinence is a problem that usually responds well to professional medical treatment, even among elderly and institutionalized patients. If complete bowel control cannot be restored, the impact of incontinence on everyday life can still be lessened considerably in most cases. When incontinence remains a problem despite medical treatment, disposable underwear and other commercial incontinence products are available to make life easier. Physicians and nurses can offer advice on coping with incontinence, and people should not be embarrassed about seeking their assistance. Counseling and information are also available from support groups.

Health care team roles A patient may report fecal incontinence to a health care professional, or it may be assessed by the nurse or physician in an inpatient setting. The physician may order diagnostic testing to determine the etiology of the incontinence. It is the nurse’s responsibility to insure the patient maintains adequate levels of hygiene. In addition, the nurse should instruct the patient and/or caregivers regarding measures of coping with incontinence and minimizing its impact.

Prevention Since fecal incontinence develops for a variety of reasons, there is no single way to prevent it. Patients should

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(the “anal wink”); if it does not, nerve damage may be present. The final phase of the examination requires the doctor to examine internal structures by carefully inserting a gloved and lubricated finger into the anal canal. This allows the doctor to judge the strength of the anal sphincter and a key muscle (the puborectalis muscle) in maintaining continence; to look for such abnormalities as scars and rectal masses; and to learn many other things about the patient’s medical situation. At this point the doctor performs the anal wink test again and asks the patient to squeeze and bear down.

Fecal occult blood test

OTHER

KEY TERMS Anus—The opening at the lower end of the rectum. Colostomy—A surgical procedure in which an opening is made in the wall of the abdomen to allow a part of the large intestine (the colon) to empty outside the body.

“Fecal Incontinence.” Omni: The UK’s Gateway to High Quality Internet Resources in Health & Medicine. . “Utility of Electromyographic Biofeedback Training Seen in Long-Term Follow-Up.” OBGYN.net. .

Deanna M. Swartout-Corbeil, R.N.

Crohn’s disease—A disease marked by inflammation of the intestines. Defecation—Passage of stools through the anus. Hemorrhoids—Enlarged veins in the anus or rectum. They are sometimes associated with fecal incontinence. Rectum—The lower section of the large intestine that holds stools before defecation. Sphincter—A circular band of muscle that surrounds and encloses an opening to the body or to one of its hollow organs. Damage to the sphincter surrounding the anus can cause fecal incontinence. Stools—Undigested food and other waste that is eliminated through the anus. Suppository—A solid medication that slowly dissolves after being inserted into the rectum or other body cavity.

Fecal occult blood test Definition The fecal occult blood test (FOBT) is a rapid test for detecting the presence of blood hidden in the stool and caused by gastrointestinal bleeding.

Purpose This test is performed to detect the presence of blood in the feces. It is also routinely used (in conjunction with a rectal examination performed by a physician) to screen for colorectal cancer, particularly after age 50. However, a positive result does not necessarily indicate cancer, as positive results can be associated with a wide variety of conditions, such as: • peptic, gastric, or stress ulcers

be encouraged to report incontinence as soon as it occurs, in order to find the most appropriate treatment for it.

• esophageal varices

Resources

• tumors

• colon or pancreatic cancer • gastritis

PERIODICALS

Bentsen, Diane. “Controlling Fecal Incontinence with Sensory

• gastrointestinal bleeding

Retraining Managed by Advanced Practice Nurses.”

• hemorrhage

Clinical Nurse Specialist 10 (July 1996): 171-176.

• ulcerative colitis

Moon, Mary Ann. “Anal Incontinence Risk With Midline

• diverticulitis

Episiotomy.” Family Practice News 30 (May 15,

• alcohol abuse

2000): 31.

• Crohn’s disease

ORGANIZATIONS

• intussusception

International Foundation for Functional Gastrointestinal Disorders. .

Precautions

National Association for Continence. . National Digestive Diseases Information Clearinghouse. 2 Information Way, Bethesda, MD 20892. (800) 891-5389. ..

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Certain foods and medicines can influence the test results. Diets rich in red meat, poultry and fish could cause false-positive FOBT results, as can excessive amounts of green leafy vegetables. Certain drugs can also

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Description In most cases, the collection of stool samples can be done at home, using a kit supplied by the physician. The kit contains a specially prepared card onto which a small sample of stool is spread, using a stick provided in the kit. The sample is placed in a special envelope and either mailed or brought to the physician’s office or test site for analysis. Most tests for occult blood test are based upon the fact that hemoglobin, the oxygen-carrying protein in blood, has peroxidase activity. In the presence of hydrogen peroxide, hemoglobin will catalyze the oxidation of a dye such as gum guaiac, benzidine, or o-toluidine, creating a blue color. The dye is present on the card. When hydrogen peroxide is applied to the card and mixed with the stool, the blue color will form if an abnormal amount of blood is present. Rapid immunochemical tests are also available.

Preparation The patient may be requested to avoid meat, fish and poultry for two or three days prior to the test.

KEY TERMS Occult blood—Blood in the stool that is not visible or easily detected.

low up on a positive result with further tests, depending upon other factors in the patient’s history or physical examination. Endoscopic exam is often recommended when the cause of GI bleeding is unknown.

Health care team roles Nurses should determine if the patient has been experiencing signs of a peptic ulcer (epigastric pain between meals), and should note any recent bleeding episodes related to dental problems. The physician, laboratory technician, or scientist should ensure that the sample is analyzed within 48 hours of collection. Resources BOOKS

Chernecky, Cynthia C, and Barbara J. Berger. Laboratory Tests and Diagnostic Procedures. 3rd ed. Philadelphia, PA: W. B. Saunders Company, 2001. Henry, J.B., ed. Clinical Diagnosis and Management by Laboratory Methods. 20th ed. Philadelphia: Saunders, 2001. Kee, Joyce LeFever. Handbook of Laboratory and Diagnostic Tests. 4th ed. Upper Saddle River, NJ: Prentice Hall, 2001.

Aftercare

ORGANIZATIONS

There is no aftercare required for this test.

National Cancer Institute (NCI). 1-800-4-CANCER (1-800422-6237), TTY: 1-800-332-8615. http: //rex.nci.nih.gov.

Complications

Victoria E DeMoranville

There are no complications associated with this test.

Results As described above, many factors can result in falsepositive and false-negative findings. Therefore, it is important to note that a true-positive finding signifies only the presence of blood; it is not necessarily an indication of cancer. The National Cancer Institute states that, in their experience, less than 10% of all positive results are caused by cancer. Alternatively, a negative result (meaning no blood was detected) does not guarantee the absence of colon cancer, which may bleed only occasionally or not at all. The physician will want to fol-

Feedback systems Definition A feedback system uses as input the total or partial output of the system. Feedback systems are used to control and regulate processes. They use the consequences of the process (i.e. too much or too little produced) to regulate the rate at which the process occurs (to decrease or increase the rate of the process).

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cause false-positive results; they include aspirin, cortisone, iron, potassium preparations, nonsteroidal antiinflammatory (NSAID) drugs, thiazide diuretics, colchicine, and reserpine. False-negative findings may result from the ingestion of large amounts of ascorbic acid (vitamin C) from dietary supplements or foods such as citrus fruits. It is also important that the specimen not be contaminated by menstrual discharge.

Feedback systems

Description A typical feedback system consists of a sensor, a control center that receives the signals of the sensor, and an effector pathway, meaning a pathway for the commands of the control center as it reacts to the information received from the sensor. In complex organisms, such as humans, feedback systems constantly monitor and regulate numerous factors, including the levels of gases like oxygen and carbon dioxide, nutrients, hormones, and chemical substances. The feedback systems insure that the amounts of these substances in body tissues and fluids remain unchanged within appropriate limits, despite changes in the external environment. Feedback systems function with the help of the nervous and endocrine systems. While nerve cells detect changes in the body and quickly respond to the brain for a rapid response, hormones of the endocrine system regulate the system more slowly. For example, hormones and nerves regulate the progress of labor contractions. When labor begins, nerve cells in the uterus alert the hypothalamus (a control center in the brain). A hormone called oxytocin is released into the blood, which causes the uterus to contract. Feedback control or regulation can be either negative or positive. With negative feedback, the activity of a system is reduced, slowed down or minimized by the presence of high amounts of a substance it produces. An example is the increased breathing resulting from the presence of high levels of carbon dioxide in extracellular fluids. The purpose of breathing is to provide the oxygen required by the body for its functioning (metabolism) and to eliminate waste carbon dioxide. In the presence of high levels of carbon dioxide, breathing increases, which increases the supply of oxygen present in the air in the lungs, thus counteracting the high amounts of carbon dioxide, which are harmful to the body. With positive feedback, the activity of a system is increased by the presence of high amounts of a substance it produces. Positive feedback systems thus speed up or maximize the rates of processes. For example, they are used in the production of nerve impulses and blood clotting. In the above example, labor contractions are a positive feedback system. As oxytocin reaches the uterus, causing contractions, more stretching causes an increase in oxytocin levels, which causes more forceful contractions.

Function Almost all body functions and processes operate using feedback systems. The body maintains its overall chemical and physical internal environment constant 930

(homeostasis) using a control system activated by several feedback systems. This is because normal cell function depends on maintaining relatively constant intracellular and extracellular environments, such as pH, temperature, and the amounts of all the substances needed by the body. The body keeps these quantities within the range required to maintain life and proper function with the help of feedback systems. Feedback systems are active at all levels of body organization, whether molecular (e.g. regulation of enzymes); cellular (e.g. regulation of cell volume or chemical contents); organ (e.g. regulation of blood flow in the heart or lungs); systemic (e.g. regulation of breathing in the respiratory system), and whole-body (e.g. regulation of body temperature through shivering and sweating). Some examples include: • Enzymatic feedback inhibition. At the molecular level, a mechanism called feedback inhibition operates to limit the amount of chemical product produced by an enzyme system. An enzyme system consists of several enzymes that act one after the other to convert a substance into an end product the body needs. Overproduction of the end product is prevented by the inhibitory effect of the end product on the first enzyme in the sequence, which is called the regulatory enzyme. As the end product is used up in other chemical conversions, however, its inhibitory effect on the regulatory enzyme decreases, so that more end product can be formed by the enzyme system. In this way, the level of end product is maintained at a fairly constant level. • The pH of body fluids. The pH is a measure of the acidity of a solution, or of its hydrogen ion concentration. The normal pH of body cells and fluids is 7.4. When this value steps out of the normal range as a result of the presence of chemical substances that either increase it or decrease it, a feedback control system is triggered to remove or increase the amount of substance so as to bring back the pH to its normal value. • The amounts of small ions. The cells of the body consist of a nucleus surrounded by a fluid cytoplasm that contains several structures (organelles) required for functioning, all enclosed in a membrane. Cells can be thought of as little chemical powerhouses that require specific amounts of chemical substances, among which several small ions (elements that have a positive or negative charge) that need to be made available either inside or outside the cell membranes. For example, the potassium ion (K+ is the major intracellular positive ion (cation) and the sodium ion (Na+ is the major extracellular cation). Likewise, the major extracellular negative ions (anions) are Cl- and HCO3-. Both the amounts

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Acidity—Refers to a compound that is acid or sour. When dissolved in water, acids yield hydrogen ions. Cell—The individual units from which all the tissues and fluids of the body are formed. They consist of a nucleus surrounded by a fluid cytoplasm enclosed in a membrane. Intracellular refers to all substances found inside the membrane and extracellular refers to all substances outside the cell membrane. Chemoreceptors—Specialized cells that can detect chemical substances in the body and relay that information to the central nervous system. The substances detected may be external, such as when an individual smells or tastes something; or they can be internal, such as the carotid bodies, located in the carotid arteries, that detect the amounts of oxygen or carbon dioxide present in the blood.

Homeostasis—Stability of the body’s internal environment, achieved by a system of integrated control systems activated by feedback systems. Homeostasis is thus the maintenance of a constant internal environment (the immediate surroundings of cells) in response to changes occurring in a) the conditions of the external environment and b) the conditions of the internal body environment. Hormone—A substance secreted by specialized glands in the body that affects the behavior of other cells. Hormones serve as messengers to coordinate activities of various parts of the body. Ion—Elements consist of positively charged nuclei surrounded by negatively charged electrons. These charges are balanced and the overall charge of an element is zero. An element becomes an ion, that is a charged species, if it gains or losses electrons.

Cytokine—A protein secreted by tissues or leukocytes (a type of white blood cell) that has a regulatory function.

Metabolism—The sum of all the physical and biochemical processes occurring in the body to produce what is required to maintain life. Metabolism includes the transformation of nutrients into energy and the use of energy by the body.

Enzyme—A type of protein produced by the body that speeds up chemical reactions. Some enzymes regulate certain functions due to their ability to change their activity by modifying their structure.

pH—A measure of the acidity of a solution, or of its hydrogen ion concentration. In the human body, the solution can be the blood or the cerebrospinal fluid. The normal pH of body fluids is 7.4.

of these ions and their transport across the cell membranes are controlled by feedback systems. • Arterial oxygen partial pressure. Another feedback system regulates the oxygen partial pressure P(O2) and carbon dioxide partial pressure P(CO2) in the arteries. This is because the cells of the body obtain their energy by combining oxygen with various foodstuffs, producing carbon dioxide as a waste product, so they need a constant supply of oxygen and also need to have the carbon dioxide removed. Normally, if the arterial blood reaching a special chemical sensor (chemoreceptor), called the carotid body, has a partial pressure of oxygen lower than the normal range or an excessive carbon dioxide partial pressure, then there is an immediate and marked increase in breathing. • Internal body temperature. Body temperature is regulated by a feedback system that maintains it nearly constant at 98.6°F (37°C) throughout the day, week, month or year. As a consequence, a person can remain active

and working in the hot summer months or on cold winter days.

Role in human health The role of the many feedback systems of the human body is to maintain the homeostasis required for life. Feedback systems are activated as soon as disturbances occur in the narrow range of conditions which cellular processes need to be able to function at a level required for the continuation of life. For example, the body temperature feedback system will act to make sure that the body’s internal temperature is maintained constant in spite of the weather. The Na+ feedback regulatory system will adjust the body cells and fluids to the dietary intake of sodium (salt) from foodstuffs. The breathing feedback system will likewise seek to maintain proper oxygen and carbon dioxide pressures and amounts when disturbed, say by heavy exercise. Another feedback system will regulate blood flow and pressure whenever these quantities are increased or decreased by events

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KEY TERMS

Fertility treatments

such as disease, injury, or blood donation. In other words, whenever anything happens that changes the narrow range of the normal values of body parameters, feedback regulatory systems step in to counteract the effect of the change. And if the change is too drastic for the feedback system to handle, the result is disease and even death.

Common diseases and disorders The function and development of all body components are controlled by a variety of feedback systems. Any malfunctioning of a given regulatory feedback system will not only affect the body part or process directly controlled by that system but will also affect those functions controlled by other related feedback systems. For example, at the organ level, it is known that many use hormones and cytokines as effectors in regulatory feedback loops. It is now believed that these feedback systems are involved in some forms of human cancer. For instance, the disruption of a negative feedback system by a cancer transformation can result in the loss of growth control or in increased malignant behavior of tumor cells. Also, abnormal positive feedback loops can develop that increase tumor growth by allowing the excessive release of stimulatory factors. Resources BOOKS

Guyton, A. C. G. Guyton and F. Hall. Textbook of Medical Physiology, 9th ed. Philadelphia: W.B. Saunders Co., 1995. Sherwood, L. Human Physiology: From Cells to Systems. Pacific Grove: Wadsworth, 1997. PERIODICALS

Carl, A., Lee, H. K., Sanders, K. M., “Regulation of ion channels in smooth muscles by calcium.” American Journal of Physiology 271 (July 1996): C9-34. Freeman, M., “Feedback control of intercellular signalling in development.” Nature 408 (November 2000): 313-319. Singer, C. F., Kubista, E., Garmroudi, F., Cullen, K. J. “Local feedback mechanisms in human breast cancer.” Breast Cancer Research & Treatment 63 (September 2000): 95-104.

Monique Laberge, PhD

Female infertility see Infertility Female reproductive system see Reproductive system, female Ferritin test see Iron tests 932

Fertility treatments Definition Infertility is a problem with the reproductive system that results in the inability of a man or woman to achieve a pregnancy or of a woman to carry a pregnancy to live birth. The accepted definition within the medical profession is the absence of conception after at least one year of regular intercourse without birth control. Regular intercourse refers to intercourse at least two to three times per week. The term is also used to cover women unable to carry a pregnancy to term because of miscarriage. Infertility is not sterility, which is the term used to mean conception is not possible under any circumstances. Infertility is not a new disease or condition, but it appears as if there has been an increase in infertility rates in the past few decades. Some factors that may relate to this increase include an increase in the age of women wanting to conceive, an increase in the spread of sexually transmitted diseases, and the rise in the level of toxic chemicals in our environment. Infertility does affect people of all ages, ethnic backgrounds, socioeconomic groups, and both sexes.

Purpose The purpose of fertility treatments is to achieve a successful pregnancy and outcome. Male factors account for approximately 30-40% of all cases of infertility and female factors cause about 40% of cases. Close to 15% of cases are a result of a combination of male and female factors; whereas in 5-10% of cases, no cause can be found. Many couples may begin their quest for fertility with their primary care physician, who is usually a medical doctor certified in family medicine. The primary physician can do a physical exam on both individuals but should refer the couple to a specialist in obstetrics and gynecology to initiate the infertility evaluation process. Infertility is described as either primary or secondary. A couple who has never achieved pregnancy is experiencing primary infertility, whereas a couple who has had a pregnancy in the past, regardless of the outcome, is experiencing secondary infertility. For an egg to be fertilized, sperm produced in the testes must not only be present in sufficient number in the semen but they must be capable of moving far enough and fast enough to travel through the female reproductive system (motility), and capable of penetrating the outer layer of an egg. Male infertility may be a result of small quantities of sperm; prenatal exposure to diethylstilbestrol (DES) (a medication given to women to pre-

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A couple should consider seeing an infertility specialist (a physician certified in reproductive endocrinology and infertility) for any of the following reasons: • a woman experiencing irregular menstrual cycles or irregular ovulation • a woman with a history of three or more miscarriages • a woman older than 35 years of age • a woman with a history of pelvic infection or previous pelvic surgery • a woman who needs microsurgery for endometriosis or for tubal damage • a man with a poor semen analysis such as low count, poor motility, abnormal appearance, or requiring microsurgery • a couple with unexplained infertility whose tests came back normal but still have not conceived after two years • a couple who needs more advanced treatment, such as injectable ovulation-induction medications or assisted reproductive technology (ART) There are over 300 fertility clinics in the United States and each one has a varying rate of success. A couple should investigate the services of the ones they are considering to save time, money and emotional upheaval. In 1992, Congress passed the Fertility Clinic Success Rate and Certification Act, which requires the Centers for Disease Control and Prevention (CDC) to publish the success rates of clinics throughout the United States where ART is performed. This report is intended for laypersons who are considering using ART to achieve pregnancy and provide an objective review utilizing a common method of reporting success. Besides success rates, a couple should consider the following: • Is the physician board certified in reproductive endocrinology? • How much experience has the physician had with diagnosing and treating infertility? • What are the fees for office visits and are payment plans available? • What is the policy regarding cancellation of appointments and filing of insurance claims?

• Will a physician or someone else on staff be available twenty-four hours a day, seven days a week, including weekends and holidays? • Will lab and ultrasound facilities be open seven days a week? • Will the couple see the same physician for their visits? • Will decisions on tests, treatments and referrals be made jointly between the couple and the physician?

Precautions Couples involved in fertility treatments face many legal, ethical, psychological, emotional and financial questions. It is imperative to explore these issues before beginning a course of treatment in order to maintain a realistic attitude. It is difficult, if not impossible, to identify problems that may arise during treatment, but it is important to make an attempt to set limits, physically, financially, and emotionally, on what can be handled during the course of treatment. It is likewise crucial to consider potential legal, practical and ethical problems associated with each choice of treatment and to contact resources available to individuals with infertility problems for an objective viewpoint. Just because the treatment is available does not mean it has to be utilized. All individuals have their own ethical standards and limitations and need to investigate all courses of treatment before undergoing them. Informed consent is a medical term that means a patient gives permission for a test or invasive procedure to be performed, after being informed by the physician in clear language exactly what the test or procedure involves. If at any point in the course of treatment a patient does not understand something, he or she should be encouraged to ask questions; and if the answer is not satisfactory, the patient should know that a second opinion may be solicited. Prior to undergoing assisted reproductive technology (ART), women should be advised to avoid all pain medications other than Tylenol and discuss prescription medications with the specialist. They should not smoke cigarettes or drink alcohol, avoid caffeine-containing beverages, and inform the physician if they have active genital herpes. They should also maintain a healthy well-rounded diet and take a multiple vitamin containing folic acid every day. Men should report any fevers within three months before ART treatment, as fevers may adversely affect sperm quality. They should avoid hot tubs or saunas for three months, as the heat can affect sperm function. Men should also avoid alcohol, drug use, and cigarette smoking for three months prior to treatment and during the

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vent miscarriage in the 1950s); exposure to radiation, certain pesticides or heavy metals (lead); or diseases that reduce the body’s ability to produce sperm. Female infertility may be related to irregularities of the fallopian tubes; endometriosis (tissue resembling the lining of the uterus growing in the abdomen); irregular ovulation or lack of ovulation; abnormalities of the uterine cavity; and/or cervical problems such as abnormal mucus.

Fertility treatments

endometriosis; certain types of male factor infertility; tubal factors; and unexplained infertility. The procedure utilized for IVF may vary somewhat from clinic to clinic, but generally it involves the following: • Stimulating the woman’s ovaries to produce multiple eggs during a specific time of her menstrual cycle. • Detecting the presence of multiple eggs through the use of vaginal ultrasound.

A microscopic image of a needle (left) injecting sperm cells directly into a human egg (center). The broad object at right is a pipette used to hold the ovum steady. (Phototake NYC. Reproduced by permission.)

ART cycle as well. Any prescription drugs should be reported to the specialist along with active genital herpes. It is preferable to avoid intercourse for three days but not more than seven days before collection of semen for an ART cycle.

Description Assisted reproductive technology (ART) is defined by the U.S. Centers for Disease Control and Prevention (CDC) as “all treatments or procedures that involve the handling of human eggs and sperm for the purpose of helping a woman become pregnant.” Types of ART include in vitro fertilization (IVF), gamete intrafallopian transfer (GIFT), zygote intrafallopian transfer (ZIFT), embryo cryopreservation, egg or embryo donation, and gestational carriers. ART does not include intrauterine insemination (IUI) with either partner or donor sperm. In vitro fertilization (IVF) This name comes from the fact that fertilization occurs outside the body in a laboratory, instead of in the woman’s fallopian tube. In vitro is a Latin term that means ‘in the glass’ and refers to procedures performed outside of a living body in a laboratory or other artificial environment. Thus, IVF involves joining an egg and a sperm in a laboratory dish; if fertilization occurs, the resulting pre-embryo is transferred into the woman’s uterus for possible implantation. IVF was developed as a technique to assist women who had blocked, damaged or absent fallopian tubes to become pregnant. The first successful IVF procedure was performed in the United Kingdom and resulted in the birth of Louise Brown in 1978. Today IVF is utilized to treat infertility caused by 934

• Retrieving eggs from her ovaries (while under intravenous sedation) by means of guiding a needle through the wall of the vagina and into the follicles and aspirating them. • Determining the maturity of the eggs and adding sperm to them once mature. • Transferring the embryo into the uterus by a catheter (long, slender tube with a syringe on one end) is relatively simple and requires no anesthesia. Stimulating a woman’s ovaries to produce multiple eggs may vary by program or patient, but the majority require several days of medications to be given by injection. Two main medications are used in the stimulation phase of an IVF cycle. The first is Lupron, which suppresses the ovaries by shutting down the body’s normal production of luteinizing hormone (LH) and follicle stimulating hormone (FSH). Both of these hormones are essential to produce ovulation. Lupron is given by injection subcutaneously (just under the surface of the skin). It shuts down the ovaries completely so that when the induction drugs are given the follicles will mature evenly. The second type of medication is either pure FSH or FSH in combination with LH. It is given by injection to stimulate the ovaries to produce eggs in a controlled but hyperstimulated manner and at a dosage that will produce the highest number of good-quality eggs. With IVF, egg retrieval may take thirty minutes to one hour. The transfer process takes only about ten to twenty minutes and results in the transfer of one or more embryos because the presence of multiple embryos makes it more likely that at least one embryo will attach to the uterine lining. The transfer of multiple embryos also increases the chance of multiple pregnancy. A couple may choose to maintain additional embryos before the transfer procedure so that they can be frozen, thawed and transferred at a later date. In the United States in 1996, 300 clinics reported doing over 64,000 ART cycles, and 92% of these were IVF.

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With GIFT, conception takes place in the fallopian tube. This technique should be utilized only when sperm quality is adequate and at least one fallopian tube is open and functional. The steps involved in this technique are similar to those with IVF up to the egg retrieval. As with IVF, egg retrieval occurs under general anesthesia and eggs and sperm are transferred immediately to a catheter that is used to inject the eggs and sperm into the fallopian tube during laparoscopy. There is no ability to document fertilization or to evaluate embryo quality in a GIFT procedure. This procedure requires two small incisions, one just outside the woman’s navel and the other deep in her abdomen where a probe is inserted. Zygote intrafallopian transfer (ZIFT) This procedure is a combination of IVF and GIFT. Eggs are retrieved by transvaginal ultrasound aspiration, as with IVF, and are fertilized in a laboratory dish. The next day, before the fertilized eggs begin cell division, they are transferred into the woman’s fallopian tubes by laparoscopy. This procedure is sometimes referred to as pronuclear stage transfer (PROST). Zygote is a term used to describe an egg that has been fertilized but has not yet undergone cell division, but now it is more commonly referred to as a pronucleus. Tubal embryo transfer (TET) This procedure involves the transfer of a more developed embryo than that used in GIFT or PROST. In this case, a fertilized egg that has reached the four- to eightcell stage of division is transferred into the fallopian tube. This transfer usually occurs about 24 hours after fertilization and the developing embryo then proceeds to move into the uterus as in an unassisted pregnancy. Techniques utilized to enhance fertilization or implantation include: • Intracytoplasmic sperm injection (ICSI) uses a microsurgical needle to inject a single sperm directly into the egg to achieve fertilization. • Microinsemination concentrates sperm into a small drop of fluid and placing it around the eggs to increase chances of fertilization. • Assisted hatching is a micromanipulation technique performed after fertilization with IVF, designed to improve the implantation of the embryo by making a microscopic hole (with a microsurgical needle or chemicals) in the zona pellucida (the tansparent, noncellular, secreted layer surrounding an ovum) to facilitate the release of the embryo from the egg membrane.

The micromanipulation techniques are relatively new procedures that may not be available in all fertility clinics. Their success depends on the quality of the man’s sperm, the age of the woman, and the experience of the clinic.

Aftercare Progesterone supplements are started the day after egg retrieval and continued until the pregnancy test is negative or throughout the first trimester of pregnancy. Vaginal suppositories or gel, intramuscular injections, and oral capsules are the form of progesterone used during IVF. Clinics vary regarding instructions about activity after embryo transfer. Some may suggest a few hours of bed rest and others suggest two to three days of minimal physical activity. The patient may also have her own opinion and choose to rest longer. About 10-12 days following embryo transfer, the physician will order a hCG (human chorionic gonadotrophin) test to determine pregnancy. If the test result is borderline, another blood test will be taken in two to three days. Five weeks after the transfer, an ultrasound is performed to document a heartbeat and confirm pregnancy.

Complications Hyperstimulation syndrome is usually mild when it occurs, but it can become potentially serious. This is a result of ovaries that are extremely responsive to the medications, thereby causing them to become quite large. Hyperstimulation syndrome can lead to severe weight gain from fluid accumulation in the abdomen and low output of urine as well as potentially serious changes in blood chemistry. It is rare for a woman to experience such severe hyperstimulation that hospitalization occurs, but the syndrome can become serious enough to require close monitoring of intravenous fluids and weight, urine output, and blood chemistry. Multiple gestation is another potential complication of ART and one that can have a long-term impact on a family. These pregnancies are physically and emotionally challenging to the mother and also have the potential of severe health risks associated with premature birth, which is quite common with multiple gestation. ART procedures have resulted in multiple gestation pregnancies about 43% of the time in women younger than 35 years. The risks to a woman carrying multiple fetuses include high blood pressure, gestational diabetes, increased risk of bleeding, premature labor, and cesarean section birth. Risks to the infant include prematurity, low birth weight, and respiratory and eye complications. Premature infants are also at higher risk for congenital (from birth) abnormalities and learning disabilities. The

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Gamete intrafallopian transfer (GIFT)

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Results

KEY TERMS Cryopreservation—Maintenance of the viability of excised tissue or organs by storing at very low temperatures. Ectopic—Arising or produced at an abnormal site or in a tissue where it is not normally found. Endometriosis—A condition in which tissue more or less perfectly resembling the endometrium (the mucous membrane lining the uterus) occus outside the uterine cavity, usually in the pelvic cavity. Follicle stimulating hormone—One of the hormones that promotes the formation of follicles within the ovary for ovulation. Laparoscopy—Examination of the peritoneal cavity with an endoscope. Luteinizing hormone—One of the hormones that promotes follicle formation within the ovary for ovulation. Pronucleus—The haploid nucleus of a sex cell. Ultrasound—A procedure in which high-frequency sound waves are used to create an image of a baby. Ultrasound can be used alone or with other antepartum testing.

risks of complications to the mother and the fetus increase dramatically with the number of fetuses carried. Couples may sometimes choose to undergo a procedure called multiple gestation reduction (MGR), which involves reducing the number of fetal sacs to improve the chance of having a healthy pregnancy and a healthy baby. This decision is an individual one that must be based on ethical, moral, and personal beliefs as well as medical information. Another potential complication is the fact that a small number of ectopic, or tubal, pregnancies can occur after embryo transfer in an IVF cycle as a result of embryos traveling out into the fallopian tube from the uterine cavity. The chance of this occurring, however, is less than one percent. Twenty percent of all pregnancies, regardless of how established, are lost, and all patients should be aware of this statistic prior to treatments as well. Individuals who do become pregnant are sometimes unable to enjoy the pregnancy because of the fear surrounding the treatments needed to achieve it and fear of potential problems or adverse outcomes. 936

If all goes well, the best result would be a healthy pregnancy and a healthy baby. If any of the complications occur, the individuals could undergo the procedure again, but it is essential that they have counseling to determine their expectations and emotional status.

Health care team roles All health care workers who take part in assisted reproductive technology and care for the patients should be trained in bereavement counseling. Although it is essential to provide the appropriate physical care necessary to achieve pregnancy, the psychological and emotional impact of the treatments and adverse outcomes are much more difficult to handle. Nurses usually spend more time with the patients, and it is their responsibility to be a patient advocate. Patients will often tell the nurse things they would not discuss with the physician. In such a situation, the nurse needs to intercede for the patient to make the physician aware of problems and concerns. Often the patient simply needs a hand to hold during treatments and an understanding heart to listen, which every nurse can provide. Resources BOOKS

Aronson, D. Resolving Infertility. Oxford, MD: Amaranth, 1999. Carson, S.A., Casson, P.R., Shuman, D.J. Complete Guide to Fertility. Chicago, IL: Contemporary Books, 1999. Cooper, S. L. & Glazer, E.S. Choosing Assisted Reproduction. Indianapolis, IN: Perspectives Press, 1998. Olds, Sally B., London, Marcia L., Ladewig, Patricia A. Maternal-Newborn Nursing: A Family and CommunityBased Approach. Upper Saddle River, NJ: Prentice Hall Health, 2000. ORGANIZATIONS

American Society for Reproductive Medicine (ASRM), 1209 Montgomery Highway, Birmingham, AL 35216-2809. (205) 978-5000. . International Fertility Center, 2601 East Fortune Circle Drive, Suite 102B, Indianapolis, IN 46241. (317) 243-8793. . Resolve, 1310 Broadway, Somerville, MA 02144-1779. National HelpLine: (617)623-1156. . OTHER

Fertility Net. . Surrogacy.com. .

Linda K. Bennington, CNS

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Definition A fetal age study, also called biometry, is part of an obstetric ultrasound exam. The study uses ultrasonography to take measurements of several fetal anatomic structures, compare the results to expected values, and convert that information into an estimated gestational age of the fetus.

Purpose Biometry is used to determine fetal age. Serial biometry may be performed to assess fetal growth rate.

Precautions As imaging technology has improved resolution of the fetal structures, care must be taken that the measurements start and end at the correct locations. The skill and experience of the ultrasound technologist are a critical component in obtaining reliable results. In general, ultrasonography dating of a pregnancy is more accurate than dating using the date of the mother’s last menstrual period.

Description Accurate dating of a pregnancy is the foundation on which obstetrical management relies. The date of the mother’s last menstrual period is often used to estimate delivery date, but it is accurate to within only about two weeks. By comparison, the biometric crown-rump measurement of the six to 12-week fetus provides the most accurate measurement, within three days of true gestational age. First-trimester biometric measurements may be obtained using either an abdominal or transvaginal transducer. Transvaginal ultrasonography can visualize fetal structures about one week in advance of abdominal sonography. Since the fetal structures are better visualized in the second trimester than in the first, a routine ultrasound is usually performed during that period, usually between 16 and 20 weeks gestation. Early sonography may be performed if a first-trimester pregnancy appears to be threatened, or if there is maternal bleeding, pelvic pain, or a concern that the pregnancy may be ectopic. Biometric dating may be used to determine the best time to perform chorionic villi sampling or maternal alpha-fetoprotein levels. Since many pregnancies are not dated until the pregnancy is more advanced, different structures are measured to obtain fetal age, depending on the suspected gestational age. As gestational age increases, normal variability between fetuses increases. To some degree,

then, biometric accuracy decreases with advancing gestational age. After about the twelfth week of gestation, the fetal position and movements make crown-rump measurements less accurate. Other anatomic structures will then be measured. From 12 to 18 weeks gestation, biometric measurements are usually accurate to within a week of gestational age. After 26 weeks gestation, fetal variability has greatly increased and the dating provided by biometric measurement is less accurate, but the method is still used. By late in the third trimester, measurements are accurate only within a two- to three-week window. In general, once the crown-rump measurement is no longer reasonable to obtain, the averaging of several anatomic measurements is more accurate than the use of one measurement alone. Results outside of the expected outcome should be further evaluated, to check for fetal anomalies. The four most common measurements taken during biometry are the biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). Because normal fetal variability is present between the 10th and 90th percentiles, the basis for comparison is usually the 50th percentile. However, imaging technology is sufficiently advanced so that almost any fetal structure can be measured and compared against normal ranges. Fetal growth is based on the fetal size in relation to the expected gestational age. Normal fetal size and weight values are expected between the 10th and 90th percentiles. Fetal size or weight below the 10th percentile is considered small for gestational age (SGA). A fetus with measurements above the 90th percentile is considered large for gestational age (LGA), and may be an indication of fetal response to maternal gestational diabetes. The diagnosis of an SGA or LGA fetus impacts the future obstetric management of the pregnancy, and assists in avoiding complications related to these conditions. Imaging technology software can estimate fetal weight using the measurements obtained for size and their relation to fetal mass. Estimated fetal weight may be used to check for fetal growth, or may be used in cases of fetal surgery or when the fetus needs to receive medication or a blood transfusion.

Preparation Biometry is a non-invasive sonographic fetal assessment tool. In early pregnancy, the mother may need to drink water prior to the test, without urinating until after the test has concluded. A full bladder is necessary to allow for transmission of the sound waves. As pregnancy advances, sufficient amniotic fluid is present so that fluid consumption prior to the test is not required. In order to

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tional age will be determined. Interventions undertaken based on inaccurate findings could be considered a complication or risk of the procedure.

KEY TERMS Gestational diabetes—Diabetes that first occurs during pregnancy and resolves once the pregnancy is terminated. Transducer—The external device or probe used in conjunction with the ultrasound machine. Applied on the outside of the abdomen with a special gel, it bounces sound waves into the area being visualized, and then sends the return waves back to the computerized ultrasound machine for interpretation and visualization on the monitor. A transvaginal transducer is inserted into the vagina in order to be closer to the structures being evaluated. Trimester—The average length of pregnancy is 280 days. The pregnancy is often divided into three trimesters, as different fetal development takes place in each of the three time periods. The first trimester extends to 14 weeks, the second through 28 weeks, and the third until 40/42 weeks, or term.

perform the ultrasound, a transducer is placed externally to the mother’s abdomen. Use of a special gel allows the transducer to glide over the surface of the abdomen during scanning. Because the abdomen is exposed, privacy should be provided either with the use of a curtain or with a closed door. The mother should be asked if she would like her partner or support person with her during the test. A comfortable room temperature and warmed transducer gel assist in putting the mother more at ease. A towel or cloth placed over the mother’s clothes protect them from becoming wet from the gel.

Aftercare When the test is completed, the abdomen should be wiped dry of the transducer gel. If the mother needed to consume water prior to the test, she may need to urinate. She may require assistance in getting up from the ultrasound table. If non-reassuring test results have been conveyed to the mother, she may need a health care professional to stay with her for emotional support and to answer questions.

The biometric results obtained are compared with norms for size and age, in order to estimate fetal age. Results outside of the normal range may indicate an SGA or LGA fetus, and require additional evaluation. Biometry may be used later in pregnancy when the fetal age is unclear. In this case, serial measurements may be taken after a two- to three-week period. The fetal growth during this time period can be compared against normal growth rates to estimate the gestational age. Because of rapid periods of fetal growth, each gestational week is also broken down further into the number of days. For example, the fetus’s weight and length at 27 1/7 weeks is different from that for a fetus of 27 6/7 weeks.

Health care team roles The fetal age study is usually performed by an ultrasound technologist in the imaging department. Non-routine biometry testing may provoke maternal anxiety over her baby’s well-being. The ability of the technician to provide a calm, professional environment can help put the mother at ease. Resources BOOKS

Burrow, Gerard N. and Thomas P. Duffy, Editors. Medical Complications During Pregnancy, 5th Edition. Philadelphia: W. B. Saunders Company, 1999. Creasy, Robert K. and Robert Resnik. Maternal-Fetal Medicine, 4th Edition. Philadelphia: W. B. Saunders Company, 1999. Cunningham, F. Gary, et al. Williams Obstetrics, 20th Edition. Stamford, CT: Appleton & Lange, 1997. Scott, James. Danforth’s Obstetrics and Gynecology, Eighth Edition. Philadelphia: Lippincott Williams & Wilkins, 1999.

Esther Csapo Rastegari, R.N., B.S.N., Ed.M.

Fetal alcohol syndrome

Complications Because a fetal age study is noninvasive and observational, no complications are anticipated. If the measurements were not obtained carefully, the wrong gesta938

Results

Definition Fetal alcohol syndrome (FAS) is a pattern of birth defects and learning and behavioral problems affecting

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Description FAS is the most common preventable cause of mental retardation. This condition was first recognized and reported in the medical literature in 1968 in France and in 1973 in the United States. Alcohol is a teratogen—the term used for any drug, chemical, maternal disease, or other environmental exposure that can cause birth defects or functional impairment in a developing fetus. Some features may be present at birth, including low birth weight, prematurity, and microcephaly. Characteristic facial features may be present at birth, or may become more obvious over time. Signs of brain damage include delays in development, behavioral abnormalities, and mental retardation, but affected individuals exhibit a wide range of abilities and disabilities. Only since 1991 has the long-term outcome of FAS been observed. Emotional disorders as well as learning and behavioral problems are common in adolescents and adults with FAS. Fetal alcohol effect (FAE), a term no longer favored, is sometimes used to describe individuals with some, but not all, of the features of FAS. In 1996 the Institute of Medicine suggested a five-level system to describe the birth defects, learning, and behavioral difficulties in offspring of women who drank alcohol during pregnancy. This system contains a number of criteria that must be present, including confirmation of maternal alcohol exposure, characteristic facial features, growth problems, learning and behavioral problems, and birth defects known to be associated with prenatal alcohol exposure.

more or less susceptible to the damage that alcohol can cause. The dose of alcohol, the time during pregnancy at which the alcohol is used, and the pattern of alcohol use, all contribute to the different signs and symptoms that can be identified. There is no racial or ethnic susceptibility to FAS. Individuals from different genetic backgrounds exposed to similar amounts of alcohol during pregnancy may exhibit different signs or symptoms of FAS. Several studies have estimated that between 25% and 45% of chronically alcoholic women will give birth to a child with FAS if they continue to drink during pregnancy. The risk of FAS appears to increase the older a chronically alcoholic woman becomes in her childbearing years and continues to drink. That is, a child with FAS will often be one of the last children born to a chronically alcoholic woman, although older siblings may exhibit milder features of FAS. Binge drinking, defined as the sporadic use of five or more standard alcoholic drinks per occasion, and moderate daily drinking (two to four 12 oz bottles of beer, 8 to 16 ounces of wine, 2 to 4 ounces of liquor) can also result in offspring with features of FAS.

Causes and symptoms

The incidence of FAS varies among different populations studied, and ranges from approximately one in 200 to one in 2,000 live births. However, a study reported in 1997, utilizing the Institute of Medicine criteria, estimated the prevalence of FAS in Seattle, Washington, from 1975-1981 at nearly one in 100 live births. Avoiding alcohol during pregnancy, especially during the earliest weeks of the pregnancy, can prevent FAS. Not even the smallest amount of alcohol consumed during pregnancy has been proven to be completely safe.

Classic features of FAS include short stature, low birth weight and poor weight gain, microcephaly, and a characteristic pattern of facial features. These facial features in infants and children may include small eye openings (measured from inner corner to outer corner); epicanthal folds (folds of tissue at the inner corner of the eye); small or short nose; low or flat nasal bridge; smooth or poorly developed philtrum (the area of the upper lip above the colored part of the lip and below the nose); thin upper lip; and small chin (micrognathy). Some of these features are nonspecific, meaning they can occur in other conditions, or be appropriate for age, racial, or family background. Other major and minor birth defects that have been reported include cleft palate, congenital heart defects, strabismus, hearing loss, defects of the spine and joints, alteration of the hand creases, and small fingernails and toenails.

FAS is neither a genetic nor inherited disorder. It is a pattern of birth defects and learning and behavioral problems that result entirely from maternal alcohol use during pregnancy. Alcohol freely crosses the placenta and causes damage to the developing embryo or fetus. Alcohol use by the father cannot cause FAS. If a woman with FAS drinks alcohol during pregnancy, she, too, may have a child with FAS. Not all individuals from alcohol-exposed pregnancies have obvious signs or symptoms of FAS. Individuals of different genetic backgrounds may be

The diagnosis is sometimes more difficult in older adolescents and adults. Short stature and microcephaly remain common features but weight may normalize, and individuals may actually become overweight for their height. The chin and nose grow proportionately more than the middle part of the face, so that dental crowding may become a problem. The small eye openings and the appearance of the upper lip and philtrum may continue to be characteristic. Pubertal changes typically occur at the normal time.

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individuals whose mothers consumed alcohol during pregnancy.

Fetal alcohol syndrome

Epicanthal Folds

Short Palpebral Fissures

Flat Midface

Thin Upper Lip

Microcephaly Low Nasal Bridge

Minor Ear Anomalies

Short Nose

Micrognathia Indistinct Philtrum Facial features common in fetal alcohol syndrome. (EPD Photos. Courtesy of Gale Group.)

Newborns with FAS may have difficulties with feeding due to a poor sucking ability, have irregular sleep-wake cycles, decreased or increased muscle tone, seizures, or tremors. Delays in achieving developmental milestones such as rolling over, crawling, walking, and talking may become apparent in infancy. Behavior and learning difficulties typical in the preschool or early school years include poor attention span, hyperactivity, poor motor skills, and slow language development. Attention deficit-hyperactivity disorder (ADHD) is a common associated diagnosis. Learning disabilities or mental retardation may be diagnosed during this time. Arithmetic is often the most difficult subject for a child with FAS. During middle school and high school years, behavioral difficulties and learning difficulties can be significant. Memory problems, poor judgment, difficulties with daily living skills, difficulties with abstract reasoning skills, and poor social skills are often apparent by this time. It is important to note that animal and human studies have shown that neurologic and behavioral abnormalities can be present without the characteristic facial features. These individuals may not be identified as having FAS but may fulfill criteria for alcohol-related diagnoses as set forth by the Institute of Medicine. In 1991 Streissguth and others reported some of the first long-term follow-up studies of adolescents and adults with FAS. Among the approximately 60 individuals they studied, the average IQ was 68. In the general population, 70 is the lower limit of the normal range. However, the range of IQ was quite large, from as low as 20 (severely retarded) to as high as 105 (normal). The average achievement levels for reading, spelling, and arithmetic were, respectively, fourth grade, third grade, and second grade. The Vineland Adaptive Behavior Scale was used to measure adaptive functioning in these individuals. The composite score for this group showed functioning at the level of a seven-year-old, daily living skills 940

at a level of nine years of age, and social skills at the level of a six-year-old. In 1996 Streissguth and others published further data regarding the disabilities in children, adolescents, and adults with FAS. Secondary disabilities (that is, those disabilities not present at birth and that might be preventable with proper diagnosis), treatment, and intervention, were described. These secondary disabilities include mental health problems; disrupted school experiences; trouble with the law; incarceration for mental health problems, drug abuse, or a crime; inappropriate sexual behavior; alcohol and drug abuse; problems with employment and dependent living; and difficulties parenting their own children. In that study, only seven out of 90 adults were living and working independently and successfully. In addition to the studies by Streissguth, several other authors in different countries have now reported on the long-term outcome of individuals diagnosed with FAS. In general, the neurologic, behavioral, and emotional disorders become the most problematic for individuals with FAS. Because physical features change over time, correct diagnosis becomes more difficult in older individuals without old photographs and other historical data to review. Mental health problems included attention deficit disorder, depression, panic attacks, psychosis, and suicide threats and attempts, and overall were present in more than 90% of the individuals studied by Streissguth. A 1996 study from Germany reported that more than 70% of the FAS adolescents studied had persistent and severe developmental disabilities. Many had psychiatric disorders, the most common of which were emotional disorders, repetitive habits, speech disorders, and hyperactivity disorders.

Diagnosis FAS is a clinical diagnosis, which means there are no blood, x ray, or psychological tests that can be performed to confirm a suspected diagnosis. The diagnosis is made based on the history of maternal alcohol use, and detailed physical examination for the characteristic major and minor birth defects, and characteristic facial features. It is often helpful to examine siblings and parents of an individual suspected of having FAS, either in person or by photographs, to determine whether findings on the examination might be familial, or if other siblings may also be affected. Sometimes, genetic tests are performed to rule out other conditions that may present with developmental delay or birth defects. Individuals with developmental delay, birth defects, or other unusual features are often referred to a clinical geneticist, developmental pediatrician, or neurologist for evaluation and diagnosis of FAS. Psychoeducational testing to deter-

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Treatment There is no treatment for FAS that will reverse or change the physical features or brain damage associated with maternal alcohol use during pregnancy. Most of the birth defects associated with prenatal alcohol exposure, however, are correctable with surgery. Children with FAS should have psychoeducational evaluation to help plan appropriate educational interventions. Common associated diagnoses, such as ADHD, depression, or anxiety should be recognized and appropriately treated. Disabilities that present during childhood persist into adult life; however, some of the secondary disabilities may be avoided or lessened by early and correct diagnosis, better understanding of the life-long complications of FAS, and appropriate intervention. Streissguth has described a model in which an individual affected by FAS has one or more advocates to help provide guidance, structure, and support as the individual seeks to become independent, successful in school or employment, and develop satisfying social relationships.

Prognosis The prognosis for FAS depends upon the severity of birth defects and brain damage present at birth. Miscarriage and stillbirth, or death in the first few weeks of life, may be outcomes in very severe cases. Some factors that have been found to reduce the risk of secondary disabilities in FAS individuals include diagnosis before the age of six years; stable and nurturing home environments; never having experienced personal violence; and referral and eligibility for disability services. The longterm data help in understanding the difficulties that individuals with FAS encounter throughout their lifetime, and can help families, caregivers and professionals provide care, supervision, education, and treatment geared toward their special needs.

Health care team roles Pediatricians, obstetricians, family physicians, or nurse practitioners are most likely to make an initial diagnosis of FAS. A clinical geneticist, developmental pediatrician, or neurologist often confirms an initial diagnosis. Other physicians and surgeons may monitor and treat an affected baby. Nurses provide supportive care. Therapists provide support for parents of babies with FAS.

KEY TERMS Cleft palate—An abnormal opening in the roof of the mouth, usually in the midline, so that there is a communication between the nose and mouth cavities. Congenital—Present at the time of birth. IQ—Abbreviation for Intelligence Quotient. Compares an individual’s mental age, as measured by a test, to a true or chronological age and multiplies that ratio by 100. Microcephaly—Small head circumference. Head circumference is an indirect measure of brain size. Miscarriage—Spontaneous pregnancy loss. Placenta—Organ unique to mammals that serves to exchange nutrients and waste between the maternal and fetal circulations; sometimes called the afterbirth. Strabismus—Failure of the eyes to move together when focusing on an object; sometimes called lazy eye. Teratogen—Any drug, chemical, maternal disease, or exposure that can cause physical or functional defects in the embryo or fetus of the exposed mother.

Prevention Prevention of FAS is the key to effectively addressing the problem. Prevention efforts must include public education efforts aimed at the entire population, not just women of childbearing age; appropriate treatment for women with high-risk drinking habits; and increased recognition and knowledge about FAS by professionals, parents, and caregivers. Resources BOOKS

Abel, Ernest L. Fetal Alcohol Abuse Syndrome. Norwood: Plenum Publishing Corp., 1998. Institute of Medicine. Fetal Alcohol Syndrome: Diagnosis, Epidemiology, Prevention, and Treatment. Washington, DC: National Academy Press, 1996. Jones, Kenneth L. Smith’s Recognizable Patterns of Human Malformation, 5th ed. Philadelphia: W.B. Saunders, 1997. 555-559. Kleinfeld, Judith, Barbara Morse, and Siobhan Wescott. Fantastic Antone Grows Up: Adolescents and Adults With

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mine IQ and the presence of learning disabilities may also be part of the evaluation process.

Fetal biophysical profile

Fetal Alcohol Syndrome. Fairbanks, AK: University of Alaska Press, 2000. Streissguth, Ann, Jonathan Kanter, and Mike Lowry. The Challenge of Fetal Alcohol Syndrome: Overcoming Secondary Disabilities. Seattle, WA: University of Washington Press, 1997. Streissguth, Ann. Fetal Alcohol Syndrome: A Guide for Families and Communities. Baltimore, MD: Paul H. Brookes Publishing Co. 1997.

BoozeNews. . Fetal Alcohol Syndrome Link. . Internet Resources for Special Children. . Nemours Foundation. . Vanderbilt University School of Medicine. .

PERIODICALS

L. Fleming Fallon, Jr., M.D., Dr.P.H.

Abel, E.L. “Fetal Alcohol Syndrome: When the End Does Not Justify the Means. Journal of Pediatrics 138, no. 2 (2001): 295-296. Astley, S.J., and S.K. Clarren. “Measuring the Facial Phenotype of Individuals with Prenatal Alcohol Exposure: Correlations with Brain Dysfunction.” Alcohol and Alcoholism 36, no. 2 (2001): 147-159. Branco, E.I., and L.A. Kaskutas. “If It Burns Going Down...: How Focus Groups Can Shape Fetal Alcohol Syndrome (FAS) Prevention.” Substance Use and Misuse 36, no. 3 (2001): 333-345. Chaudhuri, J.D. “An Analysis of the Teratagenic Effects That Could Possibly Be Due To Alcohol Consumption By Pregnant Mothers.” Indian Journal of Medical Science 54, no. 10 (2000): 425-431. Chaudhuri, J.D. Medicine and Science Monitor 6, no. 5 (2000): 1031-1041. Thackray H., and C. Tifft. “Fetal Alcohol Syndrome.” Pediatrics in Review 22, no. 2 (2001): 47-55. ORGANIZATIONS

American Academy of Neurology. 1080 Montreal Avenue, St. Paul, MN 55116. (651) 695-1940. . American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. (847) 4344000. . American Public Health Association. 800 I Street, NW, Washington, DC 20001-3710. (202) 777-2742. . American Speech-Language Hearing Association. 10801 Rockville Pike, Rockville, MD 20852. (800) 638-8255. . March of Dimes. 1275 Mamaroneck Avenue, White Plains, NY 10605. (888) 663-4637. . National Institute on Alcohol Abuse and Alcoholism. 6000 Executive Boulevard - Willco Building, Bethesda, MD 20892-7003. (301) 443-3860. . National Organization on Fetal Alcohol Syndrome. 216 G Street, North East, Washington, DC 20002. (202) 7854585. . OTHER

American Academy of Pediatrics. . ARC. . 942

Fetal biophysical profile Definition The fetal biophysical profile (BPP) is a test performed to measure fetal well-being. It uses ultrasonography to measure fetal breathing, fetal movement, fetal tone, and amniotic fluid volume. A non-stress test is done to assess fetal heart rate. Each of these five variables is given a score of zero or two, for a potential total score of 10.

Purpose The purpose of the BPP is to assess fetal well-being. It is a tool used near or at term by clinicians to assess the potential risk of fetal compromise or demise due to fetal hypoxia or acidosis. Intervention such as maternal hospitalization, or delivery may follow a BPP score of four or below.

Precautions A reliable BPP score necessitates that a well-trained ultrasonographer perform the test. However, fetal parameters are recorded over a 30-minute time period, with an additional 30 minutes for the non-stress test (NST) component. Information on a very active fetus is obtained inconsiderably less time. The complete BPP can therefore be a time-consuming test. The NST records the relationship of fetal heart rate to fetal movement. It is associated, however, with a false-positive rate as high as 80%, and averaging about 50%.

Description The BPP is a test scoring five fetal vital sign variables: fetal heart rate, fetal breathing, fetal movement, fetal tone, and amniotic fluid volume. An ultrasound is used to visualize the fetus to measure these variables. The fetal heart rate is assessed through an NST. Each

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Fetal breathing (FB) is measured by watching for movement of the fetal thorax and diaphragm. This is to assure breathing, and not just chest wall movement. A score of two is given if at least one occurrence of FB lasting at least 30 seconds during the 30-minute test is noted. A score of zero is given if no FB is seen, or if the FB lasted less than 30 seconds. Fetal movement is defined by gross arm, leg, or body activity. A score of two is given if there are at least three separate limb/body movements during the 30minute test. A score of 0 is given if there are two or fewer limb/body movements during the test. Facial movement is not scored. Fetal tone is defined by active extension and flexion of the fetal limbs, trunk, or hand; or if the hand remains in a flexed position during the entire 30-minute test. A score of two is given if the hand and fingers are seen to fully extend and flex into a fist. A score of zero is given if no such movement is recorded, or with slow or partial flexion or extension. Amniotic fluid volume is estimated for sufficiency. Since fetal anatomic structures do not allow full visualization of all the amniotic fluid, it is estimated by measuring pockets of fluid from 0.39 to 0.78 in (1 to 2 cm) in height on ultrasound. A score of two is given if at least one pocket of fluid measures 0.78 in (2 cm) or more in height. A score of zero is given when no such pockets can be measured. Normal amniotic fluid volume peaks at about 750 ml at 32 weeks gestation, stays stable until term at 40 weeks, and then declines to about 400 ml by 42 weeks. Excessive amniotic fluid amounts (hydramnios), such as might be seen in diabetic mothers, may be as high as 1700 to 1900 ml. Oligohydramnios is defined by about 300 ml of fluid volume. The amniotic fluid is produced as the fetus urinates and through lung secretions. The volume is controlled by fetal swallowing and by reabsorption through the membranes. The amniotic fluid index (AFI) is also used to determine sufficiency of amniotic fluid. In this method, the largest vertical column of fluid in each of the four uterine quadrants is measured. Because of the role of the fetus in the production and control of amniotic fluid, it is one variable in fetal wellbeing assessment.

Fetal heart rate (FHR) variability is measured during a NST. The fetal heart rate is normally variable in nature. Accelerations, or increases in FHR, are usually seen in response to fetal movements and are therefore reassuring. A score of two is given for two or more accelerations of at least 15 beats per minute that last at least 15 seconds each during a 30-minute period. A score of 0 is given if fewer than two accelerations are seen within 30 minutes.

Preparation Because the BPP is done during the third trimester of pregnancy, there is sufficient amniotic fluid to provide contrast to clearly visualize the fetus. No preparation is usually required before the test is performed. The mother may be asked to have a snack prior to the test to encourage a more active fetus. Because the mother’s abdomen is exposed, curtains or a closed door should provide privacy. A comfortable room air temperature and the warming of the transducer gel can assist in putting the mother at ease. The mother should be asked if she wants her partner or support person with her during the test. A towel or cloth should cover the mother’s clothing to avoid its getting wet from the transducer gel.

Aftercare The BPP uses an external transducer to visualize the fetus and the amount of amniotic fluid. A towel or cloth can be used to wipe off excess gel and dry the abdomen after the test. In the event that test results indicate fetal compromise, a health care professional should remain with the mother to provide emotional support and answer questions as needed.

Complications Because the test is noninvasive in nature, complications from the test itself are unexpected. A non-reassuring test may be repeated four to 24 hours later for comparison. Efforts should be made to assess for false negatives or false positives. A low BPP score may be followed by interventions with their own potential complications.

Results A score of eight or ten out of ten provides a reassuring BPP score. If the score is eight, with a decrease in amniotic fluid volume, delivery may be indicated, with fetal maturity. A score of six arouses suspicions of chronic fetal hypoxia. A repeat test within four to six hours may be ordered. Delivery may be indicated if there is a reduction in the amniotic fluid volume. A score of four is

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parameter is given a score of two or zero, based on specific criteria. The total potential score is a 10. The BPP may be ordered following a non-reactive NST; after a suspicious oxytocin challenge/contraction stress test (CST); or after term, especially if there is concern about low amniotic fluid volume (oligohydramnios). The first researchers to report the results of scoring these fetal biophysical variables as a group were Manning and colleagues in 1980.

Fetal cell screen

Scott, James. Danforth’s Obstetrics and Gynecology, 8th ed. Philadelphia: Lippincott Williams & Wilkins, 1999.

KEY TERMS Fetal demise—The death of the fetus in utero. Transducer—The external device or probe used in conjunction with the ultrasound machine. Applied on the outside of the abdomen with a special gel, it bounces sound waves into the area being visualized, and then sends the return waves back to the computerized ultrasound machine for interpretation and visualization on the monitor. Variability—The fetal heart rate is expected to change, or be variable in nature. While the adult heart rate remains stable, except with exertion, the rate of the fetal heart continually moves up and down. A flat fetal heart rate is considered an ominous sign.

suspicious of chronic fetal hypoxia. A fetal lung maturity test may be done to assess readiness for delivery. Delivery is indicated if a repeat BPP after 24 hours confirms a score of four or below. A score of zero to two elicits a strong suspicion of chronic fetal hypoxia. The BPP testing period may continue for two hours instead of the usual 30 minutes. If the two-hour score is four or below, delivery is indicated if the fetus has a good chance at extrauterine survival.

Health care team roles The BPP should be performed by a trained ultrasonographer. The NST may be performed by a nurse or a radiology technician in the antenatal division of an obstetric department, in the radiology department, or in an obstetric office. As with any test, patient anxiety is heightened with concerns of fetal compromise. Therefore, the ability of the health care professional to convey accurate information in a calming manner is very important.

Esther Csapo Rastegari, R.N., B.S.N., Ed.M.

Fetal cell screen Definition The fetal cell screen is a procedure performed during pregnancy whereby blood is drawn from the mother and examined for the presence of fetal cells.

Purpose The fetal cell screen is used to assess the degree of Rh (also called Rho [D] or D) sensitization in an Rh-negative mother during gestation of an Rh-positive fetus. Fetal red cells carrying the Rh positive antigen can leak into the maternal circulation and immunize the Rh-negative mother, possibly leading to hemolytic disease of the newborn. The potential degree of isoimmunization and severity of hemolytic disease increases with each Rhincompatible pregnancy. The fetal cell screen quantifies the extent of the leakage and permits determination of how much Rh immune globulin (RhoGAM) to administer in order to prevent the mother from developing antiD antibodies against the fetus. Rho immune globulin is normally administered by intramuscular injection to Rh-negative mothers at 2830 weeks of gestation and again within 72 hours postpartum. The dosage is higher for mothers who test positive for fetal red blood cells. The treatment is performed earlier when amniocentesis or chorionic villus sampling is performed, or following spontaneous or elective abortion. Aside from Rh-incompatibility cases, the test may be ordered to investigate the severity of maternal-fetal hemorrhage following a trauma, or during post-mortem examination of a stillbirth.

Resources

Precautions

BOOKS

Burrow, Gerard N., and Thomas P. Duffy, eds. Medical Complications During Pregnancy, 5th ed. Philadelphia: W. B. Saunders Company, 1999. Creasy, Robert K. and Robert Resnik. Maternal-Fetal Medicine, 4th ed. Philadelphia: W. B. Saunders Company, 1999. Cunningham, F. Gary et al. Williams Obstetrics, 20th ed. Stamford, CT: Appleton & Lange, 1997.

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Although in principle the fetal cell screen is simple to perform, the procedure is subjective, labor-intensive, and time-consuming; and requires skill, experience, and strict attention to detail. When possible, the procedure should be scheduled with the laboratory in advance. The specimen may be rejected by the laboratory if it is delivered too long after

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The possibility that the mother has an inherited blood disorder that might produce fetal hemoglobin should be considered when interpreting a positive result.

Description The fetal cell screen allows discrimination of fetal from maternal red blood cells in a sample of maternal blood. This procedure is also known as the KleihauerBetke test; acid elution for fetal hemoglobin; fetal hemoglobin stain; and fetal-maternal hemorrhage test. At the hospital or laboratory, 3–7 ml of maternal blood is drawn, usually from a vein on the back of the hand or the inside of the elbow. The venipuncture site is cleaned with antiseptic, a needle is inserted, and the blood sample is collected into a vacutainer containing either EDTA or citrate. The procedure takes about five minutes. The nurse or phlebotomist performing the venipuncture should observe universal precautions for the prevention of transmission of bloodborne pathogens. The sample should be kept at room temperature and transported to the laboratory for analysis within 6 hours. The fetal screen test may be performed as a qualitative serological (antibody-based) test. In this method, a 3% suspension of the mother’s blood in physiological saline is mixed with an antibody to the Rho (D) antigen. The antibodies will bind to any Rh-positive fetal cells present. After the cells are incubated with the antibody, the cells are washed to remove any unbound reagent antibody, and one drop of a 3% suspension of reagent Rh positive red cells is added. These cells serve as indicators. They bind to the remaining antigen-combining sites of the antibodies attached to fetal red cells, causing formation of rosettes. The number of rosettes found in five low-power microscopic fields is determined. When greater than or equal to seven rosettes are seen, the test is considered positive. A fetal-maternal bleed of at least 30 mLs is required to give a positive test result. If this test is positive, a quantitative test is used to more accurately determine the quantity of fetal blood in the maternal circulation. The quantity of fetal cells in the maternal circulation is most often measured using a special staining technique known as the Kleihauer-Betke method. In urgent cases, such as with trauma, results can be returned in as little as one hour. The blood sample is smeared onto a microscope slide, fixed with ethanol, and allowed to air dry. The blood film is then treated with a weakly acidic phosphate solution and stained with eosin dye. Under acidic conditions, the adult hemoglobin elutes, or leaks, out of

the maternal cells, and they appear as pale “ghosts,” while the more acid-resistant fetal hemoglobin remains in the fetal red blood cells and becomes stained pink to red. The stained films are viewed under a light microscope, and the number of fetal and maternal cells found in 50 low-power fields is recorded. The number of fetal red blood cells is reported as a percentage of blood cells counted. The greater the amount of fetal blood leakage, the larger the dose of Rho immune globulin to be administered to the mother. Rho immune globulin is a potent form of anti-D that is given to Rh negative mothers to prevent formation of an antibody to the D antigen. It acts by interfering with the recognition of D antigen by the mother’s immune system. One dose can prevent immunization from up to 30 mL of fetal blood. The percentage of fetal cells is multiplied by 50 to give the mLs of fetal blood. (Each percent of fetal red cells represents 1/100th of the blood. Assuming an average maternal blood volume of 5000 mL, each percent is equivalent to 5000/100 = 50 mL.) This number is divided by 30 to give the number of doses needed. If the number to the right of the decimal is lower than 5, one dose is added. Otherwise, two doses are added to the result. The Kleihauer-Betke is currently the standard method used to detect fetal red blood cells in maternal circulation, although it is labor-intensive, subjective, and not suitable for automation. Since the mid-1990s, automated methods for quantifying fetal cells by flow cytometry have been under development. In these methods, the blood sample is treated with anti-D or anti-fetal hemoglobin antibodies that are labeled with fluoroscein isothiocyanate (FITC). The antibodies react only with the fetal cells. In the flow cytometer, the suspended blood cells in the specimen stream through a sample tube in single file past a beam of ultraviolet light and are counted as the light beam is broken. The light also causes the FITC label to fluoresce, and light detectors in the flow cytometer allow differential counting of the fluorescently tagged fetal cells as they pass. Compared to the Kleihauer-Bekte test, the automated flow cytometry method offers superior objectivity, sensitivity, specificity, and reproducibility.

Preparation No special preparation is necessary.

Aftercare After the blood sample is drawn, pressure should be applied to the puncture site until the bleeding stops to reduce bruising, and a bandage may be applied to the site. The woman may resume normal activities.

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being drawn; or if clotted, hemolyzed, or contaminated with heparin (as may happen when drawn at the same time as a sample for blood gases).

Fetal cell screen

the procedure is performed correctly. Minor discomfort while blood is drawn or bruising at the puncture site may occur, and there is a slight risk of infection.

KEY TERMS Amniocentesis—A prenatal screening procedure in which a needle inserted through the abdominal wall is used to take a sample of amniotic fluid from the amniotic sac in the uterus of a pregnant woman. Chorionic villus sampling (CVS)—A prenatal screening procedure in which a needle inserted through the vagina and cervix or through the abdominal wall is used to remove chorionic villi. Fetal hemoglobin—The oxygen-carrying pigmented protein of fetal red blood cells, distinct from adult hemoglobin. Flow cytometry—The measurement of cells or cellular properties as they move in a fluid stream past stationary detectors.

Results The percentage of fetal red blood cells in the circulation of normal non-pregnant adults is generally 0.6% fetal cells is reported as positive.

Health care team roles A physician, usually an obstetrician, orders the test. A nurse, phlebotomist, or laboratory technician collects the blood sample by venipuncture and arranges transport to the laboratory for analysis. The patient should be observed to ensure that bleeding from the puncture site stops.

Fluorescein isothiocyanate (FITC)—An organic molecule that can be covalently bound to other molecules, and that emits visible light when exposed to ultraviolet radiation.

In the laboratory, a clinical laboratory scientist/medical technologist trained in the Kleihauer-Betke staining procedure prepares, treats, and examines the blood smear, and counts and reports the numbers of maternal and fetal cells. A physician uses the reported ratio of fetal to maternal cells to calculate the amount of Rh immune globulin to be prescribed for the mother.

Hemoglobin—The oxygen-carrying pigmented protein of red blood cells.

Resources

Hemolytic disease of the newborn (HBN)—Also known as erythroblastosis neonatorum, severe neonatal anemia caused by Rh incompatibility and subsequent lysis of red blood cells. Isoimmunization—The development of antibodies in a species in response to antigens from the same species. Rh- incompatibility—The development of anti-Rh antibodies in an Rh-negative mother in response to antigens from her Rh-positive fetus. Rhogam—Trade name for Rho [D] immunoglobulin used to immunize Rh-negative mothers. Vacutainer—A glass tube fitted with a rubber stopper from which air is evacuated to produce a slight vacuum, used for blood specimen collection. Venipuncture—The puncture of a vein for therapeutic purposes or to collect a specimen.

Complications There is no risk to the mother or fetus. Complications associated with venipuncture are negligible when 946

BOOKS

Letsky, Elizabeth A., Ian Leck, and John M. Bowman. “Rhesus and other haemolytic diseases.” In Antinatal and Neonatal Screening, edited by Nicholas Ward and Ian Leck. Oxford, UK: Oxford University Press, 2000, pp.282-320. ORGANIZATIONS

ARUP Laboratories. 500 Chipeta Way, Salt Lake City, UT 84108. . OTHER

Health On the Net Foundation website. , 2001. “Kleihauer-Betke, Quantitative.” New York Presbyterian Hospital website. . “Kleihauer-Betke.” WebMD Corporation, Copyright 19962001. Moses, Scott, MD. “Kleihauer-Betke.” Family Practice Notebook website, 2000. .

Patricia L. Bounds, Ph.D.

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Fetal development

A human embryo at five to six weeks of development. (Photograph by Petit Fromat/Nestle. National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.)

Fetal development Definition The progressive growth that occurs between fertilization of an egg to the birth of a baby.

Description Pre-embryonic stage The pre-embryonic stage starts with fertilization and lasts through the first two weeks of pregnancy. FERTILIZATION. During intercourse, the male ejaculates and releases semen into the woman’s vagina. The semen contains 50 to 200 million spermatozoa per milliliter that reach the cervix within 90 seconds and the outer end of the fallopian tubes within five minutes. Fertilization results when a single sperm, or spermatozoon, penetrates an ovum. The chromosomal material of the ovum and spermatozoon then combine, forming a zygote.

IMPLANTATION. After fertilization, the zygote travels three or four days through the fallopian tube toward the body of the uterus. During this time, the cell starts to divide. By the time the zygote reaches the body of the uterus, it consists of 16 to 50 cells and is called a morula. The morula collects large cells at the periphery of the ball and becomes an outer casing with a connected inner group of cells surrounded by a fluid space. At this stage, the structure is termed a blastocyst. The blastocyst implants on the inner layer of the uterus, called the endometrium, approximately eight to 10 days after fertilization, where it will obtain nourishment. In as many as 50% of all pregnancies, the zygote fails to reach the implantation stage, in which it becomes an embryo.

Embryonic stage The embryonic stage spans the third week to the eighth week of pregnancy. Body organs form out of layers of tissue called germ cells. The three distinct layers of germ cells are called the endoderm, the ectoderm, and the mesoderm. Newborns with a congenital defect originating from one of the three layers should be evaluated for malformations that devel-

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• Fetal heart can be heard with an electronic device called a Doppler.

KEY TERMS

END OF 16 WEEKS GESTATION.

Fetus—Infant during intrauterine life. Sonogram—Ultrasound; uses sound waves to take pictures and view the fetus.

• Fetus reaches a length of 4-7 in (10 to 17 cm) and weighs 55 to 120 g. • Liver and pancreatic secretions are present. • Fetus starts to make sucking motions with the mouth.

oped from the same germ cells. For example, the heart and kidneys form from the mesoderm. A baby born with a heart defect should also have an x ray or ultrasound of the kidneys. During the embryonic period, the baby is most susceptible to invasion by teratogens, which are substances that can result in birth defects. Women should be instructed on ways to reduce their contact with teratogens.

• Fetus reaches a length of 10 in (25 cm) and weighs 223 g. • The mother starts to feel fetal movement. • Fetal heart tones can be heard with a stethoscope. END OF 24 WEEKS GESTATION.

• Fetus reaches a length of 11-14 in (28-36 cm) and weighs 550 g.

Milestones of fetal development The life of the fetus is commonly calculated from the time of ovulation or fertilization (ovulation age), but the duration of the pregnancy is usually calculated from the first day of the last menstrual period (gestational age). The following outline of fetal development milestones is based on 40 weeks of gestation. END OF FOUR WEEKS GESTATION.

• Fetus reaches a length of 0.75 to 1 cm and weighs 400 mg. • Spinal cord forms and fuses at the center. • Lateral wings bend forward meeting at the center and will eventually form the body. • Head tilts forward and makes up about one-third of the entire structure. • The rudimentary heart beats a regular rhythm. • Arms and legs have the appearance of small buds. • The beginnings of eyes, ears, and a nose are evident. END OF EIGHT WEEKS GESTATION.

• Fetus reaches a length of 1 in (2.5 cm) and weighs 20 g.

• Eyebrows and eyelashes are clearly formed. • Eyelids, which fused in the 12th week, start to open. • Pupils are reactive to light. • Fetus could possibly be viable if born now and cared for in a neonatal intensive care unit. • Surfactant, a phospholipid substance essential to lung function, is formed and excreted by cells in the alveoli. END OF 28 WEEKS GESTATION.

• Fetus reaches a length of 14-15 in (35-38 cm) and weighs 1200 g. • Testes begin descent into the scrotal sac from the lower abdominal cavity if the fetus is male. • The brain is rapidly developing. END OF 32 WEEKS GESTATION.

• Fetus reaches a length of 15-27 in (38-43 cm) and weighs 1600 g. • Fetus hears sounds and responds with movement. • Delivery presentation (vertex or breech) may be assumed.

• The heart has a definite septum and valves. • Extremities have lengthened. • External genitalia are evident, but gender is not obvious. END OF 12 WEEKS GESTATION.

• Fetus reaches a length of 2.8-3.6 in (7-9 cm) and weighs 45 g. • Some movement occurring, but usually too faint for the mother to feel. 948

END OF 20 WEEKS GESTATION.

• Iron stores begin to develop. END OF 36 WEEKS GESTATION.

• Fetus reaches a length of 17-20 in (42-49 cm) and weighs 5-6 lbs (1900-2700 g). • Soles of the feet have only one or two creases. • The central nervous system has greater control over body functions.

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• Fetus reaches a length of 19-21 in (48-52 cm) and weighs 7-7.5 lbs (3000 g). • Fingernails have grown over the fingertips. • There are creases covering at least two-thirds of the soles of the feet. • Fetus kicks vigorously and may cause the mother discomfort.

Role in human health Knowledge of fetal development can assist the mother and other family members in visualizing the fetus at the various stages of development. The parent-infant bonding that results can be an incentive for the mother to engage in healthful behaviors. Resources BOOKS

Pillitteri, Adele. Maternal & Child Health Nursing, 3rd ed. Philadelphia: Lippincott, 1999. ORGANIZATIONS

March of Dimes. 1275 Mamaroneck Avenue, White Plains, NY 10605. (888)-MODIMES (663-4637). .

Nadine M. Jacobson, RN

Fetal lung maturity test see Lipid tests

Fetoscopy Definition Fetoscopy utilizes an instrument called a fetoscope to evaluate or treat the fetus during pregnancy.

Purpose There are two different types of fetoscopes. One resembles a stethoscope, but with a headpiece. It is used externally, on the mother’s abdomen, to auscultate (listen to) the fetal heart tones. The second type of fetoscope is a fiber-optic endoscope. It is inserted into the uterus either transabdominally or transcervically to visualize the fetus, to obtain fetal tissue samples, or to perform fetal surgery.

Precautions The external fetoscope requires no preparation, nor does it have any associated risks. Its usefulness and accuracy depend on the skill of the practitioner. The endoscopic fetoscope is inserted internally and thus carries risks of infection (both maternal and fetal), premature rupture of membranes, premature labor, and fetal death. The American College of Obstetricians and Gynecologists expressed their opinion in a February 28, 2001 press release that fetal surgery should be considered experimental.

Description The external fetoscope is used to auscultate fetal heart tones for rate and rhythm. The earpieces and the headpiece allow auscultation via both air and bone conduction. It is inexpensive, is not invasive, and does not require electricity. It is difficult to clearly hear the fetal heart tones prior to 18 to 20 weeks gestation. Doppler ultrasound can measure fetal heart tones around weeks 10 to 12. External fetoscopy is compromised in a noisy environment, with an obese mother due to the large abdomen, and in the case of hydramnios. Endoscopic fetoscopy uses a thin (1 mm) fiberoptic scope. Developed in the 1970s, the endoscope was originally inserted transabdominally to visualize the fetus for gross abnormalities suspected by ultrasound or to obtain tissue and blood samples. It was performed after about 18 weeks gestation. Even with practitioner expertise, associated fetal loss was three to seven percent. In the 1980s ultrasound-guided needle sampling of cord blood replaced fetoscopy when samples of fetal blood were required. As laparoscopic and microsurgical techniques have become more common and the instrumentation has become more advanced technologically, the expertise gained has carried over to fetoscopy, improving its use for fetal diagnostic and therapeutic purposes. Fetal surgery performed through an open maternal abdomen has a higher risk of such complications as infection, premature rupture of membranes, preterm labor, or fetal death. If surgery is performed via fetoscopy, which requires a very small transabdominal incision, the risks are much smaller. Techniques have advanced enough to allow some fetoscopy to be performed in the first trimester via the cervix. The term obstetrical endoscopy may be used for surgery on the placenta, umbilical cord or on the fetal membranes. The term endoscopic fetal surgery is used for such procedures as the repair of a fetal congenital diaphragmatic hernia, enlarged bladder, and spina bifida.

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END OF 40 WEEKS GESTATION.

Fetoscopy

decreased uterine irritability, and decreased risk for early pregnancy termination.

KEY TERMS Auscultation—Auscultation uses the sense of hearing to evaluate such internal organs as the heart or bowel. While the practitioner may simply use his or her ears directly, most commonly auscultation is performed with an instrument, such as a fetoscope or stethoscope. Hydramnios—Hydramnios is the excessive production of amniotic fluid due to either fetal or maternal conditions. Supine—Lying horizontally on one’s back.

The normal fetal heart rate is 120 to 160 beats per minute, regardless of the method used for auscultation (external fetoscopy or Doppler ultrasound). Some variability of fetal heart rate is expected, as the heart rate increases with fetal activity and slows with fetal rest. Results expected using endoscopic fetoscopy will vary depending on the procedure undertaken. The goal is for the maximum benefit with the minimum of risk or complication to both the mother and fetus.

Health care team roles

Preparation The use of external fetoscopy requires access to the maternal abdomen, with the mother lying supine or in a semi-seated position. Afterwards, the mother is able to get up and resume a normal activity level. Preparation for endoscopic fetoscopy will depend on the extent of the procedure, and whether it is performed transcervically or transabdominally. Obtaining a small fetal tissue sample is a smaller procedure by comparison to fetal surgery. Other factors include outpatient versus inpatient stay and anesthesia (both maternal and fetal). For some procedures medication may be administered to temporarily decrease fetal movement to lower the risk of fetal injury. Maternal anesthesia may be local, regional, or general.

Aftercare External fetoscopy does not require aftercare. The care following fetal endoscopic use will depend on the extent of the procedure and the type of anesthesia used. If done on an outpatient basis, the mother and fetus will be monitored for a period of time to assure well-being before discharge. More extensive surgery will require inpatient hospital care.

Complications The only potential complication with external fetoscopy is the potential for missing an abnormal heart rate or rhythm. Endoscopic fetoscopy has the potential for infection to the fetus and/or mother, premature rupture of the amniotic membranes, premature labor, and fetal death. When endoscopic fetal surgery is done instead of open-uterus fetal surgery, the risks to the mother and fetus are decreased. This is because the incision is significantly smaller, with less potential blood loss, 950

Results

Individuals utilizing the external fetoscope include a nurse practitioner, nurse midwife, and obstetrician. For endoscopic fetoscopy, the procedures require a high level of skill and experience by fetal surgeons. During the procedures, a radiology technician may perform an ultrasound and a laboratory technician may be involved in blood sampling. Nurses will participate in both outpatient as well as inpatient procedures. Resources BOOKS

Creasy, Robert K. and Robert Resnik. Maternal-Fetal Medicine, 4th Edition. Philadelphia: W. B. Saunders Company, 1999. Pillitteri, Adele. Maternal & Child Health Nursing, 3rd Edition. Philadelphia: Lippincott, 1999. Scott, James R. et al., eds. Danforth’s Obstetrics and Gynecology. Philadelphia: Lippincott Williams & Wilkens, 1999. PERIODICALS

Deprest, J. A. and E. Gratacos. “Obstetrical endoscopy.” Current Opinions in Obstetrics and Gynecology 11, no. 2 (April 1999): 195–203. Deprest, J. A., T. E. Lerut, and K. Vandenberghe. “Operative fetoscopy: New perspective on fetal therapy?” Prenatal Diagnosis 17, no. 13 (December 1997): 1247–1260. Gratacos, E. and J. A. Deprest. “Current experience with fetoscopy and the Eurofoetus registry for fetoscopic procedures.” European Journal of Obstetrics, Gynecology, and Reproductive Biology 92, no. 1 (September 2000):151–159. Yang, E. Y. and N. S. Adzick. “Fetoscopy.” Seminars in Laparoscopic Surgery 5, no. 1 (March 1998): 31–39. ORGANIZATIONS

American College of Obstetricians and Gynecologists. 409 12th St., S.W., PO Box 96920. Washington, D.C. 20090–6920. .

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Florida Institute for Fetal Diagnosis and Therapy. 13601 Bruce B. Downs Boulevard, Suite 160. Tampa, FL 33613. Phone: 888-FETAL-77, (888–338–2577). Fax: (813) 872–3794. . Neonatology on the Web: Neonatology Teaching Files, Outlines, and Guidelines. .

Esther Csapo Rastegari, R.N., B.S.N., Ed.M

Fever Definition Fever is defined as an abnormally high body temperature or a regulated rise to a new set point of body temperature. While a body temperature above 100°F (37.8°C) is considered to be a fever by some clinicians, a significant fever is usually defined as an oral temperature of 102°F (39°C) or a rectal temperature of 103°F (39.5°C). Fever is a sign of inflammation and represents the body’s response to microbial invasion or to a disease process. Hyperthermia is defined as abnormally high body temperature caused by disruption of the body’s thermoregulatory mechanisms. Hyperthermia occurs when the body’s metabolic heat production or environmental heat load exceeds the normal heat loss capacity (or when normal heat loss is impaired).

Fever occurs when the hypothalamus raises the body’s temperature to a new set point. White blood cells called monocyte-macrophages release proteins called pyrogens when the cells encounter pathogenic microorganisms. The pyrogens act on the hypothalamus, causing it to reset the body’s “thermostat” upward. The vessels that supply the skin with blood often narrow as the body’s temperature is rising. This process, which is called vasoconstriction, reduces sweating and causes the body to retain more heat than it loses. Vasoconstriction in the skin and extremities allows the body to move blood toward its core, which increases the rate of metabolism and induces shivering. The chills that often accompany a fever are caused by this movement of blood to the body’s core, which leaves the skin surface and extremities relatively cool. When the infection or disease process resolves, the hypothalamus attempts to reset the body’s thermoregulation at its normal set point. The body’s cooling mechanisms switch on as the blood returns to the extremities and skin surface, and sweating occurs. Fever is an important component of the immune system’s inflammatory response, though its role is not completely understood. A rise in body temperature has several effects. The pyrogens that trigger the resetting of the body’s thermostat also increase the production of macrophages, which fight off invading bacteria or viruses. Higher temperatures also inhibit the growth of some bacteria, while at the same time activating the immune system. In addition, the increased heart rate that accompanies vasoconstriction also speeds the arrival of white blood cells to the sites of inflammation.

Causes and symptoms Description The normal temperature of the human body fluctuates between 97°F (36.1°C) and 100°F (37.8°C), with the average being 98.6°F (37°C). There is a diurnal pattern of temperature variation in humans, with body temperature being lowest in the morning and highest in late afternoon. In women of childbearing age, there is a small rise in temperature following ovulation during the menstrual cycle, and during the first trimester of pregnancy. The body’s thermoregulatory mechanisms include changes in muscle tone, vascular tone, and sweat production, which serve to balance body heat produced by metabolism with heat lost to the environment. This balance is regulated by the hypothalamus, a small structure in the brain below the thalamus.The body’s temperature regulation can be upset by environmental factors (external heat and humidity); by disorders or conditions that inhibit sweat production or evaporation; and by infectious diseases.

Causes Fever can be caused by a wide variety of diseases and disorders, including: • infectious diseases, which may be caused by viruses, bacteria, fungi, rickettsiae, or parasites • autoimmune disorders, including systemic lupus erythematosus, rheumatic fever, adult rheumatoid arthritis, Wegener’s granulomatosis, polyarteritis nodosa, and Still’s disease • disorders of the central nervous system (CNS), including head injuries, multiple sclerosis, tumors of the brain or spinal cord, and cerebral hemorrhage • cancers, including primary cancers of the colon, rectum, kidney, and liver, and metastatic cancers of the liver • cardiovascular disorders, including myocardial infarction and pulmonary embolism

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OTHER

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• reactions to such medications as methyldopa, quinidine, hydralazine, phenytoin, chlorpromazine, carbamazepine, anti-cancer drugs, and antibiotics • endocrine disorders, including hyperthyroidism (thyroid storm) and pheochromocytoma • gastrointestinal disorders, including alcoholic hepatitis, inflammatory bowel disease (IBD), and liver abscess • inflammation associated with indwelling catheters, intravenous lines, and nasogastric tubes • neuroleptic malignant syndrome, which is a rare and potentially fatal reaction to certain antipsychotic medications Fever patterns Fevers may be classified as intermittent (the patient’s temperature falls to normal at some point during the day); sustained (the temperature remains high); or relapsing (periods of fever are followed by several days of normal temperatures). The fever pattern may be helpful in the differential diagnosis; for example, fevers related to medication reactions are more often sustained than intermittent. A relapsing pattern suggests malaria. The degree of temperature elevation in a fever does not necessarily correspond to the seriousness of the illness. In general, children with fevers run higher temperatures than adults, while elderly persons and newborns may have less marked fevers.

Temperature measurement A variety of different devices are available to register body temperature, including the traditional glass thermometers used for oral or rectal temperature readings. More recently, sophisticated electronic devices have been introduced that register body temperature as a digital readout. For younger children and infants, there are forehead meter strips and pacifiers with temperature-sensitive readouts.

Treatment Routine measures Most fevers are caused by common infections, are short-lived, and do not require symptomatic treatment. The patient’s comfort, however, may be improved by measures to remove body heat, antipyretic medications, and fluid replacement. Measures to remove body heat include alcohol or cold sponges; ice bags; and ice baths. The most common antipyretic medications are aspirin or acetaminophen, 350–650 mg every four hours. Children or adolescents with influenza-like symptoms should not be given aspirin without consulting a physician because of the possibility of developing Reye’s syndrome, a rare disorder characterized by vomiting and liver dysfunction. Fluid replacement is an important part of fever treatment. Extra fluid is required to prevent electrolyte imbalance as well as to replace fluid lost through perspiration. Emergency treatment

Diagnosis The differential diagnosis of fever is complicated by the variety of possible causes. In most cases, the patient’s history—including a medication history and history of exposure to infectious diseases—vital signs, a complete blood count, and blood cultures will help to narrow the number of possible causes. In fevers of unknown origin (FUOs), however, the physician may need to schedule a chest x-ray or ultrasound and CT imaging. Fevers of unknown origin (FUOs) The origin of some fevers is difficult to determine. The term “fever of unknown origin” (FUO) has been applied to cases of fever in which the patient’s temperature remains over 101°F (38.3°C) for three weeks and in which the diagnosis is not apparent after seven or more days of studies. The most common cause of FUOs is an infectious disease of some kind, although many cancers present initially as FUOs. About 15% of FUOs never receive a definite diagnosis. 952

Body temperature over 105.8°F (41°C) in an adult is a medical emergency and requires immediate treatment. The following indications in specific patient groups may require emergency treatment: • newborns (three months or younger) with fever of 100.5°F (38°C) or higher • infants or children with fever of 103°F (39.4°C) or higher • adults with fever of 101°F or higher lasting longer than three days; or a temperature of 100.5°F lasting longer than three weeks without other symptoms A very high fever in a small child can trigger febrile seizures, and therefore requires immediate treatment. A fever accompanied by a stiff neck, severe headache, throat swelling, and changes in mental status may indicate the presence of meningitis or another serious infection, and should be brought to the immediate attention of a physician. High fever does not always produce sweating or diaphoretic symptoms, which indicates weakness in the body’s defenses against severe disease.

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Prognosis Most fevers caused by infection end as soon as the immune system rids the body of the pathogen and do not produce any lasting effects. Exceptions include fevers associated with meningitis, typhoid, or scarlet fever. High fevers can produce major disturbances of the body’s metabolism and alter the body’s responses to medications. In addition, a high fever during the first trimester of pregnancy increases the risk of such birth defects as anencephaly (absence of a portion of the skull and brain). The prognosis for fevers associated with such chronic conditions as autoimmune disorders depends on the stage of the disease and its management.

Health care team roles Nurses assess and record the fever patient’s signs and symptoms. Nurses as well as physicians can obtain relevant information from the patient’s medical history. Home health care and visiting nurses may also help to educate patients about at-home treatment of fevers. In some cases, home care nurses may counsel patients and caregivers over the phone, advising when the condition warrants in-person medical attention.

Prevention Since most fevers are caused by infectious agents, careful attention to proper methods of food handling, hand washing, and similar public health measures is an important form of prevention. Fevers related to medication reactions can sometimes be prevented by substitution of drugs that are less likely to produce such reactions. Fevers related to indwelling catheters and similar devices may be avoided by removing them as soon as they are no longer required. Hyperthermia related to environmental conditions may be prevented by proper attention to climatic conditions, adequate fluid and electrolyte intake, and acclimatization to hot environments. Educating the public about the early signs of heat disorders is another important preventive measure. Resources BOOKS

Gelfand, Jeffrey, et al. “Fever, Including Fever of Unknown Origin.” Harrison’s Principles of Internal Medicine, edited by Kurt Isselbacher, et al. New York: McGraw-Hill, 1997. Haist, Steven A., MD, John B. Robbins, MD, and Leonard G. Gomella, MD. “Fever.” Internal Medicine On Call, 2nd ed. Stamford, CT: Appleton & Lange, 1997.

KEY TERMS Antipyretic—A drug that lowers body temperature, such as aspirin or acetaminophen. Autoimmune disease—A disorder in which the immune system attacks the body’s own cells. Febrile seizure—Convulsions brought on by high body temperature and inflammation of the brain or brain covering. Hyperthermia—Abnormally high body temperature that occurs when the body’s metabolic heat production or environmental heat load exceeds the normal heat loss capacity (or when heat loss is impaired). Heat stroke is an example of hyperthermia. Hypothalamus—A region in the posterior section of the forebrain that regulates body temperature, sleep cycles, and the activity of the pituitary gland. Intermittent—A fever pattern marked by the patient’s temperature returning to normal at some point during the day. Macrophage—A type of large white blood cell that helps the body fight off pathogenic microorganisms by ingesting them. Malignant hyperthermia—A rare inherited condition in which a person develops a very high fever when given general anesthetics or muscle relaxants in preparation for surgery. Pyrogen—A substance that produces a rise in body temperature. Bacterial toxins are one type of pyrogen. Relapsing—A fever pattern in which periods of fever alternate with several days of normal temperatures. Reye’s syndrome—A rare disorder that occurs primarily in children recovering from a viral illness and associated with aspirin usage. It is characterized by vomiting, swelling of the brain, and liver dysfunction. Vasoconstriction—Narrowing of the blood vessels, which serves to conserve body heat and maintain or raise blood pressure.

“Respiratory Viral Diseases.” Chapter 162 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 1999.

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OTHER

Fever. MayoClinic.com. September 11, 2000. . (accessed June 18, 2001).

Lisette Hilton

Fever blister see Cold sore Fiber-modified diet see Diet therapy

Fibrin degradation products test Definition When injury occurs to a blood vessel wall, thrombin (a coagulation enzyme) is formed in the first stage of a complicated series of steps called the coagulation cascade. In the second phase, fibrinogen, a coagulation protein made by the liver, is converted to fibrin, which results in the formation of a gel-like meshwork at the site. This fibrin mesh is altered by the action of factor XIIIa which cross-links fibrin polypeptides, forming a stable clot. As the site heals, the clot is broken down by the enzyme plasmin. This process, called fibrinolysis, is initiated by a protein called tissue plasminogen activator that is released from blood vessel cells adjacent to the injured site. Plasminogen activator converts plasminogen to an enzyme called plasmin. The plasmin splits polypeptides from the fibrin clot. These fragments are known as fibrin degradation products (FDP). Fibrin degradation products are fragments (polypeptides) produced when either fibrin or fibrinogen is broken down by the enzyme plasmin. There are four principal fibrin degradation products called X, Y, D, and E that are liberated in various combinations. When a fibrin clot is broken down by plasmin, the last fragment to be degraded is one consisting of two D and one E subunits. This is split, releasing the E fragment and two D fragments that are covalently linked together. This fragment is called Ddimer, and it is produced from fibrin but not from fibrinogen degradation.

Purpose A test for FDP may be requested by a physician when excessive bleeding occurs and thrombosis or other serious disorder in the coagulation mechanism is suspected. The FDP assay measures amounts of the fibrin and fibrinogen split products in the blood and directly indicates the level 954

of activity of the fibrinolytic system. High levels of FDP will indicate increased fibrinolysis. Excessive fibrin degradation products are released into the plasma in three main conditions: disseminated intravascular coagulation (DIC), thromboembolytic therapy, and primary fibrinogenolysis. Fragments X, Y, E, and D are released whenever either fibrin or fibrinogen is broken down by plasmin. This degradation occurs in all three situations. Normal blood plasma does not have significant amounts of D-dimer. It is present in the blood in detectable amounts in several conditions, most notably in disseminated intravascular coagulation (DIC), a rare disruption in normal coagulation in which rapid intramicrovascular (within the blood vessels) coagulation occurs at the same time as fibrinolysis (clot dissolution mechanism). The D-dimer test is used to diagnose DIC. It is also frequently used to help diagnose deep-vein thrombosis (clots in veins); pulmonary embolism (clots in the lungs); the thrombosis of malignancy; and sickle cell anemia (a form of anemia characterized by bleeding episodes); and to monitor the effects of thrombolytic drugs. Thrombolytic drugs that may increase D-dimer levels are barbiturates, heparin, streptokinase, and urokinase. Levels of D-dimer will be elevated in these conditions.

Description When functioning normally, coagulation and fibrinolysis maintain hemostasis (the normal fluid state of blood in the circulatory system) by regulating clot formation and dissolution. When bleeding occurs, coagulation results in production of a clot at the site of injury, and subsequent fibrinolysis dissolves the clot as the vessel wall heals. The fibrinolytic system is highly complex. A deficiency of plasminogen will result in increased risk of thrombosis. Plasmin is inactivated by several proteases, which are enzymes that catalyze the breakdown of polypeptides. A deficiency of one of these can result in spontaneous bleeding. FDPs themselves can neutralize the activity of some coagulation factors and interferere with normal clot formation. In three conditions, disseminated intravascular coagulation, thromboembolytic therapy, and primary fibrinogenolysis the fibrinolytic activity of the plasma is increased. When this occurs, depletion of coagulation factors, including fibrinogen, results in uncontrolled bleeding. Measurement of FDP and Ddimer are used to identify these causes of hemorrhage. DIC results in the formation of circulating small fibrin clots formed by a condition that triggers the coagulation cascade. Coagulation factors become depleted and hemorrhage results. DIC is a rapidly progressing condition caused by an underlying disease or trauma, such as the clinical conditions shown below.

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• tissue trauma, such as major surgery, severe trauma and burns, rejection of transplant, and heatstroke • hemolytic processes (destruction of red blood cells), such as transfusion of mismatched blood, drowning, complications of infection, and certain types of poisoning • malignancies, such as solid tumors, leukemia, and other forms of cancer • infections, such as bacterial infections, septicemia, Rocky Mountain spotted fever, some viral infections, and parasitic infections • miscellaneous clinical conditions, such as diseases of the liver and pancreas, uremia, shock, stroke, severe heart failure, and aortic aneurysm (rupture of the aorta) Coronary artery disease can result in the formation of a blood clot at the site of blockage in the heart vessels. One alternative form of treatment is the administration of a thrombolytic agent such as streptokinase or tissue plasminogen activator. These drugs act by stimulating fibrinolysis, and consequently they may cause both the fibrin clot and fibrinogen to break down. Fibrinogen depletion and accumulation of FDP can interfere with coagulation, causing spontaneous hemorrhage. Primary fibrinogenolysis is a condition in which fibrinogen is broken down to fibrin in the absence of a clot. Unlike DIC, the formation of intravascular thrombi does not occur. However, if severe, hemorrhage can result because the body’s supply of fibrinogen becomes depleted. Causes include shock, hypoxia, heat stroke, hemorrhage, surgery, and liver disease. FDP tests will yield abnormal results in all three conditions described above because the fragments detected are produced when either fibrin or fibrinogen is split by plasmin. Therefore, the FDP test is not specific for thrombotic diseases such as DIC or deep vein thrombosis. The FDP test uses latex particles coated with anti-D and anti-E. When mixed with plasma, these antibodies react with D and E fragments of both fibrin and fibrinogen, forming a clump. The D-dimer test measures only the D fragments of fibrin that are covalently bound together. When a fibrin clot is stabilized by factor XIIIa, the D domains of adjacent molecules become linked together. The action of plasmin causes these to be released from the clot as a dimer, which is a molecule composed of two identical simpler molecules. Therefore, the D-dimer test will be positive only when fibrin degradation has occurred. This happens in DIC, after thromboembolytic therapy, and in such throm-

botic conditions as deep vein thrombosis and pulmonary embolism, but does not occur in primary fibrinogenolysis. D-dimer is detected by a latex agglutination test. Latex particles coated with anti-D that bind only to Ddimer are used. These particles will clump when mixed with serum that has an increased level of D-dimer. Since D-dimer levels parallel the amount of fibrinolytic activity in DIC, a quantitative test is often used to evaluate the severity of the disease. The test used is a two-site double antibody sandwich immunoassay.

Precautions Blood for FDP testing is collected by venipuncture into tubes containing EDTA, citrate, or heparin anticoagulant. The nurse or phlebotomist performing this procudure should follow universal precautions for the prevention of transmission of bloodborne pathogens. Performing a venipuncture to obtain a blood sample for the D-dimer test may be contraindicated if the patient is exhibiting prolonged bleeding from other sites. In this case the nurse or phlebotomist should consult the testing physician, who will determine an alternate means of obtaining a blood sample (such as placement of a catheter). There are no other notable precautions associated with performing the D-dimer test.

Preparation There is no special preparation for the D-dimer test. No fasting is required.

Aftercare Following venipuncture to obtain blood samples for the D-dimer test, the laboratory technologist, nurse, or phlebotomist drawing the sample should apply pressure to the site to stop any residual bleeding. The venipuncture site should then be carefully inspected to make sure that the wound has closed and no bleeding is present. If bleeding continues even after pressure is applied, this event should be reported to the testing physician.

Complications DIC often involves a rapidly changing hemostatic condition. Patients with DIC or thrombosis may be in serious condition and will likely not be ambulatory; more typically, patients with suspected DIC or thrombosis will be hospitalized. Nurses should be alert to any change in the patient’s condition. Noticeable changes in the patient’s condition at the time of venipuncture should be reported to the patient’s physician. The venipuncture site should be examined for bleeding and any prolonged

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• complications of pregnancy, such as toxemia, abortion, cesarean section, placenta previa, and other conditions

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test. Qualitative results may be reported only as positive or negative. Typical FDP results are listed below.

KEY TERMS D-dimer—A fibrin degradation fragment or product that is produced by the action of plasmin on fibrin in the clot dissolution process. Disseminated intravascular coagulation (DIC)— A disruption in hemostasis in response to an underlying disease or trauma. It is associated with the release of a tissue factor that triggers coagulation and activates rapid thrombin formation and fibrinolysis throughout the vascular system. Fibrin—A protein formed in the blood as an important component of the coagulation process. Fibrin degradation products—Known also as fibrin split products, fibrin degradation products are formed when the fibrinolytic system is activated in response to the formation of clots in the vascular system. Fibrin degradation products, including Ddimer, will be present in fibrinolysis or thrombosis. Fibrinolysis—The dissolution of clots by an activated fibrinolytic system. When clot formation occurs, the fibrinolytic system activates factors that lead to the formation of plasmin, which degenerates the fibrin in the clot. Hemostasis—A regulating process that maintains blood in a fluid state and prevents the loss of blood through clot formation when the vascular system is compromised. Plasmin—Plasmin is an enzyme formed in the activation of the fibrinolytic system to dissolve clots. Plasmin breaks down the fibrin in a clot into the fragments that are known as fibrin degradation products. Thrombolytic drugs—Anticoagulants used to inhibit clotting. Thrombolytic therapy is used when increased fibrin degradation products are present, such as in patients who have had a heart attack or who have a compromised coagulation mechanism or a history of thrombosis. Thrombosis—The presence of a clot or clots in the vascular system.

bleeding that cannot be stopped by applying pressure should be reported to the physician immediately.

A clumping reaction is reported as positive. If plasma is diluted, reporting is as follows: • If the undiluted plasma only is positive: equal to or greater than 2 mcg/mL but less than 10 mcg/mL. • If a 1:5 dilution of plasma is positive: equal to or greater than 10 mcg/mL but less then 80 mcg/mL. • If a 1:20 dilution is positive: equal to or greater than 80 mcg/mL. D-dimer results are reported as follows. • Qualitative negative: less than 250 nanograms/mL. • Qualitative positive: equal to or greater than 250 ng/mL. • Quantitative: normally less than 250 ng/mL or less than 250 micrograms/L.

Health care team roles A physician orders the FDP tests and interprets them. The testing physician must obtain an accurate patient history, especially to determine if the patient is taking any drugs that can affect the test results and to learn about any recent illness, trauma, or symptoms that could be related to DIC or thrombosis. The procedure should be explained to the patient by the unit nurse, who should be aware of the degree of seriousness of the patient’s condition. FDP tests are performed by clinical laboratory scientists/medical technologists or by clinical laboratory technicians/medical laboratory technicians. Training Laboratory technologists performing D-dimer tests will have studied hematology and coagulation, enabling them to understand coagulation and the fibrinolytic system. Hands-on clinical laboratory training will prepare technologists to perform agglutination tests or monoclonal antibody tests for D-dimer. Nursing personnel responsible for patients undergoing D-dimer testing will understand the patient’s condition and will be trained to observe changes that may signal a critical hemostatic event. Resources

Results Reference ranges for FDP tests will vary according to the test method used and the laboratory performing the 956

• Undiluted plasma is negative (no clumping): FDP is reported as less than 2 micrograms/mL.

BOOKS

Jacobs, David S. Laboratory Test Handbook, 5th ed. Hudson, OH: Lexi-Comp Inc., 2001.

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ORGANIZATIONS

American Nurses Association. 600 Maryland Ave. SW, Ste. 100 West, Washington, DC 20024. (800)274-4ANA. . American Society of Clinical Pathologists. 2100 West Harrison St., Chicago, IL 60612 (312) 738-1336. .

L. Lee Culvert

Fibrinogen test see Coagulation tests

Fibromyalgia Definition Fibromyalgia (formerly known as fibrositis) is an inflammation of the fibrous or connective tissue (muscles, joints, ligaments, and tendons) of the body. Widespread pain, fatigue, and multiple tender points characterize this condition. Other symptoms may include sleep disturbance, headache, and bowel disturbances.

Description Fibromyalgia is more common than previously thought, with as many as 3–6% of the population affected by the disorder. Fibromyalgia is more prevalent in adults than children, with more women affected than men—particularly women aged 35 to 55. Fibromyalgia symptoms have often been characterized as psychosomatic in origin. Recent research has proved that belief false, and fibromyalgia is now regarded as a disorder that can be diagnosed and treated effectively with ongoing care and follow-up.

Causes and symptoms The exact cause of fibromyalgia is not known. There are events that can precipitate the symptoms of fibromyalgia, including sports injuries, car accidents, falls, or other trauma to the body. Sometimes it occurs in several members of a family, suggesting that there may be an inherited tendency for the disorder. People with fibromyalgia are most likely to complain of three pri-

mary symptoms: pain in muscles, joints, and ligaments; stiffness; and excessive fatigue. Widespread, ongoing pain is characteristic of fibromyalgia. A careful history and physical examination may uncover additional areas of pain when the chief complaint lies in only one area of the body. The most significant area of pain may shift over time, and the pain can be intermittent. Pain is the major symptom of fibromyalgia, with aches, tenderness, and stiffness of multiple muscles, joints, and soft tissues. The pain may also tend to move from one part of the body to another. It is most common in the neck, shoulders, chest, arms, legs, hips, and back. Although the pain is present most of the time and may last for years, the severity of the pain is variable and dependent on individual patient perception. Symptoms of sleeplessness and overall fatigue may result from the individual’s chronic pain, coupled with anxiety about the problem and how to find relief. The body’s inflammatory response also produces chemicals in the brain that are known to contribute to fatigue. Other common symptoms are tension headaches, difficulty swallowing, recurrent abdominal pain, diarrhea (irritable bowel syndrome), and numbness or tingling of the extremities. Stress, anxiety, depression, lack of dietary control, or lack of sleep can increase symptoms. Intensity of symptoms varies. Some patients gradually improve, while others have recurrent episodes of their symptoms.

Diagnosis Diagnosis is difficult, and the disease may be overlooked because symptoms of fibromyalgia are vague and general. In addition, fibromyalgia may mimic symptoms of other diseases and conditions. Support staff should question the patient regarding sleep and exercise patterns, diet, and emotional conditions. Coexisting nerve and muscle disorders, such as rheumatoid arthritis, spinal arthritis, or Lyme disease, may further complicate the diagnostic process. Presently, there are no tests available to specifically diagnose fibromyalgia. The final diagnosis is frequently made after a period of time in which the physician observes the patient and rules out other medical conditions with similar symptoms. Because of the emotional distress experienced by people with this condition and the influence of stress on the symptoms themselves, fibromyalgia has often been labeled a psychosomatic condition. Recognition of the underlying inflammatory process involved in fibromyalgia has helped promote the validity of this disease. Nurses, nurse practitioners or physician’s assistants should inquire into the emotional state of the patient, and be prepared to note it in the chart. Mental health consultation may be necessary due to depression or anxiety, and

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Pagana, Kathleen D., and Timothy J. Pagana. Manual of Diagnostic and Laboratory Tests.St. Louis, MO: Mosby, Inc., 1998. “Hemostasis and Coagulation Disorders.” Sec. 11, Chapter 131, Merck Manual Online, 17th ed. Whitehouse Station, NJ: Merck & Co., Inc. 2001. .

Fibromyalgia

emphasis on the importance of a support group for fibromyalgia patients should be given. In 1990, the America College of Rheumatology developed standards for fibromyalgia that health care practitioners can use to diagnose this condition. According to these standards, a person is thought to have fibromyalgia if he or she has widespread pain in combination with tenderness for at least three months in at least 11 of the 18 sites known as trigger points. Trigger point sites include the neck, spine, hip, elbow, knee, and shoulder.

Treatment There is no known cure for fibromyalgia. Therefore, the goal of treatment is successful symptom management. Treatment usually requires a combination of therapies, including exercise, proper rest, and diet, and pharmacologic treatment. Patient education by the health care team is imperative so that the patient has a clear understanding of his or her role in the recovery process and the successful management of this condition. Physical regimens found to be helpful include a regular stretching program and low-impact aerobic activities that increase the heart rate. Exercise programs should be approved by a physician or physical therapist, and include both warm-up and cool-down sessions, with special attention given to avoiding exercises that cause joint pain. Adequate rest is essential in the treatment of fibromyalgia. Nutrition is an important component in the management of this condition. The patient’s diet should include a wide variety of fruits and vegetables to provide the body with trace elements and minerals that are necessary for healthy muscles. Avoidance of stimulating drinks (such as coffee, tea, or any drink containing caffeine), avoidance of alcohol (may lead to sleeplessness) and such medications as decongestants prior to bedtime is advised. If diet, exercise, and adequate rest do not relieve the symptoms of fibromyalgia, medication may be prescribed. Medications that have been found to have some benefit include antidepressant drugs, muscle relaxants, and nonsteroidal anti-inflammatory drugs (NSAIDS). People with fibromyalgia often need a rheumatology consultation (a meeting with a doctor who specializes in disorders of the joints, muscles, and soft tissue) to decide the cause of various rheumatic symptoms, to be educated about fibromyalgia and its treatment, and to exclude other rheumatic diseases. A physician must recommend a treatment program that is individualized to meet the patient’s needs. 958

Alternative treatment Massage therapy can be helpful, especially when a family member is instructed on specific massage techniques to manage episodes of increased symptoms. Specific attention to mental health, including behavior modification and psychological consultation, may also be important because depression and anxiety may precede or accompany an incident of fibromyalgia. Other alternative therapies, including homeopathic medicine, Chinese traditional medicine (both acupuncture and herbs), polarity therapy, and Western botanical medicine, can assist the person with fibromyalgia in day-to-day functioning and contribute to alleviation of symptoms.

Prognosis Fibromyalgia is a chronic condition, but causes no body damage or deformity. It does not cause damage to internal organs, as opposed to conditions such as rheumatoid arthritis, which leads to joint deformity. Treatment is based on the relief of symptoms, so a cure is not a realistic goal. Management of the condition may allow patients to return to a higher level of function at work, play, and home.

Health care team roles Fibromyalgia can be a stressful and frustrating condition for a majority of patients. Successful treatment often requires a period of trial and error to pinpoint which agents and activities work best for the individual patient. Patience while waiting for diagnosis and treatment should be stressed by support staff, along with reassurance that the physician is working to find a treatment regimen that will provide relief. However, there is no set treatment that works for every patient. Even the process of diagnosing fibromyalgia can take time, which also leads to patient frustration. Therefore, support from the health care team and coordination of care through followup calls to outside health care providers is needed to avoid actually worsening the patient’s condition due to undue stress. Nursing parameters are pain management, improved sleep management, introduction of relaxation techniques (including massage and biofeedback if needed), and monitoring alternative treatments and medication. There could be a wide variety of health care providers on a patient’s health care team: nurses, physicians, a rheumatologist or other subspecialist, nutritionist, physical therapist, alternative medicine caregiver, or mental health care providers. This requires that the health care providers who most frequently see the patient coordinate and record in the patient’s medical chart all treatments being undertaken at any given time. Coordination

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Prevention There is currently no way to specifically prevent fibromyalgia. However, adequate sleep and nutrition, stress management, safe levels of exercise, and annual check-ups are important in the avoidance of this condition. Resources PERIODICALS

“Information for Patients Living with Fibromyalgia.” American Family Physician 62, no. 7 (2000):1587. Millea, PJ, Holloway RL. “Treating fibromyalgia.” American Family Physician 62, no. 7 (2000):1575-1587. Wolfe, F., and H.A. Smythe, et al. “1990 Criteria for the Classification of Fibromyalgia.” American College of Arthritis and Rheumatology 33 (1990): 160-172. OTHER

“Fibromyalgia: What it is and how to manage it.” .

Michele R. Webb

Fibrosarcoma see Sarcomas Filling materials see Restorative dental materials Filmless imaging see Computed radiography

Fine motor skills Definition Fine motor skills encompass the abilities required to control the smaller muscles of the body for writing, playing an instrument, artistic expression, and craft work.

The muscles required to perform fine motor skills are generally found in the hands, feet, and head.

Description Fine motor skill involves deliberate and controlled movements requiring both muscle development and maturation of the central nervous system. Although newborn infants can move their hands and arms, these motions are reflexes that a baby cannot consciously start or stop. The development of fine motor skills is crucial to an infant’s ability to experience and learn about the world and thus plays a central role in the development of intelligence. Like gross motor skills, fine motor skills develop in an orderly progression, but at an uneven pace characterized by both rapid spurts and, at times, frustrating but harmless delays. In most cases, difficulty with acquiring certain fine motor skills is temporary and does not indicate a serious problem. However, medical help should be sought for children who are significantly behind their peers in multiple aspects of fine motor development; or if they regress, losing previously acquired skills.

Function Fine motor skills develop over a long period of time, primarily during childhood. However, athletes, musicians, jewelry makers, physicians, machinists, and others who engage in activities requiring high degrees of manual dexterity and control may spend decades improving their level of muscle coordination and fine motor skills. Infancy The hands of newborn infants are closed most of the time and, like the rest of their bodies, are not well controlled. If its palm is touched, an infant will make a very tight fist, but this is an unconscious action called the Darwinian reflex, and it disappears within two to three months. Similarly, an infant will grasp at an object placed in the hand, but without any conscious awareness of the act. At some point, hand muscles will relax, and an infant will drop an object, equally unaware that it has fallen. Babies may begin flailing at objects that interest them by two weeks of age but cannot grasp them. By eight weeks, they begin to discover and play with their hands, at first solely by touch, and then, at about three months, by sight as well. At this age, however, the deliberate grasp remains largely undeveloped. Hand-eye coordination begins to develop between the ages of two and four months, inaugurating a period of trial-and-error practice at sighting objects and grabbing at them. At four or five months, most infants can grasp an

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of care increases patient compliance, and may boost the patient’s perception of his or her level of function. Patient education is an integral part of the treatment and management of fibromyalgia and its symptoms. Patients should be supported both physically and emotionally. Chronic pain may make it more difficult to communicate with a patient in a manner that promotes professionalism and optimal care. Constant cognizance of the treatment goals (to control pain and increase level of function) is needed as and well as positive reinforcement of compliance with treatment suggestions and monitoring of patient milestones.

Fine motor skills

awkward position called the palmar grasp, which makes it difficult to hold on to and manipulate the object. By the age of eight to ten months, a finger grasp begins, but objects can only be gripped with all four fingers pushing against the thumb, which still makes it awkward to grab small objects. The development of the pincer grip, the ability to hold objects between the thumb and index finger, gives infants a more sophisticated ability to grasp and manipulate objects, and also to drop them deliberately. By about the age of one, an infant can drop an object into a receptacle, compare objects held in both hands, stack objects, and nest them within each other. Toddler period Toddlers develop the ability to manipulate objects with increasing sophistication, including using their fingers to twist dials, pull strings, push levers, turn book pages, and use crayons to produce crude scribbles. Dominance of either the right or left hand usually emerges during this period as well. Toddlers also add a new dimension to touching and manipulating objects by simultaneously being able to name them. Instead of only random scribbles, their drawings include such patterns as circles. Their play with blocks is more elaborate and purposeful than that of infants, and they can stack as many as six blocks. They are also able to fold a sheet of paper in half (with supervision), string large beads, manipulate snap toys, play with clay, unwrap small objects, and pound pegs. A six-month-old baby demonstrates fine motor skills. (Photo Researchers, Inc. Reproduced by permission.)

Preschool

object that is within reach, looking only at the object and not at their hands. Referred to as “top-level reaching,” this achievement is considered an important milestone in fine motor development. At the age of six months, infants can typically hold on to a small block for a brief period, and many have started banging objects. Although their grasp is still clumsy, they have acquired a fascination with grabbing small objects and trying to put them in their mouths. At first, babies will indiscriminately try to grasp things that cannot be grasped, such as pictures in a book, as well as those that can, such as a rattle or ball. During the latter half of the first year, they begin exploring and testing objects before grabbing, touching them with an entire hand and eventually poking them with an index finger. One of the most significant fine motor accomplishments is the pincer grip, which typically appears between the ages of 12 and 15 months. Initially, an infant can only hold an object, such as a rattle, in the palm, wrapping fingers (including the thumb) around it from one side—an 960

The more delicate tasks facing preschool children, such as handling silverware or tying shoelaces, represent more of a challenge than most of the gross motor activities learned during this period of development. The central nervous system is still in the process of maturing sufficiently for complex messages from the brain to get to a child’s fingers. In addition, small muscles tire more easily than large ones, and the short, stubby fingers of preschoolers make delicate or complicated tasks more difficult. Finally, gross motor skills call for energy, which is boundless in preschoolers, while fine motor skills require patience, which is in shorter supply. Thus, there is considerable variation in fine motor development among children of this age group. By the age of three, many children have good control of a pencil. Three-year-olds can often draw a circle, although their attempts at drawing people are still very primitive. It is common for four-year-olds to be able to use scissors, copy geometric shapes and letters, button large buttons, and form clay shapes with two or three parts. Some can print their own names in capital letters.

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School age By the age of five, most children have clearly advanced beyond the fine motor skill development of the preschool age. They can draw recognizably human figures with facial features and legs connected to a distinct trunk. Besides drawing, five-year-olds can also cut, paste, and trace shapes. They can fasten visible buttons (as opposed to those at the back of clothing), and many can tie bows, including shoelace bows. Their right- or left-handedness is well established, and they use the preferred hand for writing and drawing.

Role in human health Nurturing the development of fine motor skills is considerably more complicated than developing gross motor skills. Helping a child succeed in fine motor tasks requires planning, time, and a variety of play materials. Fine motor development can be encouraged by activities that youngsters enjoy, including crafts, puzzles, and playing with building blocks. Helping parents with everyday domestic activities, such as baking, can be fun for a child in addition to developing fine motor skills. For example, stirring batter provides a good workout for hand and arm muscles, and cutting and spooning out cookie dough requires hand-eye coordination. Even a computer keyboard and mouse can provide practice in finger, hand, and hand-eye coordination. Because the development of fine motor skills plays a crucial role in school readiness and cognitive development, it is considered an important part of a preschool curriculum. Montessori schools in particular were early leaders in emphasizing the significance of fine motor tasks and the use of learning aids such as pegboards and puzzles in early childhood education. The development of fine motor skills in children of low-income parents, who often lack the time or knowledge required to foster these abilities, is a key ingredient in the success of such programs as Head Start.

Common diseases and disorders There are a range of diseases that decrease one’s ability to perform tasks that require fine motor skills. Among young persons, such developmental problems as genetic disorders, muscular dystrophy, cerebral palsy and some neurological conditions adversely impact fine motor skill development. Among older persons, arthritis is a common condition. Arthritis affects the joints of the hands and feet, thus impairing the ability of muscles to perform fine movements. Stroke can impair fine motor

KEY TERMS Darwinian reflex—An unconscious action in infants in which if a palm is touched, the infant makes a very tight fist. This instinct disappears within two to three months. Gross motor skills—The abilities required to control the large muscles of the body for walking, running, sitting, crawling, and other activities. The muscles required to perform gross motor skills are generally found in the arms, legs, back, abdomen and torso. Locomotion—Such movements as walking. Motor—A term movement.

referring

to

muscles

and

Palmar grasp—A young infant’s primitive ability to hold an object in the palm by wrapping fingers and thumb around it from one side. Pincer grip—The ability to hold objects between thumb and index finger, which typically develops in infants between 12 and 15 months of age. Top-level reaching—The ability of an infant to grasp an object that is within reach, looking only at the object and not at their hands. Typically develops between four and five months of age.

coordination. Parkinson’s disease affects fine motor movements. Alcoholism and drug use or withdrawal all cause fine motor problems. Resources BOOKS

Hernandez, Kimberly T. Kid’s Play. Laporte, PA: Quest Publishing, 2001. Katzen-Luchenta, Jan. Awakening Your Toddler’s Love of Learning. Phoenix, AZ: Emunah Publishing, 1999. Needleman, Robert D. “Growth and development.” In Nelson Textbook of Pediatrics, 16th ed. edited by Richard E. Behrman et al. Philadelphia, PA: Saunders, 2000, 23-66. Payne, V. Gregory, and Larry D. Isaacs. Human Motor Development: A Lifespan Approach, 4th ed. New York, NY: Mayfield Publishing, 1998. Rosetta, Lani. Labyrinths for Kids. Medford, OR: Leihuna Enterprises, 2001. PERIODICALS

Case-Smith, J. “Effects of occupational therapy services on fine motor and functional performance in preschool children.” American Journal of Occupational Therapy 54, no. 4 (2000): 372-380.

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A human figure drawn by a four-year-old is typically a head atop two legs with one arm radiating from each leg.

First aid

Crowe, T.K., C. McClain, and B. Provost. “Motor development of Native American children on the Peabody Developmental Motor Scales.” American Journal of Occupational Therapy 3, no. 5 (1999): 514-518. Hemgren, E., and K. Persson. “A model for combined assessment of motor performance and behaviour in 3-year-old children.” Uppsala Journal of Medical Science 104, no. 1(1999): 49-85. Kumar, M., S. Hickey, and S. Shaw. “Manual dexterity and successful hearing aid use.” Journal of Laryngology and Otology 114, no. 8 (2000): 593-597. Luck, O., B. Reitemeier, and K. Scheuch. “Testing of fine motor skills in dental students.” European Journal of Dental Education 4, no. 1 (2000): 10-14. Stieh, J., H.H. Kramer, P. Harding, and G. Fischer. “Gross and fine motor development is impaired in children with cyanotic congenital heart disease.” Neuropediatrics 30, no. 2 (1999): 77-82.

University of Scranton. .

L. Fleming Fallon, Jr., MD, DrPH

First aid Definition First aid is the initial basic treatment of an injured or ill person. First aid requires an observer first to evaluate the injured or ill person and then to intervene, using a small amount of supplies.

Purpose

ORGANIZATIONS

American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. (847) 4344000. (847) 434-8000. . [email protected]. American Academy of Physical Medicine and Rehabilitation. One IBM Plaza, Suite 2500, Chicago, IL 60611-3604. (312) 464-9700. (312) 464-0227. . [email protected]. Coping.org, 6319 Chauncy Street, Tampa, FL 33647. (813) 631-5176. Fax: (813) 631-1119. . [email protected] OTHER

BabyCentre (UK). . Fife School District (WA). . Flinders University of South Australia School of Education. . Health on the Net Foundation. . MedHelp International. . Mesa (AZ) Community College. . Michigan State University. . Nova Southeastern University. . Tripod. . 962

First aid is provided to a person immediately following an accident or onset of illness to decrease complications and to offer psychological (emotional) and physical comfort. It is performed to decrease the individual’s pain and suffering until emergency medical technicians (EMTs) or other health care givers arrive on the scene.

Precautions The provision of first aid should never postpone the initial contact with the emergency medical system. The bystander should wear disposable latex gloves if available, in case of contact with blood or body fluids. If gloves are not available, plastic bags or wrap can be used as a protective barrier.

Description First aid is a universal term that encompasses many general concepts for rapid assessment of health crises and intervention. The following sections present the most common injuries and illnesses requiring first aid, and the interventions appropriate in these situations. Changes in mental status ASSESSMENT. With any sudden changes in a person’s brain functioning, first aid should start immediately. Assess the person for:

• unconsciousness • lightheadedness • weakness on one side of body • aggressiveness • confused state

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• headache • blurred or double vision • unsteady balance INTERVENTION. Initiate cardiopulmonary resuscitation (CPR) if the person is not breathing. Secure the area around the person by removing any potential hazards, and maintain a favorable environment by providing an adequate area ventilation and room temperature. The person should be placed in a side-lying position.

Bleeding (hemorrhage) ASSESSMENT. Assessing an injured person for bleeding must be done promptly, with first aid started immediately if there is active bleeding. All blood and body fluids must be regarded as potentially infectious, and protective barriers used. INTERVENTION. Direct pressure should be applied to the hemorrhaging (bleeding) area by placing a clean pad or bandage over the site and pressing down with the palm of the hand. If bleeding persists, increase the amount of pressure to the area. If the person is awake and no latex gloves or other protective barriers are available, have him or her apply direct steady pressure to the hemorrhaging area. If the bleeding occurs on an arm or leg, elevate the bleeding part higher than the person’s heart; this position will help decrease the amount of blood flow to the injured area. When a person is losing blood, body temperature tends to decrease. Maintaining body temperature is an essential first-aid intervention.

Poisoning: inhalation, ingestion, or exposure ASSESSMENT. Initial evaluation of a poison victim is done after the threat of exposure to the rescuer is determined. If noxious gas or fumes remain in the environment, the rescuer must first protect him- or herself and others. The rescuer must move the person to a secure environment as promptly as possible to start first aid. INTERVENTION. The first and most important intervention is to call a poison control center and get instructions on how to proceed. Having information on the type of poison ingested, if possible, as well as reading the label over the phone or spelling out the active ingredients on the bottle, will help the poison control center in determining the appropriate interventions. The rescuer must never induce vomiting or give any substance unless directed by the poison control center.

Burns ASSESSMENT. Burns are categorized by the extent of damage to the skin or underlying tissue. First-degree burns are the least critical; they cause reddening of the skin without blistering. Second-degree burns cause damage to the superficial (outer) and the internal (inner) layers of skin, creating bubble-like sores (blisters) that contain clear, watery liquid. Third-degree burns are the most severe and most damaging of all burns; the destruction of all layers of skin occurs and the burnt area is left open and charred. When applying first-aid concepts to burns, the rescuer must quickly assess the extent of damage to the person’s skin. The rescuer needs to determine through assessment what to do next. INTERVENTION. First-degree burns can usually be treated at home with a sterile burn gel, and complete healing should take place within one week. A person with a second-degree burn greater than the size of his or her palm should seek medical treatment, or if the burn is in a sensitive area like the groin. Third-degree burns need medical attention immediately. Ice application is not recommended for severe burns because ice can cause trauma to the area. Cool to lukewarm water is recommended. The burn victim must be covered, preferably with clean blankets, in order to maintain a normal body temperature.

Head/neck injuries ASSESSMENT. It is vital for the rescuer to determine the nature of the head/neck injury, as well as if the person has had any loss of consciousness. This information should be conveyed to the emergency medical responders to help determine the need for further testing. INTERVENTION. It is important to limit the movement of the victim of a head or neck injury, because it could result in more damage. Do not move the head or neck unless absolutely necessary—for example, if vomiting starts. In such a situation, the rescuer must carefully turn the person to the side in order to prevent inhalation of vomit into the lungs.

Seizure ASSESSMENT. A seizure occurs when the brain emits irregular electrical signals. The person having a seizure usually falls to the ground and shakes. The person may lose urinary or bowel functioning. INTERVENTION. It is important to clear a safe area for a seizure victim. Protecting the skull with a cushion or blanket will help decrease injuries to the head and neck. The rescuer should never restrain the victim or put anything in the mouth. When the seizure stops, place the

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• changes in orientation

First aid

Complications

KEY TERMS Emergency medical technician (EMT)—A person who is trained and certified to provide basic life support. Hemorrhage—To be actively bleeding.

Results

Superficial—A term meaning outermost or not deep.

victim in a side-lying position to avoid the breathing in of mucus and other secretions. Muscle/bone injuries ASSESSMENT. When there have been muscle or bone

injuries, the person initiating first aid should assume that the arm or the leg is broken. INTERVENTION. If the arm or leg appears misshapen,

the rescuer should not try to align it. The rescuer wants to stabilize the injured body part in order to protect it from further injury. Ice application can reduce swelling and pain. Heat should not be used, because it increases circulation to the injured site.

The results of first aid vary with the case. Successful first aid results in the improved health and recovery of the patient.

Health care team roles All health care professionals have a professional obligation to know the basics of first aid. Accidental injuries account for 2.6 million hospital admissions annually. Unplanned injury is the fifth-leading cause of fatalities in the United States. Patient education Health care professionals are in a position that allows them to provide education about first aid to patients. Emphasis on the importance of having a firstaid kit available and well stocked is valuable information to pass on to patients. Information about local areas that offer first-aid training should be offered. Training

Preparation A first-aid kit can have a variety of equipment in it. The basic items should include: • ace bandages in a variety of sizes • antibiotic ointment

Extensive training is not needed for first aid. The Occupational Safety and Health Administration (OSHA) advises that retraining in first aid should occur every three years. Good Samaritan Law

• latex gloves

Legally, health care professionals coming to a person’s aid in an emergency situation are covered under the federal Good Samaritan Law. Protection under this law requires that the situation is deemed an emergency, that no monetary compensation for the treatment is provided, and that the care provided is done “in good faith.” In most U.S. states, health care professionals have no mandatory obligation to help in an emergency situation, but the Good Samaritan Law is in place to protect from liability those who do offer assistance.

• a protective barrier/shield for use in CPR • sterile gauze pads and wraps in a variety of sizes • sealed alcohol packets • scissors • tape • tweezers

Aftercare

Resources

The care needed after first aid varies widely, depending on the type of injury or illness sustained. Health care professionals are excellent resources to consult about appropriate individualized aftercare. 964

Many unexpected complications can happen while providing first aid. The most severe complication is if the patient stops breathing or the heart stops beating. In such a situation, the rescuer should immediately start CPR.

PERIODICALS

American Heart Association. “Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Part 5: New Guidelines for First Aid.” Circulation 102 (August 22, 2000): 77-85.

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OTHER

Fuerst, R. “First Aid Kit Preparation from AAEM Emergency Medical and Family Health Guide: Public Health.” eMedicine.com 2001. (April 1, 2001). Levin, H. “Burns from Consumer Treatment Guidelines: Injury and Wound Problems.” eMedicine.com 2000. (November 30, 2000). Plantz, S. H. “Seizures from Wilderness Emergencies: Medical Disorders.” eMedicine.com 2000. (February 9, 2000).

Lori Ann Beck, R.N., M.S.N., F.N.P.-C.

KEY TERMS Cardiopulmonary resuscitation (CPR)—A series of steps to establish normal breathing following cardiac or respiratory arrest.

• triangular bandage to make a sling or use as a tourniquet • elastic bandage to support a sprain • safety pins to fasten bandages • medical tape to affix a gauze pad to a large wound • plastic resealable bag • scissors • CPR shield • butterfly closures to pull the edges of small wounds together • latex gloves • medicine dropper to administer medicine to children

First aid kit Definition The first aid kit is a portable container of medicines, supplies, and information. It is kept for situations in which quick medical attention is needed for minor injuries.

Purpose A first aid kit is used to treat minor illnesses and injuries in or outside the home, thereby reducing the risk of complications from minor injuries.

Description The American College of Emergency Physicians recommends that every home have a first aid kit to respond to common medical emergencies. The contents of a well-stocked kit should include the following items:

• medicine spoon • petroleum jelly to lubricate rectal thermometers for infants under one year old • heating pad/hot water bottle • tongue depressors • antiseptic wipes to cleanse hands or wounds • cotton-tipped swabs for cleaning wounds • iodine swabs for cleaning around a wound • topical calamine lotion or antihistamine cream for allergies, insect bites, and rashes • acetaminophen in appropriate doses for infants, children, and adults • cough suppressant to relieve coughing in appropriate doses for infants, children, and adults • antibacterial cream • oral rehydration fluid for the treatment of diarrhea

• thermometers for infants, children, and adults

• sunscreen

• rubbing alcohol to clean tweezers, needles, and thermometers

• insect repellent

• tweezers and needles to remove slivers and ticks

• an emergency information list

• first aid manual

• adhesive bandages in assorted sizes • sterile gauze pads (2x2, 4x4, and 5x9 inches) • non-adherent dressings, as burns or abrasions need a non-stick dressing

Operation The items in the kit can be stored in a box or a tote bag where adult members of a family or other group

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Brown, S. M. “Good Samaritan Laws: Protection and Limits.” RN 62 (November 1999): 65-67. Fiske, S. “Why Employees Need First Aid Training.” Occupational Hazards 61 (February 1999): 55-57.

First aid kit A well-stocked first aid kit is essential for every home and workplace. (Custom Medical Stock Photo. Reproduced by permission.)

know where it is located. The kit should be stored out of reach of children, and products should have child safety caps. Follow the manufacturer’s guidelines for the correct use of medications and supplies. The kit should be compact enough to be transported in a car, suitcase, or rucksack if traveling.

Maintenance The kit should be inspected monthly to ensure that the contents are not damaged or out of date.

Health care team roles All members should have knowledge of the appropriate use of all equipment and medication, and the ability to recognize situations in which immediate medical attention is required. The emergency information list should include the following: • telephone numbers of family physicians and pediatricians • the regional Poison Control Center number • numbers of local police, fire, and ambulance services 966

In addition, a list should be compiled of any allergies that a family or team member has, and the treatment required.

Training Adults with access to the first aid kit should have an understanding of the first aid manual and the correct use of all medications and equipment. Attendance at a course in basic first aid will enable them to respond quickly and appropriately to any emergency, equipping them with a knowledge of life-threatening situations and the first aid treatment to be given. At least one person in every large group should be trained in first aid and cardiopulmonary resuscitation (CPR). Resources BOOKS

Schmitt, B.D. “First Aid Kit.” Clinical Reference Systems Annual. 2000, p670. ORGANIZATIONS

American College of Emergency Physicians (ACEP). 1125 Executive Circle, Irving, TX 75038. (800) 798-1822.

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Margaret A Stockley, RGN

Fitness testing see Endurance testing

Flow cytometry analysis Definition Flow cytometry analysis is the classification of cell populations based upon the analysis of light scattering and fluorescence facilitated by a laser. Cells are counted and analyzed as they pass singly through the counting area created by a liquid sheath that flows past the laser. Cells scatter the light from the laser; forward and right-angle scatter are measured to determine size and granularity. This initial light scattergraph (dot plot) is used to select a specific cell population for testing using specific antibodies covalently bound to fluorescent dyes. The laser excites the fluorochrome causing it to emit visible light, so that the cells bound to the dye can be detected.

Purpose Principles of flow cytometry are incorporated into some automated hematology analyzers to determine the reticulocyte (stage preceding a mature red cell) count and the percentage of each type of white blood cell (automated differential count). Flow cytometers are specialized instruments that can measure specific cell subpopulations in blood, bone marrow aspirates, body fluids and tissues. Flow cytometry has many applications including: • Counting of lymphocyte subpopulations to evaluate immunological function and immunodeficiency states. The number of B, T and NK lymphocytes can be counted by flow cytometry to evaluate a person’s cellular immune status. T helper and suppressor cells can be counted to assist in the diagnosis and staging of persons with HIV disease. • Counting of immature white blood cells (blasts) to determine the cell lineage. Cell lineage must be defined to properly classify acute and chronic leukemias and non-Hodgkins lymphomas. Flow cytometry tests for surface markers on early white blood cells to determine the cell lineage (lymphoid vs myeloid), and to determine the stage of cell maturation. • Determining the DNA content of cells. Malignant cells often possess an abnormally high DNA content.

Determination of DNA content, called ploidy analysis, is used to investigate tumor cell populations. Cells from solid tissues (for example, breast tissue) can be made into a suspension and analyzed. • Physically sorting cell subpopulations by applying an electrostatic charge to the cells and using a fluid collecting device to harvest them from droplets passing through the flow chamber. • Evaluation of autoimmune thrombocytopenia, transplant rejection, and autoimmune diseases.

Precautions Universal precautions for the prevention of transmission of bloodborne pathogens is observed when collecting and processing blood, bone marrow, body fluids and tissues for flow cytometry analysis. Blood or bone marrow aspirate specimens may be submitted in sodium heparin (green top tube), EDTA (lavender top tube), or ACD (yellow top tube). Of these, the preferred anticoagulant is sodium heparin. Lithium heparin and other anticoagulants are not used. Lymph node or other tissue specimens are not placed in fixative. They should be submitted fresh, in isotonic saline or transport medium. Specimens should be kept at room temperature if the analysis is done within 24 hours. Otherwise the specimen should be refrigerated, but not frozen.

Description A flow cytometer consists of a laser light source, flow measurement chamber, and an optical system consisting of lenses, filters, and light detectors. Two photomultiplier tubes (light detectors), one at 180 degrees and one at 90 degrees to the laser, are used to measure forward and right-angle scatter, respectively. Three fluorescence detectors, each consisting of a filter and photomultiplier tube, are used to detect fluorescence. The three detectors sense green, orange, and red fluorescence. Cells are identified by sort logic applied to all five of the detector signals using a computer. A typical analysis of blood is performed by first measuring the right-angle and forward light scatter of the cells. The resulting scattergraph is used to identify the counting gate, a set of parameters used to select a subpopulation of cells for further study. The gated area of the scattergraph is the portion in which the cells of interest are found. The gate parameters are selected so that only this cell subpopulation is reported in subsequent fluorescence studies. Portions of the specimen are treated with two monoclonal antibodies, each specific for a cell surface antigen. Each monoclonal antibody is covalently bound to a dif-

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American Red Cross. For information on first aid courses contact the Red Cross. Look in the phone book for your nearest office or email [email protected].

Flow cytometry analysis

KEY TERMS Aneuploidy—An abnormal number of chromosomes within a cell. Antigen—A molecule, usually a protein, that elicits the production of a specific antibody. In flow cytometry studies, an antigen is a cell surface marker that is recognized by a specific antibody and referred to by its cluster of differentiation (CD) number. CD marker—A monoclonal antibody for a specific CD antigen. Gating—The selection of cells that fit a specific set of parameters for further analysis. Only those cells belonging to the gated cell subpopulation are measured. Immunophenotyping—Identification of antigens on the surface of cells using fluorescent-labeled antibodies. The phenotype profile is used to classify the cell. Immune system—The body’s system of defenses against infectious diseases, which includes both cellular and humoral (antibody) responses.

ferent fluorescent dye. There are approximately twodozen fluorochromes in use with flow cytometry, but the most commonly used labels are fluorescein isothiocyanate (FITC) which produces apple-green light and phycoerythrin (PE) which produces orange-red light when excited by the laser. For DNA analysis of cells the label most often used is propidium iodide (PI), which binds to DNA of nuclei and emits orange-red light when excited. The specific surface antigen to which an antibody binds is defined by the cluster of differentiation (CD) number. Each CD number represents a specific antibody combining site on the white cell surface. When the white cell surface marker is recognized by a fluorescent-labeled monoclonal antibody, the antibody binds to the cell membrane. When the cell passes through the flow chamber, the laser will excite the fluorochrome and it will emit light stimulating one of the detectors. This process is interpreted by the computer as an event. An event is a cell that meets a set of criteria required to register a dot on the scattergraph. The process of determining the specific cell type from a panel of antibody-conjugated fluorescent stains is called immunophenotyping. For example, CD45 is a marker common to all white blood cells. CD2, CD3, CD5, and CD7 are markers for T lymphocytes. CD4 is 968

the site that defines a T-helper lymphocyte and CD8 is the marker or surface antigen that defines a suppressor or cytotoxic T lymphocyte. Therefore, a cell subpopulation that tests positive (i.e., produces a significant number of events) with antibodies to CD45, CD2, CD3, CD5, CD7 and CD4 is defined as a T-helper cell. Normally, a panel of antibodies is selected for use depending upon the characteristics of the gated population. For example, if the gated (selected) population is located in the region of the scattergraph where lymphocytes normally are seen, then lymphocyte markers are used. Two fluorescent-labeled antibodies are mixed with a small portion of the sample and measured simultaneously. One will be labeled with FITC and the other with PE. The events are shown as a plot of colored dots. The most commonly used plot consists of a square divided into four quadrants. The position of a dot (event) on the plot depends upon whether the cell is positive for one marker, both, or neither. For example, a positive staining reaction with FITC but not PE causes a dot in the lower right quadrant of the square. The percentage of events that fall into each quadrant is reported by the computer, and this report correlates with the density of the dots in the respective quadrant. A typical immunophenotyping for lymphocytes consists of the markers mentioned above and CD19 and CD20, which recognize B cells; HLA-DR, which recognizes B cells, T cells, monocytes and precursor cells; and anti-lamda and anti-kappa, which recognize the light chains of surface immunoglobulin molecules. The corresponding profile of positive results will identify the type of lymphocyte and its stage of maturation.

Preparation If possible, a person should avoid eating a heavy meal within hours of the test or engaging in strenuous exercise for the 24 hours preceding the blood test.

Aftercare The puncture site or biopsy site should be observed for excessive bleeding or infection.

Complications In rare cases, the puncture site or biopsy site may show excessive bleeding or become infected.

Results Interpretation of immunophenotyping requires the careful evaluation of known control cells to insure that the signals measured are not the result of background or nonspecific fluorescence. When performing the test to

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When performing immunophenotyping of lymphocytes for the evaluation of immunological function, such as the staging of HIV disease, the percentage of cells positive for the defining marker is multiplied by the absolute lymphocyte count (i.e., number of lymphocytes per microliter). The absolute lymphocyte count is measured by the automated hematology analyzer used for the complete blood count. For example, to quantify the number of T-helper cells, the percentage of CD4-positive gated cells is multiplied by the lymphocyte count. DNA content is measured by comparing the cells in the G0/G1 phase (resting or presynthesis of DNA) of the cell cycle to the G0/G1 phase of a normal diploid control. The ratio of G0/G1 DNA peaks is called the DNA index (DI), and is normally 1.00. Values grater than 1.00 indicate that an increased amount of DNA is present in the sample. A DI of 2.0 indicates that the cells are tetraploid (i.e, have twofold the normal number of chromosomes). Benign tissues do not display aneuploidy (an abnormal number of chromosomes), so the finding of aneuploidy points to a malignant state. Some malignant cells do not display aneuploidy, so a normal finding cannot rule out malignancy. In general DNA aneuploidy is not well correlated with prognosis, since the course of malignant disease is dependent upon the stage (progression), histological type of the tumor, and the tissue of origin. However, in some malignancies, the cancer is associated with a greater chance of recurrence or decreased survival when aneupoloidy is present

Health care team roles The physician will order the specific type of flow cytometry study, and if a biopsy is needed, will obtain a sample of the tissue. If blood is needed, the nurse or phlebotomist will draw the blood and transport the specimen to the laboratory. A clinical laboratory scientist/medical technologist with special training in flow cytometry will perform the analysis. Results are interpreted by a clinical pathologist who issues an interpretive report of the cell subpopulation(s) studied.

Resources BOOKS

American Society of Clinical Pathologists. Practical Diagnosis of Hematologic Disorders, 3rd ed., edited by Carl Kjeldsberg et al. Chicago, IL: ASCP Press, 2000. Corbett, Jane Vincent. Laboratory Tests & Diagnostic Procedures with Nursing Diagnoses, 4th ed. Stamford, CT: Appleton & Lange, 1996. Harmening, Denise M. Clinical Hematology and Fundamentals of Hemostasis, 3rd ed. Philadelphia, PA: F. A. Davis Company, 1997. Henry, John B. Clinical Diagnosis and Management by Laboratory Methods, 20th ed. Philadelphia, PA: W. B. Saunders Company, 2001. Owens, Marilyn A. and Michael R. Loken. Flow Cytometry Principles for the Clinical Laboratory Practice. New York: Wiley-Liss, Inc., 1995. Shapiro, Howard M. Practical Flow Cytometry, 3rd. ed. New York: Wiley-Liss, Inc., 1995. Turgeon, Mary Louise. Immunology & Serology in Laboratory Medicine. St. Louis, MO: Mosby-Year Book, Inc., 1996.

Mark A. Best

Flu see Influenza Fluency disorder see Stuttering

Fluid balance Definition When water intake equals water loss, the body is in fluid balance. When water loss is greater than intake, or vice versa, a fluid imbalance may result.

Description Total body water content averages 60% of body weight in young normal-weight men and is slightly lower in women at approximately 55%. Total body water can be significantly lower in obese individuals and the elderly. Approximately two-thirds of the body water is located inside the cells (intracellular) while the remaining is outside the cells (extracellular). About three-quarters of the extracellular fluid is present in the interstitial space and connective tissues surrounding cells, while the remainder is intravascular. Approximately 8% of body water is in the bloodstream. This fairly small volume of water in the bloodstream must be kept relatively constant because it is critical for proper body function.

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determine the lineage of a cell line as in leukemia, the percentage of cells that are positive for each marker is reported. These results are evaluated along with the morphology of the cells in blood and bone marrow, and the use of cytochemical stains to determine the type of precursor cell (lymphocytic, monocytic, granulocytic) and its maturation stage.

Fluid balance

Role in human health

KEY TERMS Antidiuretic hormone—A hormone that encourages the kidneys to retain water when body stores are low. Dehydration—A deficit of body water that results when the output of water exceeds intake. Diuretic—An agent or drug that eliminates excessive water in the body by increasing the flow of urine. Electrolyte—A substance that dissociates into electrically charged atoms (ions) when dissolved in water. Homeostasis—An organism’s regulation of body processes to maintain internal equilibrium in temperature and fluid content. Overhydration—An excess of body water that results when water intake exceeds output.

Function The kidney is responsible for maintaining fluid balance through the elimination of waste products and excess water. Water is primarily absorbed through the gastrointestinal tract and excreted by the kidneys as urine. Water intake can vary widely on a daily basis, influenced by such factors as access to water, thirst, habit, and cultural factors. The variation in water volume ingested is dependent on the ability of kidneys to dilute and concentrate the urine as needed. There is a reservoir of water outside of the bloodstream that can replace or absorb excess water in the blood when necessary. The body also works to maintain water balance through mechanisms such as the thirst sensation. When the body requires more water, nerve centers in the hypothalamus of the brain are stimulated to encourage a person to drink in order to replenish the water stores. The pituitary gland in the brain is also involved in maintaining fluid balance through secretion of antidiuretic hormone (ADH) into the blood. This hormone encourages the kidney to retain water when body stores are low. During water conservation by the kidneys, water is transferred from a large reservoir in the cells into the blood in order to maintain blood pressure and blood volume until water intake is increased. The thirst mechanism is suppressed when the body has excess water, small amounts of ADH are secreted, and through function of the kidneys, excess water is excreted in the urine. 970

For a normal adult, a daily intake between 0.74-0.84 US quarts (700-800 ml) is required to meet water losses and maintain fluid balance. To protect against dehydration and developing kidney stones, a greater water consumption between 1.5-2 US quarts/day (1.4-2 L/day) is advised. Water losses occur through evaporation in expired air and through the skin. Sweat losses are usually minimal but can be significant in warmer climates or with accompanying fever. The body can accommodate extreme changes in water intake when the brain and kidneys are functioning normally. It is usually possible for a person to consume enough water to maintain blood volume and electrolyte balance in the blood. However, if a person is unable to consume enough water to equal excessive water loss, dehydration may result.

Common diseases and disorders Dehydration Dehydration is a deficit of body water that results when the output of water exceeds intake. Dehydration stimulates the thirst mechanism, instigating water consumption. Sweating and the output of urine both decrease. If water intake continues to fall short of water loss, dehydration worsens. Causes of dehydration may include: • vomiting • diarrhea • diuretics • excessive heat • excessive sweating • fever • decreased water intake Dehydration induces water to move from the reservoir inside cells into the blood. If dehydration progresses, body tissues begin to dry out and the cells start to shrivel and malfunction. The most susceptible cells to dehydration are the brain cells. Mental confusion, one of the most common signs of severe dehydration, may result and can lead to coma. Dehydration can occur when excessive water is lost with such diseases as diabetes mellitus, diabetes insipidus, and Addison’s disease. Dehydration is often accompanied by a deficiency of electrolytes, sodium and potassium in particular. Water does not move as rapidly from the reservoir inside of the cells into the blood when electrolyte concentration is decreased. Blood pressure can decline due to a lower

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TREATMENT OF DEHYDRATION. Consumption of plain water is usually sufficient for mild dehydration, although when both water and electrolyte losses have occurred after vigorous exercise, electrolytes must be replaced; sodium and potassium in particular. Adding a little salt to drinking water or consuming such drinks as Gatorade during or following exercise can replace lost fluids. Individuals with heart or kidney problems should consult a physician regarding the replacement of fluids after exercise.

Sodium chloride may be administered intravenously by medical personnel if blood pressure decreases enough to induce shock or risk of shock. The underlying cause of dehydration must be addressed along with treatment to replace fluids. For example, if the cause of dehydration is due to diarrhea, then drugs may be given to alleviate diarrhea as well. Following treatment of the cause, individuals may be monitored to ensure that oral fluid intake is adequate to maintain fluid hydration.

transfer water into the reservoir within cells. Conditions such as heart failure and liver cirrhosis may induce volume overload, whereby fluid accumulates around cells in the abdomen, chest, and lower legs. TREATMENT OF OVERHYDRATION. Treatment of overhydration depends somewhat upon the cause, although whatever the underlying condition, fluids must be limited. Drinking less than about 1 US quart (1 L) of fluid a day usually improves overhydration over several days. Fluids should only be limited at a physician’s request. A diuretic may be prescribed to increase water output by the kidneys. Diuretics are particularly beneficial for treatment of excess blood volume where overhydration is accompanied by excess blood volume.

Resources BOOKS

Shaw, Patricia, ed. Fluids & Electrolytes Made Incredibly Easy! Springhouse, PA: Springhouse Publishing Co., 1997. Speakman, Elizabeth and Weldy, Norma Jean. Body Fluids and Electrolytes, 8th ed. London, UK: Mosby Incorporated, 2001. Workman, M. Linda. Introduction to Fluids, Electrolytes and Acid-Base Balance. London, UK: W. B. Saunders Co., 2001. PERIODICALS

Overhydration Overhydration is an excess of body water that results when water intake exceeds output. Drinking large amounts of water does not typically lead to overhydration if the kidneys, heart, and pituitary gland are functioning properly. An adult would have to drink more than 2 US gallons per day (7.6 L per day) to exceed the body’s ability to excrete water. Excessive body water causes electrolytes in the blood, including sodium, to become overly diluted. Overhydration occurs in individuals whose kidneys do not function normally, primarily in kidney, heart, or liver disease. People with these conditions may have to limit their water and dietary salt intake. Similar to dehydration, the brain is the most sensitive organ to overhydration. The brain cells can adapt to increased fluid volume when overhydration increases slowly; however, when it occurs rapidly, mental confusion, seizures, and coma can result. Overhydration can occur alone or in conjunction with excess blood volume. Distinguishing between the two conditions may be quite complicated. Overhydration induces water accumulation within and around the cells but does not typically show symptoms of fluid accumulation. On the other hand, with excess blood volume, there is an accumulation of sodium and the body cannot

Beck, L. H. “The aging kidney. Defending a delicate balance of fluid and electrolytes.” Geriatrics 55, no. 4 (2000): 2628, 31-32. Gennari, F. J. “Hypokalemia.” New England Journal of Medicine 339 (1998): 451-458. Sawka, M. N. and S. J. Montain. “Fluid and electrolyte supplementation for exercise heat stress.” American Journal of Clinical Nutrition 72, Suppl. 2 (2000): 564S-572S. OTHER

Nr-Space, et al. Fluids & Electrolytes CD-ROM Delmar Publishers, 2001.

Crystal Heather Kaczkowski, MSc.

Fluorescence in situ hybridization test see Genetic testing

Fluoride therapy Definition Fluoride therapy is the use of fluoride products topically (applied to the tooth surface) or systemically

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volume of water circulating in the bloodstream. A drop in blood pressure can cause lightheadedness, or a feeling of impending blackout, especially upon standing (orthostatic hypotension). Continued fluid and electrolyte imbalance may further reduce blood pressure, causing shock and damage to many internal organs including the brain, kidneys, and liver.

Fluoride therapy

(ingested in supplements or water) to prevent or reduce the incidence of dental caries (tooth decay).

Purpose Fluoride therapy may be initiated systemically before a child’s teeth emerge during tooth development in order to strengthen tooth enamel (the hard outer surface of a tooth) and prevent dental caries. Fluoride may also be applied in the form of gels, foams, and varnishes to the tooth surface, which provides temporary protection. Topical methods are effective for adults and children. The use of fluoridated toothpaste and mouth rinses is another means of delivering fluoride therapy.

Precautions Fluoride therapy is contraindicated for children who are drinking fluoridated water and/or who are also receiving the optimal fluoride dosage (about 1.0 ppm) from foods and bottled beverages. Fluoride in dentifrices (toothpastes) and mouth rinses also has the potential of being ingested. Overexposure to fluoride while a child’s teeth are forming under the gums results in fluorosis, an abnormal condition that affects the appearance of tooth enamel and can be very mild (a few white spots on a tooth) to severe (etching, pitting, and brown discoloration on many teeth). Pediatricians, oral care professionals, and dental hygienists assess the amount of fluoride in a child’s natural environment and caries risk before prescribing fluoride supplements or topical fluoride therapy. Usually, if a child lives in an area where fluoride has been added to the drinking water, supplements are not necessary. A pediatrician or oral care professional may recommend supplements if the child exhibits moderate-to-high risk for dental caries. However, supplementation should be done with caution, weighing the risks of fluoride overexposure against slightly more added protection.

Description Fluoride therapy can be administered through fluoride supplements, fluoridated water, and some bottled beverages containing fluoride. Carbonated drinks, juices, and bottled waters can contain fluoride in varying amounts. Often, the fluoride in these products is not printed on the labels. Some other foods and beverages are high in fluoride, including fish with bones, tea, poultry products, cereals, or infant formula made with fluoridated water. Food cooked in Teflon-coated pans also provides fluoride. 972

Breast-fed infants usually do not need supplements until after they are six months old. By that time, they may be drinking water from a cup or eating some foods that contain fluoride, so supplements still may not be necessary. Fluoride supplements are dispensed in the United States and Canada as lozenges, oral solutions, tablets, and chewable tablets. Fluoride can also be prescribed in combination with a vitamin supplement as chewable tablets or in an oral solution. In the United States, common brand names for fluoride supplements are Fluoritab, Fluorodex, Flura, Flura-Drops, Flura-Loz, Karidium, Luride, Luirde Lozi-Tabs, Pediaflor, Pharmaflur, and Phos-Flur. The vitamin/fluoride combination is sold as Adeflor, Cari-Tab, Mulvidren-F, Poly-Vi-Flor, Tri-ViFlor, and Vi-Daylin/F. These supplements are available only by prescription from a pediatrician or a oral care professional. Dosing of fluoride supplements is different for every child. When determining the amount to prescribe, pediatricians and oral care professionals should consider all fluoride exposure in the child’s environment and prescribe supplements with fluoride limits in mind. Recommended total daily fluoride intake has been set at 0.1 to 1.5 mg for the infant and child to three years of age, 1–2.5 mg for the four-to-six-year old, 1.5–1.5 mg for the seven-to-ten year old, and 1.5–4 mg for an adolescent and an adult. Calcium supplements, or any products with aluminum hydroxide, should not be taken along with fluoride supplements. Each dose should be spaced at least two hours apart to achieve the maximum benefit of each. Overexposure to fluoride is a concern to pediatricians and oral care professionals because it can result in fluorosis. Fluorosis, which is caused by exposure to excessive amounts of fluoride while the enamel is being formed, can affect both the primary (baby) teeth and permanent teeth. It does not affect the permanent teeth once they have fully developed. Most often, the fluorosis appears on the front incisors (front teeth) and less frequently on the molars. This characteristic poses a high cosmetic problem because the front teeth are most exposed when children speak or smile. There is no cure for fluorosis except cosmetic restoration, which can be costly. Fluoride gels and foams are the most common form of topical fluoride application at the oral care professional’s office. A flavored gel containing a concentration of fluoride is offered in a tray to the patient. There is one tray for the upper teeth and one for the lower teeth. The patient should sink his or her teeth into the tray and let the teeth bathe in the fluoride for a specific amount of

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Fluoride varnishes that are being used in Europe have been found to be easier to apply and more durable for the patient; however, varnishes have not been approved for use as a fluoride treatment in the United States. With the varnishes used in Europe, the patient may also eat or drink soon after application. The residue is removed only when the patient’s teeth are brushed. Finally, the use of fluoride toothpaste and fluoridated mouth rinses may also be recommended for adults and children. According to the American Dental Association, young children under six often use too much fluoride toothpaste, and consistently swallow it. This has contributed significantly to excess fluoride ingestion. Careful monitoring of toothpaste amounts by parents and encouragement to spit, instead of swallowing the toothpaste, can drastically decrease the amount of fluoride a child ingests from dentifrices. Composite resins and adhesives with fluoride are used by oral care professionals when filling cavities and cementing crowns into place. Sufficient amounts of topical fluoride are applied to protect adjacent teeth that normally are at risk for further wear and decay due to the location of the cavity (e.g., deep pits in molars) or the stress due to bridge and crown fittings. Dental and medical insurance usually cover fluoride therapy as “routine care.”

Preparation The oral care professional should thoroughly dry the patient’s teeth before applying fluoride gels or foams. The varnishes, however, can be applied to damp teeth and still produce the desired effect. Fluoride dentifrices and mouth rinses require no special preparation.

Aftercare When varnishes are used, the patient can generally eat before 30 minutes, the time he or she is required to wait after a fluoride treatment. This detail can be extremely important for patients with diabetes, who must eat frequently.

Results Fluoride treatments provide temporary protection against dental caries. They are not as effective as systemic intake of fluoridated water, but they can be extremely helpful to children who are at moderate-tohigh risk for dental caries. Furthermore, they can also

Fluoride therapy

time. The mouth should be emptied but not rinsed; then, the patient is instructed not to eat or drink for 30 minutes.

KEY TERMS Dental caries—Tooth decay. Dentifrices—Toothpastes. Enamel—The hard outer surface of a tooth. Fluoride—A fluorine ion used to treat water or apply directly to tooth surfaces to prevent dental caries. Incisors—Front teeth used for biting. Includes central and lateral incisors. Primary teeth—The teeth a child has before permanent ones; primary teeth; baby teeth. Systemic—Ingested as tablets or drops and circulates throughout the human body. Topical—On the surface of a tooth.

help in patients who need extra protection against root caries due to gum recession and xerostomia (dry mouth).

Health care team roles The pediatrician has an important role in a child’s oral health. The first person to be consulted about a child’s dental needs, the pediatrician can monitor a child’s oral hygiene, determine when to make referrals, and regulate fluoride therapy. Oral care professionals and dental hygienists provide fluoride therapy, monitor oral hygiene, and also assess the amount of fluoride in a person’s environment. The oral care professional also makes detailed repairs and suggests therapeutic plans for the child’s dental health. The pediatrician plays an important role in the education of parents regarding fluoride excess and safety issues about fluoride toothpastes and mouth rinses. Nurses and teachers also participate in parent education about fluoride usage and good dental habits. They can teach children about proper tooth brushing, especially the amount of toothpaste to use. These are lessons all adults need to learn as well. The educators can also encourage periodic testing of the water for fluoride levels in the community or at home, especially if water filters are used. Resources BOOKS

Harris, N.O. and F. Garcia-Godoy, eds. Primary Preventive Dentistry. Stamford, CT: Appleton & Lange, 1999.

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PERIODICALS

Author unspecified. “Sodium fluoride (Systemic).” USP DIVolume II Advice for the Patient: Drug Information in Lay Language. (April 2000): 0038. Author unspecified. “Vitamins and Fluoride. (Systemic).” USP DI-Folume II Advice for the Patient: Drug Information in Lay Language. (April 2000): 0074. Beaulieu, E. and L.A. Dufour. “Early Childhood Caries: How You Can Help Preserve Teeth for Life.” Consultant 40, no. 6 (May 2000): 1129. Beltran-Aquilar, E.D., Goldstein, J.W., and S.A. Lockwood. “Fluoride Varnishes: A Review of Their Clinical Use, Cariostatic Mechanism, Efficacy, and Safety.” Journal of the American Dental Association. 131, no. 5 (May 2000): 589-597. Hale, K.J. and K. Heller. “Fluorides: Getting the Benefits, Avoiding the Risks.” Comtemporary Pediatrics. 17, no. 2 (February 2000): 121. Heilman, J.R., Kiritsy, M.C., Levy, S.M., and J.S. Wefel. “Assessing Fluoride Levels of Carbonated Soft Drinks.” Journal of the American Dental Association. 130, no. 11 (November 1999): 1593-1600. Kuritzky, L. “Fluoride and Bacterial Content of Bottle Water vs. Tap Water.” Neurology Alert. 18, no. 11 (July 2000): 15. Lewis, C.W., Grossman, D.C., Domoto, P.K., and R.A. Deyo. “The Role of the Pediatrician in the Oral Health of Children: A National Survey.” Pediatrics. 106, no. 6 (December 2000): 1475. Warren, D.P., Henson, H.A., and J.T. Chan. “Dental Hygienist and Patient Comarisons of Fluoride Varnishes to Fluoride Gels.” Journal of Dental Hygiene. 74, no. 2 (Spring 2000): 94.

Janie F. Franz

Fluorine toxicity see Fluorosis

Fluoroscope Definition A fluoroscope is an x-ray device that allows live images to be projected onto a viewing monitor during diagnostic and interventional procedures.

Purpose A fluoroscope is used for real-time imaging of various anatomical areas during a diagnostic or interventional procedure. Fluoroscopy produces a live image of the area of interest, and can be used to view such motion as blood flow and catheter insertion. In contrast, radiography, or x-ray imaging, produces a still image on film. 974

Specific procedures that use fluoroscopy include aneurysm repair, hip and knee replacement, arthroscopy, catheter placement, needle biopsy, location of foreign bodies, swallowing studies, fracture reduction, discography, lithotripsy, brachytherapy, pacemaker insertion, endoscopic retrograde cholangiopancreatography (ERCP), and gastrointestinal evaluation (e.g., bowel studies). Fluoroscopy may also be used to detect bone cancer or digestive cancers, and digestive ulcers; however, computed tomography (CT) imaging is now routinely used to detect these conditions.

Description The term fluoroscope generally refers to a mobile radiographic/fluoroscopic unit, also called a mobile Carm because of its shape. A mobile C-arm system consists of two wheeled units: one carries the imaging arm, x-ray generator, and control console, and the other carries the image display monitors and image processing and recording devices. The imaging arm, which is shaped like the letter C, has an x-ray tube mounted on one end and an image intensifier mounted on the other end. The x-ray generator supplies the power to the x-ray tube, which emits x rays that pass through the patient and are absorbed by the image intensifier. The image intensifier is a phosphor screen that converts the x rays into light, which is then scanned and transmitted by a charge-coupled device (CCD) camera to a display monitor. Fluoroscopy is also performed using larger stationary radiographic/fluoroscopic systems that include a patient table, an x-ray generator, an x-ray tube, an image intensifier, and an image display system configured in a shielded room. The term fluoroscope may be used to refer to the components of this stationary system that perform fluoroscopy, but it is most commonly used in reference to a mobile system. Fluoroscopy is performed in surgical, orthopedic, critical care, emergency care, and diagnostic radiology settings. In addition, mobile fluoroscopes are used to image patients on stretchers, beds, or examination/procedure tables when they cannot be transported to the radiology department. Scaled-down compact fluoroscopes that can be handheld are also available and are designed for fast, continuous imaging of the extremities at various angles. Mini C-arms may be used in the emergency department, during surgery, in a physician’s office, in sports medicine and physical therapy, and in the field such as an accident site. In 2000, a fluoroscope with a navigational or surgical guidance computer was introduced to improve instru-

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Operation The fluoroscope is maneuvered in such a way that the patient, and the anatomical area of interest, is positioned between the x-ray tube and the image intensifier. The operator uses the control console to set imaging parameters. The intensity of the x rays is controlled with the milliamperage (mA) setting, and the energy and intensity of the x rays are controlled with the peak kilovoltage (kVp) setting. A typical fluoroscopy image setting is 70 kVp at 2 mA. Most mobile C-arms have capabilities for magnified views, automatic brightness stabilization to maintain a constant brightness during the exam, and last-image hold to freeze the last acquired image on the monitor. During fluoroscopic imaging, the patient is exposed to radiation; continuous fluoroscopy for long periods (e.g., during a surgical procedure) can deliver a significant radiation dose. Therefore, most systems have a pulsed fluoroscopy mode, which allows the x-ray output to be pulsed for periods ranging from 10 milliseconds to 30 times per second, and displays the image acquired with each pulse. Although the image on the monitor may be jumpy, radiation exposure to the patient can be reduced by as much as 75% with this mode. Dose reduction is especially important in pediatric patients and young adult patients of reproductive age. Clinical staff are also exposed to radiation, and portable radiation shields, lead aprons, and radiation badges should be worn by all staff present during fluoroscopy. All images displayed on the monitor can be saved to a disk, video disk, compact disk, or tape. Some systems have digital capabilities that allow storage in digital memory or on a computer network. A videocassette recorder or digital recorder can be used to record several minutes of real-time fluoroscopy. Snapshot images can also be printed as hard copy using video printers, thermal printers, or a multi-format camera (a camera that records and prints multiple images; for example, four images on one film).

Maintenance A fluoroscope is usually maintained either through a service contract with the manufacturer, a third-party service company, or by the hospital biomedical engineering department. The x-ray technologist operating the fluoroscope may perform periodic performance testing to check image quality, radiation dose, and other imaging parameters. A quality control program should be imple-

KEY TERMS Brachytherapy—A radiation therapy treatment in which a radioactive source material is inserted, injected, or implanted into the cancerous area; fluoroscopy is frequently used to guide placement of brachytherapy sources. Discography—A radiographic/fluoroscopic imaging procedure that involves injecting contrast material into an intervertebral disk. Endoscopic retrograde cholangiopancreatography (ERCP)—A procedure that involves inserting an endoscope through the mouth, esophagus, stomach, and into the first part of the small intestine (the duodenum) to examine the pancreas, pancreatic ducts, and bile ducts. A catheter is threaded through the endoscope to inject dye, and x-ray and fluoroscopic imaging are performed. Lithotripsy—A procedure that uses fluoroscopic guidance to locate and break up stones in the urinary tract and gallbladder. Myelography—A fluoroscopic imaging procedure that examines the spinal cord and is used for diagnosing such conditions as spinal abscesses, tumors, and dislocated intervertebral disks.

mented to ensure optimal image quality and minimal radiation doses.

Health care team roles Fluoroscopic imaging may be performed by x-ray technologists, radiologists, surgeons, cardiologists, and other health care professionals. For such diagnostic procedures as an upper gastrointestinal (GI) series, the fluoroscopic examination is performed by a radiologist and an x-ray technologist in a hospital radiology department or an outpatient imaging center. For such orthopedic procedures as arthroscopy, an orthopedic surgeon and x-ray technologist perform the fluoroscopic examination. For interventional diagnostic and therapeutic procedures, an interventional radiologist, cardiovascular specialist, and x-ray technologist are involved in the fluoroscopic procedure. Nursing staff may be present to assist during fluoroscopic procedures, depending on the condition of the patient and whether medication administration is necessary. Mini-C-arms have clinical applications outside the hospital, and thus may be used in medical emergencies at

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ment placement and imaging during minimally invasive surgical procedures, particularly those involving the spine.

Fluorosis

sporting events, and in sports medicine and physical therapy facilities.

Classification and descriptive criteria for dental fluorosis

Training Classification

Descriptive criteria

Normal

Enamel shows no evidence of fluorosis. The surface of the tooth is smooth, glossy, and typically has a pale, creamy white color.

Very mild

Evidence of fluorosis in the enamal is shown by areas with parchment-white color that total up to 25% of the tooth surface. This includes fluorosis seen only on the incisal edges of anterior teeth and cusp tips of bicuspids or molars (“snowcapping”).

Resources

Mild

Parchment-white fluorosis can be seen on more than 25% but less than 50% of the tooth surface.

BOOKS

Moderate

Light to very dark brown staining occurs on the enamel, along with the parchment-white coloration of fluorosis.

Severe

All enamel surfaces are affected, and the anatomy of the tooth may be altered. Discrete or confluent pitting of the enamel surface exists. Dark-brown stain is usually present and may be widespread, presenting a corroded appearance of the teeth.

Use of a fluoroscope requires training in radiographic and fluoroscopic principles and techniques. X-ray technologists should have completed appropriate educational programs (registered technologist programs). Any staff using fluoroscopic equipment should participate in clinical training provided by the equipment manufacturer.

Dendy, P.P., and B. Heaton. Physics for Diagnostic Radiology, 2nd edition. Philadelphia, PA: Institute of Physics Publishing, 1999. PERIODICALS

Aliabadi, D et al. “Rapid Bedside Coronary Angiography with a Portable Fluoroscopic Imaging System.” Catheterization and Cardiovascular Diagnosis 41, no.4 (August 1997): 449-55. Hernandez, R. J., and M. M. Goodsitt. “Reduction of Radiation Dose in Pediatric Patients Using Pulsed Fluoroscopy.” American Journal of Roentgenology 167, no. 5 (November 1996): 1247-53. ORGANIZATIONS

tooth). Fluorosis can be very mild, as a few white spots on a tooth; or severe, showing etching, pitting, and brown discoloration on many teeth.

Description

American College of Radiology. 1891 Preston White Drive, Reston, VA 20191-4397. (800) 227-5463. . American Registry of Radiologic Technologists. 1255 Northland Drive, St. Paul, MN 55120-1155. (651) 6870048. . American Society of Radiologic Technologists (ASRT). 15000 Central Avenue SE, Albuquerque, NM 87123-2778. (800) 444-2778. .

Fluoridated community water systems and toothpaste with fluoride have significantly contributed to the prevention and mitigation of dental caries (tooth decay) in developed countries, reducing the number of cavities by 70%. Even at the safe level of 1 ppm of fluoride in drinking water, 22% of the people drinking that water have reported some form of fluorosis. In some areas, the rate of incidence is 50%.

Jennifer E. Sisk, M.A.

Though fluorosis is mainly a cosmetic problem, it has become a marker for overexposure to fluoride in a child’s environment.

OTHER

FluoroNav Fluoroscopy. .

Fluorosis does not affect the permanent teeth once they have fully appeared. Fluorosis may occur in primary (baby) teeth as well as permanent teeth. Most often, the condition appears on the front incisors (front teeth) and less frequently on the molars. This characteristic poses a high cosmetic problem because the front teeth are most exposed when children speak or smile.

Fluorosis Definition Fluorosis is an abnormal condition of the tooth enamel caused by excessive exposure to fluoride (a nutrient used to prevent tooth decay) while a child’s teeth are forming under the gums. Excessive fluoride affects the formation of tooth enamel (the hard outer surface of a 976

Causes and symptoms

Symptoms can range from mild to severe. Very mild fluorosis is seen as tiny white spots on 25% of a tooth surface. Mild fluorosis covers 26% to 50% of a tooth surface. Moderate fluorosis compromises all of a tooth’s surface and is most characterized by brown discoloration

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Excess fluoride exposure is often accidental. Naturally occurring fluoride in well water can sometimes be much higher than water from artificially fluoridated, community or municipal systems that are kept at strict levels. Drought conditions can also concentrate fluoride levels. According to the ADA, young children under six often use too much toothpaste that contains fluoride, and they consistently swallow it. This alone has been the biggest cause of excess fluoride ingestion. Some children drink fluoridated water and also drink large amounts of bottled beverages that have fluoride in them. Carbonated drinks and juices have fluoride in varying amounts. Often, the fluoride in these products is not printed on the labels. Still other children are offered foods high in fluoride (fish with bones, tea, poultry products, cereals, or infant formula made with fluoridated water) in addition to fluoridated water. Finally, fluorosis may be caused by some pediatricians who prescribe fluoride supplements without determining the amount of fluoride exposure the child has in his or her environment. Topical applications of fluoride gels applied by dentists to the surfaces of a child’s teeth and fluoride mouth rinses available through dentists or over the counter (OTC) are other ways that a child can add to her fluoride quota. These methods are extremely helpful for older children and adults, but they often add to the cumulative fluoride exposure a young child can have, especially if she swallows fluoride residues.

Diagnosis Fluorosis can be identified through examination by a dentist or dental hygienist. Very mild fluorosis sometimes can be detected only through x rays. Often the dentist uses the Fluorosis Index to classify the severity of the condition from very mild to severe. (See Causes & Symptoms for details of each classification.)

Treatment There is no treatment for fluorosis except cosmetic restoration.

KEY TERMS Deciduous teeth—The teeth a child has before permanent ones; baby teeth. Dental caries—Tooth decay. Enamel—The hard outer surface of a tooth. Fluoride—A fluorine compound used to treat water or apply directly to tooth surfaces to prevent dental caries. Incisors—Front teeth used for biting.

however, remain the most effective ways to discourage dental caries (tooth decay). With more awareness of the amount of fluoride in a child’s environment, pediatricians and dentists are becoming more accurate in prescribing fluoride supplements to infants and young children. Parents are becoming educated about the risks of their children swallowing fluoride toothpaste and fluoride mouth rinses.

Health care team roles The pediatrician has an important role in a child’s oral health because the pediatrician is usually the first health-care professional a child sees about his or her dental needs. The pediatrician can monitor a child’s oral hygiene, determine when to make referrals, and regulate fluoride therapy in relation to a child’s specific fluoride needs. The pediatrician can also educate parents about fluoride excess and safety issues. The dentist regulates the amount and frequency of fluoride therapy, monitors a child’s oral hygiene, and also assesses the amount of fluoride in a child’s environment. The dentist also suggests and implements therapeutic plans for the child’s dental health. Parent education is also a part of the dentist’s role. Dental hygienists, nurses, and teachers participate in parent education about fluoride usage and good dental habits, teach children about proper tooth brushing—especially the amount of toothpaste to use—and encourage periodic testing of the water for fluoride levels in the community or at a child’s home, where filters that may lower fluoride concentrations in tap water may be used.

Prevention Prognosis There are many more ways to deliver fluoride than through drinking water and toothpaste. These methods,

Fluorosis can be prevented by monitoring the amount of fluoride children are exposed to before the age of six. Professionals can educate parents about diet,

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of the tooth. Severe fluorosis involves pitting of the enamel and more serious brown staining. Approximately 94% of dental fluorosis is very mild to mild.

Folic acid

fluoridated water, proper tooth brushing, and safe amounts of toothpaste to use. Children under six should be monitored during tooth brushing, shown to use only a pea-sized drop of toothpaste, and encouraged to not swallow toothpaste. Children under six should also not use fluoridated mouth rinses. Parents should limit the amount of fluoride in bottled beverages, and substitute milk for between-meal snacks. Pediatricians and dentists should adhere to the new guidelines for fluoride supplements. These supplements are not recommended for children who are exposed to adequate amounts of fluoridated water. Resources

ed from the body rather than stored for later use. This is why sufficient daily intake of folic acid is necessary. Folic acid is also known as folate or folacin. It is one of the nutrients most often lacking in the Western diet, and there is evidence that deficiency is a problem on a worldwide scale. Folic acid is found in leafy green vegetables, beans, peas and lentils, liver, beets, brussel sprouts, poultry, nutritional yeast, tuna, wheat germ, mushrooms, oranges, asparagus, broccoli, spinach, bananas, strawberries, and cantaloupes. In 1998, the U.S. Food and Drug Administration (FDA) required food manufacturers to add folic acid to enriched bread and grain products to boost intake and to help prevent neural tube defects (NTD).

BOOKS

General use

Griffen, A.K., ed. Pediatric Oral Health. Philadelphia: Saunders, 2000. PERIODICALS

Author unspecified. “Position of the American Dietetic Association: The Impact of Fluoride on Health.” Journal of the American Dietetic Association 101, no. 1 (January 2001):126. Hale, K.J., and K. Heller. “Fluorides: Getting the Benefits, Avoiding the Risks.” Contemporary Pediatrics 17, no. 2 (February 2000): 121. Schmitt, B.D. “Tooth Decay Prevention.” Clinical Reference Systems (Annual 2000): 1639. ORGANIZATIONS

American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. (847) 4344000. . American Dental Association. 211 East Chicago Ave., Chicago, IL 60611. (800)947-4746, (312)440-2500. . National Association of Pediatric Nurse Associates & Practitioners. 1101 Kings Highway, N., Suite 206, Cherry Hill, NJ 08034-1912. .

Janie F. Franz

Folate see Folic acid

Folic acid Description Folic acid is a water-soluable vitamin belonging to the B-complex group of vitamins. These vitamins help the body break down complex carbohydrates into simple sugars to be used for energy. Excess B vitamins are excret978

Folic acid works together with vitamin B12 and vitamin C to metabolize protein in the body. It is important for the formation of red and white blood cells. It is necessary for the proper differentiation and growth of cells and for the development of the fetus. It is also used to form the nucleic acid of DNA and RNA. It increases the appetite and stimulates the production of stomach acid for digestion and it aids in maintaining a healthy liver. A deficiency of folic acid may lead to anemia, in which there is decreased production of red blood cells. Anemia reduces the amounts of oxygen and nutrients that are able to get to the tissues. Symptoms may include fatigue, reduced secretion of digestive acids, confusion, and forgetfulness. During pregnancy, a folic acid deficiency may lead to preeclampsia, premature birth, and increased bleeding after birth. People who are at high risk of strokes and heart disease may greatly benefit by taking folic acid supplements. An elevated blood level of the amino acid homocysteine has been identified as a risk factor for some of these diseases. High levels of homocysteine have also been found to contribute to problems with osteoporosis. Folic acid, together with vitamins B6 and B12, helps break down homocysteine, and may help reverse the problems associated with elevated levels. Pregnant women have an increased need for folic acid, both for themselves and their child. Folic acid is necessary for the proper growth and development of the fetus. Adequate intake of folic acid is vital for the prevention of several types of birth defects, particularly NTDs. The neural tube of the embryo develops into the brain, spinal cord, spinal column, and the skull. If this tube forms incompletely during the first few months of pregnancy a serious, and often fatal, defect results in spina bifida or anencephaly. Folic acid, taken from one year to one month before conception through the first

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Research shows that folic acid can be used to successfully treat cervical dysplasia, a condition diagnosed by a Pap smear, of having abnormal cells in the cervix. This condition is considered to be a possible precursor to cervical cancer, and is diagnosed as an abnormal Pap smear. Daily consumption of 1,000 mcg of folic acid for three or more months has resulted in improved cervical cells upon repeat Pap smears. Studies suggest that long-term use of folic acid supplements may also help prevent lung and colon cancer. Researchers have found that alcoholics who have low folic acid levels face a greatly increased possibility of developing colon cancer.

Preparations To correct a folic acid deficiency, supplements are taken in addition to food. Since the functioning of the B vitamins is interrelated, it is generally recommended that the appropriate dose of B-complex vitamins be taken in place of single B vitamin supplements. The Recommended Dietary Allowance (RDA) for folate is 400 mcg per day for adults, 600 mcg per day for pregnant women, and 500 mcg for nursing women. Medicinal dosages of up to 1,000-2,000 mcg per day may be prescribed.

Precautions Folic acid is not stable. It is easily destroyed by exposure to light, air, water, and cooking. Therefore, the supplement should be stored in a dark container in a cold, dry place, such as a refrigerator. Many medications interfere with the body’s absorption and use of folic acid. This includes sulfa drugs, sleeping pills, estrogen, anti-convulsants, birth control pills, antacids, quinine, and some antibiotics. Using large amounts of folic acid (e.g., over 5,000 mcg per day) can mask a vitamin B12 deficiency and thereby risk irreversible nerve damage.

Side effects At levels of 5,000 mcg or less, folic acid is generally safe for use. Side effects are uncommon. However, large doses may cause nausea, decreased appetite, bloating, gas, decreased ability to concentrate, and insomnia. Large doses may also decrease the effects of phenytoin (Dilantin), a seizure medication.

KEY TERMS Homocysteine—An amino aid involved in the breakdown and absorption of protein in the body. Preeclampsia—A serious disorder of late pregnancy in which the blood pressure rises, there is a large amount of retained fluids, and the kidneys become less effective and excrete proteins directly into the urine. Raynaud’s disease—A symptom of various underlying conditions affecting blood circulation in the fingers and toes and causing them to be sensitive to cold. Recommended Daily Allowance (RDA)— Guidelines for the amounts of vitamins and minerals necessary for proper health and nutrition established by the National Academy of Sciences in 1989. Water-soluble vitamins—Vitamins that are not stored in the body and are easily excreted. They must, therefore, be consumed regularly as foods or supplements to maintain health.

Interactions As with all B-complex vitamins, it is best to take folic acid with the other B vitamins. Vitamin C is important to the absorption and functioning of folic acid in the body. Resources BOOKS

Braverman, Eric R., M.D., Carl C. Pfeiffer, M.D., Ph.D., Ken Blum, Ph.D., and Richard Smayda, D.O. The Healing Nutrients Within. New Canaan, CT: Keats Publishing, 1997. Kirschmann, John D., and Gayla J. Kirschmann. Nutrition Almanac. New York: McGraw-Hill, 1996. PERIODICALS

Fallest-Strobl, Patricia, Ph.D., David Koch, James Stein, and Patrick McBride. “Homocysteine: A New Risk Factor for Atherosclerosis.” American Family Physician (October 15, 1997): 1607-14. Giovannuci, Edward, et al. “Alcohol, low-methionine-lowfolate diets, and risk of colon cancer in men.” Journal of the National Cancer Institute (February 15, 1995): 265-73. Shaw, Gary M., et al. “Risks of orofacial clefts in children born to women using multivitamins containing folic acid periconceptually.” The Lancet (August 12, 1995): 393-96.

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four months of pregnancy, can reduce the risk of NTDs by 50-70%. It also helps prevent a cleft lip and palate.

Food poisoning

ORGANIZATIONS

Centers for Disease Control and Prevention. 4770 Buford Highway NE, MSF-45, Atlanta, GA 30341-3724. (888)232-6789. [email protected]. . OTHER

Adams, Suzanne L. The Art of Cytology: Folic Acid/ B-12 Deficiency [email protected]. . “Folic Acid.” . “Folic Acid: Coming to A Grocery Store Near You.” . “Folic acid (oral/injectible).” Dr. Koop.com.Inc. 700 N. Mopac, Suite 400, Austin, TX 48731. . Pregnancy and Nutrition Update. .

Patience Paradox

Careless food handling creates conditions for the growth of bacteria that make people sick. Food can become contaminated at many different points during its trip from farm to table. Vegetables that are eaten raw, such as lettuce, may be contaminated by bacteria in soil, water, and dust during washing and packing. Home canned and commercially canned food may be improperly processed at too low a temperature or for too short a time to kill the bacteria. Raw meats carry many foodborne bacterial diseases. The United States Food and Drug Administration (FDA) estimates that 90% or more of raw poultry sold at retail carries some disease-causing bacteria. Other raw meat products and eggs are contaminated to a lesser degree. Thorough cooking kills the bacteria and makes the food harmless. However, properly cooked food can become recontaminated if it comes in contact with plates, cutting boards, counter tops, or utensils that were used with raw meat and not cleaned and sanitized.

Folic acid test see Vitamin tests Follicle-stimulating hormone test see Pituitary hormone tests

Food poisoning Definition Food poisoning is a general term for health problems arising from eating contaminated food. Food may be contaminated by bacteria, viruses, environmental toxins, or toxins present within the food itself, such as the poisons in some mushrooms. Symptoms of food poisoning usually involve the prompt onset of vomiting and diarrhea. Some toxins also affect the nervous system.

Description Every year millions of people suffer from bouts of vomiting and diarrhea that they blame on “something I ate.” These people are generally correct. The Centers for Disease Control and Prevention (CDC) estimates that there are from six to 33 million cases of food poisoning in the United States each year. Many cases are mild and pass so rapidly that they are never diagnosed. Occasionally a severe outbreak creates a newsworthy public health hazard. Classical food poisoning, sometimes incorrectly called ptomaine poisoning, is caused by a variety of dif980

ferent bacteria. The most common are Salmonella, Staphylococcus aureus, Escherichia coli O157:H7, Shigella, and Clostridium botulinum. Each has a slightly different incubation period and duration, but all except C. botulinum cause inflammation of the intestines and diarrhea. Sometimes food poisoning is called bacterial gastroenteritis or infectious diarrhea. Food and water can also be contaminated by viruses (cholera, rotavirus), environmental toxins (heavy metals), and poisons produced within the food itself (mushroom poisoning or fish and shellfish poisoning).

Cooked foods can also be contaminated after cooking by bacteria carried by food handlers or from bacteria in the environment. It is estimated that 50% of healthy people have the bacterium Staphylococcus aureus in their nasal passages and throat, as well as on their skin and hair. Rubbing a runny nose, then touching food can introduce the bacteria into cooked food. Bacteria flourish at room temperature and will rapidly grow into quantities capable of making people sick. To prevent this growth, food must be kept hot or cold, but never just warm. Although the food supply in the United States is probably the safest in the world, anyone can get food poisoning. Serious outbreaks are rare. When they occur, the very young, the very old, and those with immune system weaknesses have the most severe and life-threatening cases. For example, this group is 20 times more likely to become infected with the Salmonella bacterium than the general population. Travel outside the United States to countries where less attention is paid to sanitation, water purification, and good food handling practices increases the chances that a person will get food poisoning. People living in institu-

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Rotavirus is the most common cause of severe diarrhea in children and accounts for the hospitalization of an estimated 55,000 children in the United States and over 600,000 deaths of children worldwide per year. Other less common but serious food-borne illnesses may arise from consuming animals infected with Bovine spongiform encephalopathy. Bovine spongiform encephalopathy (BSE) is a degenerative disorder affecting the central nervous system in cattle. It is also commonly referred to as “mad cow disease.” BSE results from an “unconventional transmissible agent” which is yet to be determined precisely but is thought to be a pathogenic protein. Cell death leads to holes in the brain, creating a “sponge-like” consistency, which results in the animal’s death. As of November 2000, there have been more than 177,500 cases of BSE confirmed in the United Kingdom (UK). However, no cases have been reported in the United States, where the food supply has been monitored closely. Imports of ruminants (suborder of mammals that includes sheep) and ruminant products have been restricted to some degree from countries where BSE was reported and has extended to all European countries. BSE is believed to be linked to a new variation of Creutzfeldt-Jakob disease (CJD) in humans, which is a progressive neurological disorder that can lead to death.

Causes and symptoms The symptoms of food poisoning occur because foodborne bacteria release toxins or poisons as a byproduct of their growth in the body. These toxins (except those from C. botulinum) cause inflammation and swelling of the stomach, small intestine and/or large intestine. The result is abdominal muscle cramping, vomiting, diarrhea, fever, and the chance of dehydration. The severity of symptoms depends on the type of bacteria, the amount consumed, and the individual’s general health and sensitivity to the bacterial toxin. Salmonella According to the CDC, approximately 1.4 million cases of Salmonella contamination occur annually in the US, with about 40,000 being culture-confirmed cases reported to the CDC. Salmonella is found in egg yolks from infected chickens, in raw and undercooked poultry and in other meats, dairy products, fish, shrimp, and many more foods. The CDC estimates that one out of every 50 consumers is exposed to a contaminated egg yolk each year. However, thorough cooking kills the bacteria and makes the food harmless. Salmonella is also found in the feces of such pet reptiles as turtles, lizards, and snakes.

About one out of every 1,000 people get food poisoning from Salmonella. Of these, two-thirds are under age 20, with the majority under age nine. Most cases occur in the warm months between July and October. Salmonella poisoning manifests itself as salmonellosis, mostly caused by Salmonella enteritidis and Salmonella typhimurium. The incidence of salmonellosis has increased dramatically during the last two decades, due in part to the growing popularity of pet iguanas. Symptoms of food poisoning begin 12–72 hours after eating food, water, or contact with animals contaminated with Salmonella. These include the traditional food poisoning symptoms of abdominal pain, diarrhea, vomiting, and fever. The symptoms generally last two to five days. Dehydration can be a complication in severe cases. People generally recover without antibiotic treatment, although they may feel tired for a week after the active symptoms subside. The CDC estimates that there are over 500 fatalities per year in the US, with 2% of the cases complicated by chronic arthritis. Staphylococcus aureus Staphylococcus aureus is found in dust, air, and sewage. The bacteria are spread primarily by food handlers using poor sanitary practices. Almost any food can be contaminated, but salad dressings, milk products, cream pastries, and any food kept at room temperature, rather than hot or cold, are likely candidates. It is difficult to estimate the number of cases of food poisoning from Staphylococcus aureus that occur each year, because its symptoms are so similar to those caused by other foodborne bacteria. Many cases are mild and the victim never sees a doctor. Symptoms appear rapidly, usually two to eight hours after the contaminated food is eaten. The acute symptoms of vomiting, diarrhea, and severe abdominal cramps usually last only three to six hours and rarely more than 24 hours. Most people recover without medical assistance. Deaths are rare. Escherichia coli (E. coli) There are many strains of E. coli, and not all of them are harmful. The strain that causes most severe food poisoning is E. coli O157:H7. Food poisoning by E. coli occurs in three out of every 10,000 people. Foodborne E. coli is found mainly in food derived from cows such as dairy products and beef, especially ground beef. Symptoms of food poisoning from E. coli are slower to appear than those caused by some of the other foodborne bacteria. E. coli produces toxins in the large intestine rather than higher up in the digestive system. This

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tions such as nursing homes are also more likely to get food poisoning.

Food poisoning

factor accounts for the delay in symptoms and the fact that vomiting rarely occurs in E. coli food poisoning.

by fever, confusion, headache, lethargy, and a stiff neck that resembles meningitis.

One to three days after eating contaminated food, the victim with E. coli O157:H7 begins to have severe abdominal cramps and watery diarrhea that usually becomes bloody within 24 hours. There is little or no fever, and rarely does the victim vomit. The bloody, watery diarrhea lasts from one to eight days in uncomplicated cases. E. coli is the most common cause of “travelers’ diarrhea,” affecting people travelling to many highrisk areas such as Latin America, Asia, Africa, and the Middle East. It is most often caused by water or foods contaminated with fecal matter.

The disease runs its course in two to three days. Dehydration is a common complication. Most people recover on their own, although they may feel exhausted. Children who are malnourished or have weakened immune systems may die.

Campylobacter jejuni (C. jejuni) According to the FDA, C. jejuni is the leading cause of bacterial diarrhea in the United States. It is responsible for more cases of bacterial diarrhea than Shigella and Salmonella combined. Anyone can get food poisoning from C. jejuni, but children under five and young adults between the ages of 15 and 29 are more frequently infected. C. jejuni is carried by healthy cattle, chickens, birds, and flies. It is not carried by healthy people in the United States or Europe. The bacterium is also found in ponds and stream water. The ingestion of only a few hundred C. jejuni bacteria can make a person sick. Symptoms of food poisoning begin two to five days after eating food contaminated with C. jejuni. These symptoms include fever, abdominal pain, nausea, headache, muscle pain, and diarrhea. The diarrhea can be watery or sticky and may contain blood. Symptoms last from seven to 10 days, and relapses occur in about one quarter of people who are infected. Dehydration is a common complication. Other complications such as arthritis-like joint pain and hemolytic-uremic syndrome (HUS) are rare. Shigella Shigella is a common cause of diarrhea in travelers to developing countries. It is associated with contaminated food and water, crowded living conditions, and poor sanitation. The bacterial toxins affect the small intestine. Symptoms of food poisoning by Shigella appear 36 to 72 hours after eating contaminated food. These symptoms are slightly different from those associated with most foodborne bacteria. In addition to the familiar watery diarrhea, nausea, vomiting, abdominal cramps, and fever, up to 40% of children with severe infections show neurological symptoms, including seizures caused 982

Clostridium botulinum (C. botulinum) C. botulinum, which causes both adult botulism and infant botulism, is unlike any of the other foodborne bacteria. First, C. botulinum is an anaerobic bacterium that can live only in the absence of oxygen. Second, the toxins from C. botulinum are neurotoxins. They poison the nervous system, causing paralysis without the vomiting and diarrhea associated with other foodborne illnesses. Third, toxins that cause adult botulism are released when the bacteria grow in an airless environment outside the body. They can be broken down and made harmless by heat. Finally, botulism is much more likely to be fatal, even in tiny quantities. Adult botulism outbreaks are usually associated with home canned food, although occasionally commercially canned or vacuum-packed foods are responsible for the disease. C. botulinum grows well in non-acidic, oxygenfree environments. If food is canned at too low heat or for too brief a time, the bacterium is not killed. It reproduces inside the can or jar, releasing its deadly neurotoxin. The toxin can be made harmless by heating the contaminated food to boiling for ten minutes. However, even a very small amount of the C. botulinum toxin can cause serious illness or death. Symptoms of adult botulism appear about 18 to 36 hours after the contaminated food is eaten, although there are documented times of onset ranging from four hours to eight days. Initially a person suffering from botulism feels weakness and dizziness followed by double vision. Symptoms progress to difficulty speaking and swallowing. Paralysis moves down the body, and when the respiratory muscles are paralyzed, death results from asphyxiation. People who show any signs of botulism poisoning must receive immediate emergency medical care to increase their chance of survival. Infant botulism is a form of botulism first recognized in 1976. It differs from foodborne botulism in its causes and symptoms. Infant botulism occurs when a child under the age of one year ingests the spores of C. botulinum. These spores are found in soil, but a more common source of spores is honey. The C. botulinum spores lodge in the baby’s intestinal tract and begin to grow, producing their neurotoxin.

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Food poisoning

COMMON PATHOGENS CAUSING FOOD POISONING Pathogen

Common Host(s)

Campylobacter

Poultry

E.coli 0157:H7

Undercooked, contaminated ground beef

Listeria

Found in a variety of raw foods, such as uncooked meats and vegetables, and in processed foods that become contaminated after processing

Salmonella

Poultry, eggs, meat, and milk

Shigella

This bacterium is transmitted through direct contact with an infected person or from food or water that become contaminated by an infected person

Vibrio

Contaminated seafood

Source: Food Safety and Inspection Service, U.S. Department of Agriculture

(Illustration by Standley Publishing. Courtesy of Gale Group.)

Onset of symptoms is gradual. Initially the baby is constipated, which is followed by poor feeding, lethargy, weakness, drooling, and a distinctive wailing cry. Eventually the baby loses the ability to control its head muscles. From there the paralysis progresses to the rest of the body. Rotavirus The clinical characteristics of rotavirus include vomiting and watery diarrhea for three to eight days with abdominal pain and fever also frequently occurring. The incubation period is about two days. Subsequent bouts of rotavirus tend to be less severe than the initial infection. Illness can occur when in contact with contaminated food, water, or surfaces. Rotavirus infections are higher in countries with temperate climates (November to April in the United States) with most infections occurring in children under two years old. Adult cases tend to be milder. Bovine spongiform encephalopathy and Creutzfeldt-Jakob disease It is extremely unlikely that bovine spongiform encephalopathy will become a foodborne illness in the United States, because the feeding of ruminant by-products to other animals was probably a factor that lead to the outbreak in the United Kingdom. Furthermore, the FDA implemented a ban on ruminant feed in 1997 due to evidence that BSE can be transmitted to humans.

Creutzfeldt-Jakob disease has atypical clinical symptoms, including psychiatric or sensory symptoms early in its course, and neurological abnormalities and dementia later on. Incidence of CJD in people under 30 years is extremely rare in the US (less than 5 cases per 1 billion per year). In the UK, it primarily affects younger people, with over half of the patients who have died of CJD under 30 years old.

Diagnosis One important aspect of diagnosing food poisoning is for doctors to determine if a number of people have eaten the same food and show the same symptoms of illness. When a cluster of cases occurs, food poisoning is strongly suspected. The diagnosis is confirmed when the suspected bacterium is found in a stool culture or a fecal smear from the person. Other laboratory tests are used to isolate bacteria from a sample of the contaminated food. Botulism is usually diagnosed from its distinctive neurological symptoms, since rapid treatment is essential. Many cases of food poisoning go undiagnosed, since a definite diagnosis is not necessary to effectively treat the symptoms. Because it takes time for symptoms to develop, it is not necessarily the most recent food one has eaten that causes the symptoms.

Treatment Treatment of most food poisoning, except that caused by C. botulinum, focuses on preventing dehydra-

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azole (Septra, Bactrim), ampicillin (Amcill, Polycill) or ciprofloxacin (Ciloxan, Cipro) are most frequently used.

KEY TERMS Diuretic—Medication that increases the urine output of the body. Electrolytes—Salts and minerals that produce electrically charged particles (ions) in body fluids. Common human electrolytes are sodium chloride, potassium, calcium, and sodium bicarbonate. Electrolytes control the fluid balance of the body and are important in muscle contraction, energy generation, and almost all major biochemical reactions in the body. Lactobacillus acidophilus—This bacterium is found in yogurt and changes the balance of the bacteria in the intestine in a beneficial way. Platelets—Blood cells that help the blood to clot.

tion by replacing fluids and electrolytes lost through vomiting and diarrhea. Electrolytes are salts and minerals that form electrically charged particles (ions) in body fluids. Electrolytes are important because they control body fluid balance and are important for all major body reactions. Pharmacists can recommend effective, pleasant-tasting, electrolytically balanced replacement fluids that are available without a prescription. When more fluids are being lost than can be consumed, dehydration may occur. Dehydration is more likely to happen in the very young, the elderly, and people who are taking diuretics. To prevent dehydration, a doctor may give fluids intravenously. In very serious cases of food poisoning, medications may be given to stop abdominal cramping and vomiting. Anti-diarrheal medications are not usually given. Stopping the diarrhea keeps the toxins in the body longer and may prolong the infection. People with food poisoning should modify their diet. During the period of active vomiting and diarrhea, they should not try to eat and should drink only clear liquids frequently but in small quantities. Once active symptoms stop, they should eat bland, soft, easily digested foods for two to three days. Such foods include bananas, rice, applesauce, and toast, all of which are easy to digest. Milk products, spicy food, alcohol, and fresh fruit should be avoided for a few days, although babies should continue to breastfeed. These modifications are often all the treatment that is necessary. Severe bacterial food poisonings are sometimes treated with antibiotics. Trimethoprim and sulfamethox984

Botulism is treated in a different way from other bacterial food poisonings. Botulism antitoxin is given to adults but not infants if it can be administered within 72 hours after symptoms are first observed. If given later, it provides no benefit. Both infants and adults require hospitalization, often in the intensive care unit. If the ability to breathe is impaired, patients are put on a mechanical ventilator to assist their breathing and are fed intravenously until the paralysis passes. Alternative treatment Alternative practitioners offer the same advice as traditional practitioners concerning diet modification. In addition, they recommend taking charcoal tablets, Lactobacillus acidophilus, Lactobacillus bulgaricus, and citrus seed extract. An electrolyte replacement fluid can be made at home by adding one teaspoon of salt and four teaspoons of sugar to one quart of water. For food poisoning other than botulism, two homeopathic remedies, either Arsenicum album or Nux vomica, are strongly recommended.

Prognosis Most cases of food poisoning (except botulism) clear up on their own within one week without medical assistance. The patient may continue feel tired for a few days after active symptoms stop. So long as the sick person does not become dehydrated, there are few complications. Deaths are rare and usually occur in the very young, the very old, and people whose immune systems are already weakened. Complications of Salmonella food poisoning include arthritis-like symptoms that occur three to four weeks after infection. Although deaths from Salmonella are rare, they do occur, mostly in elderly people in nursing homes. Adults usually recover without medical intervention, but many children need to be hospitalized as the result of E. coli food poisoning. E. coli toxins may be absorbed into the blood stream where they destroy red blood cells and platelets, which are important in blood clotting. About 5% of victims develop hemolytic-uremic syndrome, which results in sudden kidney failure and makes dialysis necessary. (Dialysis is a medical procedure used to filter the body’s waste product when the kidneys have failed.)

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Health care team roles Definitive identification of food poisoning is made by a physician, usually with the aid of stool or blood cultures. Nurses, medical technologists, and other health care professionals often aid in taking and analyzing cultures, and in educating patients about preventive measures they can take to avoid food poisoning.

Prevention

OTHER

Agriculture Network Information Center. . The Food and Nutrition Information Center (FNIC), part of the U.S. Department of Agriculture (USDA) and the Agricultural Research Service (ARS). . FoodSafety.gov. U.S. Food and Drug Administration. Center for Food Safety and Applied Nutrition. . National Food Safety Information Network . U.S. Food and Drug Administration. Center for Food Safety and Applied Nutrition. Bad Bug Book. .

Food poisoning is almost entirely preventable by practicing good sanitation and good food handling techniques. These include:

Crystal Kaczkowski, MSc.

• Keep hot foods hot and cold foods cold. • Cook meat to the recommended internal temperature. Use a meat thermometer to check. Cook eggs until they are no longer runny. • Refrigerate leftovers promptly. Do not let food stand at room temperature. • Avoid contaminating surfaces and other foods with the juices of uncooked meats. • Wash fruits and vegetables before using. • Purchase pasteurized dairy products and fruit juices. • Throw away bulging or leaking cans, or any food that smells spoiled. • Wash hands well before and during food preparation and after using the bathroom. • Sanitize food preparation surfaces regularly. Resources PERIODICALS

Sanders, TA. “Food production and food safety.” British Medical Journal 318 (1999):1689-93. ORGANIZATIONS

Centers for Disease Control and Prevention. . United States Department of Agriculture. Food Safety and Inspection Service. Washington, DC 20250. (800) 5354555. . USDA/FDA Foodborne Illness Education Information Center. National Agricultural Library/USDA. Beltsville, MD 20705-2351. (301) 504-5719. Fax (301) 504-6409. Email: [email protected]. .

Foot care Definition Foot care involves all aspects of preventive and corrective care of the foot and ankle. Physicians specializing in foot care are called podiatrists.

Purpose During an average lifetime, each person walks about 115,000 miles; and 75% of all people have foot problems at some point in their lives. Foot problems can arise from wearing ill-fitting shoes, from general wear and tear, as a result of injury, or as a complication of disease. People with diabetes mellitus or circulatory diseases are 20 times more likely to have foot problems than the general public. Podiatrists specialize in treating the foot and ankle. Other doctors who have experience with foot problems are family physicians, orthopedists, sports medicine specialists, and those who care for diabetics. Problems with the feet include foot pain, joint inflammation, plantar warts, such fungal infections as athlete’s foot, nerve disorders, torn ligaments, broken bones, bacterial infections, and such tissue injuries as frostbite.

Precautions People with diabetes or circulatory disorders should be alert to even the smallest of foot problems. In this patient population, a break in the skin can lead to possible infection, gangrene, and amputation.

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Botulism is the deadliest of the bacterial foodborne illnesses. With prompt medical care, the death rate is less than 10%.

Foot orthoses

Description

Health care team roles

Daily foot care for people likely to develop foot problems includes washing the feet in tepid water with mild soap and moisturizing the feet with lanolin-based lotion. Toenails should be cut straight across above the level of the skin after soaking the feet in tepid water. Corns and calluses should not be cut. If they need removal, it should be done under the care of a doctor. If they develop in high-risk patients, athlete’s foot and plantar warts should also be treated by a doctor. Many people with diabetes or circulatory disorders suffer with the problem of cold feet. A problem with cold feet can be helped by not smoking (it constricts the blood vessels); not crossing the legs while sitting or sitting in one position too long; wearing warm socks; and avoiding constricting stockings. People with circulatory problems should not use heating pads or hot water bottles on their feet, as even moderate heat can damage the skin if the circulation is impaired. The patient who is at risk for foot problems should also choose socks that are soft and cushioned. Cotton material is best at wicking moisture away from the feet. Good shoes should be worn whenever the patient is ambulating or out of bed. Flat shoes are preferred, and the fit should allow about 0.75 inch (about 2 cm) between the end of the big toe and the shoe. The patient should not walk barefoot. A routine part of foot care includes an assessment of the feet for changes or injury. These can include blisters, cuts, redness, scratches, or other breaks in the skin.

Preparation

Resources PERIODICALS

Author unspecified. “Preventive Foot Care in People with Diabetes.” Diabetes Care 23 (January 2000): 55. Author unspecified. “Secrets of Preventing Foot Problems.” Diabetes Forecast 54 (February 2001): 71. Roberts, Shauna S. “Caring for Feet.” Diabetes Forecast 53 (January 2000): 10. ORGANIZATIONS

American Diabetes Association. 1701 North Beauregard Street, Alexandria, VA 22311. (800) DIABETES. .

Deanna M. Swartout-Corbeil, R.N.

Foot orthoses Definition A foot orthosis is an assistive device used in occupational and physical therapy. It is designed to support a person’s foot in a way that makes it more functional following disease or injury.

Purpose

No special preparation is necessary other than understanding the nature of foot problems.

Aftercare Foot care is preventative and should be ongoing throughout a person’s life.

Persons with foot and ankle disorders, such as arthritis, ulcers, diabetes, bunions, various forms of tendinitis, and other deformities, can benefit from foot orthoses. Typically, foot orthoses are inlays placed in a client’s shoe. The orthosis supports, cushions, and/or pads the foot.

Description Types of foot orthoses

Complications There are no complications associated with foot care. The risks are in ignoring the feet and allowing problems to develop.

Results With regular care, such foot disorders as infections, skin ulcers, and gangrene can be prevented. 986

The nurse plays an important role in identifying patients at risk for foot problems and in providing foot care. The patient should be instructed on appropriate foot care and the measures that can be taken to prevent complications.

Most clients with foot problems benefit from massproduced, prefabricated orthoses. They are relatively common and may absorb shock in the foot or provide added arch under the foot, for example. Occasionally a prefabricated orthosis is modified in some way to better accommodate a client, and this is referred to as a customized orthosis. These may be molded to better fit a client’s foot or have additional padding.

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American Physical Therapy Association. 1111 North Fairfax Street, Alexandria, VA 22314-1488. (703) 684-2782. .

Meghan M. Gourley

Operation In order for a client to use a foot orthosis appropriately, he/she must go through a thorough assessment that evaluates the position and range of motion (ROM) of foot and ankle joints in all parts of the foot. Clients should be tested while walking and bearing weight as well as while standing. Clients must be tested for rigidity and flexibility in addition to assessing any foot or ankle pain.

Maintenance Clients who are prescribed footwear need to maintain their orthoses with proper cleaning and repairs when necessary. As the condition of the foot may change or worsen, a previously prescribed orthosis may become ineffective or unnecessary, just as a prescription drug might. Periodic follow-up with a physician, occupational therapist, or appropriate health care professional is necessary to ensure that the foot orthosis remains as functional as possible.

Health care team roles A variety of health care professionals can help a client determine the most appropriate foot orthosis. Occupational or physical therapy practitioners can provide assessments and evaluations of the effectiveness of foot orthoses. Orthotists and prosthetists, although typically consulted by patients who have lost limbs, also can help in choosing an appropriate orthosis. Pedorthists can evaluate a client in need of an orthosis, provide and fit the shoe, and follow-up the client. However, a prescription for a foot orthosis is necessary. Resources BOOKS

Myerson, Mark S., ed. Foot and Ankle Disorders. Philadelphia: W.B. Saunders Company, 2000. PERIODICALS

Chen, Chiung-Ling, et al. “Anterior Ankle-Foot Orthosis Effects on Postural Stability in Hemiplegic Patients.” Archives of Physical Medicine and Rehabilitation 80 (December 1999): 1587–1592. ORGANIZATIONS

American Occupational Therapy Association. 4720 Montgomery Lane, Bethesda, MD 20824-1220. (301) 652-2682. .

Foreign bodies Definition “Foreign” means “originating elsewhere” or simply “outside the body.” Foreign bodies typically become lodged in the eyes, ears, nose, airways, and rectum of human beings.

Description Both children and adults experience problems caused by foreign objects getting stuck in their bodies. Young children in particular are naturally curious and may intentionally put such shiny objects as coins or button batteries into their mouths. They are also prone to inserting objects in their ears and nostrils. Adults may accidentally swallow a non-food object or inhale a foreign body that gets stuck in the throat or lungs. Even if an object like a toothpick successfully passes through the esophagus and into the stomach, it can get stuck inside the rectum. Airborne particles can lodge in the eyes of people at any age. Foreign bodies can be in hollow organs (like swallowed batteries) or in tissues (like bullets). They can be inert or irritating. If they irritate they will cause inflammation and scarring. They can bring infection with them or acquire it and protect it from the body’s immune defenses. They can obstruct passageways either by their size or by the scarring they cause. Some foreign bodies can be toxic.

Causes and symptoms Eyes Dust, dirt, sand, or other airborne material can lodge in the eyes, causing minor irritation and redness. More serious damage can be caused by hard or sharp objects that penetrate the surface and become embedded in the cornea or conjunctivae (the mucous membranes around the inner surface of the eyelids). Swelling, redness, bleeding from the surface blood vessels, sensitivity to light, and sudden vision problems are all symptoms of foreign matter in the eyes.

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However, some clients with severe foot deformities or disorders may not be able to use a prefabricated orthosis or even a customized orthosis. These clients require custom-molded orthoses that are made from the mold of the client’s foot for a perfect, tight fit.

Foreign bodies

Ears and nose

Diagnosis

Children will sometimes put objects into their noses, ears, and other openings. Beans, popcorn kernels, raisins, and beads are just a few of the many items that have been found in these bodily cavities. On occasion, insects may also fly into the ears and nose. Pain, hearing loss, sounds or a sense of something stuck in the ear are symptoms of foreign bodies in the ears. A smelly, bloody discharge from one nostril is a symptom of a foreign body in the nose.

Treatment Eyes

Airway and stomach At a certain age children will eat anything. A very partial list of items recovered from young stomachs includes the following: coins, chicken bones, fish bones, beads, rocks, plastic toys, pins, keys, round stones, marbles, nails, rings, batteries, ball bearings, screws, staples, washers, a heart pendant, a clothespin spring, and a toy soldier. Some of these items will pass completely through the digestive system to be excreted some time later. The progress of metal objects has been successfully followed with a metal detector. Others, like sharp bones, can get stuck and cause problems. Batteries are corrosive and must be removed immediately. Children eat things and stick things into their bodily openings of their own volition. But they inhale them unwittingly. The most commonly inhaled item is probably a peanut. A crayon and a cockroach have been found in the windpipes (tracheas) of children. These items always cause symptoms (difficulty swallowing and spitting up saliva, for instance) and may elude detection for some time while a child is being treated for asthma or recurring pneumonia. Adults are not exempt from unorthodox inedibles. Dental devices are commonly swallowed. Adults with mental illness or subversive motives may swallow such inappropriate objects as toothbrushes. Rectum Sometimes a foreign object will successfully pass through the throat and stomach only to get stuck at the juncture between the rectum and the anal canal. Items may also be self-introduced to enhance sexual stimulation and then get stuck. Sudden sharp pain during elimination may signify that an object is lodged in the rectum. Other symptoms vary depending upon the size of the object, its location, how long it has been in place, and whether or not infection has set in. 988

The symptoms of foreign bodies are as diverse as the objects and their locations. The most common manifestation of a foreign object anywhere in the body is infection. Even if an object entered in a sterile condition, bacteria still seem to find it and are able to hide from the body’s defenses there. Blockage of passageways—breathing, digestive or excretory—is another result. Pain is common.

Small particles like sand may be removable without medical help, but if the object is not visible or cannot be retrieved, prompt emergency treatment is necessary. Trauma to the eyes can lead to loss of vision and should never be ignored. Before attempting any treatment, a person should move to a well-lighted area where the object can be more easily spotted. Hands should be washed, and only clean, preferably sterile, materials should make contact with the eyes. If the particle is small, it can be dislodged by blinking or pulling the upper lid over the lower lid and flushing out the speck. A clean cloth can also be used to pick out the offending particle. Afterwards, the eye should be rinsed with clean, lukewarm water or an ophthalmic wash. If the foreign object cannot be removed at home, the eye should be lightly covered with sterile gauze to discourage rubbing. A physician will use a strong light and possibly special eyedrops to locate the object. Surgical tweezers can effectively remove many objects. An antibiotic sterile ointment and a patch may be prescribed. If the foreign body has penetrated the deeper layers of the eye, an ophthalmic surgeon will be consulted for emergency treatment. Ears and nose A number of ingenious extraction methods have been devised for removing foreign objects from the nose and ears. A bead in a nostril, for example, can often be popped out by blowing into the mouth while holding the other nostril closed. Skilled practitioners have removed peas from the ears by tiny improvised corkscrews. Marbles have been extracted by using cotton swabs and super glue. Tweezers often work well. Insects can be floated out of the ear by pouring warm (not hot) mineral oil, olive oil, or baby oil into the ear canal. Items that are lodged deep in the ear canal are more difficult to remove because of the possibility of damaging the ear drum. These require emergency treatment from a qualified physician.

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Mechanical obstruction of an airway, which commonly occurs when food gets lodged in the throat, can be treated by applying the Heimlich maneuver. If the object is lodged lower in the airway, a bronchoscope (a special instrument to view the airway and remove obstructions) can be inserted. On other occasions, as when an object is blocking the entrance to the stomach, a fiberoptic endoscope (an illuminated instrument that views the interior of a body cavity) may be used. A physician typically administers a sedative and anesthetizes the throat. The foreign object will then either be pulled out or pushed into the stomach, depending on whether or not the physician thinks it will pass through the digestive tract on its own. Objects in the digestive tract that are not irritating, sharp or large may be followed as they continue on through. Sterile objects that are causing no symptoms may be left in place. Surgical removal of an offending object is necessary only if it causes symptoms. Rectum A rectal retractor can remove objects that a physician can feel during physical examination. Surgery may be required for objects deeply lodged within the rectum.

Prognosis Once foreign objects are removed, persons have no further medical problems. If surgery is required (such as to remove a bullet), permanent damage may be sustained when the object initially enters the body. Once surgical incisions have healed, many persons have no further medical problems. Counseling may be needed to help persons cope with potential after-effects.

Health care team roles First aid may be provided by trained persons. Emergency medical technicians may provide support while transporting people to a hospital or emergency treatment facility. Physicians remove most foreign objects. Surgeons may be needed to remove some objects from the eye (ophthalmologists), ears (otolaryngologists), gastrointestinal system (gastroenterologists), brain (neurosurgeons) or body tissues (general surgeons). Radiologists may document progress of an object through the body. Nurses supply supportive care and prevention education to the patient or family. Therapists may be needed to cope with such after-effects as physical impairment, mental distress or simple embarrassment.

KEY TERMS Bronchoscope—An illuminated instrument that is inserted into the airway to inspect and retrieve objects from the bronchial tubes. Conjunctivae—Mucous membranes around the inner surface of the eyelid. Cornea—The rounded, transparent portion of the eye that covers the pupil and iris and lets light into the interior. Endoscopy—The surgical use of long, thin instruments that have both viewing and operating capabilities. Heimlich maneuver—An emergency procedure for removing a foreign object lodged in the airway that is preventing the person from breathing. To perform the Heimlich maneuver on a conscious adult, the rescuer stands behind the victim and encircles the choking person’s waist. The rescuer makes a fist with one hand and places the other hand on top, positioned below the rib cage and above the waist. The rescuer then applies pressure by a series of upward and inward thrusts to force the foreign object back up the choking person’s trachea. Trachea—Windpipe. The tube that connects the pharynx with the lungs.

Prevention Using common sense and following safety precautions are the best ways to prevent foreign objects from entering the body. For instance, parents and grandparents should toddler-proof their homes, storing batteries in a locked cabinet and properly disposing of used batteries, so they are not in a location where curious preschoolers can retrieve them from a wastebasket. To minimize the chance of youngsters inhaling food, parents should not allow children to eat while walking or playing. Adults should chew food thoroughly and not talk while chewing. Foods should not be thrown up into the air and caught in an open mouth. Many eye injuries can be prevented by wearing safety glasses while using power tools. Resources BOOKS

Orenstein, David M. “Foreign bodies in the larynx, trachea and bronchi.” In Nelson Textbook of Pediatrics, 16th Edition, edited by Richard E. Behrman et al., Philadelphia: Saunders, 2000, 1279-1282.

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Airways and stomach

Fractures

Schwartz, Seymour, Tom Shires, and Frank C.Spencer, Principles of Surgery, 7th ed. New York: McGraw Hill, 1998. Simon, Robert R., and Barry E. Brenner, Emergency Procedures and Techniques. Philadelphia: Lippincott Williams & Wilkins, 2001. Tintinalli, Judith E, J Stephen Stapcynski, and Gabor D. Kelen, Emergency Medicine. New York: Appleton and Lange, 2000. Townsend, Courtney M. Sabiston Textbook of Surgery: The Biological Basis of Modern Surgical Practice, 16th ed. Philadelphia: Saunders, 2001. PERIODICALS

Cook DS. “Dietary dangers: ingestion of a bread bag clip.” Journal of Clinical Pathology 54, no. 1 (2001): 79-81. Eliashar R, Gross M, Dano I, Sichel JY. “Esophageal fish bone impaction.” Journal of Trauma 50, no. 2 (2001): 384-385. Faust J, Schreiner O. “A swallowed toothbrush.” Lancet 357, no. 9261 (2001): 1012-1014. Horton LK, Jacobson JA, Powell A, Fessell DP, Hayes CW. “Sonography and radiography of soft-tissue foreign bodies.” American Journal of Roentgenology 176, no. 5 (2001): 1155-1159. Lau KF, Jayaram R, Fitzgerald DA. “Diagnosing inhaled foreign bodies in children.” Medical Journal of Australia 174, no. 4 (2001): 194-196. Nakashabendi IM, Maldonado ME, Brady PG. “Chest pain: overlooked manifestation of unsuspected esophageal foreign body.” Southern Medical Journal 94, no. 3 (2001): 333-335. Reedy IS. “Foreign bodies in the nasal cavities: a comprehensive review of the aetiology, diagnostic pointers, and therapeutic measures.” Postgraduate Medicine Journal 77, no. 905 (2001): 215-217. ORGANIZATIONS

American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. (847) 4344000. Fax: (847) 434-8000. E-mail: [email protected]. American College of Radiology. 1891 Preston White Drive, Reston, VA 20191. (703) 648-8900. Fax: (703) 262-9319. . [email protected]. American Osteopathic College of Radiology. 119 East Second St., Milan, MO 63556. (660) 265-4011. Fax: (660) 2653494. . [email protected]. OTHER

American Society for Gastrointestinal Endoscopy. . Baylor College of Medicine. . Mayo Clinic. and . 990

Stanford University Medical Center. . University of Maryland. . University of the Philippines. .

L. Fleming Fallon, Jr., MD, DrPH

Fractures Definition A fracture is a complete or incomplete break in a bone resulting from the application of excessive force. An injury may be classified as a fracture-dislocation when a fracture involves the bony structures of any joint with associated dislocation of the same joint.

Description Fractures usually result from traumatic injury to a bone, causing the continuity of bone tissues or bony cartilage to be disrupted or broken. Fracture classifications include simple, compound, incomplete, and complete. Simple fractures (more recently termed closed fractures) are not obvious on the surface, as the skin has not been broken and remains intact. Compound fractures (now commonly referred to as open fractures) break the skin, exposing bone and causing additional soft tissue injury and possible infection. Single and multiple fractures refer to the number of breaks in the same bone. Fractures are termed complete if the break is completely through the bone, and described as incomplete or “greenstick” if the fracture occurs partly across a bone shaft. This latter type of fracture is often the result of bending or crushing forces applied to a bone. Fractures are also named by the specific portion of the bone involved and the nature of the break. Identification of a fracture line can further classify fractures. Types include linear, oblique, transverse, longitudinal, and spiral fractures. Fractures can be further subdivided by the positions of bony fragments and are described as comminuted, non-displaced, impacted, overriding, angulated, displaced, avulsed, and segmental. Fracture lines identification Linear fractures have a break that runs parallel to the bone’s main axis or in the direction of the bone’s shaft. For example, a linear fracture of the arm bone could

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Fractures An x ray can be used to diagnose a fracture, as in this x ray of a fractured humerus bone. (Bates MD/Custom Medical Stock Photo. Reproduced by permission.)

extend the entire length of the bone. Oblique and transverse fractures differ in that an oblique fracture crosses a bone at approximately a 45° angle to the bone’s axis. In contrast, a transverse fracture crosses a bone’s axis at a 90° angle. A longitudinal fracture is similar to a linear fracture. Its fracture line extends along the shaft but is more irregular in shape and does not run parallel to the bone’s axis. Spiral fractures are described as crossing a bone at an oblique angle, creating a spiral pattern. This type of break usually occurs in the long bones of the body such as the upper arm bone (humerus) or the thigh bone (femur). Bony fragment position identification Comminuted fractures have two or more fragments broken into small pieces, in addition to the upper and lower halves of a fractured bone. Fragments of bone that maintain their normal alignment following a fracture are described as being non-displaced. An impacted fracture is characterized as a bone fragment forced into or onto another fragment, resulting from a compressive force. Overriding is a term used to describe bony fragments that

overlap and shorten the total length of a bone. Angulated fragments result in pieces of bone being at angles to each other. A displaced bony fragment occurs from disruption of normal bone alignment with deformity of these segments separate from one another. An avulsed fragment occurs when bone fragments are pulled from their normal position by forceful muscle contractions or resistance from ligaments. Segmental fragmented positioning occurs if fractures in two adjacent areas occur, leaving an isolated central segment. An example of segmental alignment occurs when the arm bone fractures in two separate places, with displacement of the middle section of bone.

Causes and symptoms Individuals with high activity levels appear to have a greater risk for fractures. This group includes children and athletes participating in contact sports. Because of an increase in bone brittleness with aging, elderly persons are also included in this high-risk population. It has been recognized that up to the age of 50, more men suffer from fractures than women due to occupational hazards. However, after the age of 50, more women suffer frac-

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tures than men. Specific diseases causing an increased risk for fractures include Paget’s disease, rickets, osteogenesis imperfecta, osteoporosis, and prolonged disuse of a nonfunctional body part such as after a stroke. Symptoms of fractures usually begin with pain and swelling at the involved site. There may also be a great deal of tenderness in the area near the fracture. The skin in the area may be pale and an obvious deformity may be present. In more severe cases, there may be a loss of pulse below the fracture site (such as in the extremities), accompanied by numbness, tingling, or paralysis below the fracture. An open or compound fracture is often accompanied by bleeding or bruising. If a leg is fractured, weakness will usually accompany the injury, causing difficulty with weight bearing.

Diagnosis Diagnosis begins immediately with an individual’s own observation of symptoms. A thorough medical history and physical exam completed by a physician or advanced practice nurse often provides enough information to determine if further testing is necessary. An x ray of the injured area is the most common test used to determine the presence of a bone fracture and its associated displacement. However, it is important to note that not all fractures are apparent on an initial x ray. Rib fractures are often difficult to diagnose and may require several views at different angles to see any fracture lines. If a fracture is open and occurs in conjunction with soft tissue injury, further laboratory studies are often conducted to determine if blood loss has occurred. In the event of exercise-related stress fractures (micro-fractures due to excessive stress), a tuning fork can provide a simple, inexpensive test. The tuning fork is a metal instrument with a stem and two prongs that vibrate when struck. If an individual has increased pain when the tuning fork is placed on a bone, such as the lower leg bone or shinbone, the likelihood of a stress fracture is high. Bone scans are also helpful in detecting stress fractures. In this diagnostic procedure, a radioactive tracer is injected into the blood stream and images are taken of specific areas or the entire skeleton.

Treatment Fracture treatment depends on the type of fracture, its severity, and the individual’s age and general health. The first priority in treating any fracture is to address the entire medical status of an individual. If an open fracture is accompanied by serious soft tissue injury, it may be necessary to control bleeding and the shock that can accompany loss of blood. 992

First aid is the appropriate initial treatment in emergency situations. It includes proper splinting, control of blood loss, and monitoring vital signs such as breathing and circulation. Immobilization Immobilization of a fracture site can be done internally or externally. The primary goal of immobilization is to maintain the realignment of a bone long enough for healing to start and progress. Immobilization by external fixation uses splints, casts, or braces. This may be the primary and only procedure for fracture treatment. Splinting to immobilize a fracture can be done with or without traction. In emergency situations, splinting is a useful form of fracture management if the injured individual must be moved by someone other than a trained medical professional. Splinting should be done without causing additional pain and without moving the bone segments. In a clinical environment, plaster of Paris casts are used for immobilization. Braces are also useful, as they often allow movement above and below a fracture site. Treatments for stress fractures include rest and decreasing or stopping any activity that causes or increases pain. Fracture reduction Fracture reductions are either closed or open. Closed reduction refers to realigning bones without breaking the skin. It is accomplished using manipulation and/or traction and is commonly done with some kind of anesthetic. Open reduction primarily refers to surgery that is performed to realign bones or fragments. Fractures with little or no displacement may not require any form of reduction. Traction is used to help reposition a broken bone. It works by applying pressure to restore proper alignment. The traction device immobilizes the area and maintains realignment as the bone heals. A fractured bone is immobilized by applying opposing forces at both ends of an injured area, using an equal amount of traction and countertraction. Weights provide the traction pull needed, or the pull is achieved by positioning the individual’s body weight. Traction is a form of closed reduction and is sometimes used as an alternative to surgery. Since it restricts movement of an affected limb or body part, it may confine a person to bed rest for an extended period of time. A person may need open reduction if there is an open, severe, or comminuted fracture. This procedure allows a physician to examine and surgically correct associated soft tissue damage while reducing the fracture and, if necessary, applying internal or external devices. Internal fixation is a surgical procedure that is required

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Alternative treatment In addition to the importance of calcium for strong bones, many alternative treatment approaches advocate mineral supplements to help build and maintain a healthy, resilient skeleton. Some physical therapists use electrostimulation over a fractured site to promote healing. Chinese traditional medicine may be helpful by working to reconnect chi through the meridian lines along the line of a fracture. Homeopathy can enhance the body’s healing process. Two particularly useful homeopathic remedies are arnica (Arnica montana) and symphytum (Symphytum officinalis). If possible, applying contrast hydrotherapy to an extremity (e.g., a hand or foot) of a fractured area can assist healing by enhancing circulation.

Prognosis Fractures can normally be cured with proper first aid and appropriate aftercare. If determined necessary, the fractured site should be manipulated, realigned, and immobilized as soon as possible. Realignment has been shown to be much more difficult after six hours. Healing time varies from person to person, with the elderly generally needing more time to heal completely. A non-union fracture may result when a fracture does not heal, such as in the case of an elderly person or an individual with medical complications. Recovery is complete when there is no bone motion at the fracture site, and x rays indicate complete healing.

Health care team roles When treating most fractures, an orthopedic surgeon is the head of the health care team. These physicians have specialized training in bones. They are responsible for reducing, realigning, and immobilizing fractured bones. In the absence of an orthopedic surgeon, a general surgeon or a family practitioner may treat simple, closed fractures. Emergency medical service providers may render immediate first aid to persons with fractures. After fracture reduction and healing have occurred, physical therapists may assist in returning injured body parts to their normal levels of function.

Prevention Adequate calcium intake is necessary for strong bones and can help decrease the risk of fractures. People

Fractures

when a fracture cannot be reduced by closed fracture methods. Internal fixation devices include plates, nails, screws, and rods. When healing is complete, the physician may or may not elect to remove these devices.

KEY TERMS Avulsion fracture—A fracture caused by the tearing away of a fragment of bone where a strong ligament or tendon attachment forcibly pulls the fragment away from the bone tissue. Axis—A line that passes through the center of the body or body part. Comminuted fracture—A fracture in which there are several breaks in a bone, creating numerous fragments. Contrast hydrotherapy—A series of hot and cold water applications. A hot compress (as hot as an individual can tolerate) is applied for three minutes followed by an ice cold compress for 30 seconds. These applications are repeated three times each and ending with the cold compress. Osteogenesis imperfecta—A genetic disorder involving defective development of connective tissues, characterized by brittle and fragile bones that are easily fractured by the slightest trauma. Osteoporosis—Literally meaning “porous bones,” this condition occurs when bones lose an excessive amount of their protein and mineral content, particularly calcium. Over time, bone mass and strength are reduced leading to increased risk of fractures. Paget’s disease—A common disease of bone of unknown cause, usually affecting middle-aged and elderly people, characterized by excessive bone destruction and unorganized bone repair. Reduction—The restoration of a body part to its original position after displacement, such as the reduction of a fractured bone by bringing ends or fragments back into original alignment. The use of local or general anesthesia usually accompanies a fracture reduction. If performed by outside manipulation only, the reduction is described as closed; if surgery is necessary, it is described as open. Rickets—A condition caused by the deficiency of vitamin D, calcium, and usually phosphorus, seen primarily in infancy and childhood, and characterized by abnormal bone formation. Traction—The process of placing a bone, limb, or group of muscles under tension by applying weights and pulleys. The goal is to realign or immobilize the part or to relieve pressure on that particular area to promote healing and restore function.

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who do not get enough calcium in their diets can take a calcium supplement. Exercise can help strengthen bones by increasing bone density, thereby decreasing the risk of fractures from falls. A University of Southern California study reported that older people who exercised one or more hours per day had approximately half the incidence of hip fractures as those who exercised fewer than 30 minutes per day or not at all. Fractures can be prevented if safety measures are taken seriously. These measures include using seat belts in cars and encouraging children to wear protective sports gear. Estrogen replacement for women past the age of 50 has been shown to help prevent osteoporosis and the fractures that may result from this condition. In one study, elderly women on estrogen replacement therapy demonstrated a lower risk of hip fractures when compared to similar women not on estrogen replacement therapy. Resources BOOKS

Burr, David B. Musculoskeletal Fatigue and Stress Fracture. Boca Raton, FL: CRC Press, 2001. Jupiter, J. Fractures and Dislocations of the Hand. St. Louis, MO: Mosby, 2001. Moehring, H. David and Greenspan, Adam. Fractures: Diagnosis and Treatment. New York: McGraw Hill, 2000. Ogden, John A. Skeletal Injury in the Child. New York: Springer Verlag, 2000. Schenck, Robert C. and Barnes, Ronnie P. Athletic Training and Sports Medicine, 3rd ed. Chicago, IL: American Academy of Orthopaedic Surgery, 1999. Wiss, Donald A., and Williams, Christopher B. Fractures. Baltimore, MD: Williams and Wilkins, 1998. PERIODICALS

Lesho, Emil P. “Tuning Fork Test Finds Fractures.” Military Medicine 162 (1997): 802-803. ORGANIZATIONS

American Academy of Orthopaedic Surgeons. 6300 North River Road, Rosemont, IL 60018-4262. (847) 823-7186 or (800) 346-2267. Fax: (847) 823-8125. . American College of Sports Medicine. P.O. Box 1440, Indianapolis, IN 46206-1440. 401 W. Michigan St., Indianapolis, IN 46202. (317) 637-9200, Fax: (317) 6347817. Children’s Orthopedics of Atlanta. . Nemours Foundation. . 994

OTHER

Family Practice Notebook. . National Library of Medicine. .

L. Fleming Fallon, Jr., MD, PhD, DrPH

Frostbite and frostnip see Cold injuries

Fungal culture Definition Fungal (mycotic) cultures are microbiology laboratory tests to detect or rule out the presence of fungi (plural of fungus) in specimens taken from patients, animals, and the environment. The laboratory uses optimal conditions to grow and identify any fungus present in the specimen while attempting to eliminate or identify contaminants. The specimen is cultured by spreading a small portion of it on various agar media (inoculation). The media are then incubated in a warm, moist environment and examined regularly to detect growth of any organisms. The isolated fungus is identified primarily by its colony morphology and microscopic structures. Mycology, the study of fungi Fungi are simple plantlike organisms that do not have roots, stems, or leaves and that live off organic matter such as skin, hair, and vegetation. The group includes mushrooms, yeast, rusts, smuts, molds, and mildews, but only yeast and molds typically cause disease in humans. The basic structural unit of a fungus is either a single yeast cell, or multicellular filamentous hyphae, which are the tubular projections of molds. Molds grow by elongation and branching of hyphae during the vegetative (feeding) stage and produce spores during the reproductive stage. Spores are small reproductive bodies that are capable of sprouting new hyphae. Multiple, loosely intertwined hyphae strands called mycelia are the fluffy, colorful colonies seen as mold growing on rotting fruit. These mycelia are spore producing structures. Yeast primarily reproduce by budding, which is the out-pouching and eventual pinching off of part of the cell. A chain of budding yeast cells adhering together may appear to be like hyphae and are called pseudohyphae. Some fungi, capable of existing in either a yeast or filamentous mold form, depending on the environment, are called dimorphic. The term fungal elements includes any of the structures that may be seen during examination of specimens

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Fungi differ from higher plants in that they do not contain chlorophyll and thus cannot manufacture their own carbohydrates. They must use preformed carbon and nitrogen compounds made by other organisms and are therefore either saprophytic (living on dead or decaying organic matter) or parasitic (living on or within other living organisms). Most fungi trace back to a soil origin. All are obligate aerobes (require oxygen to survive), and tend to thrive in a dark, moist, undisturbed atmosphere. They grow well at room temperature, but some of the pathogenic (disease causing) dimorphic fungi also grow well at body temperature. Of the more than 50,000 species of fungi, only 100 to 150 species of yeast and molds cause disease in humans. The number routinely seen is much lower. Humans are generally resistant to fungi even when they become accidental hosts by inhaling spores or by having a cut or scrape exposed to a fungus. However, inhalation of spores of some of the dimorphic fungi produces illness ranging from mild cough and fever to severe disseminated disease. People with weakened immune systems (immunocompromised) are susceptible to illness from many normally harmless fungi. The characteristics of fungi that make them pathogenic to humans are: • a small enough spore size to be able to reach the alveoli of the lungs • the ability to grow at body temperature • the ability of a dimorphic fungus to convert from a mold to a yeast form within the host • toxin production

Purpose The purpose of the fungal culture is to attempt to grow and identify any fungus originating from a patient’s specimen when the medical staff of a hospital, clinic or doctor’s office suspects fungal infection. Further, the goal is to determine whether the isolated fungus is clinically significant; that is, the causative agent of the patient’s disease. While the physician makes the final decision regarding clinical significance, the laboratory may assist in this process by noting the presence of common contaminants, etc. Since the goal is also to provide information in a timely manner, fungal cultures will usually include smears and stains taken directly from the specimen for microscopic examination. The direct examination attempts to visually detect such fungal elements as hyphae, yeast, or spores.

Precautions Contraindications It should be noted that 90% of fungal infections are due to dermatophytes (fungi that infect skin, hair and nails), which do not normally need a fungal culture for diagnosis. A dermatologist can generally make the diagnosis in the office from a KOH preparation (see section on direct examination of specimens) along with the patient’s symptoms and site of infection. However, a culture may be needed to prove that a skin condition is not due to nerves, psoriasis, or metabolic imbalances. Another contraindication for fungal cultures is if the patient has already been treated with antifungal medication. Many patients who see their doctor for the first time with a possible fungal infection have already been treating themselves with such over-the-counter antifungal medication as imidazoles. A fungus may be causing an infection in the patient, yet antifungal agents present within the specimen suppress the growth of the organism in culture. All topical antifungal therapy should be stopped for at least one week prior to culture. Safety precautions The medical staff should observe their institution’s procedures to protect both themselves and their patients from spread of infectious diseases. The use of such protective barriers as gloves, gowns, aprons, masks or protective eyewear can reduce the risk of exposure of the health care worker to potentially infective materials. All medical staff should take precautions to prevent injuries by needles, scalpels and other sharp instruments during procedures; when cleaning used instruments; and during disposal of used needles. Gloves should be changed after contact with each patient. Hands and other skin surfaces should be washed immediately after gloves are removed. When collecting blood, genital, tissue, cerebrospinal and other body fluid specimens universal cautions for the prevention of transmission of bloodborne pathogens should be followed. Laboratory personnel need to take several precautions when working with fungal cultures. The cultures should never be sniffed. Fungus colonies may release airborne spores that can be inhaled. Processing of specimens and all work with exposed fungus cultures should be performed in a biological safety hood. Spattering of infectious material by careless flaming of wire needles or loops should be avoided. Cultured petri dishes should be sealed with oxygen-permeable tape. Test tubes should have screw-type caps rather than cotton plugs. All contaminated materials must be autoclaved before discarding, and the work area should be disinfected daily.

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or cultures: yeast, budding yeast, hyphae, pseudohyphae, spores, and mycelia.

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Description The fungus culture is a microbiology laboratory test that is part of a comprehensive attempt to determine if any microorganism is causing an infection in a patient. The physician and nursing staff must first suspect the possibility of infection and order the appropriate cultures. The possibilities include testing not only for fungi, but also for aerobic and anaerobic bacteria; mycobacteria (also called acid-fast bacteria, AFB, a family of bacteria which includes the tuberculosis organism); viruses; or parasites. Many fungal infections are clinically similar to mycobacterial infections and so the same specimen is often cultured for both fungi and mycobacteria. Although fungal cultures are usually covered by insurance, they are costly and timeconsuming. Cultures should be ordered only when the medical staff is reasonably suspicious of a fungal infection or when the patient is very ill and the culture is a critical part of assessing the illness. The test is also performed in the offices of dermatologists who frequently encounter fungal skin infections. The office staff may report the presence of dermatophytes or yeast, but a reference laboratory is usually required for specific identification. Direct examination of specimens The direct examination of specimens is an important first step in processing the specimen for several reasons. Since fungi take days to weeks to grow in culture on agar media, a direct examination result provides a rapid report to the physician, which may allow early treatment to begin. Sometimes easily identifiable morphological characteristics of a fungus may be seen on a direct exam, giving a clue as to the identification of the organism. This information may be helpful not only to the physician but also to the laboratory personnel who can set up additional specialized media to hasten the identification of the fungus. The information may also indicate the need to harvest specimens from other body sites and order serological tests. Direct examinations may also provide evidence of infection even when the fungus culture is negative. KOH PREPARATION WITH CALCOFLUOR WHITE. The potassium hydroxide (KOH) preparation is used to detect fungal elements in virtually all types of clinical specimens, especially skin, nails, hair, sputum, concentrated urine, and tissue. A 10% to 20% solution of KOH is mixed with the specimen on a slide, a coverslip is placed on top of the preparation and the slide is gently heated. The preparation is then viewed under the 10x (low power) objective of a light microscope with fairly low illumination. KOH dissolves keratin and other cellular material but leaves the fungal structures intact and refractile. Hyphae, pseudohyphae, yeast, and spores can be seen. Calcofluor white, a fluorescent dye, may be added

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to the KOH preparation to aid in visualizing the fungal elements. Calcofluor white binds to polysaccharides in the cell wall of fungi, and fluoresces either apple-green or blue-white, depending on the combination of filters used in a fluorescent microscope. INDIA INK PREPARATION AND CRYPTOCOCCAL ANTIGEN TEST. Traditionally, India ink preparations have

been used to examine cerebrospinal fluid (CSF) and other clear body fluids for the presence of the encapsulated yeast Cryptococcus neoformans. A drop of India ink is mixed with a drop of sediment from a centrifuged specimen and the preparation is examined under the light microscope. Budding yeast in CSF surrounded by a large clear capsule against a black background is presumptive evidence of C. neoformans meningitis. Since only 50% of these meningitis patients have at least one positive India ink preparation, many laboratories now use the latex agglutination test for cryptococcal antigen in place of the India ink examination. This test detects the capsular polysaccharide antigen of C. neoformans in the supernatant of centrifuged CSF and serum. OTHER DIRECT PREPARATIONS. Stains used in other parts of the laboratory will detect fungal elements. The gram stain, which is performed on specimens sent for bacterial culture, will detect most fungi, if present. The acid-fast stain used for the detection of mycobacteria will also detect Blastomyces dermatitidis. The Papanicolaou stain, which is used to examine secretions for the presence of malignant cells, also stains fungal elements well. The Wright stain, which is used routinely on peripheral blood smears and bone marrow aspirates, will also detect Histoplasma capsulatum and Cryptococcus neoformans. Common tissue stains that are excellent for the detection of fungal elements are the periodic acid-Schiff (PAS) stain, the Gomori methenamine-silver nitrate (GMS) stain, and the Mayer mucicarmine stain. Fluorescent antibody stains can be used to detect fungi directly in tissue or fluids and stains for specific organisms are available at the national Centers for Disease Control (CDC) in Atlanta, Georgia. Molecular probes capable of detecting fungi in clinical specimens are promising but not yet commercially available.

Culturing specimens As the direct examination of the specimen is proceeding, the specimen is set up as a culture without delay. The viability of fungi decreases with time, and contaminant overgrowth may hinder the recovery of the pathogen. When delay cannot be avoided, the specimens, with the exception of blood, CSF, and dermatological (skin, hair, nail) specimens, can be refrigerated for a short time. It is not necessary to concentrate most mycology

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For optimal recovery of fungi, a battery of agar media should be inoculated. Common media for primary fungal isolation include Sabouraud dextrose agar and brain-heart infusion agar, either in petri dishes or screwtop tubes. The media may be enriched with 5% to 10% sheep blood to support the growth of certain fungi. Specimens that are likely to be contaminated with other microorganisms, such as urine or sputum, are set up on agar media containing antimicrobials. Chloramphenicol, streptomycin, or penicillin are incorporated into the agar to inhibit the growth of bacteria, and cycloheximide is used to inhibit the growth of contaminant fungi. Fungus cultures are incubated at either at 30°C. (86°F.) or at room temperature (22-25°C or 72-77°F). A temperature of 30°C is recommended because nearly all pathogenic fungi grow better and more rapidly at this temperature. A relative humidity of 40% to 50% is desired to prevent the agar from drying out over time and can be achieved by placing an open pan of water in the incubator. Cultures should be incubated for 30 days and examined at least three times weekly before reporting as negative. Dermatophyte cultures should be incubated six weeks at room temperature. Identification of positive cultures The fungi grown in positive cultures are identified by noting their growth rate, colonial morphology, and microscopic structures. Rapid-growing fungi appear in one to three days, intermediate growers take five to nine days to colonize and slow growers take up to four weeks to appear. Colonial morphology traits include color, size, texture, and topography of the colony. Yeast colonies resemble bacterial colonies (moist, rounded, opaque and raised), whereas mold colonies are described variously as wrinkled, heaped, folded, etc. The pigments of both the underside and top of the colony are noted. The examination of microscopic structures of fungi usually provides definitive identification for molds. Microscopic morphological features that are looked for are the type, size, shape and arrangement of spores and the size and color of hyphae. It is also important to note whether the hyphae have cross walls (septations). Yeast identification may require biochemical tests for fermentation and assimilation of carbohydrates.

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specimens except for body fluids over 5 milliliters, such as urine. If such respiratory secretions as sputum are highly viscous, mucolytic agents may be added to liquefy the secretions and facilitate plating on agar media. Tissue samples are ground with a mortar and pestle in a small amount of sterile saline before being inoculated onto media.

Fungus culture topography. (Delmar Publishers, Inc. Reproduced by permission.)

Microscopic observation of molds is done by using several techniques, always prepared in a biological safety hood. Transparent tape preparations are a rapid method for observing the arrangement of spores. The tape is pressed, sticky side down, on the surface of a mold colony and then onto a slide containing a drop of dyemounting fluid such as lactophenol cotton blue (LPCB). The preparation is then examined under low and high magnification on the microscope for spore type and arrangement. In a wet mount preparation, portions of colonies are teased apart with a dissecting needle, transferred to a drop of LPCB and observed under a coverslip on the microscope. Occasionally, a slide culture is needed to observe spore production. In this procedure, a small cube of agar media is inoculated on four sides with the fungus, placed between two coverslips and incubated five to ten days. When spores are evident, the coverslips are removed and mounted in LPCB and examined under the microscope. Susceptibility testing Susceptibility testing of fungal isolates to antifungal agents is generally done only after treatment failure. Testing is done by a reference microbiology laboratory using the minimal inhibitory concentration (MIC) method. Common antifungal agents include amphotericin B, griseofulvin, fluconazole, itraconazole, ketoconazole, miconazole, clotrimazole, flucytosine and nystatin.

Preparation Specimen collection The proper collection of appropriate specimens is critical to successful fungus cultures and diagnosis of

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mycotic infections. The laboratory should be sent fresh specimens, properly obtained and labeled, of satisfactory volume, and accompanied by pertinent, critical patient information. All specimens for fungus culture should be transported to the microbiology laboratory and processed as soon as possible. Since many pathogenic fungi grow slowly, any delay in processing increases the possibility of overgrowth by rapidly growing contaminants and decreases the probability of isolating the causative agent. Although almost any tissue or body fluid can be submitted for fungal culture, the most common specimens are respiratory tract secretions, hair, skin, nails, tissue, blood, bone marrow, and CSF.

Blood cultures are helpful to detect disseminated fungal infections. Blood from patients that are septic (growing organisms in their blood) can harbor a wide variety of fungal pathogens as well as opportunistic saprophytes. Yeast are adequately recovered from any of several automated bacterial blood culture systems in use in microbiology laboratories, but filamentous fungi may require specialized techniques for isolation and fungal blood cultures should be specified. A lysis-centrifugation system may be employed which lyses red and white blood cells that may be harboring fungi. After lysis, centrifugation concentrates the organisms before culturing on fungal media.

Direct microscopic examination of specimens for fungal elements should always be requested along with fungus culture. Specimens or cultures that need to be sent to a reference laboratory over a long distance should be sent by air-express service. Taped screw-top tubes must be placed in a container, then placed in a second container. The outside label must include a biohazard label.

Cerebrospinal fluid for fungal culture should ideally be of a volume of one to two milliliters or more. The specimen is transported to the lab immediately in a sterile, leak-proof tube. The second or third tubes collected in the lumbar puncture are preferred for any microbiology culture. An India-ink preparation and latex agglutination for cryptococcal antigen test should be requested along with fungal culture.

Specimen types Respiratory tract secretions including sputum, bronchial washings, and tracheal aspirates are the most common specimen types submitted for fungus cultures, as many fungal infections have a primary focus in the lungs. Patients ideally should provide sputum from a deep cough after rising in the morning. All respiratory specimens should be collected into sterile, leak-proof, screw-top containers. Hair, skin, and nail scrapings submitted for dermatophyte culture are generally contaminated with bacteria and/or rapidly growing contaminant fungi. Skin and nails should be disinfected with 70% isopropanol before sampling. Skin samples are gently scraped from the outer edge of a surface lesion using a sterile scalpel. Nail specimens may be submitted as either scrapings or cuttings and occasionally as a complete nail. The best nail specimen is crumbly material from the nail bed. A sterile scalpel blade, small curette, or scissors is used to harvest the nail. A Wood’s lamp (ultraviolet radiation from a mercury-vapor source) can be used to detect infected hairs. Hairs infected with such fungi as Microsporum species and Trychophyton schoenleinii fluoresce when a Wood’s lamp is shone on the scalp. Sterile forceps should be used to pluck the hair for culturing. These hair, skin, and nail specimens should be transported to the laboratory in sterile petri dishes, or screw top containers. A potassium hydroxide (KOH) wet mount should be requested. Specimens should not be refrigerated. 998

Other sterile body fluids, deep tissue samples and bone marrow aspirates should be collected by the physician in a sterile manner and transported to the lab in sterile syringes or screw-top tubes. A minimum of 0.5 milliliters of fluid is required, but any size tissue is acceptable. Bone marrow aspirates require sterile anticoagulant. Urine to be cultured for fungus should be collected by the clean-catch, midstream (CCMS) void method into a sterile screw-top container. First-voided morning urine specimens are preferred, as they are more concentrated. Twenty-four-hour or quantitative urine samples are not acceptable for culturing. Abscess fluids and wound drainage may be cultured for fungus. Actual tissue from the wound site will greatly increase the likelihood of recovering a fungal pathogen. Urogenital and fecal specimens may occasionally be sent for fungal culture but are generally screened only for yeast. Swabs are acceptable for these cultures, as well as for throats and wounds, but the medical staff should be aware that only yeast, no molds, would be isolated.

Aftercare The care of patients after the collection of a specimen varies with the specimen type. Scrapings of skin or nails, plucking of hair, urine or stool collection and sputum production should involve little or no discomfort or subsequent care. Urogenital and throat swabs may be momentarily uncomfortable. Collection of some respiratory-type specimens such as bronchoscopy or bronchial

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Following the sterile collection of blood for fungal cultures, firm pressure is applied to the draw site for a few minutes, followed by a bandage. Collection of bone marrow aspirates, deep tissue biopsies and sterile body fluids are invasive procedures performed by trained physicians observing sterile procedures. The patient should be monitored afterward to avoid hemorrhage at the site of aspiration or biopsy. Lumbar puncture for the collection of CSF requires special aftercare. The patient should lie prone for four to twelve hours to avoid headaches and the aspiration site is monitored for swelling or bleeding. Any of the invasive procedures may result in some normal aches for one to two days.

Complications Complications for the patient whose specimen is being sent for fungus culture is dependent on the type of specimen being collected. Drawing of blood cultures can sometimes result in hematoma (bruising) at the draw site and should be done by a well-trained phlebotomist who is familiar with sterile drawing procedures. More invasive procedures such as tissue biopsy, aspiration of bone marrow and other body fluids may be complicated by hemorrhage or infection of the sampling site. Complications for lumbar puncture for CSF collection may include numbness, tingling or pain in the legs.

Results Validity of results Fungus cultures are fraught with false-positive and false-negative test results and the medical staff must interpret culture results in light of the patient’s health status. Any direct microscopic examination may be falsely called negative, giving the physician and patient the early impression that no fungal infection exists. The false-negative direct examination may be due to examiner error through inexperience or lack of thoroughness. The portion of the specimen selected to be examined may have very few organisms, or the organisms may be missed amongst background debris in the smear. Likewise, a direct microscopic examination may be called falsely positive when an examiner misinterprets background artifacts as fungal elements in a preparation. This happens with the widely used KOH preparation and thorough training and experience is essential. A false-positive direct examination may cause antifungal treatment to be initiated unnecessarily. It is important to be aware that falsely negative fungal cultures may result if the patient has already had anti-

KEY TERMS Dermatophyte—A fungus that infects only epidermal tissues in which keratin is abundant: hair, skin and nails. Dimorphic fungus—A fungus capable of existing in both a yeast and mold form, generally as a yeast at body temperature and mold at room temperature. Some dimorphic fungi cause disease in humans. Fungal elements—Microscopic structures of fungi that may be observed in specimens or from positive cultures: yeast, budding yeast, hyphae, pseudohyphae, spores, mycelium. Hyphae—Multicellular filaments or tubular projections composing the mycelium of a mold. Mycelium—A mass of loosely intertwined hyphae extended out from a mold colony. Mycosis—Any disease caused by a fungal infection. Opportunistic pathogen—An organism that normally is present in the environment or as part of the normal flora of a host without causing disease, but which causes disease when the host becomes debilitated. Pseudohyphae—chains of budding yeast that adhere together and appear to look like hyphae during microscopic examination. Spore—A small, reproductive body of a fungus that is capable of sprouting new hyphae. Yeast—A single-celled, rounded fungi that usually reproduce by budding.

fungal treatment. Inhibitory agents within the patient’s tissues and specimens may suppress the growth of organisms in culture. False positive cultures result when a fungus contaminates a culture. Certain species of fungi are known to routinely be contaminants of fungal cultures; thus a positive culture report should lead to a discussion between the patient’s doctor and the microbiology laboratory or infectious disease specialists, if necessary. Repeating the culture is sometimes indicated. Mycoses The fungal diseases, or mycoses, have been categorized as superficial or cutaneous, subcutaneous, and sys-

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washes may result in coughing or hoarseness. The patient should be observed for hypoxia (low oxygen), bloody sputum or hemorrhage.

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temic, depending on the tissue or organs involved. The superficial or cutaneous mycoses involve the keratinized tissues of hair, skin, and nails without invasion of deeper tissue. The superficial types are mild, chronic infections of hair and the most superficial layer of the skin. In general they are of little medical consequence except for their cosmetic effect. Included in this group are conditions known as tinea and piedra. The cutaneous mycoses are sometimes referred to as the dermatomycoses, as they are caused by a group of fungi called dermatophytes. These fungi penetrate into epidermal tissue and include the agents of athlete’s foot and ringworm. Dermatophytes belong to three genera: Epidermophyton, Microsporum, and Trichophyton. The subcutaneous mycoses include a diverse group of infections that are characterized by the formation of a lesion at the inoculation site, often the result of injury. Generally, the fungus grows slowly in the subcutaneous tissues at the site, causing gradual spreading of the lesion, but does not disseminate to distant parts of the body. Examples of subcutaneous mycoses include chromoblastomycosis, mycetoma, and sporotrichosis. The systemic mycoses are those fungal diseases involving the internal organs, often spreading from an initial lung infection. They may become widely disseminated and involve any organ system where they can produce abscesses and granulomas (inflammatory nodules). Prior to effective antifungal therapy, these disseminated mycoses were almost invariably fatal. Traditionally, this group included dimorphic fungi from the genera Blastomyces, Histoplasma, Coccidioides and Paracoccidioides, as well as the yeast Cryptococcus. Recently, Penicillium marneffei has been added to this group. Opportunistic pathogens comprise another category of mycosis, which is becoming increasingly common. Opportunistic infections are caused by organisms normally found in the environment, or as part of the normal body flora, which do not cause illness unless the host becomes debilitated. Opportunists cause infection in patients that are immunocompromised, either by underlying disease or such immunosuppressive agents as steroids or cytotoxic drugs. Examples of such opportunists are Aspergillus species, which are among the most ubiquitous molds in the human environment. These fungi may inadvertently cause infection in a hospital setting through such portals as dialysis bags, air conditioning ducts and airborne particles associated with construction. Another frequent opportunist is Candida albicans, a yeast commonly carried in the mouth, vagina and intestinal tracts of healthy humans. C. albicans is the causative agent of oral thrush, vaginal yeast infections and occasionally systemic disease. 1000

In the last two decades there has been a striking increase in the incidence of opportunistic infections, not only because the number of immunocompromised patients, such as AIDS patients, is increasing, but also because some modern treatments permit the proliferation and invasion of vital organs by opportunistic molds and yeast. Such things as prolonged use of indwelling catheters, prosthetic heart valves, and immunosuppressive drugs for organ transplants have contributed to the increase.

Health care team roles Members of the health care team play essential roles in the diagnosis of a fungal infection. Doctors and nurses must be aware of when to suspect an infection in general and fungal infections in particular. Signs of any infection include fever, chills, headache, loss of appetite, bad odor, persistent cough, localized pain, burning or bloody urination, diarrhea, pus or discharge from a wound or lesion, and elevated white blood cell count. The very young patient (less than one year), the very old, and the debilitated or immunocompromised patient are more susceptible to infection. Predisposing factors for fungal infection include patients who have received broad-spectrum antibiotics, which eradicate the normal bacterial flora and allow fungi to overgrow. Steroid treatment decreases the body’s normal protective inflammatory response to invading fungi. Cytotoxic drugs used during cancer chemotherapy suppress the immune system and make the patient more susceptible to fungi in their environment. Patients who have very low white blood cell counts (less than 1,000 cells per cubic millimeter), or such underlying disorders as AIDS, pneumonia, diarrhea, leukemia, hepatitis, or transplanted organs are more prone to fungal infections. Skin conditions that may indicate fungal infection include scaling of skin, blisters of hands or feet, scaling of scalp with broken-off hairs, and discolored toenails or fingernails. Fungus infections of the cornea are more common in farm workers, contact lens wearers, topical steroid users, and those who have corneal injury due to such organic material as a tree branch. Certain fungal infections are more common in particular areas of the world and the medical staff needs to be aware of what fungi are endemic (constantly present) in their area and also inquire about a patient’s travel history. For example, Histoplasma capsulatum, the cause of histoplasmosis, is endemic in the Ohio and Mississippi River valleys of the United States. The medical staff also has a critical role in selecting the appropriate specimen for fungus culture and should be knowledgeable about their institution’s requirements

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The mycology section of the microbiology laboratory has the important role of notifying the medical staff promptly of positive direct examination results as well as positive culture results. The cytology and surgical pathology laboratories must work closely with the microbiology laboratory as these former laboratories may detect fungal elements with their tissue stains. The experienced microbiology technologist’s knowledge of common fungal contaminants is invaluable to the doctor. A discussion between the doctor and the lab is often helpful in distinguishing between a contaminant and an opportunistic infection. Fungi that would have once been disregarded as contaminants on a culture are now known to be responsible for serious disease in debilitated hosts. Resources BOOKS

Barnett Lammon, Carol. “Assisting with Diagnostic Procedures.” In Clinical Nursing Skills. Philadelphia: W.B. Saunders Company, 1995. Forbes, Betty A., Daniel F. Sahm, and Alice S. Weissfeld. “Laboratory Methods in Basic Mycology.” In Bailey & Scott’s Diagnostic Microbiolgy,10th ed. St. Louis, MO: Mosby, Inc., 1998. Larone, Davise H. Medically Important Fungi, A Guide to Identification, 3rd ed. Washington, D.C.: American Society for Microbiology, 1995. Nettina, Sandra M. “Infectious Diseases.” In The Lippincott Manual of Nursing Practice, 7th ed. Philadelphia: Lippincott, 2001. PERIODICALS

Padhye, A.A., et al. “Biosafety considerations in handling medically important fungi.” Medical Mycology 36, Suppl 1 (1998): 258-65. ORGANIZATIONS

The American Society for Microbiology. 1752 N Street NW, Washington, D.C. 20036. (202) 737-3600. . .

Marianne F. O’Connor, MT,MPH

Fungi Definition Fungi are eukaryotic organisms (each containing a membrane-bound nucleus) that develop from reproductive bodies called spores. Fungi may be the cause of any

number of diseases in humans, animals, and plants; fungal infections are called mycoses (singular, mycosis).

Description Mycology is the branch of science that studies organisms of the kingdom Fungi. Scientists estimate that over 200,000 species of fungus exist in nature. These species include yeasts, moulds, mildews, mushrooms, lichens, and smuts. There are a number of characteristics that fungi share: they are eukaryotic (containing a nucleus that is bound by a nuclear membrane); they develop from reproductive bodies called spores; their cell walls are composed mostly of chitin, a nitrogen-containing carbohydrate; and they are heterotrophic (they cannot synthesize their own food and therefore absorb food from an external source through their cell walls). Most fungi obtain their nutrients from dead organic matter and are called saphrophytes. Saphrophytes play an important ecological role in the decomposition of dead plants, animals, and other organic matter: they release large amounts of carbon dioxide into the atmosphere and recycle nitrogen and other important nutrients for use by plants and other organisms. Other fungi are parasites (obtaining their nutrients from a living host organism in a relationship that usually harms the host) or mutualists (involved in a mutually beneficial relationship with another organism). Another important characteristic of fungi is that they do not contain chlorophyll. Chlorophyll is a green pigment that enables plants and such other photosynthetic organisms as algae and cyanobacteria to absorb energy from sunlight and use it to synthesize carbohydrates (photosynthesis). Because fungi are not reliant on sunlight as an energy source, they can grow in dark or lowlight environments and in directions not normally observed in plants. Morphology Most fungi may be classified according to two major growth forms: yeasts or molds. Yeasts are round, unicellular (single-celled) organisms that form a vegetative body called a thallus. The thallus may consist of cells in groups or in branched chains called pseudo-hyphae. Examples of yeasts include Saccharomyces cerevisiae, used in making bread and alcoholic beverages; and Candida albicans, the causative agent of yeast infections. Molds, on the other hand, are composed of long filaments called hyphae (singular, hypha). Hyphae may be further classified as septate (containing cross walls) or aseptate. A mass of hyphae is called a mycelium.

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for collecting the specimen properly. See the Preparation section for proper specimen collection.

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(disease-causing). Still others are pathogenic to plants and animals important in the food chain. Food manufacturing Different yeasts in the genus Saccharomyces are employed by bakers, brewers, and vintners to make their bread, beer, or wine. For instance, S. cerevisiae is commonly used as baker’s yeast and in the production of ales. Candida milleri is a yeast used in conjunction with an acid-producing bacteria to yield sourdough bread.

Oral candidiasis (thrush) in an infant, showing a white coating over the tongue. This infection is caused by a yeast-like fungus, usually Candida albicans. (Photograph by Dr. P. Marazzi. Science Source/Photo Researchers. Reproduced by permission.)

Whereas yeast cells each contain a single nucleus, cells in septate hyphae may be uninucleate (containing one nucleus), binucleate (containing two nuclei), or multinucleate (containing many nuclei). An example of a mold is Penicillium roqueforti, used to make blue cheese. Some fungi are dimorphic: they may exist in either yeast or mold form. What form a fungus assumes depends on such environmental factors as the temperature or nutrients present. Some examples of dimorphic fungi include Histoplasma capsulatum and Coccidioides immitis. Reproduction All fungi can reproduce asexually by the production of single-celled structures called spores. The number of chromosomes (structures in the nucleus containing genetic material) remains unchanged when cells duplicate their genetic material and then divide. This is not the ideal state for a fungus and is thus called the imperfect state. (It is often observed in the laboratory when fungi that are normally pathogenic to humans are allowed to reproduce.) Sexual reproduction can also occur in most fungi and is called the perfect state. In this process, one cell divides to become two haploid cells (each containing a single set of unpaired chromosomes). Two cells can then fuse together to become a diploid cell (containing a full set of chromosomes); that cell can then divide.

Role in human health Some fungi have been found to be directly or indirectly beneficial to humans, while others are pathogenic 1002

Various species of mushrooms are cultivated specifically for human consumption. These include Agaricus bisporus (accounting for 38% of the world’s cultivated mushroom supply), Lentinus edodes (shiitake mushrooms), Volvariella volvacae (the paddy straw mushroom), and the Pleurotus family (oyster mushrooms). Other edible fungi include truffles (fungi of the family Tuber that grow in a special subterranean (mycorrhizal) association with certain trees), morels (of the Morchella family), and the blue-green mold of the Penicillium family that is essential in the production of certain cheeses. Medicinal and recreational drugs Discovered in 1929, a metabolite of the fungus Penicillium notatum (later to be called penicillin) became the first antibiotic (a substance produced by a microorganism that can selectively treat an infectious disease). Other fungi that are the source of clinically important antibiotics include those in the family Streptomyces: S. nodosus (amphotericin B), S. erythreus (erythromycin), S. fradiae (neomycin), S. griseus (streptomycin), S. orientalis (vancomycin), and S. rimosus (tetracycline). Some species of fungi are known as hallucinogens (substances inducing false sensations in the absence of true stimuli) and have been used by many cultures during religious ceremonies (for example, Amanita muscaria). Claviceps purpurea (the ergot fungus) and fungi of the Psilocybe family are also known for their hallucinogenic effects. Biomedical research Phycomyces blakesleeanus is a fungus that grows on animal feces in nature. The sporangiophores (the stalks on which spores are produced) of Phycomyces have been shown to respond to a variety of stimuli, including light, gravity, wind, and nearby objects. One important finding was that the light sensitivity of the sporangiophore is about the same as the eyes of humans. Furthermore, like humans, the sporangiophore can adapt to a one-billionfold change in ambient light intensity.

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Common disease and disorders Human mycoses can be classified as superficial, cutaneous, subcutaneous, systemic, or opportunistic. Superficial and cutaneous mycoses These fungal infections do not invade underlying muscle or bone and are mostly restricted to the outer layers of the skin, nails, and/or hair. Superficial mycoses involve only the outermost layers of skin and result in a change in hair or skin pigment. For example, tinea nigra, caused by Exophiala werneckii, results in black lesions on the skin. Piedraia hortai, the causative agent of black piedra, creates hard dark-colored nodules on scalp hair, eyebrows, and/or eyelashes. Cutaneous mycoses are generally caused by infection with a dermatophyte (a skin-infecting fungus). Common families of dermatophytes are Epidermophyton, Microsporum, and Trichophyton. Some of the more commonly seen cutaneous infections include: • tinea corporis (body, “ringworm”) • tinea capitis (scalp, eyebrows, eyelashes) • tinea barbae (beard, “barber’s itch”) • tinea cruris (groin, “jock itch”) • tinea inguium (nails) • tinea pedis (feet, “athlete’s foot”) Subcutaneous mycoses In the case of subcutaneous fungal infection, muscle, bone, connective tissue, and/or overlying skin may be involved. Subcutaneous mycoses may begin at the site of a laceration or even a seemingly innocuous scratch or puncture wound; fungi are introduced from soil or plant material. These mycoses, however, typically remain localized rather than spread from the site of infection. Sporotrichosis (caused by Sporothrix schenckii) and mycetoma (caused by Madurella grisea, among others) are two noted exceptions; sporotrichosis may spread along the lymphatic system, and mycetoma to deeper muscle and bone.

Fungi

Biologists have recently shown that Neurospora crassa, also known as red bread mold, can produce spores at approximately 24-hour intervals (known as a circadian rhythm) when in a constant environment. The fungus is therefore being used as a model organism for investigating circadian rhythms, which occur in many different organisms including humans.

KEY TERMS Cyanobacteria—Photosynthetic bacteria, commonly known as blue-green algae. Dermatophyte—A fungus that can cause a skin infection. Hypha—Cellular unit of the fungi; typically a branched and tubular filament. Lichen—A fungus that grows a symbiotic relationship with algae. Meningitis—Inflammation of the meninges, the membranes surrounding the brain and spinal cord. Metabolite—A substance produced by way of a metabolic process. Morphology—The study of the shape and structure of an organism. Mutualism—Close relationship of two or more organisms, which typically involves exchange of food or other resources. Mycorrhiza—Subterranean symbiotic relationship between a fungus and a plant root. Septum—Wall that separates the cells of a fungal hypha into segments.

Systemic mycoses Systemic fungal infections usually involve more than one type of body tissue. The lungs are often a site of primary infection when airborne spores are inhaled. Often the primary infection is asymptomatic (shows no signs of infection) or resolves quickly. If the fungus spreads to the bloodstream, however, it may disseminate to other organs or systems. The following are the most commonly seen systemic mycoses: • Blastomycosis, caused by Blastomyces dermatitidis; begins as a pulmonary infection but may disseminate to bone and/or skin. • Coccidioidomycosis, caused by Coccidioides immitis; begins as a pulmonary infection (although 60% of infections are asymptomatic) but may disseminate to the central nervous system, bone, and/or skin. • Cryptococcosis, caused by Cryptococcus neoformans; begins as a pulmonary infection but may disseminate to the central nervous system to cause meningitis.

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• Histoplasmosis, caused by Histoplasma capsulatum; begins as a pulmonary infection but may disseminate to the lymph nodes, spleen, and/or liver. • Paracoccidioidomycosis, caused by Paracoccidioides immitis; begins as a pulmonary infection but may disseminate to the mucous membranes, lymph nodes, and/or skin. Opportunistic mycoses Opportunistic fungi do not normally cause disease in healthy humans, but can cause infection in individuals who are immunocompromised, such as those with acquired immune deficiency syndrome [AIDS] or those who have undergone organ transplantation. Some important opportunistic mycoses include: • Aspergillosis, a mycosis caused by members of the Aspergillus family. Common mechanisms of infection include hypersensitivity (an allergic reaction); local pulmonary infection; opportunistic infection (leading to pneumonia and the development of a characteristic “fungal ball”); and systemic infection (leading to abscesses in the brain, liver, kidneys, skin, or bone. • Candidiasis. Candida albicans is a yeast that causes oropharyngeal candidiasis, also known as thrush. Thrush is an often-seen opportunistic infection in patients with acquired immune deficiency syndrome

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(AIDS). Candida albicans is also the cause of the majority of cases of vulvovaginitis (yeast infection). Resources BOOKS

Fisher, Frances W. Fundamentals of Diagnostic Mycology. Philadelphia: W. B. Saunders Company, 1998. Spicer, W. John. Clinical Bacteriology, Mycology, and Parasitology. London, UK: Churchill Livingstone, 2000. OTHER

“Mycology.” Microbiology and Immunology On-line Textbook. University of South Carolina. 3 April 2001. 2 August 2001. . “Mycoses.”Doctor Fungus Website. 12 April 2001. 2 August 2001. . “Penicillin and Other Antibiotics.” The Microbial World Website. University of Edinburgh. 2 August 2001. . “What are yeasts?” Yeast WWW Virtual Library. Stanford University. 2 August 2001. .

Stéphanie Islane Dionne

Furunculosis see Boils

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G Gait and balance assessment Definition Gait or walking is a coordinated action of the neuromuscular and musculoskeletal systems. The coordination of muscle contraction, joint movement, and sensory perception allows the human body to move in the environment. Individuals with neuromuscular and/or musculoskeletal involvement may have abnormal or inappropriate muscle activation, joint motion, or sensory perception. The result may be decreased mobility and function, and altered gait. Gait assessment is important to help identify areas of impairment. Once a reason for gait impairment is determined, a treatment plan can be developed. The goals of therapy are to minimize functional loss, restore mobility, and promote safety. Balance is the ability to sit, stand, or walk safely without postural deviation, falling, or reaching for external items for support. Balance, like gait, is a coordinated response of the neuromuscular and musculoskeletal systems, as well as vision and sensory perception. Vestibular and cortico-cerebellar levels in the brain are also involved in maintaining stability. Balance assessment is used to evaluate the patient’s ability to maintain appropriate posture during functional activities. It is usually evaluated statically and dynamically.

Both gait and balance evaluations are useful in identifying areas of impairment so that safe and proficient function and mobility can be restored.

Precautions During gait and balance assessment, individuals with impairment are at risk for further injury, especially from falls. Clinicians who evaluate patients with suspected gait and balance deficits must provide close supervision and ensure that the testing areas are safe.

Description Gait can be analyzed with a variety of techniques, involving a range of difficulty. One basic method is simply watching the patient walk and interact in the environment, noting any deviations or instability. More advanced techniques use motion analysis, force platform data, and electromyography in an effort to gain a global representation of joint motions, joint forces, and electrical activity of muscles during walking. Balance is very complex and requires many systems to work at optimum levels. A problem or injury affecting strength, joint motion, vision, sensory perception, or vestibular apparati may lead to functional impairment. Balance needs to be evaluated both statically and dynamically, and if a deficit is present, further testing is indicated.

Preparation Purpose The goal of gait assessment is to evaluate walking in an effort to isolate dysfunction. Areas of impairment may include muscle weakness, loss of joint range, incoordination, or poor postural control. During balance assessment, a patient’s stability during activities is evaluated to identify areas of impairment, the reason for impairment, and the effect on function.

In a simple gait analysis, the patient is observed during standing (static testing) and walking (dynamic testing). Initially, the patient is examined in the standing position to evaluate posture as well as bone and soft tissue symmetry. The clinician evaluates the foot and ankle during standing to assess any deviation in the rear foot and forefoot. The patient is then asked to walk across the floor while the clinician evaluates the gait cycle. The clinician assesses joint range of motion, speed, and quality

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KEY TERMS Berg balance scale—An assessment tool used to evaluate stability during functional activities. The patient is scored on 14 different tasks.

Motion analysis—Use of an instrumented system to record whole body and joint movement for later analysis.

Cortico-cerebellar—Pertaining to the cerebellum and the cerebral cortex of the brain.

Musculoskeletal system—Pertaining to the muscle and skeletal systems.

Dynamic—Movement such as walking that is due to muscles contracting.

Neuromuscular—Pertaining to the nervous and muscle systems.

Electromyography—An evaluation tool that detects electrical activity of muscles.

Normative—A group that is free from dysfunction compared to a group that has dysfunction. For example, in groups with and without knee osteoarthritis, the group without the osteoarthritis is the normative group.

Force platform—A large plate, usually mounted in the floor, that records forces when an individual stands or walks on it. Forefoot—The front portion of the foot from the ankle. Functional reach test—A test that evaluates stability when reaching out beyond an individual’s base of support. In this test the patient stands and tries to reach out with one hand as far as possible without losing balance. The reach is recorded in inches. Get-up-and-go test—Evaluates balance during a functional activity. The test is scored based on the patient’s ability to get up from a chair, walk forward about 10 feet (3 m), return to the chair and sit down. The test may be timed to monitor progress.

of gait, and synchrony of all upper and lower extremity joints. The patient should be evaluated walking barefoot as well as while wearing normal walking shoes. The clinician should observe walking from the back, front, and side. In more complex gait assessments, videography is used to record patient movement and joint motion, and force plates and electromyography provide additional information. Unfortunately, the equipment used in complex analyses is expensive and thus cost-prohibitive to the average clinician. However, there are gait laboratories that have equipment specializing in instrumented gait analysis. Various tests are used for balance assessment. Certain tests are specific to visual, cerebellar, muscular, or proprioceptive areas. Sensory integration tests and the Romberg test are used to try to isolate involvement of vision, sensation, and cerebellar integrity. Other tests commonly used are the Berg balance scale, the get-up1006

Proprioception—The ability to sense movement and position of the body. Rear foot—The back portion of the foot that includes the ankle and heel. Sensory perception—The ability to perceive touch, pressure, pain, and joint position in the limbs and trunk. Static—Without movement, i.e. standing still, with or without muscle contraction. Tinnetti balance test—A battery of tests to assess balance and identify individuals at risk for falling. Vestibular—Pertaining to the apparatus in the inner ear that senses orientation and movement of the body in space.

and-go test, the functional reach test, and the Tinnetti balance tests. These tests provide quantitative data that allow the clinician to compare individual results with a normative group and document progress over time.

Aftercare The treatment of an individual with a gait abnormality may include stretching, strengthening, joint mobilization, splinting or bracing, education, or a change in footwear. The treatment of an individual with a balance deficit may include stretching, strengthening, postural awareness exercises, various weight-shifting exercises, and increasing environmental stimuli in an effort to retrain proprioception. Treatment is individualized according to a patient’s problem. For example, strengthening exercises are recommended for an identified muscle weakness.

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A major concern is safety during a gait or balance assessment. If impaired balance or gait abnormalities increase the likelihood of falling, appropriate measures need to be taken, such as clear and safe pathways, adequate lighting, and good guarding techniques by staff members.

Results Gait or balance assessments are usually recommended for a decline in function, self-reported loss of balance, or unexplained falls. The patient may be fearful of falling, and restoring confidence often needs to be addressed. Ideally, areas of impairment are identified during the assessment so that appropriate treatments can be directed at the problem.

Health care team roles Nursing and other allied health professionals in hospitals, outpatient clinics, diagnostic centers, skilled nursing facilities, and assisted living facilities need to be aware of their patients’ gait, posture, and general mobility. When a patient is using an assistive device inappropriately, or gait and balance appear to have changed, it is the health care provider’s role to address the problem to minimize the risk of falls. A request for further evaluation, such as a gait or balance assessment, may be an appropriate next step. Resources BOOKS

Bennett S.E., J.L. Karnes. Neurological disabilities, assessment and treatment. Philadelphia: Lippincott, 1998. Hertling D., R.M. Kessler. Management of Common Musculoskeletal Disorders. Baltimore, MD: Lippincott, Williams & Wilkins, 1996. Lehmkuhl L.D., L. K. Smith. Brunnstroms Clinical Kinesiology. Philadelphia: F.A. Davis Co., 1996.

Mark Damian Rossi, Ph.D, P.T., C.S.C.S.

Gait and balance problems Definition Gait and balance problems exist when a disease process, trauma, or aging result in the inability to control

one’s center of gravity (COG) over the base of support (BOS) in static or dynamic tasks and environments.

Description Any number of factors may contribute to gait and balance problems. Postural control, the task that involves controlling one’s position in space, involves maintaining a relationship among the body, the task at hand, and the given environment. Difficulty in maintaining an appropriate relationship may occur due to: • impaired sensory processes (visual, vestibular, somatosensory) • inadequate neuromuscular responses (signaling of brain to/from muscle) • musculoskeletal problems (impaired range of motion, strength, flexibility) • decreased cognition (inability to anticipate or adapt to postural needs) Due to the wide variety of factors, many individuals can be affected with gait and balance problems at some point in their lives. Inability of peripheral sensory receptors to gain information about the environment results in the inability to use that information for postural control. This type of loss may occur in people who have visual, vestibular, or somatosensory deficits not based in the central nervous system (CNS). Examples include, but are not limited to, diabetic retinopathy, cataracts, glaucoma, temporal bone fracture, acoustic neuroma, Ménière’s disease, spinal cord injury, peripheral neuropathy, and amputation. The CNS is responsible for integrating the environmental information that is supplied through peripheral sensory receptors; this is called sensory processing. Motor planning, on the other hand, is an individual’s ability to plan movement to accomplish a task. Individuals who have experienced injury to the CNS in the form of a stroke, brain trauma, or disease process like multiple sclerosis, Parkinson’s or cerebellar ataxia, may exhibit gait and balance problems due to difficulty with sensory processing and/or motor planning. Musculoskeletal problems, whether orthopedic or neurologic in origin, can contribute to balance and gait difficulties because certain levels of mobility and strength are required to execute movements within functional parameters. Automatic postural strategies, such as an ankle or hip strategy, operate to keep the body over the center of gravity when a disturbance to balance is presented. The larger the disturbance is, the more intense the response. If there is inadequate range of motion at the

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Complications

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is very common to find gait problems in conjunction with cerebellar lesions; in one study, 60% of patients with cerebellar problems displayed ataxic gait, which resembles intoxicated gait. Basal ganglia dysfunction The basal ganglia are three nuclei at the base of the cerebral cortex. It appears that the basal ganglia play a large role in preparing an individual for motion. This may include preparing the cortex, setting postural reflexes, and organizing sensory input. When there is dysfunction in this area, such as in Parkinson’s or Huntington’s disease, disturbances in central sensory processing, along with rigidity and akinesia (inability to move), contribute to postural instability and gait difficulties. Hemiplegia

A balance machine is used in the assessment of balance problems. (Photograph by Will & Deni McIntyre. Science Source/Photo Researchers. Reproduced by permission.)

ankle, or weakness in hip musculature, these strategies cannot be adequately used. Impaired cognition is an important contributor to balance and gait problems. Poor attention, decreased judgment and slow processing can increase risk of loss of balance. Without awareness of environmental hazards and necessary safety precautions, patients who have had a stroke or brain trauma have an increased propensity to fall.

Causes and symptoms Cerebellar lesions Cerebellar lesions are one cause of disturbed balance. Depending upon the area affected, the disturbance may be slight or severe. The cerebellum also contains proprioceptive feedback loops, in addition to receiving input from the spinal cord. When these areas are affected, the postural changes that take place affect balance. It 1008

Hemiplegia (paralysis of one side of the body) as a result of a cerebrovascular accident, or stroke, is also a common cause of balance and gait difficulties. Loss of trunk control results in the inability to maintain weight evenly over the pelvis. In the early stages of recovery, along with upper extremity dysfunction, lower extremity positioning in standing may be marked by pelvic depression, hip and knee flexion (decreasing the angle of the joints), and ankle plantarflexion on the affected side. Later, extensor patterns (increasing the angle of the joints) become more available, and the pelvis may be elevated, with the knee hyperextended and ankle plantarflexed. Sensory loss may manifest itself in many ways, from loss of discrimination and localization to complete neglect of the affected side. All of these factors contribute to balance and gait problems due to inadequate sensory processing, musculoskeletal tightness or weakness, and/or cognitive deficits. Vestibular hypofunction While problems with central processing of vestibular input can create balance and gait difficulties in individuals with CNS problems, peripheral vestibular hypofunction (the under-functioning of inner ear structures associated with balance) also is a common contributor to balance deficits. Peripheral vestibular hypofunction may result from temporal bone fracture, acoustic neuroma, ototoxicity (damage to the eighth cranial nerve due to aminoglycoside antibiotics), or unknown causes. One or both sides may be damaged, resulting in dizziness and vertigo that lead to decreased balance. Although these are some of the main pathologies that are known to cause balance and gait problems, any disease process or trauma resulting in impairments of sensory processing, neuromuscular response, muscu-

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Diagnosis The pathologies that underlie gait and balance problems are diagnosed by physicians using a variety of methods, including signs and symptoms, diagnosis of exclusion, imaging, etc. Discussion of specific diagnostic criteria for each disease process that could contribute to a balance disorder is beyond the scope of this entry. A physical therapy diagnosis of decreased balance or abnormal gait is made based on a thorough examination that includes a patient history and systems review. In addition, tests and measures may be used to assess any or all of the following possible contributors to balance and gait disturbances: aerobic endurance, cognitive status, cranial and peripheral nerve integrity, assistive devices, muscle strength, range of motion, posture, reflexes, sensory integrity, and functional abilities. Balance, gait, and locomotion may be tested in a variety of ways, which usually include observation or video analysis of quiet standing, active standing, or functional activities. In some clinical tests such as the Clinical Test for Sensory Interaction on Balance, the physical therapist will purposefully manipulate the environment to change one component of sensory feedback (e.g., the patient stands on foam to challenge the somatosensory system). In some cases, the physical therapist manipulates the individual (e.g., the Hallpike-Dix maneuver). Other tests include a variety of functional skills that must be completed. A large number of balance tests exist; the key is choosing the right one. It is important to understand the purpose of a test before using it and to match that purpose with the impairments and goals of the patient or client being tested. For example, a test that measures stability in quiet standing may be appropriate for a patient who is recovering from a stroke, but not so appropriate for an athlete training to return to professional sports.

Treatment Medical and surgical management of pathologies underlying balance and gait disturbances includes, but is not limited to, the following: • levo-dihydroxy-phenylalanine (L-dopa) and/or amantadine for Parkinson’s disease • surgery to alter connectivity in the basal ganglia in Parkinson’s • dopamine antagonists in Huntington’s chorea

• anti-spasticity medication (diazepam, baclofen, dantrolene) for patients who have had a stroke, head injury or other neurological insult • particle repositioning maneuvers for benign paroxysmal positional vertigo (dizziness) • surgery for Ménière’s disease or acoustic neuroma (a tumor in the auditory canal) These interventions can help to decrease the contributors to balance and gait disorders such as dyskinesia (impaired ability to move voluntarily), rigidity, hypertonicity (diminished muscle tone), or vertigo. Balance and gait, however, often must be retrained using physical therapy. Successful treatment intervention based on theories of motor learning addresses the interactions of the individual, task and environment. In the individual, it is important to recognize what impairments contribute to difficulties, and whether or not they can be realistically corrected or if compensation will be necessary. The patient must be evaluated for cognitive ability to relearn balance skills, and for the level he or she is at in learning a skill (acquisition, refinement, or retention/transfer). In evaluating a task, the clinician must determine what is predominantly required—mobility, stability or both— and the timing, force and duration needed. The environment also must be analyzed and manipulated to best aid the patient in preparing for function in the real world. Treatments may involve the manipulation of sensory input while performing a task. This may be done for any of the three systems responsible for providing sensory feedback. For example, to encourage use of vestibular input, visual and somatosensory information may be challenged. Visual input is challenged by taking it away (e.g., eyes closed) or by destabilization (e.g., involving head and eye movements in the task). Unstable surfaces (e.g., rocker board or rough terrain) or compliant surfaces (e.g., foam) help to challenge somatosensory input. Vestibular input may be manipulated by changing the position of the vestibular organ (e.g., neck extension or repeated head movements). Other physical therapy treatment for balance and gait focuses on the patient’s ability to control his or her COG over the BOS. Exercises related to functional activities are performed and progressed according to patient ability. Initially, treatment may begin with practicing the ability to establish static balance in a position with a wide BOS, such as sitting and using hands for support. Eventually, the BOS is narrowed and/or destabilized to train automatic, anticipatory and voluntary postural responses. This type of progression can take place in sitting, standing, walking, etc., with or without the addition of such concurrent tasks as putting on a shoe while sitting or reading signs on a wall while walking. Specific bal-

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loskeletal function, or cognition can result in balance and gait disturbances. Due to changes that take place in the proprioceptive (self-awareness of movement) and vestibular systems, even normal aging has an effect on balance and gait.

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Health care team roles

KEY TERMS Ankle strategy—An automatic posture response in which the body moves as a unit over the feet to control postural sway. Base of support—The location on a body or object where most of the weight is supported. Center of gravity—The center of weight in a body or object. Hip strategy—An automatic posture response in which control comes from the pelvis and trunk. Posturography—The study of posture and its effects on health. Somatosensory system—The components of the central and peripheral nervous systems that process information about the muscles, pain, temperature, pressure and joint position. Vestibular system—Interaction among the inner ear structures associated with balance and position sense, and the central nervous system. Visual system—Components that transmit information from the retina to the brain.

ance training on a force plate designed to provide visual feedback about a patient’s COG has not been shown to be convincingly more effective than conventional physical therapy in adults with hemiplegia. This may be due to the fact that weight shifting on a force plate may not carry over to such higher-level tasks as walking.

Examination The examination includes a patient history and systems review of cardiovascular, pulmonary, integumentary, musculoskeletal, neuromuscular and/or cognitive status. Physical therapists also use a wide variety of tests and measures to determine extent of impairment and functional limitations. Some of the more common balance tests used include: Romberg, Functional Reach, Clinical Test for Sensory Interaction on Balance, Berg Balance Scale, Get Up and Go, Tinetti Performance Oriented Assessments of Balance and Gait, Fugl-Meyer Sensorimotor Assessment of Balance Performance, Functional Obstacle Course, and posturography. These tests assess tasks ranging from quiet and active standing to the ability to maneuver an obstacle course of different floor surfaces, obstacles and stairs. Evaluation, diagnosis and prognosis The therapist must use his or her clinical judgment and expertise to establish a physical therapy diagnosis and prognosis, including the plan of care. The diagnosis indicates the primary dysfunction(s) toward which intervention will be directed. The prognosis and plan of care must encompass many factors such as current level of function, comorbidity, familial and social considerations and overall health. Intervention

Prognosis Prognosis depends on the cause of pathology, level of impairment, and such other factors as comorbidity. The basal ganglia disorders are progressive; therefore, while medical and physical therapy management may be effective in slowing the decline of function and training compensatory strategies, the overall prognosis is fair at best. Cerebellar lesions or cerebral stroke may allow for slight to significant return to function, depending upon the extent of the damage to the brain tissues. In a study on gait recovery following stroke, prognostic indicators included the ability to weight shift immediately poststroke; and later in recovery, affected knee extension strength. In true orthopedic cases with no neurological involvement, recovery may be less complicated if it depends purely on restoration of range of motion or strength to a musculoskeletal structure. 1010

Upon diagnosis of pathology by a physician and referral of an individual to physical therapy, the physical therapist is responsible for examination, evaluation, diagnosis, prognosis, and intervention.

Intervention includes treatment of any impairments that hinder function, as described in the treatment section above. In addition, patient education is of utmost importance. Education may include information regarding: the prognosis and plan of care, specific exercises to perform outside of therapy sessions, fall and injury prevention, compensatory strategies, assistive or adaptive device recommendations and usage, and social/community resources.

Prevention Gait and balance problems, as discussed earlier, are usually impairments resulting from a pathological process. In some cases, such as in Parkinson’s or multiple sclerosis, intentional prevention of pathology is difficult because its causes are not completely understood. Some causes, however, may be modified. For example,

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Resources BOOKS

American Physical Therapy Association. Guide to Physical Therapist Practice, 2nd ed. Fairfax, VA: American Physical Therapy Association, 2001. Shumway-Cook, Anne, and Marjorie Woollacott. Motor Control: Theory and Practical Applications. Baltimore, MD: Williams & Wilkins, 1995. Umphred, Darcy A. Neurological Rehabilitation. 3rd ed. St. Louis, MO: Mosby Yearbook, Inc, 1995. PERIODICALS

Geiger, Ruth Ann, et. al.”Balance and Mobility Following Stroke: Effects of Physical Therapy Interventions With and Without Biofeedback/Forceplate Training.” Physical Therapy 81 no. 4 (April 2001): 995-1005. Means, Kevin M., et. al. “Comparison of a functional obstacle course with an index of clinical gait and balance and postural sway.” Journals of Gerontology - Series A: Biological Sciences & Medical Sciences 53A no. 5 (September 1998): M331-5. Nadeau S., et. al. “Analysis of the clinical factors determining natural and maximal gait speeds in adults with a stroke.” American Journal of Physical Medicine and Rehabilitation 78 no. 2 (March/April 1999): 123-30. Suzuki K., et. al. “Determinants and predictors of the maximum walking speed during computer-assisted gait training in hemiparetic stroke patients.” Archives of Physical Medicine and Rehabilitation 80 no. 2 (February 1999): 179-82. Walker,Catherine, et. al. “Use of Visual Feedback in Retraining Balance Following Acute Stroke.” Physical Therapy 80 no. 9 (September 2000): 886-895. ORGANIZATIONS

American Physical Therapy Association. 1111 North Fairfax Street, Alexandria, VA 22314-1488. (703)684-2782. .

Gait training Definition Gait training refers to helping a patient relearn to walk safely and efficiently. Gait training is usually done by rehabilitation specialists who evaluate the abnormalities in the person’s gait and employ such treatments as strengthening and balance training to improve stability and body perception as these pertain to the patient’s environment. Gait training often incorporates the use of such assistive devices as parallel bars, walkers or canes to promote safe and proficient ambulation. In order to walk again without assistance, the patient will need mental attentiveness and adequate sensation, coordinated with adequate musculoskeletal functioning and motor control.

Purpose A person’s gait is a pattern of stepping or walking that is specific to that individual. Gait training is needed to help a specific patient gain proficient and safe ambulation within and outside the home with or without an assistive device. Patients usually require gait training if there is some lower trunk or lower limb dysfunction. This dysfunction is often associated with neurological or orthopedic impairment. Complications that may require gait training include: • muscle weakness • deformity • spasticity (the presence of abnormal involuntary muscular contractions) • loss of sensation due to injury or disease that results in inaccurate sensory information and unsafe or inefficient motion • pain in the weight-bearing joints of the lower extremities, which causes distortion of normal gait These complications may result from injury to or amputation of the lower extremities; surgery; osteoarthritis or other disorders of the weight-bearing joints; muscular dystrophy; muscle atrophy due to long periods of inactivity or bed rest; lesions of the brain or spinal cord; or changes in perception and other body functions that are part of the aging process. Normal gait

OTHER

Net Wellness Consumer Health Information. Ask an Expert website. Apr. 12, 2001. .

Peggy Campbell Torpey, MPT

In order to understand gait training, the reader may find a descriptive outline of normal human gait helpful. Human gait is measured from heel strike to heel strike, also known as the gait cycle or “one stride.” The gait cycle has two phases, the stance (about 60% of the cycle)

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high cholesterol levels contribute to risk of thrombi. Some medications may cause peripheral vestibular damage or dizziness. Reduced range of motion, decreased strength, and inactivity in the elderly can lead to balance and gait problems. Safety education, environmental adaptations, strengthening, flexibility and balance exercises, gait training, good shoes, orthotics, and assistive devices are all key factors in prevention of falls due to balance and gait problems.

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• Hip. Deviations of swing include circumduction and “hip hiking.”

KEY TERMS

• Trunk. Deviations of stance include lateral lean (Trendelenberg gait), backward lean (gluteus maximus gait), and forward lean.

Ataxia—Loss of muscular coordination. Cadence—The rhythm of a person’s walk. Double stance—The point in the gait cycle at which both feet are touching the ground. It is also sometimes called double support time. Gait—A person’s habitual pattern of walking or stepping. Gait cycle—A unit of measurement used in evaluation of gait abnormalities. The gait cycle consists of two phases, stance and swing, and is measured from heel strike to heel strike (the length of one stride). Gait velocity—The speed of a person’s walk. Muscular dystrophy—An inherited disease characterized by progressive wasting of the muscles. Osteoarthritis—A degenerative joint disease that causes inflammation and pain in the peripheral and spinal joints. Spasticity—A condition marked by sudden abnormal involuntary muscle contractions, with associated hyperactivity of deep tendon reflexes. It may be associated with rigidity.

and the swing (about 40%). The point at which the body’s weight is transferred from one foot to the other, when both feet are touching the ground, is called double stance or double support time. The speed of a person’s walk is called the gait velocity, and the rhythm of their walk is called the cadence. Cadence is usually related to the length of the person’s leg and their overall height; short people typically take smaller steps at a more rapid cadence while taller people take larger steps at a slower cadence. Deviations in gait Deviations from normal gait can occur in any portion of the lower extremity. Common abnormalities include: • Ankle/foot. Deviations of stance include foot slap and foot flat. Deviations of swing include toe drag (foot drop). • Knee. Abnormalities of stance include hyperextension of the knee. Abnormalities of swing include limited flexion of the knee. 1012

• Other. Ataxia (loss of muscular coordination) and antalgia (limping from pain). Deviations can occur together as a group of compensations for one impairment. For example, a patient’s gait may show foot drop as well as hip hiking.

Precautions Before gait training the clinician must review all medical records and examine any pathologies or impairments that may affect the patient’s ability to walk. Furthermore, through the rehabilitation evaluation, the clinician should have an understanding of the patient’s present abilities and prior level of function. Once gait training begins, the clinician must choose the appropriate assistive device that will provide optimal stability and still allow the patient mobility. The therapist should use a gait belt or similar device to help support the patient if he or she loses balance. Gait training should be done in a safe environment with few visual distractions, and with the patient wearing appropriate footwear. Some rehabilitation specialists have designed mechanical gait trainers with parachute harness systems that allow patients to practice their gait without overstraining the therapist.

Preparation Patient assessment In determining the patient’s readiness for gait training, the therapist will evaluate the patient’s physical abilities (weight-bearing, strength, stability, coordination and balance) and his or her mental and emotional readiness for gait training. Routine evaluation of elderly patients who are begining to develop gait problems may be done by a primary care physician, but assessment of complex disorders usually requires a gait specialist. A simple evaluation of a patient’s gait can be performed in a straight hallway without pictures or other objects that may distract the eye. The examiner will need a stopwatch for timing and a Tsquare to measure the length of the patient’s stride. Advanced evaluation of gait kinetics, however, requires a laboratory with computer and video technology. Assistive devices Patients with gait problems caused by pain in the lower extremities; decreased ability to bear weight; or

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The most stable assistive device is a set of parallel bars, followed in descending order of stability by walkers, crutches, single crutches, bilateral canes, and single canes. In terms of the demands that assistive devices place on the patient’s coordination, parallel bars are the least demanding, followed in ascending order by walkers, single canes, bilateral canes, axillary (under the armpit) crutches, and forearm crutches. Choosing a device and gait pattern The therapist must consider not only the type of assistive device most appropriate to the patient’s needs, but also the gait pattern (pattern of the patient’s movement) that will be most helpful. For example, a walker can be used with either a swinging or a stepping-through-androlling motion. Crutches can be used with either a reciprocating (uses both lower extremities) or nonreciprocating (favors the weight-bearing lower extremity). A so-called four-point gait will be used with a cane or single crutch. In this pattern the crutch or cane advances forward first, followed by the opposite lower extremity, then the other limb, all in a reciprocal pattern. In a three-point gait, one lower extremity is full weight-bearing and the other is non-weight-bearing. An example of a three-point gait would be a patient with bilateral crutches, with one limb lifted and one in contact with the ground. A two-point gait is a pattern in which the patient’s assistive device is a cane or single crutch that moves simultaneously with the opposite lower limb. The progression of various gait patterns from use of assistive devices to full independence depends on the type of impairment as well as the patient’s mental and physical abilities; it also depends to some extent on the experience of the clinician. Once selected, the assistive device is fitted to accommodate the patient’s height and weight. The cost varies: while a standard cane costs about $25 and a quad cane about $50, crutches cost between $65 and $110, with walkers costing between $80 and $150. Most health insurance policies, however, cover assistive devices. Patient education After the assistive device has been selected and fitted to the patient, the therapist demonstrates the appropriate gait pattern, including weight-bearing; shows the patient how to check the assistive device for safety and points of wear; teaches the patient how to move from a

sitting to a standing position; helps the patient practice the gait pattern; and shows the patient how to move from a standing to a sitting position. The next stage in training involves learning the gait pattern on different types of surface. The patient must know how to use the assistive device on uneven surfaces, curbs, and stairs as well as level surfaces. In stair gait training, the patient is taught a basic rule regarding the affected and unaffected sides of his or her body: “Up with the good, down with the bad; the device stays below.”

Aftercare Aftercare for gait training includes helping patients cope with the various disadvantages of assistive devices. Crutches and walkers, for example, are difficult to use in small or crowded areas. In addition, walkers offer little or no protection from backward falls. The use of axillary crutches may place too much pressure on the patient’s underarm area. Quad canes are hard to use on stairs and may be unstable on some surfaces, since the patient must have all four cane legs down on the floor or pavement with hand pressure centered over the legs.

Results The results of gait training vary according to the cause of the patient’s gait abnormalities, his or her overall health and mental attitude, and the prognosis. Some patients may be able to walk again without assistive devices, while others may make only limited progress. The importance of encouraging physical activity, however, cannot be overemphasized. Even modest amounts of exercise help to prevent muscle atrophy, benefit the cardiovascular system, and may lessen the pain of osteoarthritis. In addition, most gait training patients find that a greater degree of physical independence is good for their spirits as well as their bodies.

Health care team roles In addition to the roles of physicians and rehabilitation specialists in patient assessment and gait training, nurses and other allied health professionals should monitor the walking patterns of their patients and any use or misuse of assistive devices. Gerontologists should routinely assess elderly patients for changes in gait velocity, cadence, step length, or other indications of fears of falling. Furthermore, nurses and other allied health professionals should monitor all patients for changes in ambulation in an effort to maximize their safety.

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loss of strength, balance, endurance, or coordination may use a range of assistive devices as part of their gait training. The physical therapist will take into account the patient’s prognosis, home or institutional environment, capacity for standing, and the demands of the device itself in selecting an appropriate assistive device.

Gallbladder

Resources BOOKS

Bennett, S.E., and J.L. Karnes. Neurological Disabilities, Assessment and Treatment. Philadelphia: Lippincott, 1998. “Gait Disorders.” Chapter 21 in The Merck Manual of Geriatrics, 3rd ed. Whitehouse Station, NJ: Merck Research Laboratories, 1995. Hertling, D., and R.M. Kessler. Management of Common Musculoskeletal Disorders. Baltimore, MD: Lippincott, Williams & Wilkins, 1996. Lehmkuhl, L.D., and L. K. Smith. Brunnstrom’s Clinical Kinesiology. Philadelphia: F.A. Davis Co., 1996. Magee, D. J. Orthopedic Physical Assessment. Philadelphia: W.B. Saunders Co., 1997. Norkin, C.C., and P.K. Levangie. Joint Structure and Function: A Comprehensive Analysis. Philadelphia: F.A. Davis Co., 1992. Perry, J. Gait Analysis: Normal and Pathological Function. Thorofare, NJ: SLACK Inc., 1992. Pierson, F.M. Principles and Techniques of Patient Care.Philadelphia: W.B. Saunders Co., 1999. ORGANIZATIONS

National Rehabilitation Information Center and ABLEDATA (database). 8455 Colesville Road, Suite 935, Silver Spring, MD 20910. (800) 346-2742 or (800) 227-0216.

Mark Damian Rossi, Ph.D., P.T.

A close-up view of an inflamed gallbladder. (Custom Medical Stock Photo. Reproduced by permission.)

Function The gallbladder acts like a storage tank for bile (a bitter, greenish yellow liquid composed in part of cholesterol, bile salts, and bile pigment). Bile is made in the liver and travels through the hepatic duct to be stored and concentrated in the gallbladder until the body needs it to help break down ingested fats. When the gallbladder receives a signal from cholecystokinin (a hormone) in the small intestine, it contracts and releases bile into the common bile duct, where it travels to the small intestine to help digest fats.

Role in human health While the body can function normally without a gallbladder, this accessory organ of digestion is important to the proper digestion of fats.

Gallbladder

Common diseases and disorders

Definition The gallbladder, an organ of the gastrointestinal system involved in the storage and concentration of bile, is shaped like a deflated balloon or pear, and lies on the surface of the right lobe of the liver.

Description The gallbladder is pear-shaped and generally about 3–4 in (7.6–10.2 cm) in length. It consists of three parts. The fundus is the closed, bottom portion of the gallbladder that borders the liver. The body is the largest section of the gallbladder. In adults, the gallbladder can hold between 0.67 and 1.69 fl oz (20–50 ml) of bile. The neck of the gallbladder is much narrower than the body and empties into the cystic duct. 1014

One of the most common disorders of the gallbladder occurs when cholesterol mixes with bile and calcium, forming gallstones. Gallstones occur most frequently in middle-aged women, but they can also occur in people suffering from obesity, diabetes, hyperthyroidism, or any other disease that results in increased levels of cholesterol. When the stones stay in the body of the gallbladder they generally cause no pain or other symptoms. However, if a stone travels out into the neck of the gallbladder or into one of the bile ducts, nausea, vomiting, and severe pain follow. The patient may also become jaundiced. Gallstones usually have to be removed surgically. In severe cases, the entire gallbladder must be removed. Other diseases can also cause obstruction of the neck of the gallbladder, causing symptoms like those of gall-

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KEY TERMS Adenocarcinoma—Any one of a large group of cancerous, epithelial cell tumors of the glands. Biliary tree—Also referred to as biliary tract, it includes all of the parts associated with the passage of bile, beginning at the liver and ending at the opening of the bile duct into the small intestine.

Ashmallala, Hani, et al. “Recurrent Cholangiocarcinoma: Negative Autopsy Results After Aggressive Management.” South Medical Journal vol. 93, no. 6 (2000): 603-605.

Susan Joanne Cadwallader

Gallbladder ultrasound see Abdominal ultrasound

Cholecystitis—Acute or chronic inflammation of the gallbladder. Cholecystokinin—The hormone manufactured in the lining of the small intestine that signals the gallbladder to release bile. Cystic duct—The duct that allows passage of bile from the gallbladder to the common bile duct.

stones. Crohn’s disease, pancreatitis (inflammation of the pancreas), echinococcosis (infestation of the digestive system by tapeworms), and ascariasis (infestation of the digestive system by parasitic nematode worms) can all produce swellings that obstruct the gallbladder’s neck. Cholecystitis, or inflammation of the gallbladder, causes sharp, severe pain in the upper right portion of the abdomen. Cholecystitis causes fever, nausea, and vomiting; and, if left untreated, can be life-threatening. Cancer that invades any portion of the biliary tree can interrupt or prevent the normal flow of bile and result in multiple complications. Two of the most common malignancies that occur in the biliary tract involve adenocarcinoma of the gallbladder itself or of the bile ducts that carry bile from the gallbladder. Resources BOOKS

Anatomy and Physiology. Springhouse, PA: Springhouse Corporation, 1998, pp.126-7. Bray, John J., et al. Human Physiology. 4th ed. Malden, MA: Blackwell Science, Inc., 1999, p. 495. Higgins, Christopher. Understanding Laboratory Investigations. Malden, MA: Blackwell Science, Inc., 2000, p.162. The Merck Manual, edited by Mark H. Beers, and Robert Berkow. 17th ed. Whitehouse Station, NJ: Merck Research Laboratories, 1999, pp. 400-1. Wilson, Denise D. Nurse’s Guide to Understanding Laboratory and Diagnostic Tests. Philadelphia, PA: Lippincott Williams & Wilkins, 1999, p. 306.

Gallbladder x rays Definition Gallbladder x rays are diagnostic studies of the gallbladder (GB), a small pear-shaped sac that stores bile and is located under the liver. The study involves taking tablets containing iodine compounds a day before the x ray. The tablets are absorbed by the intestine, excreted by the liver and then concentrated in the gallbladder. In some clinics and hospitals the tablets are taken over a two day period, in hope of a better visualization of the gallbladder. This is known as a double-dose oral cholecystogram. This test was once the standard for diagnosing diseases of the GB; however, in recent years it is not often requested due to the advances in diagnostic ultrasound.

Purpose This test, also known as an oral cholecystogram or OCG, is usually ordered to help physicians diagnose disorders of the gallbladder, such as gallstones, inflammation, and tumors. The test is usually ordered when a gallbladder ultrasound has proved non-diagnostic. It is used in the investigation of patients complaining of upper abdominal pain after eating a fatty meal. Obese women over forty with a diet high in fat and low in fiber are at risk for gallstones. This test also measures gallbladder function, since the failure of the organ to visualize can signify a non-functioning or diseased gallbladder. The gallbladder may also not visualize if the bilirubin level is over four, and the study should not be performed under these circumstances. A CT scan, MRI (magnetic resonance imaging), or an ERCP (endoscopic retrograde cholangio-pancreatography) would be done instead.

Precautions The physician must be notified if the patient is pregnant or allergic to iodine. Patients with a history of severe

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PERIODICALS

Gallbladder x rays

the pelvis). Tall thin patients will need to be turned more since the gallbladder tends to lie lower and closer to the spine than in shorter, heavier patients. If the gallbladder is well seen on the first film, the x-ray technologist or radiologist will take another film coned-down and centered directly on the gallbladder. At least one more film in an upright or a lateral decubitus position will be done, since gallstones tend to sink downward or float in the gallbladder, as compared to a tumor or polyp, which remains in the same position. The gallbladder can displace to a considerably lower position when the patient is upright, so the radiography technologist must take into account the bodily habitus (size and shape) of each individual patient.

An x-ray image showing a healthy gallbladder outlined as a sac-like opaque mass. (Science Source/Photo Researchers. Reproduced by permission.)

kidney damage have an increased risk of side effects from this procedure. Ultrasound is commonly used instead of the x-ray examination when gallstones are suspected. Some people experience side effects from the contrast material (iodine tablets), especially diarrhea. During preparation for the test, patients should not use any laxatives. Diabetics should discuss the need for any adjustment in medication with their physician.

Description The exam is performed in the radiology department. The iodine tablets are purchased at a pharmacy or supplied by the hospital. The night before the test, patients swallow six tablets (one at a time) with plenty of water. If a double-dose OCG is requested, this will be done over a two day period. The patient will be asked to put on a hospital gown. The x-ray technologist will take a preliminary or scout film to see if the gallbladder is well visualized. The patient is placed prone with the right side slightly raised to prevent superimposition of the spine. The first film should show all of the right side of the abdomen, from the lateral side of the spine down to the iliac crest (top of 1016

The radiologist will review the x-rays and then take a series of coned-down (spot) films of the gallbladder with a fluoroscope (a special apparatus that projects the image onto a video monitor to be seen immediately). The radiologist may ask for another film to be taken 30 minutes after a fatty meal. The patient will be given a glass of egg nog or in some instances buttered toast and coffee or tea with cream. This meal will cause the gallbladder to contract and release bile, so the gallbladder should diminish in size on the post-fatty meal film (PFM). Delayed films may be taken if this doesn’t occur. The exam usually takes one hour to complete and may be done in a hospital or a clinic that is certified to take x rays.

Preparation The day before the test, patients are instructed to eat a normal breakfast and lunch and a light fat-free dinner (no fried or fatty foods, cream, milk, or butter). The night before, six Telepaque pills (iodine tablets) are taken one at a time, five minutes apart, with a large glass of water. Only water or juice is permitted until midnight. After midnight no food or liquids are allowed until after the exam. In some instances the clinic or hospital may prefer that a double-dose OCG be routinely done. This involves taking the Telepaque tablets over a two-day period. The pills may be taken two at a time with each fat-free meal or all at once, depending on the routine requested by the radiology department.

Aftercare No special care is required after the study.

Complications There is a small chance of an allergic reaction to the contrast material. In addition, there is a low level of radiation exposure. X rays are monitored and regulated to provide the minimum amount of radiation exposure

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Results A normal OCG will show a normal gallbladder. The gallbladder should visualize, and be free of any solid structures, such as stones, polyps, or tumors. It should empty freely with no obstruction after the PFM (post-fatty meal). Abnormal results may show gallstones, tumors, or cholesterol polyps (a tumor growing from the lining that is usually non-cancerous). Typically stones will “float” or move around as the patient changes position, whereas tumors will stay in the same place.

Health care team roles The radiography technologist works closely with the nurses (if the patient is hospitalized) to make sure the patient is given the Telepaque tablets and follows a fatfree diet. Any diarrhea or vomiting must be noted and the radiology department advised. The x-ray technologist must also be aware of the bilirubin level, which could indicate liver disease and a non-functioning gallbladder. In the case of a high bilirubin level the exam would not be done. All x-ray technologists must be certified and registered with the American Society of Radiologic Technologists or an equivalent association, depending on where the exam is being done. Patient education Patients must understand the importance of taking the contrast tablets and following a fat-free diet. All women of child-bearing age should be aware of the dangers of x rays to a fetus, and will be protected as much as possible without obstructing the image of the gallbladder. Resources BOOKS

Levenson, Deborah E. and Hans Fromm. “Oral Cholecystogram.” In Hepatology: A Textbook of Liver Disease, edited by David Zakim and Thomas D. Boyer et al. Philadelphia: W.B. Saunders Company. 1996, p.1883. Zeaman, Robert K. “Oral Cholecystography.” In Bockus Gastroenterology, edited by William S. Haubrich et al. Philadelphia: W.B. Saunders Company. 1995, pp. 208211.

KEY TERMS Bile—A yellow-green liquid produced by the liver, which is released through the bile ducts into the small intestines to help digest fat. Bilirubin—A reddish-yellow pigment formed from the destruction of red blood cells, and metabolized by the liver. Levels of bilirubin in the blood increase in patients with liver disease or blockage of the bile ducts. Body habitus—The size and shape of a person’s body. ERCP—An endoscopic retrograde cholangio-pancreatography. A flexible telescope is placed through the nose or mouth into the stomach, upper intestine and then the common bile duct to visualize the GB and pancreas. This is done when there is poor visualization of the gallbladder on an ultrasound examination, CT scan or OCG. Ultrasound—A noninvasive procedure based on changes in sound waves of a frequency that cannot be heard, but respond to changes in tissue composition. Patients must be fasting for at least six hours but no contrast material is given. There is no radiation used in an ultrasound exam, so it is the exam of choice for the diagnosis of stones in the gallbladder, but is less accurate in diagnosing stones in the bile ducts. Gallstones as small as 2 mm can be identified.

OTHER

Gall Bladder Exam from Harvard Medical School. . Gallbladder X-ray. . Gallstones from NIDDK. . Information on Gallstone Disease from the University of Connecticut Health Center. . Oral cholecystogram from healthanswers.com. . Methodist Health Care System. . Women’s healthabout.com. .

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needed to produce the image. Most experts feel that the risk is low compared with the benefits. Pregnant women and children are more sensitive to the risks of x rays, and the risk versus the benefits should be discussed with the treating physician. In some cases diarrhea or vomiting may occur. The x-ray technologist should be informed, since the gallbladder might not be well visualized.

Gallium scan of the body

Gallium scan of the body

KEY TERMS

Definition A gallium scan of the body is a diagnostic imaging test that utilizes a radionuclide, Ga67, to detect areas of infection and inflammation, or to detect certain types of tumors.

Gallium—An element whose radioactive form, Ga 67, is used for gallium scans. Sarcoidosis—A chronic, progressive disease of unknown etiology that can affect almost any organ or tissue.

Purpose In cases where patients have a suspected infection or inflammation, a gallium scan is useful to establish the site of origin, particularly with bone or orthopedic infections, and with such diseases as sarcoidosis. Patients with a chronic infection accompanied with a fever of unknown origin are also candidates for a gallium scan. Gallium is also used to localize primary tumors and locate metastases; to diagnose Hodgkin’s and other lymphomas; and to determine the stage of a lymphoma. Gallium scans are also performed to follow up patients who have received therapeutic treatment, to demonstrate the regression, progression, or recurrence of disease.

Precautions Ga67 is radioactive; therefore, patients who are pregnant are cautioned against having this test unless the benefits outweigh the risks. Women who are breastfeeding will need to stop breastfeeding for a specified period of time, usually for several weeks, depending on the dose.

Description The patient is required to come to the testing facility, usually a hospital nuclear medicine department or outpatient radiology facility, to receive an intravenous injection of the Ga67. After the injection, the patient must return anywhere from six hours to ten days later for the images, depending on the disease or condition being evaluated. The study itself takes approximately one hour, unless a more detailed SPECT (single photon emission computed tomography) is performed, which requires more time. The patient lies on an imaging table while a gamma camera obtains the necessary data to produce an image. In most cases, the camera is moved across the patient’s body, or, in the case of a SPECT study, the camera will circle around the body. The camera does not give off radiation, but instead detects the radiation from any areas where the gallium has accumulated. Images are obtained, posteriorly, anteriorly, and sometimes laterally. The camera may occasionally touch the patient but will not cause any discomfort. 1018

Preparation No special preparation is necessary, although some patients may be required to have light or clear meals within a day or less of the procedure. Some patients may need to take laxatives or an enema prior to the scan, to eliminate any residual gallium from the bowel.

Aftercare There is no particular aftercare required.

Complications There are no complications. There is a minimal risk of exposure to radiation from the Ga67, but the exposure from one gallium scan is generally less than exposure from many common x-ray procedures.

Results It is normal for the gallium to accumulate in the liver, spleen, bones, and large bowel. An abnormal concentration of gallium in areas other than those where it normally concentrates may indicate the presence of disease. Abnormal concentrations may be due to inflammation, infection, or presence of a tumor. Further investigation with ultrasound or CT is usually necessary to confirm the suspicions of abnormal findings, or to distinguish between a malignant and a benign tumor.

Health care team roles The injection and scan are performed by a nuclear medicine technologist, who is specially trained to handle radioactive materials and to operate the equipment used for this study. The technologist will obtain any pertinent medical history and explain the test to the patient. The technologist processes the data obtained during the scan. A doctor who is a radiologist or nuclear medicine specialist interprets the images and may make recommendations for follow-up tests or for further diagnostic procedures. If the patient is hospitalized during the time in

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Resources BOOKS

Illustrated Guide to Diagnostic Tests. Springhouse, PA: Springhouse Corporation, 1998. Klingensmith, William C., III, M.D., Dennis Eshima, Ph.D., John Goddard, Ph.D. Nuclear Medicine Procedure Manual 2000-2001. OTHER

“Gallium Scan.” .

Christine Miner Minderovic, B.S., R.T., R.D.M.S.

Gallstone analysis see Stone analysis Gamete intrafallopian transfer see Fertility treatments

Gangrene Definition Gangrene is the death of tissue caused by the lack of blood supply.

Description The severity of gangrene is wide-ranging. It can affect a minuscule skin area or a finger or toe, or even an entire limb such as an arm, a foot, or a leg. Gangrene is usually classified into two categories, dry gangrene and wet gangrene. Dry gangrene Dry gangrene occurs when a portion of bodily tissue dies because its blood supply has been decreased or completely cut off. This type of gangrene will not spread to other healthy tissue, and infection is not present. It is usually a slow process, with the affected area gradually becoming cold, discolored, and eventually totally black. Shrinkage and withering away of the affected tissue occurs as the tissue dies.

Wet gangrene Dry and wet gangrene are two terms often applied to different phases of the same death of tissue. Wet gangrene (also called moist gangrene) occurs when dry gangrene becomes infected, often due to injury, and the infection causes the tissue to die. In the United States, approximately 50% of moist gangrene cases are the result of a severe traumatic injury; 40% occur following surgery. Car and industrial accidents, crush injuries, and gunshot wounds are the most common traumatic causes. Because of prompt surgical management of wounds with the removal of dead tissue, the incidence of gangrene from trauma has significantly diminished. Surgeries involving the bile ducts or intestine are the most frequent procedures causing gangrene. Approximately two-thirds of cases affect the extremities, and the remaining one-third involve the abdominal wall. One particularly dangerous type of wet gangrene is termed gas gangrene, or myonecrosis. This particular type is caused by the infection of injured tissue or surgical wounds from the Clostridium species of bacteria, an especially virulent pathogen. In anaerobic conditions, that is, conditions in which oxygen levels are low, Clostridium can rapidly produce poisonous substances called toxins that cause tissue to die. Four of the Clostridium toxins, Alpha, Beta, Epsilon, and Iota, are capable of causing death. Gas gangrene differs from other wet gangrenes because it is more involved with muscle than skin tissue. Not only do the toxins manufactured by Clostridium cause the death of tissue, but they also destroy blood cells, constrict blood vessels, thus decreasing circulation, and damage blood vessels so that they leak. Fortunately, in peacetime, and with improvements in medical care, gas gangrene is not a frequently occurring phenomenon. (It occurs in only between one and three thousand people in the United States each year.) However, in the past, in wartime, gas gangrene has killed literally millions.

Causes and symptoms Dry gangrene Some of the most common causes of dry gangrene include: • arterial obstruction, or occlusion of an artery, caused by arteriosclerosis, diabetes mellitus, AIDS or blood clot • severe blunt trauma to a part of the body causing damage and therefore obstruction of an artery

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which the gallium scan is performed, the nursing staff may be needed to administer the enema and, if indicated, to oversee that the patient received a specified diet. The patient receives the results of this test from their personal physician or the doctor who ordered the test.

Gangrene

appearing pallor and is cold to the touch. As tissues begin to die, dry gangrene may continue to cause some pain; but it may go unnoticed, especially in the elderly or in those individuals with diminished sensation to the affected area. As more tissue dies, its color changes to brown, and finally purplish-black. This dead tissue will gradually separate from the healthy tissue and fall off.

A close-up of gangrene in the toes of a diabetic patient. (Photo Researchers, Inc. Reproduced by permission.)

• frostbite, which occurs when tissue becomes so cold that it is literally deprived of blood and therefore oxygen, and dies • diseases that affect the blood vessels, and especially the arteries, such as Buerger’s disease or Raynaud’s disease • traumatic occurrences such as crushing injuries, fractures, burns, and even injections given into skin or muscle

• edema, or swelling, at the injury site that expands quickly • pain in the area surrounding the skin injury • crepitus, a bubbly, crackling sound often heard upon palpation • pallor at the injury site, then increasingly dusky discoloration • low-grade to moderate temperature elevation • tachycardia, or increased heart rate • diaphoresis, or clammy, sweaty skin

Wet gangrene

• formation of blisters filled with rust-colored fluid

Causative organisms for wet gangrene infection include: • Streptococcus • Staphylococcus A serious but rare form of infection with Group A Streptococcus can impede blood flow and, if untreated, can progress to gangrene caused by chemical reaction. This type of gangrene is more commonly called necrotizing fasciitis, or infection of the skin and tissues directly beneath the skin. Gas gangrene, the most serious form of wet gangrene, often is caused by Clostridium bacteria, which are normal inhabitants of the gastrointestinal, respiratory, and female genital tracts. They often infect thigh amputation wounds, especially in those individuals who have lost control of their bowel function (incontinence). Gangrene, incontinence, and debility are often combined in patients with diabetes, and it is in the amputation stumps of diabetic patients that gas gangrene often occurs. Areas of either dry or moist gangrene are initially characterized by a red line on the skin that marks the border of the affected tissues. The onset of dry gangrene is normally characterized by dull, aching pain at the site. The skin usually develops an abnormal, unhealthy1020

Gas gangrene has a dramatically sudden, rapid onset. It is frequently first noticed as a marked swelling and either a pallid or brownish-red colored area surrounding the wound site. The borders of the infected site can expand literally within minutes. Symptoms of gas gangrene include:

• wound drainage, foul-smelling and rusty or bloody in appearance • in severe cases, shock (Symptoms of shock include generalized pallor, hypotension, rapid pulse, and cold hands and feet.)

Diagnosis A diagnosis of gangrene is based on a combination of the patient history, a physical examination, and the results of blood and other laboratory tests. A physician will look for a history of recent trauma, surgery, cancer, or chronic disease. Blood tests will be used to determine whether infection is present and determine the extent to which an infection has spread. A sample of drainage from a wound, possibly obtained through surgical exploration, may be cultured with oxygen (aerobic) and without oxygen (anaerobic) to identify the microorganism causing the infection and to aid in determining which antibiotic will be most effective. A gangrenous sample will contain few if any white blood cells and, when stained (with Gram stain) and examined under the microscope, will show the presence of purple (Gram-positive) rod-shaped bacteria.

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Precise diagnosis of gas gangrene often requires surgical exploration of the wound. During such a procedure, the exposed muscle may appear pale, beefy-red, or in the most advanced stages, black. If infected, the muscle will fail to contract with stimulation, and the cut surface will not bleed.

Treatment Gas gangrene is a potentially lethal condition requiring immediate action. It is recommended that anyone having any or all of the symptoms of gas gangrene contact a health provider immediately. Generally, once a diagnosis of gas gangrene is made, infected, gangrenous tissue must be removed surgically. To assure its complete removal, it is often necessary to remove all tissue surrounding the infection or even to amputate a portion of the body. Aggressive use of antibiotics, usually intravenously to start, is also begun as soon as possible. Pain medication will also usually be necessary. Areas of dry gangrene that remain free from infection (aseptic) in the extremities are most often left to wither and fall off. Treatments applied to the wound externally (topically) are generally not effective without adequate blood supply to support wound healing. Assessment by a vascular surgeon, along with x rays to determine blood supply and circulation to the effected area, can help determine whether surgical intervention would be beneficial. Once the causative organism has been identified, moist gangrene requires the prompt initiation of intravenous, intramuscular, and/or topical broad-spectrum antibiotic therapy. In addition, the infected tissue must be removed surgically (debridement), and amputation of the affected extremity may be necessary. Pain medications (analgesics) are prescribed to control discomfort. Intravenous fluids and, occasionally, blood transfusions are indicated to counteract shock and replenish red blood cells and electrolytes. Adequate hydration and nutrition are vital to wound healing. Although still controversial, some cases of gangrene are treated by administering oxygen under pressure greater than that of the atmosphere (hyperbaric) to the patient in a specially designed chamber. The theory behind using hyperbaric oxygen is that more oxygen will

dissolve in the patient’s bloodstream, and therefore more oxygen will be delivered to the gangrenous areas. By providing optimal oxygenation, the body’s ability to fight off the bacterial infection is believed to be improved, and there is a direct toxic effect on the bacteria that thrive in an oxygen-free environment. Some studies have shown that the use of hyperbaric oxygen produces marked pain relief, reduces the number of amputations required, and reduces the extent of surgical debridement required. Patients receiving hyperbaric oxygen treatments must be monitored closely for evidence of oxygen toxicity. Symptoms of this toxicity include slow heart rate; profuse sweating; ringing in the ears; shortness of breath; nausea and vomiting; twitching of the lips, cheeks, eyelids, nose; and convulsions. The emotional needs of the patient suffering from gangrene are also a large component of treatment. The individual with gangrene should be offered moral support, along with an opportunity to share questions and concerns about changes in body image. In addition, particularly in cases where amputation is required, physical, vocational, and rehabilitation therapy will also be required.

Prognosis Except in cases where the infection has been allowed to spread through the blood stream, as in the case of severe gas gangrene, prognosis for survival is generally favorable. Anaerobic wound infection can progress quickly from initial injury to gas gangrene and the spread of the infection to the blood stream within one to two days. Between 20 and 25% of gas gangrene victims do not survive. If recognized and treated early, however, approximately 80% of patients survive, and only 15 to 20% require any form of amputation. Unfortunately, the individual with dry gangrene most often has multiple other health problems that complicate recovery, and it is usually these health problems that can prove fatal.

Health care team roles • In most cases, gangrene is discovered while the patient is still in a healthcare facility following trauma, surgery, or treatment of serious medical conditions. A diagnosis of gangrene is generally made by a primary care physician or surgeon. • Both registered nurses (RNs) and licensed practical nurses (LPNs) must complete a prescribed course in nursing and pass a state examination. RNs typically have a degree in nursing. Both RNs and LPNs care for patients afflicted by gangrene both in general hospitals,

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X ray studies and more sophisticated imaging techniques, such as computed tomography scans (CT) or magnetic resonance imaging (MRI), may be helpful in making a diagnosis, since gas accumulation and muscle death (myonecrosis) may be visible. These techniques, however, are not sufficient alone to provide an accurate diagnosis of gangrene.

Gangrene

KEY TERMS Aerobic—A type of organism that grows and thrives only in environments containing oxygen. Anaerobic—A type of organism that grows and thrives in an oxygen-free environment. Arteriosclerosis—Build-up of fatty plaques within the arteries that can lead to the obstruction of blood flow. Aseptic—Without contamination with bacteria or other microorganisms. Crepitus—A crackling sound. Gram stain—A staining procedure used to visualize and classify bacteria. The Gram stain procedure allows the identification of purple (Grampositive) organisms and red (Gram-negative) organisms. Hyperbaric oxygen—Medical treatment in which oxygen is administered in specially designed chambers under pressures greater than that of the atmosphere in order to treat specific medical conditions. Incontinence—A condition characterized by the inability to control urination or bowel functions. Myonecrosis—The destruction or death of muscle tissue. Sepsis—The spreading of an infection in the bloodstream. Thrombosis—The formation of a blood clot in a vein or artery that may obstruct local blood flow; or may dislodge, travel downstream, and obstruct blood flow at a remote location.

homes, or other healthcare facilities. Good nursing care and observation are primary requirements. These will include taking vital signs, monitoring surgical wounds or injuries for signs and symptoms of infection, providing aseptic (germ-free) treatment to wounds and injuries, collecting specimens of wound drainage to be tested, and making all efforts necessary to keep the patient as comfortable as possible. Education about the underlying cause of the gangrene (diabetes, infection, etc.) is an important aspect of caring for these patients. • Clinical laboratory scientists have specialized training and must pass a state examination. They do the necessary tests on wound drainage specimens to determine the organism involved in the infection. 1022

• Radiologic technologists have specialized training and must pass a state examination. They take X rays and other tests to visualize and monitor the course of the gangrene. • Physical therapists must complete a prescribed course and pass a state examination in order to be licensed. Typically they have a degree. Physical therapists work with patients that have sustained an amputation because of gangrene to maintain and maximize mobility in walking, wheelchair use, and transferring (from wheelchair to toilet or from standing to sitting, for example). The physical therapist advises on such mobility aids as wheelchairs, braces, and canes. • Social workers have a degree in social work. A social worker may help coordinate services and ease the transition out of the hospital back into the home or extended care facility, if necessary. Social workers may help counsel the patient and the family during the difficult rehabilitation period. • Occupational therapists must complete a prescribed course and pass a state examination in order to be licensed. Typically they have a degree. They help people disabled after an amputation or loss of function caused by gangrene to relearn necessary functions needed to carry out normal activities of daily living such as bathing, dressing, and preparing meals. All healthcare team members need to be aware that the person with gangrene, and possibly an amputation, and the family members who may care at home for the person will need to learn an entirely new set of skills and adaptations. Both the patient and family often experience stress, anxiety, and depression. Both may need teaching regarding both physical and mental symptoms that often follow gangrene or amputation, and the family may need to be taught how to deliver necessary care. For the patient with gangrene, finding other individuals or a support group composed of people that have had similar illness or injury can be one of the most important steps in the rehabilitation process.

Prevention Patients with diabetes or severe arteriosclerosis need to take particular care of their hands and feet because of the risk of infection associated with even a minor injury. Education about proper foot care is vital. Diminished blood flow as a result of narrowed vessels will not lessen the body’s defenses against invading bacteria. Measures taken towards the reestablishment of circulation are recommended whenever possible. Any abrasion, break in the skin, or infected tissue should be cared for immedi-

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and open heart surgery, that allow air into the circulatory system.

Penetrating abdominal wounds should be surgically explored and drained, any tears in the intestinal walls closed, and antibiotic treatment begun early. Patients undergoing elective intestinal surgery should receive preventive antibiotic therapy. Use of antibiotics prior to and directly following surgery has been shown to significantly reduce the rate of infection from 20-30% to between 4 and 8%.

Sometimes, the term “the bends” is used to describe any manifestation of decompression sickness, including gas embolism. Specifically, the bends refers to a condition caused by dissolved nitrogen leaving the tissues too quickly on ascent during a dive. It is manifested by pain, often in the limbs and joints.

Resources

Gas embolism occurs independently of diving depth. It may occur in as little as 6 ft (2 m) of water if the swimmer has access to a source of air and takes even one breath underwater. Gas embolism is frequently caused when divers hold their breath during ascent. It may also result from an airway obstruction or other condition that prevents a diver from fully exhaling.

BOOKS

Berkow, Robert and Andrew Fletcher. The Merck Manual of Diagnosis and Therapy. Merck Research Laboratories, 1992. Nettina, Sandra. The Lippincott Manual of Nursing Practice. Philadelphia: J.B. Lippincott Company, 2001. Wyngaarden, James B., Lloyd H. Smith, and J. Claude Bennett. Cecil Textbook of Medicine. Philadelphia: W.B. Saunders Company, 1992. OTHER

“Gas Gangrene.” Medline, U.S. Department of Health and Human Services, National Institutes of Health. . May 16, 2001.

Joan M. Schonbeck

Gas embolism Definition Gas embolism, also called air embolism or arterial gas embolism, is the presence of gas bubbles in the bloodstream that obstruct circulation.

Description Gas embolism may occur with decompression from increased pressure. It typically occurs in ascending divers who have been breathing compressed air. If a diver does not fully exhale upon ascent, the air in the lungs expands as the pressure decreases, overinflating the lungs and forcing bubbles of gas (emboli) into the bloodstream. When gas emboli reach the arteries to the brain, the blood blockage causes unconsciousness. Gas embolism is second only to drowning as a cause of death among divers. In rare cases, gas embolism may also result from trauma or medical procedures, such as catheterization

Causes and symptoms

The primary sign of gas embolism is immediate loss of consciousness, which may or may not be accompanied by convulsions.

Diagnosis Any unconscious diver should be assumed to be the victim of gas embolism, regardless of whether consciousness was lost during or promptly after ascent. A doctor may also find pockets of air in the victim’s chest around the lungs and, occasionally, a collapsed lung from overinflation and rupture. Coughing up blood or a bloody froth around the mouth are visible signs of lung injury.

Treatment Prompt recompression treatment in a hyperbaric (high-pressure) chamber is necessary to deflate the gas bubbles in the bloodstream, dissolve the gases into the blood, and restore adequate oxygenated blood flow to the brain and other organs. Transport to a suitable recompression chamber should take precedence over nonessential procedures. Recompression by returning the diver to deeper water will not work, and should not be attempted. The patient should be kept lying down and given oxygen while being transported for recompression treatment. Before the diver receives recompression treatment, other lifesaving efforts may be necessary. If the diver is not breathing, artificial respiration (also called mouth-tomouth resuscitation or rescue breathing) should be administered. In the absence of a pulse, cardiopulmonary resuscitation (CPR) must be performed.

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ately. Any dying or infected skin must be removed promptly to prevent the spread of bacteria.

Gas exchange

abuse are also discouraged from diving. Individuals with certain other medical conditions, such as diabetes, may be able to dive safely with careful training and supervision.

KEY TERMS Compressed air—Air that is held under pressure in a tank to be breathed underwater by divers. Compression—An increase in pressure from the surrounding water that occurs with increasing diving depth. Decompression—A decrease in pressure from the surrounding water that occurs with decreasing diving depth. Emboli—Plural of embolus. An embolus is an object that blocks the blood flow in a blood vessel, as in a gas bubble, a blood clot, a fat globule, a mass of bacteria, or other foreign body. Hyperbaric chamber—A sealed compartment in which patients are exposed to controlled pressures up to three times normal atmospheric pressure. Hyperbaric treatment may be used to regulate blood gases, reduce gas emboli, and provide higher levels of oxygen more quickly in cases of severe gas poisoning. Recompression—Restoring the elevated pressure of the diving environment to treat gas embolism by decreasing bubble size.

Resources BOOKS

Martin, Lawrence. Scuba Diving Explained: Questions and Answers on Physiology and Medical Aspects of Scuba Diving. Flagstaff, AZ: Best Publishing, 1997. PERIODICALS

Everhart-McDonald, Mary Ann. “How to Keep Scuba Diving Safe.” Physician and Sportsmedicine 28 (May 2000): 94-6. Wilmshurst, Peter. “Diving and oxygen.” British Medical Journal 317 (October 1998): 996-9. ORGANIZATIONS

American College of Hyperbaric Medicine. P.O. Box 25914130, Houston, TX 77265. (713) 528-0657. . Divers Alert Network. The Peter B. Bennett Center, 6 West Colony Place, Durham, NC 27705. (919) 684-8111. (919) 684-4326 (diving emergencies). (919) 684-2948 (general information). . Undersea and Hyperbaric Medical Society. 10531 Metropolitan Avenue, Kensington, MD 20895. (301) 9422980. .

Jennifer F. Wilson

Prognosis The prognosis is dependent upon the promptness of recompression treatment and the extent of the damage caused by oxygen deprivation. Gas embolism may cause a stroke.

Definition

Health care team roles A gas embolism is an emergency situation. Any unconscious diver should be assumed to be the victim of gas embolism. Maintaining air supply is the most crucial step, and artificial respiration or CPR should be administrated as needed. Fluids should be administered, either orally if the patient is conscious, or intravenously.

Prevention

Gas exchange is the process by which oxygen is transferred from the atmosphere to bodily tissues for use in metabolism; and the gas produced by metabolism, carbon dioxide, is transferred from tissues to the atmosphere.

Description and function Overview of gas exchange

All divers should receive adequate training in the use of compressed air and a complete evaluation of fitness for diving. People with a medical history of lung cysts or spontaneous collapsed lung (pneumothorax), and those with active asthma or other lung disease, must not dive, for they would be at extreme risk for gas embolism. Patients with such conditions as alcoholism and drug 1024

Gas exchange

The process of gas exchange has several steps. The following is a summary of the steps: • ventilation (breathing) • interchange of CO2 and O2 between air in the lungs’ alveoli and blood in lung capillaries by diffusion • transport of CO2 and O2 through the bloodstream

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Ventilation The transfer of oxygen from the atmosphere to the tissues starts with the inspiration of air into the lungs. The lungs consist mainly of tiny air-containing alveolar sacs. The alveoli are small hollow sacs connecting to the larger terminal bronchioles of the airways. The air adjacent to the surfaces of the alveolar wall are lined by a single cell layer of flat epithelial cells called type I alveolar cells. In between these type I cells are thicker and more rounded type II alveolar cells, which produce a detergent-like fluid. In the alveolar walls, the fluid and connective tissue fills the interstitial space and is interspersed with capillaries. In some places the interstitial space is nonexistent, and the epithelial cell membranes are in direct contact with the capillaries. The blood in the capillaries is separated from the air molecules by a single layer of flat epithelial cells. The surface area in a single alveolus, because of the undulating terrain of type I and II epithelial cells, is roughly the size of a medium-sized room. There are around 300 million alveoli in the adult male. Therefore, there is a large amount of surface area placing air and the blood stream in close proximity. This trait is needed for gas exchange to easily occur. The respiratory system also needs a continual supply of fresh air. This air is supplied to the lungs through the nose and mouth, trachea, and bronchi. Ventilation is the interchange of air between the atmosphere and the alveoli by bulk flow. Bulk flow is the movement of air from a region of high pressure to one of low pressure. The physics of gas exchange In order to understand why oxygen and carbon dioxide are able to diffuse from their respective areas of high concentration, Dalton’s Law must first be presented. It states that in a mixture of gases, the pressure exerted by each gas is independent of the pressure exerted by the others. It is why carbon dioxide can move out of the bloodstream while oxygen is diffusing into the blood stream. The concentration of oxygen (O2) will not affect the activity of carbon dioxide (CO2). Henry’s law explains why CO2 can move from the blood stream into the airspace of the lung, and O2 can move from that airspace into the bloodstream. It states that the amount of gas dissolved will be directly proportional to the partial pressure of the gas with which the liquid is in equilibrium. At equilibrium, the partial pressures of the gas molecules in liquid and gaseous phases must be identical. Elemental gas can move from air into or out of a liquid where there is a pressure difference.

Interchange During inspiration, the partial pressure of oxygen (PO2) in the lung (105 mmHg) is higher than that in the arteries of the alveoli (40 mmHg). This pressure difference allows O2 to transfer into the blood stream. The partial pressure of carbon dioxide (PCO2) in the lung (40 mmHg) is less than the arterial partial pressure of the alveoli (46 mmHg). This pressure difference allows carbon dioxide to diffuse into the lung and eventually into the atmosphere. The ventilation of the lungs allows for the continual renewal of imbalance and need for breathing and metabolism to continue. Transport The circulatory system continually supplies blood in need of oxygenation and the ventilation of CO2 to the lungs. It arrives in the lungs with a PO2 of 40 mmHg and a CO2 of 46 mmHg and leaves the lungs with a PO2 of 100 mmHg and a CO2 of 40 mmHg. From the lungs, the oxygenated blood travels through the pulmonary veins to the left side of the heart and into the systemic arteries. The blood eventually flows to the tissue capillaries where another pressure difference occurs. Use and transport At the capillaries the PO2 is 100 mmHg and the PCO2 is 40 mmHg. In the tissues the PO2 is less than 40 mmHg and the PCO2 is greater than 46 mmHg. The O2 in the capillaries diffuses into the tissue and the CO2 produced by metabolism comes into the capillaries. Deoxygenated blood travels from the tissues to the right side of the heart via the systemic veins and then returns to the lungs for more O2 through the pulmonary arteries, where the process begins again. Hemoglobin Each liter of oxygenated blood normally contains 200 ml of pure gaseous O2 at atmospheric pressure (760 mmHg). It exists in the blood stream dissolved in the plasma and erythrocyte water or combined with hemoglobin molecules in the erythrocytes. Oxygen is relatively insoluble in water and only 3 ml will be dissolved in one liter of blood at the arterial partial pressure of 100 mmHg. It is consistent with Henry’s law because the amount of O2 dissolved in the blood is directly proportional to the partial pressure of the blood. This leaves another 197 ml of O2 in need of a way to be dissolved in the blood stream. The hemoglobin molecule is a protein with four subunits. Each subunit is made up of a heme (a molecular group) with a polypeptide attached. Heme contains one

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• interchange of CO2 and O2 between blood in lung capillaries and alveolar air by diffusion • use of O2 and production of CO2 by cells through metabolism

Gas exchange

KEY TERMS Chemoreceptor—A type of cell activated by a change in its chemical balance that results in a nerve impulse. Metabolism—The sum of physical and chemical changes in the tissue including anabolism, catabolism, energy production and synthesis of molecules. Ventilation—Movement of gases into and out of the lungs; tidal exchange between the lungs and the atmosphere.

atom of Iron (Fe) to which one O2 molecule can bind. This means that every hemoglobin molecule can bind four O2 molecules. The four polypeptides in hemoglobin are called globin. With O2 attached to the molecule, it is known as oxyhemoglobin (HbO2) and without it is known as deoxyhemoglobin (Hb). The bonding of O2 to hemoglobin allows a full 200 ml of O2 to dissolve completely in the blood. In reference to Dalton’s law it allows for a greater difference in the concentration of O2 between the O2 in the lung and the bloodstream, and the blood. The O2 tied up by the hemoglobin cannot be considered when looking at concentration differences. Conversely the concentration difference between the tissues and the capillaries at the tissue level causes the O2 to dissociate from the hemoglobin, leaving the O2 free to diffuse into tissue and the hemoglobin free to bond to the carbon dioxide leaving the tissue. By tying up carbon dioxide with hemoglobin, even more CO2 can be carried to the lungs by the blood. CO2 is far more soluble in water than O2. Only ten percent of the carbon dioxide that enters the blood is dissolved in water. Thirty percent of the carbon dioxide bonds with hemoglobin to form carbaminohemoglobin. Sixty percent of the carbon dioxide is converted to bicarbonate. Deoxyhemoglobin serves as a buffer in the bloodstream as well. It has an affinity for acidic hydrogen atoms left in the bloodstream by the formation of bicarbonate. This allows the blood to maintain a pH of around 7.4 and explains why even venous blood maintains this pH. Regulation of gas exchange The exchange of gases in the body will occur with the respective differences of partial pressure between the blood and tissues, and the lung and alveoli. Respiratory rate must be controlled in order to suit the O2 needs of the 1026

body and ensure a balanced supply of O2 to the tissues. Respiratory rate is controlled by the peripheral chemoreceptors located high in the neck, where the common carotid arteries split, as well as on the arch of the aorta. They are called carotid bodies and aortic bodies respectively. These chemoreceptors are stimulated by the minor elevation of PCO2 levels, causing an increase in ventilation. Chemoreceptor response to the PCO2 level in the blood is the primary and most immediate indicator of gas deficiency and surplus in the blood stream. Elevated levels of PCO2 normally cause an increase in breathing, and lower levels normally cause a decrease. This response system allows for a balance of gases available for use in metabolism. Conversely, a decrease in arterial PO2 levels and an increase in blood acidity do not affect a minimal increase in ventilation stimulated by chemoreceptors until PO2 goes below 60 mmHg. Oxygen transport at the tissues will not be reduced until the blood PO2 reaches 60 mmHg. Thus, the chemoreceptors are not triggered for lack of PO2 in normal circumstances. If there is lung disease, or in high altitudes, these receptors can be stimulated and will affect an increase in the respiratory rate.

Role in human health Gas exchange provides a needed fuel (O2) for metabolism to occur and a means to expel the gaseous byproduct (CO2) of metabolism from the body. Without gas exchange the body would not function. The hindrance of gas exchange by disease, disorder, or chemicals can slow body functions and even cause death.

Common diseases and disorders The interference of gas exchange occurs when the function of a number of different organs and tissues is impaired. The most common form of impairment to gas exchange is hypoxia, which is the lack of oxygen in the tissues. Hypoxia can be caused by hypoventilation, diffusion impairment, shunt, and or ventilation-perfusion (the rate of ventilation relative to CO2 production)inequality. Hypoventilation is the reduced alveolar ventilation in comparison to the metabolic CO2 production in which the PCO2 levels increase above normal. It is caused by disease in the lung, abnormalities in the thoracic cage, or deficits in the respiratory control pathway from the medulla to the chemoreceptors. Diffusion impairment occurs when there is a decrease in the surface area or thickening of the alveolar membranes. Diseases or disorders in the lung can cause this impairment.

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Chronic obstructive pulmonary disease (COPD) refers to emphysema, chronic bronchitis or a combination of the two. Cigarette smoking is a major cause of this and the following diseases associated to COPD. Chronic bronchitis is characterized by excessive mucus production in the bronchi and chronic inflammatory changes in the small airways. Emphysema is a major cause of hypoxia and is characterized by the destruction of the alveolar walls, and the atrophy and collapse of the lower airways. Pneumonia is normally caused by bacterial or viral infection. The alveolar spaces fill with mucus, inflammatory cells, and fibrin. Other disorders that impact gas exchange are hyperventilation, in which ventilation is increased relative to the metabolic CO2 production, and in which the PCO2 drops below normal levels; and the effects of high altitude (called altitude sickness), in which the lack of O2 in the atmosphere causes the body to compensate for that deficiency.

(P), temperature (T), and the amount (n) of gas present (see Gases, properties of). The properties of gases were already being studied and described as early as the seventeenth century. Unlike solids, which have a fixed shape and volume, and liquids, which have a fixed volume but can change shape according to the container, gases assume both the shape and the volume of their container. The volume of space occupied by a sample of gas depends on the number of gas molecules present and the sample’s pressure and temperature.

Simple gas laws Boyle’s law: volume is inversely proportional to pressure Boyle’s law, formulated by English scientist Robert Boyle in 1662, states that the pressure of a fixed amount of gas at a constant temperature is inversely proportional to its volume. In other words, when a sample of gas is allowed to expand to occupy a larger volume, its pressure decreases; and when it is compressed into a smaller volume, its pressure increases. Mathematically, this inverse relationship may be formulated:

Resources

P1V1 = P2V2

BOOKS

or

Bullock, John et. al. National Medical Series for Independent Study: Physiology, third edition. Philadelphia: Williams & Wilkins, 1995. Vander, Arthur et. al. Human Physiology-the Mechanisms of Body Function, eighth edition. New York: McGraw-Hill, 2001. ORGANIZATIONS

American Lung Association 1740 Broadway New York, NY 10019. (212) 315-8700. . OTHER

“Gas Exchange I.” John Carroll University. Accessed August 8, 2001. .

V = constant ÷ P In continental Europe, this gas law is known as the law of Mariotte, after Edme Mariotte, who published the results of his studies of the properties of gases a few years later than Boyle. The working of a syringe can be used to illustrate Boyle’s law. When the plunger of a syringe is drawn back, the volume of the air inside the syringe barrel is increased and the pressure decreased relative to the exterior of the syringe, and fluid is pulled into the syringe. When the plunger is depressed, the volume is decreased, the pressure increased, and fluid is forced out.

Sally C. McFarlane-Parrott

Gas gangrene see Gangrene

Gas laws Definition The gas laws are mathematical formulations of the interrelationships among the four variables that describe the behavior of a gas sample: its volume (V), pressure

Charles’s law: volume is directly proportional to temperature Charles’s law, which was formulated by French physicist Jacques Charles in 1787, states that the volume of a sample of gas kept at constant pressure is directly proportional to the temperature; or, more simply stated, a gas sample will expand upon heating and contract when cooled. This may be formulated mathematically as: V1 ÷ T1 = V2 ÷ T2 or V = constant  T

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Asthma is an intermittent disease characterized by a chronic inflammation of the airway, which causes smooth muscle contraction in the airway.

Gas laws

equal volume at a given temperature and pressure contain equal numbers of gas molecules. Alternatively, samples of two different gases containing the same number of molecules will occupy equal volumes. Avogadro’s law mathematically formulated is: V1 ÷ n1 = V2 ÷ T2 or V = constant  n. At standard temperature and pressure (STP), one mole of any gas occupies 22.4 L. As an example of the law of Avogadro, consider that, during respiration, the amount of air in the lungs is alternately increased and decreased by the movement of the diaphragm that causes the volume of the lungs to be alternately increased and decreased.

Charles’s law states that the temperature and volume of a gas are directly related under constant pressure conditions. This demonstration shows the volume of air in the balloons decreasing (balloons shrinking) when they are held in a flask of liquid nitrogen (cooled), and reexpanding when the air in the balloons is allowed to warm to room temperature. (Photograph by Charles D. Winters. Science Source/Photo Researchers. Reproduced by permission.)

A hot air balloon demonstrates the principle of Charles’s law. When the balloon is fired, the air is heated and expands to fill the balloon. Gay-Lussac’s law: pressure is directly proportional to temperature This gas law, published in 1802 by Frenchman Joseph Louis Gay-Lussac, describes the relationship between the gas’s pressure and temperature. At constant volume, the pressure of a gas sample is directly proportional to its temperature. In other words, a sample of gas exerts more pressure on its surrounding container when hot than when cold. The mathematical formulation of this law is P1 ÷ T1 = P2 ÷ T2

Ideal gas law The ideal gas law, first derived in 1834 by Emil Clapeyron, compiles the simple gas laws into a single expression with a single constant, called the ideal gas law: PV = nRT The single constant R is called the universal gas constant. The value of the constant depends on the units used to express pressure and volume. The standard units for measuring volume, pressure, amount, and temperature are, respectively, the liter (L), the atmosphere (atm), the mole (mol), and Kelvin (K), giving rise to the value R = 0.082 liter atm mol-1 K-1;. All of the relationships established by the simple gas laws are preserved in the expression of the ideal gas law: • The volume of a gas is inversely proportional to its pressure. • The volume of a gas is directly proportional to its temperature. • The pressure of a gas is directly proportional to its temperature.

or P = constant  T Avogadro’s law: volume is directly proportional to amount In the early nineteenth century, the Italian Count Amadeo Avogadro hypothesized that different gases of 1028

It should be noted that all gaseous substances behave alike according to these laws. Also, in each of the formulations above, the proportionality constant has a different meaning and is expressed in different units. Moreover, in calculations, temperature must be expressed in terms of the Kelvin, or absolute, temperature scale.

• The volume of a gas is directly proportional to the amount of gas present. An ideal, or perfect, gas is a hypothetical gas that obeys the gas laws in terms of its pressure, volume, and temperature behavior. Such a gas would have to be composed of molecules that do not interact with one another.

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Dalton’s law of partial pressures The simple and ideal gas laws describe the behavior of pure gaseous substances. Mixtures of gases also behave like ideal gases, provided the different components do not undergo a reaction, or interact in some other way. This concept—that each individual gas in a mixture expands to exert its partial pressure as if the other gas components were not present—was developed by John Dalton in 1801 and is known as Dalton’s law of partial pressures. Given that the pressure of a gas is directly related to the number of moles of gas present, and that all gases behave alike, it follows that the total pressure exerted by a mixture of gases is equal to the sum of the pressures of each of the components of the gas mixture. The pressure exerted by a component gas in a mixture is referred to as the partial pressure of that gas. Thus, for a mixture of gases, A, B,..., tot

= PA + PB +...

Each component gas experiences the same temperature and volume conditions as all other components. Application of the ideal gas equation to each pressure term allows formulation of a useful term known as the mole fraction (X) of a gas. The mole fraction is defined as the ratio of the number of moles of one component to the total number of moles of gas in the mixture, which is equal to the ratio of the partial pressure to the total pressure (XA = nA÷ntot = PA÷Ptot. V = nART

Gay-Lussac’s law of combining volumes In 1808, Gay-Lussac, in collaboration with Alexander von Humbolt, studied the reactions of gases. They determined that, at a given temperature and pressure for the reactions involving gaseous substances, the volumes of the reactant and product gases are in ratios of small whole numbers. For example, two volumes of hydrogen gas react with one volume of oxygen gas to form two volumes of water vapor. Resources BOOKS

Amend, J.R., B.P. Mundy, and M.T. Armold. General, Organic and Biological Chemistry. Fort Worth, Philadelphia, San Diego, New York, Orlando, Austin, San

Gas laws

Real gases are not always accurately described by the ideal gas equation. Under ordinary conditions, however, the observed behavior of a real gas is only negligibly different from that predicted for an ideal gas.

KEY TERMS Celsius (centigrade) and Kelvin temperature scales—On the Celsius scale, the temperature at which water freezes is defined as zero degrees and the temperature at which water boils is defined as 100°. The Kelvin scale is the official temperature scale of the International System of Units (SI), the units preferred by most international scientific agencies. The Kelvin scale is based on the Celsius scale, with zero defined as the temperature at which molecular motion ceases, equal to –273.15°C. Gas—One of the three physical states in which matter can exist; gaseous matter conforms to the shape and volume of its container. Mole—An amount of substance containing a number of atoms or molecules equal to Avogadro’s constant, 6.022  10 23. Pressure—The force or weight per unit area exerted by matter on its surroundings. For calculations involving gas properties, pressure is usually measured in atmospheres (atm); other units of pressure include lb/in.2, bar, torr, and mm mercury. Standard conditions of temperature and pressure (STP)—For gases, standard conditions are 0°C and 1 atm. Volume—The three dimensional space occupied by a substance, measured in liters (l).

Antonio, Toronto, Montreal, London, Sydney, and Tokyo: Saunders College Publishing, 1993. Brown, T.G., H.E. LeMay Jr., and B.E. Bursten. Chemistry: The Central Science. Eaglewood Cliffs: Prentice Hall, 1994. OTHER

Green, J.M., and A. Peterson. Woodrow Wilson Leadership Program in Chemistry website. 1998. . Logan, R.H. Gas Laws website. 1996. . Park, J.L. ChemTeam website. 1996. .

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Patricia L. Bounds, Ph.D. 1029

Gases, properties of

Gases, properties of Definition The fundamental physical properties of a gas are related to its temperature, pressure, and volume. These properties can be described and predicted by a set of equations known as the gas laws. While these laws were originally based on mathematical interpretations for an ideal or perfect gas, modern atomic and kinetic theory of gases has led to a modified expression that more accurately reflects the properties of real gases.

Description Current understanding of gas properties came as a result of study of the interaction between volume, pressure, and temperature. Robert Boyle was the first to describe the relationship between the volume and pressure of a gas. In 1660 he learned that if an enclosed amount of a gas is compressed to half its original volume while the temperature is kept constant, the pressure will double. He expressed this mathematically as PV = constant, where P stands for pressure, V stands for volume, and the value of the constant depends on the temperature and the amount of gas present. This expression is known as Boyle’s law. The second fundamental property of gases was defined by Jacques Charles in 1787. He found that the temperature and volume of a gas are directly related. Charles observed that a number of gases expanded equally as heat was applied and the pressure was kept constant. Charles’s ideas were expanded upon in research by others in the field, most notably Joseph Gay-Lussac, who also studied the thermal expansion of gases. The volume/temperature relationship is known as Charles’s law. The third property of gases was described by GayLussac who, in addition to his work with volume and temperature, researched the connection between pressure and temperature. In 1802, he formulated an additional law. These three laws can be combined into one generalized equation that expresses the interrelation between pressure, temperature and volume. This equation, called the ideal gas law, is written as PV = nRT. While the ideal gas law works very well in predicting gas properties at normal conditions, it does not accurately represent what happens under extreme conditions. Neither does it account for the fact that real gases can undergo phase change to a liquid form. Modern atomic theory helps explain these discrepancies. It describes molecules as having a certain freedom of motion in space. Molecules in a solid material are arranged in a reg1030

ular lattice such that their freedom is restricted to small vibrations about lattice sites. Gas molecules, on the other hand, have no macroscopic spatial order, and they can move about their containers at random. The motion of these particles can be described by the branch of physics known as classical mechanics. The study of this particulate motion is known as the kinetic theory of gases. It states that the volume of a gas is defined by the position distribution of its molecules. In other words, the volume represents the available amount of space in which a molecule can move. The temperature of the gas is proportional to the average kinetic energy of the molecules, or to the square of the average velocity of the molecules. The pressure of a gas, which can be measured with gauges placed on the container walls, is a function of the particle momentum, which is the product of the mass of the particles and their speed.

Function The human body requires certain gases to function. Oxygen and carbon dioxide are respiratory gases that move between the blood and air through the lungs. Respiratory gases are exchanged between the body and the environment through the mechanisms of convection and diffusion. Convection is also called mass flow. Convection moves the air from the air in the environment into the lungs. Convection also moves the blood between the body tissues and the lungs. Diffusion moves the oxygen and carbon dioxide across membranes and transports gases between air and blood in the lungs and between blood and respiratory tissues in the body.

Role in human health The gases in the human body that are most significant are oxygen and carbon dioxide. If the gases are not exchanged in the proper quantities and adequately transported through the body, then both minor and major health problems can result.

Common diseases and disorders Many common diseases or disorders can affect the adequate exchange of gases throughout the human body. These diseases or ailments can range from severe respiratory diseases, such as emphysema, to the common cold. Both lung disease and heart disease can lead to abnormalities in the composition of blood gases. Following is a list of just a few of the diseases or disorders that can cause abnormalities in the exchange of gases in the human body.

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Ideal gas law—The mathematical expression that predicts the behavior of a “perfect” gas. Kinetic theory of gases—The physical principles that describe how gas molecules interact.

• emphysema • chronic obstructive pulmonary disease • congestive heart failure • pneumonia Resources BOOKS

Holum, John R. Fundamentals of General, Organic and Biological Chemistry. Wiley and Sons, 1994. Tortora, Gerard, and Sandra Grabowski, eds. Principles of Anatomy and Physiology, 8th edition. New York: HarperCollins, 1996. PERIODICALS

Adcock, Louis H. “The Egg in the Bottle Revisited: Gas pressure and Amonton’s Law (Charles’s Law).” Journal of Chemical Education 75, no. 12 (Dec. 1998):1567. OTHER

“Physical Properties of Gases.” Pump.Net .

Peggy Elaine Browning

millimoles of H+ per hour of each specimen is then evaluated.

Purpose A gastric analysis is performed to evaluate gastric function by measuring the contents of a fasting patient’s stomach the for acidity, appearance, and volume. The basal gastric secretion test is indicated for patients with obscure gastric pain, loss of appetite, and weight loss. It is also utilized for suspected peptic ulcer, severe gastritis, and Zollinger-Ellison (Z-E) syndrome. The gastric acid stimulation test is indicated when abnormalities are found during the basal secretion test. These abnormalities can be caused by a number of disorders, including duodenal ulcer, pernicious anemia, and gastric cancer. While this test will detect abnormalities, x rays and other studies are necessary to obtain a definitive diagnosis.

Precautions Because both the basal acid output test and the gastric acid stimulation test require gastric intubation through the mouth or nasal passage, neither test is recommended for patients with esophageal problems, aortic aneurysm, severe gastric hemorrhage, or congestive heart failure. The gastric acid output test is also not recommended in patients who are sensitive to pentagastrin (the drug used to stimulate gastric acid output).

Description This test, whether performed for basal gastric acid secretion, gastric acid stimulation, or both, requires gastric intubation by mouth or through the nasal passage.

Gastric analysis Definition Gastric analysis consists of a series of tests used to analyze the contents of the stomach. The complete series involves: • collecting residual gastric fluid from a fasting patient • collecting basal secretions every 15 minutes for four hours • intramuscular administration of a drug that stimulates gastric acid output • collecting stomach secretions every 15 minutes for 90 minutes The appearance, blood, bile, pH, volume, millimoles of H+ per liter, millimoles of H+ per volume, and

Basal gastric acid secretion The patient should be fasting overnight (12 hours) prior to intubation. After allowing approximately 10 to 15 minutes for the patient to adjust to the presence of the tube, and with the patient in a sitting position, specimens are obtained every 15 minutes for a period of 90 minutes. The first two specimens are examined visibly for blood and volume but are discarded to eliminate gastric contents that might be affected by the stress of the intubation process. The patient is allowed no liquids during the test, and saliva must be ejected to avoid diluting the stomach contents. The final four specimens collected during the test constitute the basal acid output. Each sample is titrated to pH 3.5 using 0.1 N sodium hydroxide. The millimoles of hydrogen ion in each sample are calculated from the

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KEY TERMS

Gastric analysis

tion of the highest two to calculate the acid produced in millimoles per hour.

KEY TERMS Achlorhydria—An abnormal condition in which hydrochloric acid is absent from the secretions of the gastric glands in the stomach. Intubation—Insertion of a tube into a body canal or hollow organ, as into the stomach. Pernicious anemia—One of the main types of anemia, caused by inadequate absorption of vitamin B12. Symptoms include tingling in the hands, legs, and feet, spastic movements, weight loss, confusion, depression, and decreased intellectual function.

Analyses and calculations The appearance, blood, bile, pH, volume, millimoles of H+ per liter, millimoles of H+ per volume, and millimoles of free H+ per hour of each specimen are then evaluated. In addition, the basal acid output (BAO) is computed, as is the maximal acid output (MOA) or peak acid output (PAO). BAO is calculated by averaging the output of the three closest samples. MAO is calculated as the average of the four specimens. PAO is calculated by taking the mean of the two highest post-stimulation values.

Subcutaneously—Under the skin. Zollinger-Ellison syndrome—A rare condition characterized by severe and recurrent peptic ulcers in the stomach, duodenum, and upper small intestine, caused by a tumor or tumors, usually found in the pancreas. The tumor secretes the hormone gastrin, which stimulates the stomach and duodenum to produce large quantities of acid, leading to ulceration. Most often cancerous, the tumor must be removed surgically; otherwise total surgical removal of the stomach is necessary.

amount of base used to neutralize the stomach acid of each. The results of the closest three samples are averaged and multipled by four to give the millimoles of free hydrogen ions per hour. If analysis suggests abnormally low gastric secretion, the maximum acid output test is performed immediately afterward. Gastric acid stimulation test After the basal samples have been collected, the tube remains in place for the gastric acid stimulation test. Pentagastrin, or a similar drug that stimulates gastric acid output, is injected subcutaneously. After 15 minutes, a specimen is collected every 15 minutes for one hour. These specimens are called the post-stimulation specimens. As is the case with the basal gastric secretion test, the patient can have no liquids during this test, and their saliva must be ejected to avoid diluting the stomach contents. The maximal acid output (MAO) is determined by titrating each of the four specimens and averaging the results. The average is used to determine the millimoles of hydrogen ion produced per hour. Alternatively, the peak acid output (PAO) is determined by titrating each specimen and using the average hydrogen ion concentra1032

Preparation The patient should be fasting (nothing to eat or drink after the evening meal) on the day prior to the test, but may have water up to one hour before the test. Antacids, anticholinergics, cholinergics, alcohol, H2-receptor antagonists (Tagamet, Pepcid, Axid, Zantac), reserpine, adrenergic blockers, and adrenocorticosteroids should be withheld for one to three days before the test, as the physician requests. If pentagastrin is to be administered for the gastric acid secretion test, medical supervision should be maintained, as possible side effects may occur. Additionally, because such external factors as the sight or odor of food, as well as psychological stress, can stimulate gastric secretion, accurate testing requires that the patient be relaxed and isolated from all sources of sensory stimulation.

Aftercare Such complications as nausea, vomiting, and abdominal distention or pain are possible following removal of the gastric tube. If the patient has a sore throat, soothing lozenges may be given. The patient may also resume the usual diet and any medications that were withheld for the test(s).

Complications There is a slight risk that the gastric tube may be inserted improperly, entering the trachea instead of the esophagus. If this happens, the patient may experience difficulty breathing or a coughing spell until the tube is properly inserted. Also, because the tube can be difficult to swallow, if a patient has an overactive gag reflex, there may be a transient rise in blood pressure due to anxiety. Other complications may include bleeding, dysrhyth-

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Results Reference values for the basal acid output test and gastric acid stimulation test vary by laboratory, but are usually within the following ranges: • Fasting volume: 20-100 mL. • Fasting pH: less than 2.0. • BAO for men: 0 to 5 mmol/hour. • BAO for women: 0 to 4 mmol/hour.

Resources BOOKS

Chernecky, Cynthia C, and Barbara J. Berger, Laboratory Tests and Diagnostic Procedures. 3rd ed. Philadelphia, PA: W. B. Saunders Company, 2001. Kee, Joyce LeFever. Handbook of Laboratory and Diagnostic Tests. 4th ed. Upper Saddle River, NJ: Prentice Hall, 2001. Cahill, Mathew. Handbook of Diagnostic Tests. Springhouse, PA: Springhouse Corporation, 1995. Jacobs, David S. Laboratory Test Handbook, 4th ed. Hudson, OH: Lexi-Comp Inc., 1996. Pagana, Kathleen Deska. Mosby’s Manual of Diagnostic and Laboratory Tests. St. Louis, MO: Mosby, Inc., 1998.

• MAO for men: 5 to 26 mmol/hour. Victoria E. DeMoranville

• MAO for women: 7 to 15 mmol/hour. An abnormal basal acid output is considered nonspecific and must be evaluated in conjunction with the results of a gastric acid stimulation test. However, elevated secretion may suggest different types of ulcers; and markedly elevated results may be suggestive of Zollinger-Ellison syndrome. Depressed secretion may indicate a gastric cancer, while complete absence of secretion (achlorhydria) may suggest pernicious anemia.

Gastrin test see Gastric analysis

Elevated gastric secretion levels in the gastric acid stimulation test may be indicative of duodenal ulcer; highest levels of secretion suggest Zollinger-Ellison syndrome, a gastrin-secreting tumor.

Gastritis commonly refers to inflammation of the lining of the stomach, but the term is often used to encompass a variety of symptoms resulting from stomach lining inflammation, as well as symptoms of burning or discomfort. True gastritis comes in several forms and is diagnosed using a combination of tests. In the 1990s scientists discovered that the main cause of true gastritis is infection from a bacterium called Helicobacter pylori (H. pylori).

Measurement of plasma gastrin by radioimmunoassay is often performed when the gastric acid level is abnormal. Frankly elevated serum gastrin levels occur in pernicious anemia and atrophic gastritis, which are both associated with low gastic acid output; and in ZollingerEllison syndrome, which is associated with high gastric acid output. Gastrin levels are not elevated in persons with duodenal ulcers and are normal or slightly increased in persons with gastric ulcers.

Health care team roles A physician orders the gastric analysis and interprets the results. The testing physician must obtain an accurate patient history, especially to determine if the patient is taking any drugs that can affect the test result and to learn about any recent illness, trauma, or symptoms that could be related to gastric function. The procedure should be explained to the patient by the unit nurse, who should be aware of the degree of seriousness of the patient’s condition. Gastric analysis is performed by clinical laboratory scientists/medical technologists or by clinical laboratory technicians/medical laboratory technicians.

Gastritis Definition

Description Gastritis should not be confused with common symptoms of upper abdominal discomfort. Gastritis has been associated with resulting ulcers, particularly peptic ulcers. In some cases, chronic gastritis can lead to more serious complications. Nonerosive Helicobacter pylori (H. pylori) gastritis The main cause of true gastritis is H. pylori infection. H. pylori is indicated in an average of 90% of persons with chronic gastritis. This form of nonerosive gastritis is the result of infection with the H. pylori bacterium, a microorganism whose outer layer is resistant to the normal effects of stomach acid in breaking down bacteria. This resistance means that the bacterium may rest in the stomach for long periods of times, even years, and eventually cause

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mias, esophageal perforation, layrngospasm and decreased mean pO2 (a measure of blood oxygen levels).

Gastritis

symptoms of gastritis or ulcers when other factors are introduced, such as the ingestion of nonsteroidal antiinflammatory drugs (NSAIDs). It also seems to be activated in people with a genetic predisposition. Study of the role of H. pylori in development of gastritis and peptic ulcers has disproved the former belief that stress led to most stomach and duodenal ulcers. This understanding has resulted in improved treatment and reduction of stomach ulcers. H. pylori is most likely transmitted between humans, although the specific routes of transmission were still under study in 2001. Studies are also underway to determine the role of H. pylori and resulting chronic gastritis in the development of gastric cancer. Erosive and hemorrhagic gastritis After H. pylori, the second most common cause of chronic gastritis is the use of NSAIDs. These commonly used pain killers, including aspirin, fenoprofen, ibuprofen, and naproxen—among others—can lead to gastritis and peptic ulcers. Other forms of erosive gastritis are those due to ingestion of alcohol and corrosive agents, or due to such trauma as ingestion of foreign bodies. Other forms of gastritis Clinicians differ on the classification of the less common and specific forms of gastritis, particularly since there is so much overlap with H. pylori in development of chronic gastritis and complications of gastritis. Other types of gastritis that may be diagnosed include: • Acute stress gastritis. This is the most serious form of gastritis and usually occurs in persons who are critically ill, such as those in intensive care. Stress erosions may develop suddenly as a result of severe trauma or stress to the stomach lining. • Atrophic gastritis. This is the result of chronic gastritis that is leading to atrophy (a decrease in size and wasting away) of the gastric lining. Gastric atrophy is the final stage of chronic gastritis and may be a precursor of gastric cancer. • Superficial gastritis. This is a term often used to describe the initial stages of chronic gastritis. • Uncommon forms of gastritis. These are nonspecific forms of gastritis that include granulomatous, eosinophilic, and lymphocytic gastritis.

study in 2001 and clinicians assume there may be more than one route for the bacterium to enter a body. Its prevalence and distribution differ in nations around the world. The presence of H. pylori has been detected in between 86% and 99% of persons with chronic superficial gastritis. However, physicians are still learning about the link between H. pylori and chronic gastritis and peptic ulcers, since many persons with H. pylori infection do not develop symptoms of gastritis or peptic ulcers. H. pylori is also seen in approximately 90% to 100% of people with duodenal ulcers. Symptoms of H. pylori gastritis include abdominal pain and reduced acid secretion in the stomach. However, the majority of people with H. pylori infection suffer no symptoms, even though the infection may lead to ulcers and resulting problems. Ulcer symptoms include dull, gnawing pain, often two to three hours after meals, and pain in the middle of the night when the stomach is empty. Erosive and hemorrhagic gastritis The most common cause of this form of gastritis is use of NSAIDs. Other causes may be alcoholism, or stress from surgery or critical illness. The role of NSAIDs in development of gastritis and peptic ulcers depends upon the dosage level. Although even low doses of aspirin or other NSAIDs may cause some gastric upset, such low doses generally will not lead to gastritis. However, as many as 10%–30% of persons on higher and more frequent doses of NSAIDs, such as those with chronic arthritis, may develop gastric ulcers. As of 2001, studies were underway to determine the role of H. pylori in gastritis and ulcers among persons using NSAIDs. Individuals with erosive gastritis may also experience no symptoms. When symptoms do occur, they may include anorexia nervosa, gastric pain, nausea, and vomiting. Other forms of gastritis Less common forms of gastritis may result from a number of generalized diseases, or from complications of chronic gastritis. Any number of mechanisms may cause various less common forms of gastritis that may differ slightly in their presentation, symptoms, and clinical signs. However, they all have in common inflammation of the gastric mucosa.

Causes and symptoms Diagnosis

Nonerosive H. pylori gastritis H. pylori gastritis is caused by infection from the H. pylori bacterium. It is believed that most infection occurs in childhood. The route of its transmission was still under 1034

Nonerosive H. pylorigastritis H. pylori gastritis is easily diagnosed through the use of the urea breath test. This test detects the active pres-

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Erosive or hemorrhagic gastritis The patient’s clinical history may be particularly important in the diagnosis of this type of gastritis, since its cause is most often the result of chronic use of NSAIDs, alcohol, or other erosive substances. Other forms of gastritis Gastritis that has developed to the stage of duodenal or gastric ulcers usually requires endoscopy for diagnosis. The endoscopy allows a physician to perform a biopsy for possible malignancy and for H. pylori. Sometimes, an upper gastrointestinal x-ray study with barium is ordered. Some diseases, such as Zollinger-Ellison syndrome, an ulcerative disease of the upper gastrointestinal tract, may show large mucosal folds in the stomach and duodenum on radiographs or in endoscopy. Other tests check for changes in gastric function.

Treatment H. pylori gastritis The discovery of H. pylori’s role in development of gastritis and ulcers has led to improved treatment of chronic gastritis. In particular, relapse rates for duodenal and gastric ulcers have been reduced with successful treatment of H. pylori infections. Since the infection can be treated with antibiotics, the bacterium can be completely eliminated up to 90% of the time. Although H. pylori can be successfully treated, the treatment can be inconvenient, and relies heavily on the patient’s compliance. As of 2001 studies were underway to identify the best treatment method based on simplicity, personal cooperation, and results. No single antibiotic had been found at that time that would eliminate H. pylori, so a combination of antibiotics is prescribed to treat the infection. DUAL THERAPY. Dual therapy involves the use of an antibiotic and a proton pump inhibitor. Proton pump inhibitors are medications that help reduce stomach acid by halting the mechanism that pumps acid into the stomach. This combination also helps promote healing of

ulcers or inflammation. Dual therapy has not been proven to be as effective as triple therapy, but may be ordered for some people who are unable to consistently comply with the use of a larger number of medications, and who will therefore more likely follow the two-week course of therapy. TRIPLE THERAPY. As of 2001, triple therapy was the preferred treatment for persons with H. pylori gastritis. It is estimated that triple therapy successfully treats between 80% and 95% of H. pylori cases. This treatment regimen usually involves a two-week course of three drugs. An antibiotic such as amoxicillin or tetracycline, and a second antibiotic such as clarithromycin or metronidazole, are used in combination with bismuth subsalicylate, a substance found in the over-the-counter medication Pepto-Bismol, that helps protect the lining of the stomach from acid. Physicians are experimenting with various combinations of drugs and times of treatment to balance side effects with effectiveness. Side effects of triple therapy are not serious, but may cause enough discomfort that people are not inclined to follow the treatment regimen. OTHER TREATMENT THERAPIES. Scientists have experimented with quadruple therapy, which adds an antisecretory drug—one that suppresses gastric secretion—to the standard triple therapy protocol. One study showed this therapy to be effective with only a one-week course of treatment in more than 90% of patients. Shortcourse therapy was attempted with triple therapy involving antibiotics and a proton pump inhibitor, and seemed effective in eliminating H. pylori in one week for more than 90% of patients. The goal is to develop the most effective therapy combination that can work in a treatment period of one week or less. MEASURING H. PYLORI TREATMENT EFFECTIVENESS.

In order to ensure that H. pylori has been eradicated from the gatrointestinal tract, physicians will test persons following treatment. The breath test is, once again, the preferred method. Treatment of erosive gastritis Since few people with this form of gastritis show symptoms, treatment may depend upon severity of symptoms. When symptoms do occur, patients may be treated with therapy similar to that for H. pylori, especially since some studies have demonstrated a link between H. pylori and NSAIDs in causing gastric ulcers. Avoidance of NSAIDs will most likely be prescribed. Other forms of gastritis Specific treatment will depend upon the cause and type of gastritis. These may include prednisone or antibi-

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ence of H. pylori infection. Other serological tests, which may be readily available in a physician’s office, may be used to detect H. pylori infection. Newly developed versions offer rapid diagnosis. The choice of test will depend upon cost, availability, and the physician’s experience, since nearly all of the available tests have an accuracy rate of 90% or better. Endoscopy, or the examination of the stomach area using a hollow tube inserted through the mouth, may be ordered to confirm diagnosis. A biopsy of the gastric lining may also be ordered.

Gastritis

KEY TERMS Duodenal—Refers to the duodenum, or the first part of the small intestine. Gastric—Relating to the stomach. Mucosa—The mucous membrane, or the thin layer of tissue that lines many body cavities and passages. Ulcer—A break in the skin or mucous membrane. It can fester and create exudate like a sore.

otics. Critically ill persons at high risk for bleeding may be treated with preventive drugs to reduce risk of acute stress gastritis. If stress gastritis does occur, the patient is treated with a constant infusion of a drug to stop bleeding. Sometimes surgery is recommended, but must be weighed against the possibility of surgical complications or death. Once torrential bleeding occurs in acute stress gastritis, mortality rates can exceed 60%. Alternative treatment Alternative forms of treatment for gastritis and ulcers should be used cautiously and in conjunction with conventional medical care, particularly now that scientists have confirmed the role of H. pylori in gastritis and ulcers. Such alternative treatments as diet, nutritional supplements, herbal medicine, and Ayurvedic medicine can help address gastritis symptoms. It is believed that zinc, vitamin A, and beta-carotene aid in the stomach lining’s ability to repair and regenerate itself. Herbs thought to stimulate the immune system and reduce inflammation include echinacea (Echinacea spp.) and goldenseal (Hydrastis canadensis). Ayurvedic medicine involves meditation. There are also certain herbs and nutritional supplements aimed at helping to treat ulcers.

Prognosis The discovery of H. pylori has improved the prognosis for persons with gastritis and ulcers. Since treatment exists with the potential to eradicate the infection, recurrence is much less common. As of 2001, people requiring treatment for H. pylori were those at high risk because of such factors as NSAIDs use, or those with ulcers and other complicating factors or symptoms. Research will continue into the most effective treatment of H. pylori, especially in light of the bacterium’s resistance to certain antibiotics. Regular treatment of persons with gastric and duodenal ulcers has been recommended, since H. pylori plays such a consistently high role in development of ulcers. It is believed that H. pylori also 1036

plays a role in the eventual development of serious gastritis complications and cancer. Detection and treatment of H. pylori infection may help reduce occurrence of these diseases. The prognosis for persons with acute stress gastritis is less encouraging, with a 60% or higher mortality rate among those experiencing heavy bleeding.

Health care team roles A family physician or internist usually makes a diagnosis of gastritis, prescribes treatment, and provides follow-up testing to ascertain the effectiveness of the prescribed treatment regimen. Surgeons occasionally remove a portion of stomach when gastritis is caused by factors other than H. pylori or by cancer. Nurses play an important role in patient education, particularly in relation to medication, diet, prevention, compliance with treatment, and treatment side effects.

Prevention The widespread detection and treatment of H. pylori as a preventive measure in gastritis has been discussed but not resolved. Until more is known about the routes by which H. pylori is spread, specific prevention recommendations cannot be made. Erosive gastritis from NSAIDs can be prevented by discontinuing the use of these drugs. In 1998 an education campaign was launched to educate people, particularly an aging population of arthritis sufferers, about the risk of ulcers from NSAIDs and alternative drugs. As of 2001 the success of this campaign had not been evaluated. Resources BOOKS

Brandt, Lawrence J., and Frederick Daum. Clinical Practice of Gastroenterology. New York: Churchill Livingstone, 1999. Burton Goldberg Group. Alternative Medicine: The Definitive Guide. Puyallup, WA: Future Medicine Publishing, Inc., 1994. Debas, Haile, and Susan Orloff. “Peptic Ulcer Disease: Surgical Therapy.” In Cecil Textbook of Medicine, 21st ed. Ed. Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, 680-684. Friedman, Lawrence S., and Walter L. Peterson. “Peptic Ulcer and Related Disorders.” In Harrison’s Principles of Internal Medicine, 14th ed. Ed. Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 1596-1616. Graham, David Y., Robert M. Genta, and Michael F. Dixon. Gastritis. Philadelphia: Lippincott Williams & Wilkins, 1999. Graham, Donald Y. “Peptic Ulcer Disease: Medical Therapy.” In Cecil Textbook of Medicine, 21st ed. Ed. Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, 675-678.

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PERIODICALS

Bartolome Resano R, B. Martinez, Echeverria A. Martinez, Penuela J. Martinez, Abadia A. Isturiz, Flamarique F. Olcoz, and Cativiela J. del Cazo. “Gastritis Caused by Helicobacter Heilmannii.” Gastroenterology and Hepatology 24, no. 4 (2001): 202-204. Choe Y.H., T.S. Hwang, H.J. Kim, S.H. Shin, S.U. Song, and M.S. Choi. “A Possible Relation of the Helicobacter Pylori pfr Gene to Iron Deficiency Anemia.” Helicobacter 6, no. 1 (2001): 55-59. Finn L.S., and D.L. Christie. “Helicobacter Pylori and Meckel’s Diverticula.” Journal of Pediatric Gastroenterology and Nutrition 32, no. 2 (2001): 150155. Gold B.D. “New Approaches to Helicobacter Pylori Infection in Children.” Current Gastroenterology Reports 3, no. 3 (2001): 235-247. Moshkowitz M., S. Brill, F.M. Konikoff, M. Averbuch, N. Arber, and Z. Halpern. “Additive Deleterious Effect of Smoking on Gastroduodenal Pathology and Clinical Course in Helicobacter Pylori-Positive Dyspeptic Patients.” Israel Medical Association Journal 2, no. 12 (2000): 892-895.

Orihara T, H. Wakabayashi, A. Nakaya, K. Fukuta, S. Makimoto, K. Naganuma, A. Entani, and A. Watanabe. “Effect of Helicobacter Pylori Eradication on Gastric Mucosal Phospholipid Content and its Fatty Acid Composition.” Journal of Gastroenterology and Hepatology 16, no. 3 (2001): 269-275. Parente F., R. Negrini, V. Imbesi, G. Maconi, M. Sainaghi, L. Vago, and G.B. Porro. “Presence of Gastric Autoantibodies Impairs Gastric Secretory Function in Patients with Helicobacter Pylori-Positive Duodenal Ulcer.” Scandinavian Journal of Gastroenterology 36, no. 5 (2001): 474-478. Podolski, J.L. “Recent Advances In Peptic Ulcer Disease: H. Pylori Infection and its Treatement.” Gastroenterology Nursing 19, no. 4: 128-136. Schowengerdt C.G. “Standard Acid Reflux Testing Revisited.” Digestive Disease Science 46, no. 3 (2001): 603-605. Spaziani E., M. Catani, A. Mingoli, P. Del Duca, A. Di Filippo, R. De Milito, P. Siciliano, M. Chiaretti, and R. Corsi. “Duodenal Ulcer and Helicobacter Pylori.” Minerva Medicine 92, no. 1 (2001): 1-5. Urakami Y., and T. Sano. “Endoscopic Duodenitis, Gastric Metaplasia and Helicobacter Pylori.” Journal of Gastroenterology and Hepatology 16, no. 5 (2001): 513-518. Xia H.H., B.C. Yu Wong, N.J. Talley, and S.K. Lam. “Helicobacter Pylori Infection—Current Treatment Practice.” Expert Opinion in Pharmacotherapy 2, no. 2 (2001): 253-266. ORGANIZATIONS

American College of Gastroenterology. 4900 B South 31st Street, Arlington VA 22206. (703) 820-7400. . National Digestive Diseases Information Clearinghouse (NDDIC). 2 Information Way, Bethesda, MD 208923570. . OTHER

American Academy of Family Physicians. . American Academy of Pediatrics. . American College of Gastroenterology. . Centers for Disease Control and Prevention. . Health Answers. . Medical College of Wisconsin. . Merck Manual. . National Digestive Diseases Clearinghouse. . National Library of Medicine. and and . Rush University College of Medicine. . University of Maryland College of Medicine. .

L. Fleming Fallon, Jr., M.D., Dr.P.H.

Gastroesophageal reflux scan Definition Gastroesophageal reflux disease (GERD) is one of the most common gastrointestinal problems among children or adults. It is defined as the movement of solid or liquid contents from the stomach into the esophagus. Gastrointestinal reflux imaging encompasses methods used to visualize and diagnose GERD.

Purpose The purpose of gastroesophageal reflux scanning is to visualize the interior of the upper stomach and lower esophagus. Such inspections assist in making an accurate diagnosis and in planning appropriate treatment.

Precautions For all tests used to evaluate GERD, persons must not have other medical complications such as high blood pressure, asthma, or esophageal varices. They should not be experiencing other acute medical conditions.

Description A brief description of gastroesophageal reflux disease assists in understanding the scanning methods used. Gastroesophageal reflux disease is the term used to describe the symptoms and damage caused by the backflow (reflux) of the contents of the stomach into the esophagus. Stomach contents are usually acidic. Because of their acidity, they have the potential to cause chemical burns in unprotected tissues such as those lining the esophagus. Gastrointestinal reflux is common in the American population. Approximately one adult in three reports experiencing some occasional reflux, commonly referred to as heartburn. Approximately 10% of these persons experience reflux on a daily basis. Most persons have very mild disease. Occasionally, persons experience 1038

burning as a result of reflux. This is described as reflux esophagitis when it occurs in the esophagus. There are several causes of gastroesophageal reflux. These include the following: • Incompetent lower esophageal sphincter. When the muscular sphincter that is the boundary of the esophagus and stomach relaxes, reflux can occur. This is the most common cause for gastroesophageal reflux. Reflux usually occurs when persons bend, lift a weight, or strain. Persons with esophageal strictures or Barrett’s esophagus are more likely to experience gastroesophageal reflux than are others. • Acidic irritation. Gastric contents are acidic, with a pH less than 3.9. Such acid is very caustic to the lining of the esophagus. Repeated exposure to acidic gastric contents leads to scarring. If the exposure is sufficiently severe or prolonged, strictures can develop. Occasionally, pancreatic enzymes or bile reflux into the stomach and lower esophagus. These contents are extremely acidic (with a pH less than 2.0). • Abnormal esophageal clearance. Acid reflux is washed away by saliva that is swallowed over the course of a day. During the night, swallowing is decreased. This results in a longer contact time between acidic stomach contents and the esophagus. The net result is a chemical injury. Sjögren’s syndrome, radiation to the oral cavity, and some medications (anticholinergics) also decrease the flow of saliva and can result in chemical injury. Saliva also contains bicarbonate, which neutralizes some acid content. This, too, is diminished at night, contributing to nocturnal exposure and irritation over a period of time. Other medical conditions such as Raynaud’s disease and scleroderma are often associated with abnormal esophageal clearance. Hiatal hernia is present in more than 90% or persons with erosive disease. • Delayed gastric emptying. When gastric outflow is obstructed or gastric motility is impaired, gastric contents do not leave the stomach in a timely manner. This enhances the opportunity for gastric reflux. Heartburn associated with gastroesophageal reflux occurs 30 to 60 minutes after eating. It also occurs when a person reclines. Most persons who experience gastroesophageal reflux can obtain relief with baking soda (Alka-Seltzer) or antacid tablets. This pattern is often sufficient for diagnostic purposes. Under these conditions, physical examination and laboratory findings are usually within normal limits. Persons with complicated GERD, or those who do not respond to the usual remedies (baking soda or antacid tablets), require special examinations. There are several

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Upper endoscopy Upper endoscopy is the standard procedure for diagnosis, determination of the degree of tissue damage, and documentation of GERD. Between half and three-quarters of all persons with GERD will display abnormalities in their esophageal mucosa. The abnormalities include erosion, tissue fragility, and erythema. Upper endoscopy is also used to document esophageal strictures and Barrett’s esophagus. Approximately half of all persons who undergo endoscopy have normal findings. Endoscopy is indicated for persons who have such symptoms as hematemesis, iron deficiency anemia, guaiacpositive stools, or dysphagia. An endoscope is passed through the oral cavity into the esophagus. The mucosal lining of the esophagus, the gastroesophageal junction, and the lining of the upper portion of the stomach are visualized directly. Biopsy specimens can be obtained at the same time.

Esophageal manometry When surgery is anticipated, esophageal manometry is useful. It provides data about esophageal peristalsis and minimum esophageal sphincter closing pressure. Esophageal manometry measures the pressure within the esophagus. It can be used to evaluate the action of muscle waves in the main portion of the esophagus, as well as the muscular sphincter at the end of the esophagus. A thin soft tube is passed through the nose, or occasionally the mouth. Upon swallowing, the tip of the tube enters the esophagus and is positioned at the desired location. The patient then swallows air or water while a technician records the pressure at the tip of the tube.

Preparation Upper endoscopy Prior to the test, persons are instructed not to eat or drink for six hours. A mild sedative is usually given to calm persons who are about to be tested. Ambulatory esophageal pH monitoring

Ambulatory esophageal pH monitoring This test provides information concerning the frequency and duration of acid reflux. It can also provide information related to the timing of episodes of reflux. It is the standard procedure for documenting abnormal acid reflux. However, it is not needed for most persons with GERD as they can be adequately diagnosed on the basis of history or by using upper endoscopy. In this test, a tiny catheter (about 2 millimeters) with two electrodes is passed through the nose and throat. One electrode is positioned about 5 cm above the esophageal sphincter. The other electrode is positioned just below the esophageal sphincter. Data on pH are obtained every four seconds for 24 hours. Persons tested are instructed to keep a diary recording symptoms. Special emphasis is placed on coughing episodes, meal times, time of lying down for sleep, and time of rising in the morning. The electrodes are removed after 24 hours. The patients’ diaries are reviewed. Barium esophagography A water solution containing barium is slowly swallowed. X-rays are taken during swallowing and are analyzed for signs of reflux, inflammation, dysmotility, strictures, and other abnormalities. This test can diagnose, or provide important information about, a number of disorders involving esophageal function, including craniopharyngeal achalasia (a swallowing disorder of the throat); decreased or reverse peristalsis; and hiatal hernia.

No special preparations are needed. A short-acting anesthetic spray is sometimes used to relieve any discomfort associated with placing the electrodes. Barium esophagography Prior to the test, persons are instructed not to eat or drink for six hours. Esophageal manometry Persons are asked not to eat or drink for the eight hours prior to the test. Prior to the test, persons are instructed not to eat or drink for six hours. An anesthetic spray is often used to reduce the irritation experienced when the manometry tube is passed through the nose and oral cavity.

Aftercare Upper endoscopy After the test, persons must be driven home due to lingering effects of the sedative. Ambulatory esophageal pH monitoring There are no special steps to be taken after the electrodes have been removed. Barium esophagography There are no special instructions after the test.

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imaging methods used in the diagnosis of GERD. Details concerning each of the procedures follow.

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KEY TERMS

Complications are very rare.

Barrett’s esophagus—An abnormal condition of the (usually) lower esophagus in which normal mucous cells are replaced by changed cells. The condition is often a prelude to cancer. Dysphagia—Difficulty in swallowing. Erythema—Redness. Esophageal varices—Varicose veins at the lowermost portion of the esophagus. These are easily injured. Bleeding from esophageal varices is often difficult to stop. Esophagus—The tube that connects the mouth to the stomach. Hematemesis—Vomit that contains blood, usually seen as black specks in the vomitus. pH—A measure of acidity; technically, a measure of hydrogen ion concentration. Raynaud’s disease—A disease of the arteries in hands or feet. Reflux—Backflow, also called regurgitation. Sjögren’s syndrome—An autoimmune disorder characterized by dryness of the eyes, nose, mouth, and other areas covered by mucous membranes. Sphincter—A physiologic valve comprised of muscle.

Endoscopy documents the condition of mucosa in the lower esophagus and upper stomach, evaluating the extent of GERD progression. Ambulatory esophageal pH monitoring Measurements of pH are used to evaluate the degree of GERD. Barium esophagography Barium esophagography can detect many abnormalities. including reflux. Esophageal manometry This documents the ability of the esophageal sphincter to close and keep stomach contents from refluxing.

Health care team roles A family physician, pediatrician, internist, or cardiologist usually makes the initial diagnosis of GERD. A gastroenterologist usually performs the tests required for diagnosis. A radiology technologist performs the barium esophagography and a radiologist interprets it.

BOOKS

There are no special instructions after the test.

Complications Upper endoscopy Patients may feel as if they are choking as the endoscope proceeds down the throat. Actual choking is uncommon due to sedation. Ambulatory esophageal pH monitoring There are no common complications. Barium esophagography Constipation after the test is an infrequent complication. This is routinely treated by administration of a

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Resources

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laxative.

Results

Bentley D., M. Lawson, and C. Lifschitz. Pediatric Gastroenterology and Clinical Nutrition. New York, NY: Oxford University Press, 2001. Davis M., and J. D. Houston. Fundamentals of Gastroenterology. Philadelphia, PA: Saunders, 2001. Herbst, J.J. “Gastroesophageal reflux (chalasia).” In Nelson Textbook of Pediatrics, 16th ed., edited by Richard E. Behrman et al., Philadelphia, PA: Saunders, 2000, pp.1125-1126. Isselbacher K. J., and D.K. Podolsky. “Approach to the patient with gastrointestinal disease.” In Harrison’s Principles of Internal Medicine. 14th ed., edited by A. S. Fauci, et al. New York, NY: McGraw-Hill, 1998, pp.1579-1583. Murry T., and R. L. Carrau. Clinical Manual for Swallowing Disorders. Albany, NY: Delmar, 2001. Orlando, R. Gastroesophageal Reflux Disease. New York, NY: Marcel Dekker, 2000. Owen W.J., A. Adam, and R.C. Mason. Practical Management of Oesophageal Disease. Oxford, UK: Isis Medical Media, 2000.

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PERIODICALS

Carr M.M., M.L. Nagy, M.P. Pizzuto, C.P. Poje, and L.S. Brodsky. “Correlation of findings at direct laryngoscopy and bronchoscopy with gastroesophageal reflux disease in children: a prospective study.” Archives of Otolaryngology, Head and Neck Surgery 127, no. 4 (2001): 369-374. Carr M.M., A. Nguyen, C. Poje, M. Pizzuto, M. Nagy, and L. Brodsky. “Correlation of findings on direct laryngoscopy and bronchoscopy with presence of extraesophageal reflux disease.” International Journal of Pediatric Otorhinolaryngology 54, no. (2000): 27-32. Mercado-Deane M.G., E.M. Burton, S.A. Harlow, A.S. Glover, D.A. Deane, M.F. Guill, and V. Hudson. “Swallowing dysfunction in infants less than 1 year of age.” Pediatric Radiology 31, no. 6 (2001): 423-428. Stordal K., E.A. Nygaard, and B. Bentsen. “Organic abnormalities in recurrent abdominal pain in children.” Acta Paediatrica 90, no. 5 (2001): 638-642. ORGANIZATIONS

American College of Gastroenterology, 4900 B South 31st Street, Arlington, VA, 22206. (703) 820-7400. . American College of Radiology. 1891 Preston White Drive, Reston, VA, 20191. (703) 648-8900. . American Osteopathic College of Radiology. 119 East Second St., Milan, MO 63556. (660) 265-4011. . OTHER

American Academy of Family Physicians. . American College of Gastroenterology. . American Medical Association. . National Digestive Diseases Clearinghouse. . National Library of Medicine. . Thomas Jefferson University. . University or Maryland. .

L. Fleming Fallon, Jr., MD, DrPH

Gene therapy Definition Gene therapy is a rapidly growing field of medicine in which genes are introduced into the body to treat diseases. Genomics is the DNA which is found in an organism’s total set of genes and is passed on to the offspring as information necessary for survival. Genetics is the study of the patterns of inheritance of specific traits. Genes control heredity and provide the basic biological code for determining a cell’s specific functions. Gene therapy seeks to provide genes that correct or supplant the disease-controlling functions of cells that are not performing in a normal manner. Somatic gene therapy introduces therapeutic genes at the tissue or cellular level to treat a specific individual. Germ-line gene therapy inserts genes into reproductive cells or possibly into embryos to correct genetic abnormalities that could be passed on to future generations. Initially conceived as an approach for treating inherited diseases such as cystic fibrosis and Huntington’s disease, the scope of potential gene therapies has grown to include treatments for cancer, arthritis, and infectious diseases.

Description The history of gene therapy In the early 1970s, scientists proposed “gene surgery” for treating inherited diseases caused by abnormally functioning genes. The idea was to take out the disease-causing gene and surgically implant a gene that functioned correctly. Although sound in theory, and after some advances in science, this technique has not yet been successful. However, in 1983, a group of scientists from Baylor College of Medicine in Houston, Texas, proposed that gene therapy could one day be a viable approach for treating Lesch-Nyhan disease, a rare neurological disorder. The scientists conducted experiments in which an enzyme-producing gene (a specific type of protein) for correcting the disease was injected into a group of cells for replication. The scientists theorized the cells could then be injected into people with Lesch-Nyhan disease, thus correcting the genetic abnormality that caused the disease. As the science of genetics advanced throughout the 1980s, gene therapy grew in the estimation of medical scientists as a promising approach to treatments for specific diseases. One of the major reasons for the growth of gene therapy was the increasing body of knowledge

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Richter, J.E. Gastroesophageal Reflux Disease: Current Issues and Controversies. Basel, SWI: Karger Publishing, 2000. Wuittich, G. R. “Diagnostic imaging procedures in gastroenterology.” In Cecil Textbook of Medicine, 21st ed,, edited by Lee Goldman and J. Claude Bennett, Philadelphia, PA: W.B. Saunders, 2000, pp.645-649.

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available to assist in identifying the specific genetic malfunctions that caused inherited diseases. Interest grew as further studies of DNA and chromosomes (where genes reside) showed that specific genetic abnormalities in one or more genes occurred in successive generations of certain family members who experienced diseases like intestinal cancer, manic-depression (bipolar disorder), Alzheimer’s disease, heart disease, diabetes, and many more. Although genes may not be the only cause of the disease in all cases, they may make certain individuals more susceptible to developing a particular condition due to such environmental influences as smoking, pollution, and stress. In fact, some scientists theorize that all diseases may have a genetic component. The biological basis of gene therapy Gene therapy has grown out of the science of genetics or how heredity functions. Scientists know that life begins in a cell, the basic building block of all multicellular organisms. Humans, for instance, are made up of trillions of cells, each performing a specific function. Within each cell’s nucleus (the center part of a cell that regulates its chemical functions) are pairs of chromosomes. These threadlike structures are made up of deoxyribonucleic acid (DNA), which carries the blueprint of life in the form of codes, or genes, that determine dominant or recessive inherited characteristics. A DNA molecule looks like two ladders with one of the sides taken off both and then twisted around each other—a formation known as the double helix. The rungs of these ladders meet (resulting in a spiral staircase-like structure) and are called base pairs. Base pairs are made up of nitrogen-containing molecules and arranged in specific sequences. Millions of these base pairs, or sequences, constitute a single gene, specifically defined as a segment of the chromosome and DNA that contains certain hereditary information. The gene, or combination of genes formed by these base pairs, ultimately directs an organism’s growth and characteristics through the production of certain chemicals—primarily proteins that carry out most of the body’s chemical functions and biological reactions. Scientists have long known that alterations in the genes present within cells may cause such inherited diseases as cystic fibrosis, sickle-cell disease, and hemophilia. Similarly, errors in entire chromosomes may cause such conditions as Down syndrome or Turner syndrome. As the study of genetics advanced, however, scientists learned that altered genetic sequences may also make people more susceptible to such diseases as atherosclerosis, cancer, and schizophrenia. These diseases have a genetic component, but are also influenced by 1042

such environmental factors as diet and lifestyle. The objective of gene therapy is to treat diseases by introducing functional genes into the body to alter the cells involved in the disease process, either by replacing missing genes or by providing copies of functioning genes to replace nonfunctioning ones. The inserted genes may be naturally occurring genes that produce the desired effect or may be engineered (or altered) genes. Scientists have known how to manipulate a gene’s structure in the laboratory since the early 1970s through a process called gene splicing. The process involves removing a fragment of DNA containing a specific desired genetic sequence and then inserting it into the DNA of another gene. The resultant product is called recombinant DNA, and the process is called genetic engineering. This technique is used in preparing some new therapies (monoclonal antibodies, blood component replacements for hemophilia, antiinflammatory therapy for collagen diseases). There are two types of gene therapy. Germ-line gene therapy introduces genes into reproductive cells (sperm and eggs) to participate in germination. Some scientists hope that it may eventually be possible to insert genes into embryos in hopes of correcting genetic abnormalities that can then be passed on to future generations. Most of the current work in applied gene therapy, however, has been in the realm of somatic therapy. In this type of gene therapy, therapeutic genes are inserted into tissue or cells to produce a naturally occurring protein or substance that is lacking or not functioning correctly in an individual. Viral vectors In both types of therapy, scientists need a mechanism to transport either an entire gene or a recombinant DNA to a cell’s nucleus, where the chromosomes and DNA reside. In essence, vectors are molecular delivery trucks. One of the first and most widely used vectors to be developed were viruses, because they invade cells as part of their natural infection process. Viruses have the potential to be excellent vectors because they have a specific relationship with a host in that they colonize certain cell types and tissues in specific organs. As a result, vectors are chosen according to their attraction to certain cells and areas of the body. One of the first classes of vectors used were retroviruses. Because these viruses are easily cloned (artificially reproduced) in the laboratory, scientists have studied them extensively and learned a great deal about their biologic action. They have also learned how to remove the genetic information that governs viral replication, thus reducing the chances of infection from the host vector.

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Another class of viruses, called adenoviruses, may also prove to be good gene vectors. These viruses effectively infect non-dividing cells in the body, where the desired gene product is then expressed naturally. In addition to being a more efficient approach to the problem of gene transportation, these viruses, which are known to cause respiratory infections, are more easily purified and stabilized than are retroviruses. The result is less liklihood of unintended viral infection. However, these viruses live for several days in the body, and there is some concern about the possibility of infecting other people with the viruses through sneezing or coughing. Other viral vectors include influenza viruses, Sindbis virus, and a herpesvirus that infects nerve cells. Scientists have also studied nonviral vectors. These vectors rely on the natural biologic process in which cells take up (or gather) macromolecules. One approach is to use liposomes, globules of fat produced by the body and taken up by cells. Scientists are also investigating the introduction of raw recombinant DNA by injecting it into the bloodstream or placing it on microscopic beads of gold injected into the skin using air pressure. Another possible vector under development is based on dendrimer molecules. A class of polymers (naturally occurring or artificial substances that have a high molecular weight and are formed by smaller molecules of the same or similar substances) is constructed in a laboratory by combining these smaller molecules. They have been used in manufacturing styrofoam, polyethylene cartons, and Plexiglas. In the laboratory, dendrimers have shown the ability to transport genetic material into human cells. They can also be designed to form an affinity for particular cell membranes by attaching to certain sugars and protein groups. Much additional research must be conducted before dendrimers can be used on a routine basis.

Viewpoints On September 14, 1990, a four-year old girl who had a genetic disorder that prevented her body from producing a crucial enzyme became the first person to undergo gene therapy in the United States. Because her body

could not produce adenosine deaminase (ADA), she had a weakened immune system, making her extremely susceptible to severe, life-threatening infections. W. French Anderson and colleagues at the National Institutes of Health’s Clinical Center in Bethesda, Maryland, took white blood cells (which are crucial to proper immune system functioning) from the girl, inserted ADA-producing genes into them, and then transfused the cells back into the girl. Although the young girl continued to show an increased ability to produce ADA, debate arose as to whether the improvement resulted from the gene therapy or from an additional drug treatment she received. Although gene therapy testing in humans has advanced rapidly, many questions surround its use. For example, some scientists are concerned that the therapeutic genes themselves may cause disease. Others fear that germ-line gene therapy may be used to control human development in ways not connected with disease, such as intelligence or physical appearance. Nevertheless, a new era of gene therapy began as more and more scientists sought to conduct clinical trial (testing in humans) research in this area. In that same year, gene therapy was tested on persons with melanoma (skin cancer). The goal was to help them produce antibodies (disease fighting substances in the immune system) to battle the cancer. The relative success of these experiments prompted a growing number of attempts at gene therapies designed to perform a variety of functions in the body. For example, a gene therapy for cystic fibrosis aims to supply a gene that alters cells, enabling people with cystic fibrosis to produce a specific protein to battle the disease. Another approach was used for people with brain cancer, in which the inserted gene was designed to make the cancer cells more likely to respond to drug treatment. A third gene therapeutic approach for people experiencing artery blockage, which can lead to strokes, induces the growth of new blood vessels (collateral circulation) near clogged arteries, thus ensuring relatively normal blood circulation. As of 2001, there are a host of new gene-therapy agents in clinical trials. In the United States, both nucleic acid-based (in vivo) treatments and cell-based (ex vivo) treatments are being investigated. Nucleic acid-based gene therapy uses vectors (such as viruses) to deliver modified genes to target cells. Cell-based gene therapy requires removal of cells from a person, genetically altering the cells and then reintroducing them into the body of the person being treated. Presently, gene therapies for the following diseases are being studied: cystic fibrosis (using adenoviral vector), HIV infection (cell-based), malignant melanoma (cell-based), Duchenne muscular

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Retroviruses work best in actively dividing cells, but most cells in a human body are relatively stable and do not often divide. As a result, these cells are used primarily for ex vivo (outside the body) manipulation. First, the cells are removed from a person’s body, and the vector, or virus carrying the gene, is inserted into them. Next, the cells are placed into a nutrient culture where they grow and replicate. Once enough cells are gathered, they are returned to the body, usually by injection into the blood stream. Theoretically, as long as these cells survive, they will provide the desired therapy.

Gene therapy

dystrophy (cell-based), hemophilia B (cell-based), kidney cancer (cell-based), Gaucher disease (retroviral vector), breast cancer (retroviral vector), and lung cancer (retroviral vector). When a cell or individual is treated using gene therapy and successful incorporation of engineered genes has occurred, the cell or individual is said to be transgenic. The medical establishment’s contribution to transgenic research has been supported by increased government funding. In 1991, the U.S. government provided $58 million for gene therapy research, with increases in funding of $15-40 million dollars a year over the following four years. With fierce competition over the promise of societal benefits in addition to huge profits, large pharmaceutic corporations have moved to the forefront of transgenic research. In an effort to be first in developing new therapies, and armed with billions of dollars of research funds, such corporations are making impressive progress toward making gene therapy a viable reality in the treatment of once elusive diseases. The Human Genome Project

Professional implications Diseases targeted for treatment by gene therapy

Although great strides have been made in gene therapy in a relatively short time, its potential usefulness has been limited by lack of scientific data concerning the multitude of functions that genes control in the human body. For instance, it is now known that much genetic material is contained in non-coding regions. That is, they merely store information that may be used at different times in a cell’s life cycle. Some of these large portions of the genome are involved in control and regulation of gene expression. Each individual cell in the body carries thousands of genes that have coding for proteins. Some experts estimate this number to be 150,000 genes. For gene therapy to advance to its full potential, scientists must discover the biologic role for each of these individual genes and identify the location on the DNA helix for each of the base pairs that comprise them. To address this issue, the National Institutes of Health initiated the Human Genome Project in 1990. Led by Dr. James Watson (one of the co-discoverers of the chemical makeup of DNA) the project’s 15-year goal is to map the entire human genome (a combination of the words gene and chromosome). A genome map would clearly identify the location of all genes as well as the more than three billion base pairs that comprise them. With a precise knowledge of gene locations and functions, scientists may one day be able to conquer or control diseases that have plagued humanity for centuries. Scientists participating in the Human Genome Project have identified an average of one new gene a day, but many expect this rate of discovery to increase. In 1044

February of 2001, scientists published a rough draft of the complete human genome. With fewer than the anticipated number of genes found, between 30,000 and 40,000, the consequences of this announcement are potentially profound. Scientists caution, however, that the initial publication is only a draft of the human genome, and much more work is still ahead for the completion of the project. By the year 2005, their goal is to determine the exact location of all the genes on human DNA and the exact sequence of the base pairs that make them up. Some of the genes identified through this project include a gene that predisposes people to obesity; one associated with programmed cell death (apoptosis); a gene that guides HIV viral reproduction; and the genes of inherited disorders like Huntington’s disease, amyotrophic lateral aclerosis (Lou Gehrig’s disease), and some colon and breast cancers. As the human genome is completed, more information will be available for gene therapy research and implementation.

The potential scope of gene therapy is enormous. More than 4,200 diseases have been identified as resulting directly from non-functioning or abnormal genes, and countless others that may be partially influenced by a person’s genetic makeup. Initial research has concentrated on developing gene therapies for diseases whose genetic origins have been established and for other diseases that can be cured or ameliorated by substances genes produce. The following are examples of potential gene therapies. People with cystic fibrosis lack a gene needed to produce a salt-regulating protein. This protein regulates the flow of chloride into epithelial cells, (the cells that line the inner and outer skin layers) that cover the air passages of the nose and lungs. Without this regulation, people with cystic fibrosis have a buildup of thick mucus in their lungs. In turn, this mucus makes these patients prone to lung infections and respiratory problems, and usually leads to death within the first 29 years of life. A gene therapy technique to correct this abnormality might employ an adenovirus to transfer a normal copy of what scientists call the cystic fibrosis transmembrane conductance regulator (CTRF) gene. The gene is introduced into a person by spraying it into the nose or lungs. Familial hypercholesterolemia (FH) is also an inherited disease, resulting in the inability to process cholesterol properly, which leads to high levels of artery-clogging fat in the bloodstream of even the youngest family members. Persons with FH often suffer heart attacks and strokes because of blocked arteries. A gene therapy

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Gene therapy has also been tested on persons with acquired immune difficiency syndrome (AIDS). AIDS is caused by the human immunodeficiency virus (HIV), which weakens the body’s immune system to the point that people with the condition are unable to fight off such diseases as pneumonia and cancer. In one approach, genes that produce specific HIV proteins have been altered to stimulate immune system functioning without causing the negative effects that a complete HIV molecule has on the immune system. These genes are then injected in a person’s blood stream. Another approach to treating AIDS is to insert, via white blood cells, genes that have been genetically engineered to produce a receptor that would attract HIV and reduce its chances of replicating. As of 2001, these approaches are experimental and have not been approved for treatment. Several cancers also have the potential to be treated with gene therapy. A therapy tested for melanoma, a progressive, agressive skin cancer, would introduce a gene with an anticancer protein called tumor necrosis factor (TNF) into test tube samples of a person’s own cancer cells, which are then reintroduced into the person’s body. In brain cancer, the approach is to insert a specific gene that increases the cancer cells’ susceptibility to a common drug used in fighting the disease. Gaucher disease is an inherited disease caused by a mutant gene that inhibits the production of an enzyme called glucocerebrosidase. Persons with Gaucher disease have enlarged livers (hepatomegaly) and spleens (splenomegaly). Clinical gene therapy trials will focus on inserting the gene for producing the missing enzyme. Gene therapy is also being considered as an approach to solving a problem associated with a surgical procedure known as balloon angioplasty. In this procedure, a stent (a piece of tubular material resembling a straw) is used to open the clogged artery. However, in a “fail-safe” response to the trauma of the stent insertion, the body initiates a natural healing process that produces too many cells in the artery and results in restenosis or reclosing of the artery. The gene therapy approach to preventing this unwanted side effect is to cover the outside surfaces of an inserted stent with a soluble gel containing vectors for genes that may reduce an overactive healing response.

The future of gene therapy Gene therapy seems elegantly simple in its concept: supply the human body with a gene that can correct a biologic malfunction causing a disease. However, there are many obstacles and some distinct questions concerning the viability of gene therapy. For example, viral vectors must be carefully controlled lest they infect a person with a viral disease. Some vectors, like retroviruses, can also enter normally functioning cells and interfere with natural biologic processes, possibly leading to other diseases. Other viral vectors, such as adenoviruses, are often recognized and destroyed by the immune system so their therapeutic effects are short-lived. Maintaining gene expression so that it performs its role properly after vector delivery is difficult. As a result, some therapies need to be repeated often to provide long-lasting benefits. One of the most pressing issues, however, is gene regulation. Genes work in concert to regulate their functioning. In other words, several genes may play a part in turning other genes on and off. For example, certain genes work together to stimulate cell division and growth; but if these are not regulated, the inserted genes could cause tumor formation and cancer. Another difficulty is learning how to make the gene go into action only when needed. For the best and safest therapeutic effort, a specific gene should turn on, for example, when certain levels of a protein or enzyme are low and must be replaced. But the gene should also remain dormant when not needed to ensure that it does not oversupply a substance and disturb the body’s delicate chemical balance. One approach to gene regulation is to attach other genes that detect certain biologic activities and then react as a type of automatic off-and-on switch, regulating the activity of other genes according to biologic cues. Although still in the rudimentary stages, researchers are making progress in inhibiting some gene functioning by using a synthetic DNA to block gene transcriptions (the copying of genetic information). This approach may have applications for gene therapy. The ethics of gene therapy While gene therapy holds promise as a revolutionary approach for treating disease, ethical concerns over its use and ramifications have been expressed by scientists and lay people alike. For example, since much needs to be learned about how these genes actually work and their long-term effects, is it ethical to test these therapies on humans, in whom they could have a disastrous result? As with most clinical trials concerning new therapies, including many drugs, the people participating in these studies have usually not responded to more established

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approach used to address FH is much more intricate than most gene therapies because it involves partial surgical removal of persons’ livers (ex vivo transgene therapy). Corrected copies of a gene that acts to reduce cholesterol build-up are inserted into the liver sections, which are then transplanted back into the people.

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KEY TERMS Cells—The smallest living units of the body that carry a full complement of the DNA, and which group together to form tissues and help the body perform specific functions. Chromosome—Threadlike structures in a cell that carry most of the genetic material in the form of DNA and genes. Clinical trial—The testing of a drug or some other type of therapy in a specific human population. Clone—A cell or organism derived through asexual (without sex) reproduction, and which contains the identical genetic information of the parent cell or organism. DNA (deoxyribonucleic acid)—The specific molecules that comprise chromosomes and genes. Embryo—The earliest stage of development of the zygote before the human or animal is considered a fetus (which is usually the point at which the embryo takes on the basic physical form of its species). Embryos are formed in vivo (in utero) or in vitro (in a laboratory) in preparation for implantation. Enzyme—A type of molecule made by cells that, when released, facilitates chemical reactions in the body. Eugenics—A social movement in which the population of a society, country, or the world is to be improved by selective mating, controlling the passage of hereditary information. Gene—A specific biologic component found in the cell nucleus that carries the instructions for the formation of an organism and its specific traits, such as eye or hair color. Gene transcription—The process by which genetic information is copied from DNA to RNA, resulting in a specific protein formation.

therapies and are often so ill that the novel therapy is their only hope for long-term survival. Another questionable outgrowth of gene therapy is that scientists could potentially manipulate genes to control traits in human offspring that are not related to health. For example, perhaps a gene could be inserted to ensure that a child would not be bald, a seemingly harmless goal. However, what if genetic manipulation were 1046

Genetic engineering—The manipulation of genetic material to produce specific results in an organism. Genetics—The study of hereditary traits passed on through genes. Genome—The total set of genes carried by an individual or cell. Genomics—The DNA which is found in the organism’s total set of genes carried by an individual or cell and is passed on to offspring as information necessary for survival. Germ-line gene therapy—The introduction of genes (natural or engineered) into reproductive cells or embryos to correct inherited genetic abnormalities that can cause disease by replication. Liposome—Fat organelle made up of layers of lipids. Macromolecule—A large molecule composed of thousands of atoms. Nitrogen—An element that is a component of the base pairs in DNA. Nucleus—The central part of a cell that contains most of its genetic material, including chromosomes and DNA. Protein—Macromolecule made up of long sequences of amino acids. Proteins comprise the dry weight of most cells and are involved in structures, hormones, and enzymes in muscle contraction, immunological response, and many other functions essential to life. Somatic gene therapy—The introduction of genes into tissue or cells to treat a genetic-related disease in an individual. Vector—Something used to transport genetic information to a cell.

used to alter skin color, prevent homosexuality, or ensure good looks? If a gene is found that can enhance intelligence of children who are not yet born, will all members of society have access to the technology, or will it be so expensive that only the elite can afford it? The Human Genome Project, which plays such an integral role for the future of gene therapy, also has social repercussions. If individual genetic codes can be deter-

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Some of these concerns can be traced back to the eugenics movement that was popular in the first half of the twentieth century. This genetic philosophy was a societal movement that encouraged people with so-called positive traits to reproduce while those with less desirable traits were sanctioned from having children. Eugenics was used to pass strict immigration laws in the United States, barring less suitable people from entering the country lest they reduce the quality of the country’s collective gene pool. Probably the most notorious example of eugenics in action was the rise of Nazism in Germany, which fostered the Eugenic Sterilization Law of 1933. The law required sterilization for those with certain disabilities and even for some persons who were simply deemed to be unattractive. To ensure that this novel science is not abused, many governments have established organizations specifically for overseeing the development of gene therapy. In the United States, the Food and Drug Administration and the National Institutes of Health require scientists to take a precise series of steps and meet stringent requirements before approving clinical trials. In fact, gene therapy has been immersed in more controversy and is surrounded by more scrutiny from both the health care and ethics communities than most other technologies (except, perhaps, for cloning) that have the potential to substantially change society. Despite the health and ethical questions surrounding gene therapy, the field will continue to grow and is likely to change medicine more quickly than any previous medical advancement. Resources BOOKS

Burdette, Walter J. The Basis for Gene Therapy. Springfield, IL, Charles C Thomas, 2001. Gomez-Navarro, Jesus, Guadalupe Bilbao, and David T. Curiel, “Gene therapy.” In Cecil Textbook of Medicine, 21st ed., edited by Lee Goldman, and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, 140-143. Hengge, Ulrich R. and Beatrix Volc-Platzer. The Skin and Gene Therapy. New York: Springer Verlag, 2000. Huard, Johnny and Freddie Fu. Gene Therapy and Tissue Engineering in Orthopaedic and Sports Medicine. Boston, MA: Birkhauser, 2000. Lemoine, Nicholas R. and Richard G. Vile. Understanding Gene Therapy. New York: Springer Verlag, 2000.

Needleman, Robert D. “Fetal growth and development.” In Nelson Textbook of Pediatrics, 16th ed. edited by Richard E. Behrman et al., Philadelphia: Saunders, 2000, 27-30. Valle, David. “Treatment and prevention of genetic disease.” In Harrison’s Principles of Internal Medicine, 14th ed. edited by Anthony S. Fauci, et al. New York: McGrawHill, 1998, 403-411. Walther, Wolfgang and Ulrike Stein. Gene Therapy of Cancer: Methods and Protocols. Totowa, NJ: Humana Press, 2000. PERIODICALS

Gottlieb S. “Gene therapy shows promise for hemophilia.” British Medical Journal, 322 no.7300 (2001): 1442A1443. Gray SG. “Pill-based gene therapy.” Trends in Genetics, 17 no.7 (2001): 380-384. McKay D. “Restoring sight by gene therapy.” Trends in Biotechnology, 19 no.7 (2001): 243-246. Newman CM, Lawrie A, Brisken AF, Cumberland DC. “Ultrasound gene therapy: on the road from concept to reality.” Echocardiography, 18 no.4 (2001): 339-347. Savulescu J. “Harm, ethics committees and the gene therapy death.” Journal of Medical Ethics, 27 no.3 (2001): 148-150. Verma IM. “Ombudsman or Hotline for Gene Therapy Clinical Trials?” Molecular Therapeutics, 3 no.6 (2001): 817-818. ORGANIZATIONS

American Academy of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211-2672, (913) 9066000, . American Society of Gene Therapy. 611 East Wells Street, Milwaukee, WI 53202, (414) 278-1341, (414) 276-3349. . World Health Organization. 20 Avenue Appia, 1211 Geneva 27, Switzerland, +41 (22) 791 4140, +41 (22) 791 4268. . OTHER

American Civil Liberties Union. . Association of American Medical Colleges. . Human Genome Project Information. . National Cancer Institute. . Public Broadcasting System (animation). . University of Pennsylvania. . US Food and Drug Administration. .

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mined, will such information be used against people? For example, will someone more susceptible to a disease have to pay higher insurance premiums or be denied health insurance altogether? Will employers discriminate between two potential employees, one with a healthy genome and the other with genetic abnormalities?

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Vanderbilt University. .

L. Fleming Fallon, Jr., MD, DrPH

General anesthetic see Anesthesia, general

ily, including health status and cause of death, is usually needed. If a family history is complicated, information from more distant relatives may be helpful, and medical records may be requested for any family members who have had a genetic disorder. Thorough examination of a family history may enable a counselor to calculate the probability of occurrence of genetic disorders in the future. Ethnicity

Genetic counseling Definition Genetic counseling is a communication process by which personal genetic risk information is translated into practical information for families. Genetic counselors are health care professionals with specialized training and experience in the areas of medical genetics and counseling. Genetic counselors are able to assist individuals and families by: • Helping people to understand information about birth defects or genetic disorders. This includes explaining patterns of inheritance, recurrence risks, natural history of diseases, and genetic testing options. • Providing nondirective supportive counseling regarding emotional issues related to a diagnosis or testing options. • Helping individuals and families make decisions with which they are comfortable, based on their personal ethical and religious standards. • Connecting individuals and families with appropriate resources, such as support groups or specific types of medical clinics, locally and nationally.

Purpose There are several purposes or aspects to be addressed within the scope of genetic counseling. These include obtaining a pedigree; tracing ethnicity; exploring issues of consanguinity; and documenting exposures to toxins, diseases, or environmental agents during pregnancy.

Consanguinity Another question a genetic counselor asks in obtaining a family history is whether the couple are related to one another by blood. The practice of marrying or having children with relatives is infrequent in the United States, but is more common in some countries. When two people are related by blood, there is an increased chance for their children to be affected with conditions that are inherited in a recessive pattern. In recessive inheritance, each parent of a child affected with a disease carries a single gene for a disease. The child gets two copies, one from each parent, and is affected. People who have a common ancestor are more likely than unrelated people to be carriers of genes for the same recessively inherited disorders. Depending on family history and ethnic background, blood tests can be offered to couples to get more information about the chance of these conditions occurring. Exposures during pregnancy

Pedigree In all types of genetic counseling, an important aspect of the counseling process is information gathering about family and medical history. Information gathering is performed by drawing a chart called a pedigree. A pedigree is made of symbols and lines that represent a family history. To accurately assess the risk of inherited diseases, information about three generations of the fam1048

In obtaining a family history, a genetic counselor asks about a person’s ethnicity or ancestral origin. There are some ethnic groups that have a higher chance of being carriers of some genetic diseases or abnormalities. For instance, the chance that an African American is a carrier of a gene for sickle cell disease is one in 10. People of Jewish or central European ancestry are likely to be carriers of several conditions, including Tay-Sachs disease, Canavan’s disease and cystic fibrosis. People of Mediterranean ancestry are likely to be carriers of a type of anemia called thalassemia. Genetic counselors discuss inheritance patterns of these diseases, carrier risks, and genetic screening or testing options.

During prenatal genetic counseling, the counselor will ask about pregnancy history. If a woman has taken medications or has had exposure to a potentially harmful substance from the environment such as a chemical, toxin, or radiation, the genetic counselor can discuss the possibility of adverse effects. Ultrasound is often a useful tool to look for some effects of exposure.

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There are no physical precautions that are needed before genetic counseling. However, persons who will receive the results of genetic tests should be prepared mentally and emotionally for the possibility of unpleasant information. This includes discussing if they want to know the results of genetic testing and what choices they may have to make based on the information supplied.

Description Types of genetic counseling Genetic counselors work with people concerned about the risk of an inherited disease or condition. These people represent several different populations. Prenatal genetic counseling is provided to couples that have an increased risk of birth defects or inherited conditions, and are expecting a child or planning a pregnancy. Pediatric genetic counseling is provided to families with children suspected of having a genetic disorder or with children previously diagnosed with a genetic disorder. Adult genetic counseling is provided to adults with clinical features of an inherited disease or a family history of an inherited disease. Cancer genetic counseling is provided to those with a strong family history of certain types of cancer. Ethics are an important component of genetic counseling.

to understand their risks, and explore how they feel about or will cope with these risks. Prenatal tests that are offered during genetic counseling include level II ultrasounds, maternal serum AFP screening, chorionic villus sampling (CVS), and amniocentesis. Level II ultrasound is a detailed ultrasound surveying fetal anatomy for birth defects. Ultrasound is limited to detection of structural changes in anatomy and cannot detect changes in chromosome number. The maternal serum AFP screening is used to indicate if a pregnant woman has a higher or lower chance of having a child with certain birth defects. This test can only provide information concerning the probability of a birth defect. The screening cannot diagnose an actual birth defect. CVS is a way of learning how many chromosomes are present in a fetus. A small piece of placental tissue is obtained for these studies during the tenth to twelfth weeks of pregnancy. Amniocentesis is also a way of learning how many chromosomes are present in a fetus. Amniotic fluid is obtained for these studies, usually between 15 and 20 weeks of pregnancy. There is a small risk of miscarriage associated with both of these tests. Genetic counseling regarding these procedures involves the careful explanation of benefits and limitations of each testing option. A genetic counselor also tries to explore how persons feel about prenatal testing and the impact of such testing on the pregnancy. Genetic counselors are supportive of any decision a person makes about whether or not to have prenatal tests performed.

Prenatal genetic counseling There are several different reasons a person or couple may seek prenatal genetic counseling. If a woman is age 35 or older and pregnant, there is an increased chance that her fetus may have a change in the number of chromosomes present. Changes in chromosome number may lead to mental retardation and birth defects. Down syndrome is the most common change in chromosome number that occurs proportionally more often in the fetuses of older women. Couples may seek prenatal genetic counseling because of abnormal results of screening tests performed during pregnancy. A blood test called the alpha fetal protein (AFP) test is offered to all pregnant women. This blood test screens for Down syndrome, open spine defects (spina bifida), and another type of mental retardation caused by a change in chromosome number called trisomy 18. When this test is abnormal, further tests are offered to get more information about the chance of these conditions actually occurring in the fetus. Another reason that people seek prenatal genetic counseling is a family history of birth defects or inherited diseases. In some cases, blood tests of the parents may be available to indicate if their children would be at risk of being affected. Genetic counselors assess risk in each case, help persons

Pediatric genetic counseling Families or pediatricians seek genetic counseling when a child has features of an inherited condition. Any child who is born with more than one birth defect; mental retardation; or dysmorphic features has an increased chance of having a genetic syndrome. A common type of mental retardation in males for which genetic testing is available is Fragile X syndrome. Genetic testing is also available for many other childhood illnesses such as hemophilia and muscular dystrophy. Genetic counselors work with medical geneticists to determine if a genetic syndrome is present. This process includes a careful examination of family history, medical history of the child, review of pertinent medical records in the family, a physical examination of the child, and sometimes blood work or other diagnostic tests. If a diagnosis is made, then a medical geneticist and genetic counselor review what is known about the inheritance of the condition, the natural history of the condition, treatment options, further examinations that may be needed for health problems common in the diagnosed syndrome, and resources for helping the family. The genetic counselor also helps the family adjust to the diagnosis by pro-

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viding emotional support and counseling. Many families are devastated by receiving a diagnosis, learning of the likely outcome for the child and by the loss of the hoped for healthy child. There would also be a discussion about recurrence risks in the family and who else in the family may be at risk. Adult genetic counseling Adults may seek genetic counseling when a person in the family decides to be tested for the presence of a known genetic condition; when an adult begins exhibiting symptoms of an inherited condition; or when there is a new diagnosis of someone with an adult-onset disorder in the family. In addition, the birth of a child with obvious features of a genetic disease leads to diagnosis of a parent who is more mildly affected. Genetic counseling for adults may lead to the consideration of presymptomatic genetic testing. Testing a person to determine the likelihood for a condition existing before any symptoms occur is an area of controversy. Huntington’s disease is an example of a genetic disease for which presymptomatic testing is available. This is a neurological disease resulting in dementia. Onset of the condition is between 30 and 50 years of age. Huntington’s disease is inherited in an autosomal dominant pattern. If a person has a parent with the disease, the risk of being affected is 50%. Would presymptomatic testing relieve or create anxiety? Would a person benefit from removal of doubt about being affected? Would knowing about the condition help a person with life planning? Genetic counselors help people sort through their feelings about such testing and whether or not the results would be helpful to them. Cancer genetic counseling A family history of early onset breast, ovarian, or colon cancer in multiple generations of a family is a common reason a person would seek a genetic counselor who works with people who have cancer. While most cancer is not inherited, there are some families in which a dominant gene is present and causing the disease. A genetic counselor is able to discuss the chances that the cancer in the family is related to a dominantly inherited gene. The counselor can also discuss the option of testing for the breast and ovarian cancer genes, BRCA1 and BRCA2. In some cases the persons seeking testing have already had cancer but others have not. Therefore, presymptomatic testing is also an issue in cancer genetics. Emotional support is important for these people, as they have often lost close relatives from cancer and are fearful of their own risks. For families in which a dominant form of cancer is detected through genetic testing, a plan can be made for increased surveillance of disease symptoms. 1050

Ethical issues in genetic counseling Prenatal diagnosis of anomalies or chromosomal abnormalities may lead to a decision about whether or not a couple wishes to continue a pregnancy. Some couples choose to continue a pregnancy. Prenatal diagnosis gives them additional time to emotionally prepare for the birth of the child and to gather resources. Others choose not to continue a pregnancy in which problems have been diagnosed. These couples have unique emotional needs. Often the child is a very much desired addition to the family and parents are devastated that the child is not healthy. Presymptomatic testing for adult-onset disorders and cancer raises difficult issues regarding the need to know and the reality of dealing with abnormal results before symptoms occur. The National Society of Genetic Counselors has created a Code of Ethics to guide genetic counselors in caring for people. The Code of Ethics consists of four ethical principles: • Beneficience is the promotion of personal well-being in others. The genetic counselor is an advocate for the person being counseled. • Non-maleficience is the concept of doing no harm to a person. • Autonomy is recognizing the value of an individual, the person’s abilities and point of view. Important aspects of autonomy are truthfulness with persons, respecting confidentiality, and practicing informed consent. • Justice is providing equal care for all, freedom of choice, and providing a high quality of care. The main ethical principle of genetic counseling is the attempt to provide nondirective counseling. This principle again points to an individual-centered approach to care by focusing on the thoughts and feelings of each person. Five percent of the Human Genome Project budget is designated for research involving the best way to deal with ethical issues that arise as new genetic tests become available. Genetic counselors can help people navigate through the unfamiliar territory of genetic testing.

Preparation Persons should be apprised of possible outcomes and given the opportunity to discuss their feelings prior to undergoing genetic tests. There is a burden associated with knowing the probability of a future outcome. Difficult decisions may be required as a result of learning genetic information through testing. The process of adequately preparing an individual for genetic counseling is called informed consent. Ethical genetic counselors always obtain informed consent prior to undertaking any genetic tests.

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Persons must be provided access to competent counselors and therapists. Such professionals can assist in processing the feelings and reactions that may emerge as a result of receiving the findings of genetic tests.

Complications The complications that arise from the process of genetic counseling are most commonly mental and emotional. Individuals and couples who have received genetic counseling often experience mental changes such as depression and anguish when they receive unfavorable results about tests. Complications include the need to make difficult decisions regarding themselves, their families, or their unborn children. This is also referred to as a burden of knowing, meaning that likely but unwanted outcomes may become known before they occur. Depending on the condition, personal preferences and situation, persons may elect to continue with a pregnancy that is likely to result in a child with one or more abnormalities, terminate a pregnancy, select a different partner, or decide not to have children. These are all difficult situations that may require the assistance and intervention of a trained mental health counselor or therapist.

Results The results given to a person during genetic counseling are highly individualized and depend on the nature of tests being performed and the issues of importance to the person being counseled. The results of the process of genetic counseling vary. Genetic counseling offers information to people, thereby allowing them to make informed choices. Some of the options may not be easy or pleasant to contemplate. However, they are based on hard data rather than on wishes, hopes, or some other non-scientific basis. Genetic counselors have an ethical duty to obtain informed consent from individuals prior to beginning genetic counseling, provide unbiased information and the ability to interact in a non-judgmental or coercive manner.

Health care team roles Genetic counselors are specially trained members of a health care team who have a master’s degree in genetic counseling. They receive referrals from obstetricians, pediatricians, family physicians, and other doctors. They interpret the results of tests from laboratory personnel, medical geneticists, and pathologists. They refer people to therapists and counselors for assistance in resolving issues that arise from the process of genetic counseling.

KEY TERMS Canavan disease—A serious genetic disease more common among the Eastern European Jewish population that causes mental retardation and early death. Canavan disease is caused by the lack of an enzyme called aspartoacylase. Cystic fibrosis—A respiratory disease characterized by chronic lung disease, pancreatic insufficiency, and an average age of survival of 29 years. Cystic fibrosis is caused by mutations in a gene on chromosome seven that encode a transmembrane receptor. Dysmorphic feature—A subtle change in appearance such as low set ears or a flattened nasal bridge that suggests a genetic syndrome may be present. Fragile X syndrome—The most common inherited cause of mental retardation in males. People with Fragile X syndrome often have large ears, a long face, hyperextensible finger joints, hyperactivity or autism. Fragile X syndrome is caused by an expansion in a gene on the X chromosome. Some females are also affected. Human Genome Project—An international collaborative project among scientists to map the genetic sequence of all the chromosomes. This project is funded by the National Institute of Health in the United States. Informed consent—Provision of complete information to a competent individual regarding a treatment or test. Part of informed consent is to ensure a person’s understanding of the advantages and disadvantages of a procedure and to obtain voluntary authorization to perform the procedure. Sickle-cell anemia—A chronic, inherited blood disorder characterized by crescent-shaped red blood cells. It occurs primarily in people of African descent, and produces symptoms including episodic pain in the joints, fever, leg ulcers, and jaundice. Tay-Sachs disease—A genetic disease affecting young children of eastern European Jewish descent. This disease is caused by the lack of an enzyme called hexosaminidase A. This deficiency results in mental retardation, convulsions, blindness and, finally, death. Thalassemia—An inherited group of anemias occurring primarily among people of Mediterranean descent. It is caused by abnormal formation of part of the hemoglobin molecule.

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Resources BOOKS

Beaudet, Arthur L. “Genetics and disease.” In Harrison’s Principles of Internal Medicine, 14th ed., edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 365-395. Eanet, Karen, and Julia B. Rauch. Genetics and Genetic Services: A Child Welfare Worker’s Guide. Washington, DC: Child Welfare League of America, 2000. Hollingsworth, Alan B. The Truth About Breast Cancer Risk Assessment. Aurora, CO: National Writers Press, 2000. Kessler, Seymour, and Robert G. Resta. Psyche and Helix: Psychological Aspects of Genetic Counseling. New York: Wiley, 2000. Meager, Anthony. Gene Therapy Technologies, Applications and Regulations: From Laboratory to Clinic. New York: Wiley, 1999. Needleman, Robert D. “Fetal growth and development.” In Nelson Textbook of Pediatrics, 16th ed. edited by Richard E. Behrman et al., Philadelphia: Saunders, 2000, 27-30. Seashore, Margretta R. “Genetic counseling.” In Cecil Textbook of Medicine, 21st ed. edited by Goldman, Lee and Bennett, J. Claude. Philadelphia: W.B. Saunders, 2000, 439-442. Weil, Jon. Psychosocial Genetic Counseling. New York: Oxford University Press, 2000. PERIODICALS

Brooks, S.S. “Genetic counseling in the neuronal ceroid lipofuscinoses.” Advances in Genetics 45 (2001): 159-167. Brunger, J.W., Matthews AL, Smith RH, Robin NH. “Genetic testing and genetic counseling for deafness: The future is here.” Laryngoscope 111, no. 4 Pt 1 (2001): 715-718. Ciske, DJ, Haavisto A, Laxova A, Rock LZ, Farrell PM. “Genetic counseling and neonatal screening for cystic fibrosis: An assessment of the communication process.” Pediatrics 107, no. 4 (2001):699-705. Edwards, R.T. “Steering a course around the genetic iceberg.” Journal of Public Health Medicine 23, no. 1 (2001): 3-4. Ralston, SJ, Wertz D, Chelmow D, Craigo SD, Bianchi DW. “Pregnancy outcomes after prenatal diagnosis of aneuploidy.” Obstetrics and Gynecology 97, no. 5 Pt 1 (2001): 729-733. Welkenhuysen, M, Evers-Kiebooms G, d’Ydewalle G. “The language of uncertainty in genetic risk communication: Framing and verbal versus numerical information.” Patient and Educational Counseling 43, no. 2 (2001): 179-187. ORGANIZATIONS

American Board of Genetic Counseling, 9650 Rockville Pike, Bethesda, MD 20814-3998. (301) 571-1825. Fax: (301) 571-1895. . American Infertility Association, 666 Fifth Avenue, Suite 278, New York, NY 10103. (718) 621-5083. 1052

. [email protected]. American Public Health Association, 800 I Street, NW, Washington, DC 20001-3710. (202) 777-2742. Fax: (202) 777-2534. . [email protected]. American Society for Reproductive Medicine, 1209 Montgomery Highway, Birmingham, AL 35216-2809. (205) 978-5000. . OTHER

American College of Physicians. . March of Dimes. . National Human Genome Research Institute. . National Library of Medicine. . National Society of Genetic Counselors. . Rush University School of Medicine. . University of Kansas Medical Center. . World Medical Association. .

L. Fleming Fallon, Jr., MD, DrPH

Genetic engineering Definition Genetic engineering involves altering the genetic structure of embryonic cells or vectors to provide them with desired traits or to eliminate undesirable traits.

Description For thousands of years, humans have engaged in primitive forms of genetic engineering. They have chosen plants or animals with survival strength and desirable characteristics for further breeding, and have combined different strains of a species in attempts to retain and emphasize desirable characteristics of both. But in the 1970s, the field of genetic engineering took a quantum technologic leap when researchers developed a technique known as recombinant DNA, or gene splicing, enabling them to directly alter the genetic code and sequence of cells. This development transformed genetic engineering

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in medicine, food production, and industry. Engineered bacteria are even being used to take the place of standard microchip circuitry for computers. Genes, which are composed of molecules of DNA, determine the physical characteristics that make organisms unique. Gene splicing, which involves introducing new genes into an organism in order to produce new characteristics, is performed in a number of ways. Sometimes a DNA “gun” is used to shoot genes directly into cells such as plant cells. When a gene cannot be directly “cut and pasted” from one organism to another, it may be placed in a harmless bacterium that duplicates repeatedly, acting as a “gene factory.” The bacteria are then used to ferry the genes into cells. A sheep named Dolly, born in 1997, was produced using a genetic engineering technique known as cloning. Here, scientists replaced the genetic material from one ewe’s egg with genetic material from another ewe, producing an animal genetically unrelated to its surrogate mother. Hundreds of animals have been cloned, including bulls, cows, mice, monkeys, and pigs. Even clones of clones have been produced. Cloning is used to produce laboratory test animals with specific disease-related characteristics. Areas of cloning research range from cloning cows and sheep to produce medicines in their milk, to using cloning to preserve endangered species such as the Indian cheetah and the Asian guar. Genetic engineering techniques are used to produce several widely used drugs. In addition to the hormone insulin, used to treat some forms of diabetes, these techniques are now used to produce the following: interferon, an antiviral and anticancer drug; tissue plasminogen activator (tPA), which dissolves blood clots; erythropoetin, which stimulates red blood-cell production; a hepatitis B vaccine; and others. In food production, genetic engineering can produce tomatoes with a longer shelf life; as well as crops with insect, herbicide, frost, and virus resistance. It is used to increase milk production in dairy cows, and to increase the size and infection-resistance of farmed fish like salmon. In addition, genetically altered bacteria have been used to decompose garbage and petroleum products. Despite all its advances, the field of genetic engineering is still in its infancy. Now that researchers have mapped much of the human genome (or DNA blueprint), and some of the genes and their mutations responsible for genetic disorders like cystic fibrosis have been found, the next challenge is to understand proteins. These are the most complex of all known molecules. Each of the body’s genes carries the code to create many different proteins (peptides), which are essentially the workers that carry out the DNA instructions. Understanding how mes-

Many steps are required to make recombinant DNA and final products such as interferon. (National Institutes of Health. Reproduced by permission.)

senger proteins work is essential to preventing or curing disease. This will be a major focus of research over the next decade. Promising areas of genetic engineering include human gene therapy and stem-cell research. Gene therapy involves repairing or replacing mutated genes in order to correct the malfunctions in protein production that can lead to disease. The use of gene therapy is being researched for diseases such as cancer, muscular dystrophy, hemophilia B, heart disease, and severe combined immune deficiency disease (known as “bubble boy disease”), among others. Stem cells are the undifferentiated cells from which specialized embryonic cells develop. They are considered one of science’s best hopes for curing disease. Modified stem cells may one day be used to replace diseased cells affecting function throughout the body’s systems. These cells also play an important role in tissue engineering, which involves the manufacture of blood products; artificial skin products; and bio-

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KEY TERMS Cloning—The production of an organism that is genetically identical to its parent. Deoxyribonucleic acid (DNA)—The genetic material of all cellular organisms and most viruses. DNA carries the information needed to direct proteins. Each molecule of DNA consists of two twisted strands, called a double helix. Eugenics—A practice involving use of genetic principles to “improve” humankind. Animal cell being microinjected with foreign genetic material. (Photograph by M.Baret/RAPHU. National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.)

genetic replacement of organs, blood vessels, and cartilage. Other examples of genetic engineering research range from the manufacture of bananas engineered to contain vaccines (to eliminate the challenge of cold vaccine storage in developing countries) to coffee plants that have been altered to “switch off” caffeine before the beans even start growing.

Viewpoints Genetic engineering is controversial and has led to many protests regarding the potential of short- and longterm health and environmental risks. Stem-cell research is particularly controversial. Stem cells have traditionally been culled from aborted fetuses or from embryos left behind after successful fertility treatments, or they are produced using cloning technology. Many fear that using stem-cell research to cure genetic disorders or produce body tissues will eventually lead to the process being used to enhance or improve humans, a practice known as positive eugenics, termed by opponents as the “search for the master race.” It is feared that altering human genomes may have unknown consequences for future generations that inherit the changes. Some individuals, including James Watson, co-discoverer of DNA’s double-helix structure, are not opposed to altering DNA to make human “improvements.” The primary concerns with genetic engineering in plants are that a transferred gene could migrate unintentionally via pollen scattering from a transgenic plant to a related species and alter the ecosystem, or that a plant designed to kill a particular pest could end up killing beneficial insects like bees and butterflies. Transgenic plants could also interbreed with weeds, producing weeds resistant to herbicides. Allergens from one food 1054

Gene—The basic unit of hereditary traits found in the cells of all living organisms, from bacteria to humans. Genes determine the physical characteristics that an organism inherits, such as hair and eye color. Human Genome Project—An international scientific collaboration that seeks to identify and clarify the entire human genetic blueprint. Protein—A molecule made of a sequence of amino acids. Proteins are the most common organic molecules in living organisms and among the most complex. Recombinant DNA—DNA that has been altered by joining genetic material from two different sources. It usually involves putting a gene from one organism into the genome of a different organism. Stem cells—The undifferentiated cells from which specialized embryonic cells develop.

crop, such as peanuts, can be transferred to another through genetic engineering. Animal-rights groups have argued that genetically engineered fish may cause problems if they interbreed with unaltered fish, which may change the characteristics of wild fish. The use of bovine growth hormone to increase dairy-cow milk production is also controversial, with critics questioning its safety for both cows and the humans who consume the milk.

Professional implications The advances in genetic engineering require health care practitioners to consider their responsibilities in handling genetic information. As genetics advances are incorporated into tools for primary health care delivery, the use of genetic assessment testing will expand in medical practice. Health care practitioners, including nurses and allied-health professionals, will need a functional

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Resources PERIODICALS

Anderson, G., R. B. Monsen, C. A. Prows, S. Tinley, J. Jenkins. “Preparing the Nursing Profession for Participation in a Genetic Paradigm in Health Care.” Journal of Nursing Outlook (2000): 48, 23-27. Collins, F. “Medical and Societal Consequences of the Human Genome Project.” New England Journal of Medicine 341, no. 1 (1999): 28-37. Lea, D. “A New World View of Genetics Service Models.” Online Journal of Issues in Nursing 5, no. 3 (2000). Available at . ORGANIZATIONS

The American Society of Human Genetics. 9650 Rockville Pike, Bethesda, MD 20814-3998. (301)571-1825. . The International Society of Nurses in Genetics. . National Coalition for Health Professional Education in Genetics. (410) 583-0600. . OTHER

The Human Genome Project. .

Ann Quigley

Genetic studies see Genetic testing

Genetic testing Definition A genetic test examines the genetic information contained inside a person’s cells, called DNA, to determine if that person has or will develop a certain disease or could transmit a disease to a child. Genetic tests also determine whether or not couples are at a higher risk than the general population for having a child affected with a genetic disorder.

Purpose Some families or ethnic groups have a higher incidence of a certain disease than do the population as a whole. For example, individuals of Eastern European, Ashkenazi Jewish descent are at higher risk for carrying genes for rare conditions such as Tay-Sachs disease (a lipid storage disease) that occur much less frequently in populations from other parts of the world. Before having a child, a couple from such a family or ethnic group may want to know if their child would be at risk of having that disease. Genetic testing for this type of purpose is called genetic screening. During pregnancy, a baby’s cells can be studied for certain genetic disorders or chromosomal problems such as Down syndrome. Chromosome testing is most commonly offered when a mother is 35 years or older at the time of delivery. When there is a family medical history of a genetic disease or there are individuals in a family affected with developmental and physical delays, genetic testing may also be offered during pregnancy. Genetic testing during pregnancy is called prenatal diagnosis. Prior to becoming pregnant, couples who are having difficulty conceiving a child or who have had multiple miscarriages may be tested to see if a genetic cause can be identified. A genetic disease may be diagnosed at birth by performing a physical evaluation of the baby and observing characteristics of the disorder. Genetic testing can help to confirm the diagnosis made by a physical evaluation. In addition, biochemical tests (e.g., blood phenylalanine measurement) are performed routinely on all newborns to screen for certain genetic diseases that can affect a newborn baby’s health shortly after birth. There are several genetic diseases and conditions in which the symptoms do not occur until adulthood. One such example is Huntington’s disease. This is a serious disorder affecting the way in which individuals walk, talk and function on a daily basis. Genetic testing may be able to determine if someone at risk for the disease will in fact develop the disease. Some genetic abnormalities may make a person more susceptible to certain types of cancer. Testing for these abnormalities can help predict a person’s risk. Other types of genetic tests help diagnose, predict, and monitor the course of certain kinds of cancer, particularly leukemia, lymphoma, and breast cancer.

Precautions Genetic tests are performed on cells derived from blood, bone marrow, amniotic fluid, or tissues. The

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understanding of the potential ethical, legal, and social issues involved with such tests; special attention must be paid to disclosures for informed consent, and medicalrecord confidentiality. A statement on the Scope and Standards of Genetics Clinical Nursing Practice has been published by the American Nurses Association to guide nurses in their practice of genetic-based health care.

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health care worker collecting the specimen should observe universal precautions for the prevention of transmission of bloodborne pathogens. Because genetic testing is not always accurate and because there are many concerns surrounding insurance and employment discrimination for an individual receiving a genetic test, genetic counseling should always be performed prior to genetic testing. A genetic counselor is an individual with a master’s degree in genetic counseling. A medical geneticist is a physician specializing and board certified in genetics. A genetic counselor reviews a person’s family history and medical records and the reason for the test. The counselor explains the likelihood that the test will detect all possible causes of the disease in question (known as the sensitivity of the test), and the likelihood that the disease will develop if the test is positive (known as the positive predictive value of the test). Learning about the disease in question, the benefits and risks of both a positive and a negative result, and what treatment choices are available if the result is positive, will help prepare a person undergoing testing. During the genetic counseling session, an individual interested in genetic testing will be asked to consider how the test results may affect his or her life, family, and future decisions. After this discussion, persons should have the opportunity to indicate, in writing, that they gave informed consent to have the test performed, verifying that the counselor provided complete and understandable information.

Description Genes and chromosomes Deoxyribonucleic acid (DNA) is a long molecule made up of two strands of genetic material coiled around each other in a unique double helix structure. Francis Crick and James Watson discovered this structure in 1953. Each strand of DNA consists of a backbone of deoxyribose sugars linked together by phosphate groups. Each sugar is bound (with a covalent bond) to one of four bases, adenine, guanine, thymine or cytosine. The two strands are held together by hydrogen bonds between the bases. Adenine pairs with thymine and guanine pairs with cytosine. Most of the DNA is found in the nucleus of the cell. Each person’s DNA is a unique blueprint, giving instructions for that person’s physical traits, such as eye color, hair texture, height, and susceptibility to disease. DNA is organized into structures called chromosomes. 1056

The instructions are contained as a code spelled out by the order of the four bases in each of the strands of DNA. When a base pair is out of order, or is missing, then cells may not produce an important protein or may produce an abnormal protein resulting in a genetic disorder. While genes are found in every nucleated cell of the human body, not every gene is functioning all of the time. Some genes are turned on during critical points in development and then remain silent for the rest of a cell’s life. Other genes remain active throughout life so that cells can produce important proteins that help humans digest food properly or fight off the common cold. In the human genome there are 3.1 billion bases and approximately 100,000 genes. Approximately 95% of DNA consists of non-coding regions called introns. The remaining 5% consists of coding regions called exons, which are the structural units that form genes. Within the exon, the specific order of the base pairs on a strand of DNA dictates the order of amino acids that comprise the protein made when the gene is transcribed and translated. A grouping of three sequential base pairs within the exon is called a codon. Each codon, or triplet, codes for an amino acid. These are added in tandem to form a protein. A string of many codons together can be thought of as a series of words all coming together to make a sentence. This sentence provides the instructions for cells to make a protein that is needed in order for the body to function properly. Human DNA strands containing a hundred to several thousand genes are found on structures called chromosomes. Each cell typically has 46 chromosomes arranged into 23 pairs. Each parent contributes one chromosome to each pair. The first 22 pairs are called autosomal chromosomes, or non-sex chromosomes and are assigned a number from one to 22. The last pair are the sex chromosomes and include the X and the Y chromosomes. If a child receives an X chromosome from each parent, the child is female. If a child receives an X from the mother, and a Y from the father, the child is male. Just as each parent contributes one chromosome to each pair, so each parent contributes one gene from each chromosome. The pair of genes produces a specific trait in the child. In autosomal dominant conditions, it takes only one copy of a gene to influence a specific trait. The stronger gene is called dominant; the weaker gene is said to be recessive. Two copies of a recessive gene are needed to express a trait while only one copy of a dominant gene is needed. Some genes, (for example, those coding for blood groups) exhibit codominant expression. In this case, both genes are active and produce traits. Human sex chromosomes, the X and the Y also contain important genes. Some genetic diseases are caused by missing or altered genes on one of the sex chromosomes. Males are

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Types of genetic mutations Genetic disease results from a change, or mutation, in a chromosome or in one of several base pairs on a gene. Some people inherit such mutations from their parents. These are called hereditary or germline mutations. Other mutations can occur spontaneously, or for the first time in an affected child. For many of the adult on-set diseases, genetic mutations can occur over the lifetime of an individual. These are called acquired or somatic mutations and occur while cells are making copies of themselves or dividing in two. Environmental effects, such as radiation or other chemicals, can also contribute to these types of mutations. There are a variety of different types of mutations that can occur in the genetic code to cause disease. For each genetic disease, there may be more than one type of mutation to cause the disease. For some genetic diseases, the same mutation occurs in every individual affected with the disease. For example, the most common form of dwarfism, called achondroplasia, is caused by a single base pair substitution. This same mutation occurs in all individuals affected with the disease. Other genetic diseases are caused by different types of genetic mutations that may occur anywhere along the length of a gene. For example, cystic fibrosis, the most common genetic disease in the Caucasian population, is caused by any of several hundred different gene mutations. Individual families may carry the same mutation as each other, but not as the rest of the population affected with the same genetic disease. Some genetic diseases occur as a result of a larger mutation that can occur when a chromosome itself is either rearranged or altered or when a baby is born with more than the expected number of chromosomes. There are only a few types of chromosome rearrangements that are possibly hereditary, or passed on from the mother or the father. The majority of chromosome alterations, where a baby is born with too many chromosomes or missing a chromosome, occur sporadically or for the first time with a new baby. The type of mutation that causes a genetic disease will determine the type of genetic test to be performed. In some situations, more than one type of genetic test will be performed to arrive at a diagnosis. The cost of genetic tests vary. Chromosome studies can cost hundreds of dollars and some gene studies, thousands. Insurance coverage also varies among companies and the policies. It may take several days or several weeks to complete a

test. Research testing, when the exact location of a gene has not yet been identified, can require several months to years for results. Types of genetic testing DIRECT DNA MUTATION ANALYSIS. Direct DNA sequencing examines the base pair sequence of a gene for specific mutations. Some genes contain more than 100,000 bases and a mutation of any one base can make the gene nonfunctional and cause disease. As the number of possible mutations increases, the less likely a test is able to detect all of them. DNA sequencing is a research tool that is used to identify the order of bases in cloned genes. Base sequencing identifies the specific mutation. Once this is known a DNA probe can be made that recognizes the mutation. DNA probes typically contain 20-60 bases to insure that they bind only to the specific mutation site. DNA testing for disease genes is usually performed on white blood cells but can also be performed on other tissues.

There are several different lab techniques used to test for a direct mutation. One early approach begins by using chemicals to separate DNA from the rest of the cell. Special enzymes (called restriction enzymes) are added to the DNA. The enzymes then function like scissors and cut the strands in specific places. Next, the DNA fragments are separated by size using a process called electrophoresis. The fragments are treated chemically to separate them into single stranded fragments and transferred to a nylon filter, a process called Southern blotting. The DNA probe is added to the fragments. The probe is designed to bind to the specific mutated portion of the gene. The probe is labeled with a radioactive isotope. When the probe hybridizes with the target sequence containing the mutation, it will render this piece of DNA on the filter radioactive. The radioactivity will expose a piece of x-ray film layered over the nylon filter, and the mutation will appear as a band in the expected location. When only small quantities of DNA are available, as in prenatal diagnosis, the target DNA from the fetal cells must first be amplified. This is accomplished by a method known as the polymerase chain reaction. This procedure can copy a specific sequence of DNA that frames the gene to be tested. Up to one million copies can be made in as little as two hours. INDIRECT DNA TESTING. Family linkage studies are performed to study a disease when the exact type and location of the genetic alteration is not known but the general location on the chromosome has been identified. These studies are possible when a chromosome marker has been found to be associated with a disease. Chromosomes contain certain regions that vary in appearance between individuals. These regions are called

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most often affected by sex chromosome diseases when they inherit an X chromosome with missing or mutated genes from their mothers.

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ties. To analyze a person’s chromosomes, cells are allowed to grow and multiply in the laboratory until they reach a certain stage of growth. The length of growing time varies with the type of cells. Cells from blood and bone marrow take one to two days, fetal cells from amniotic fluid require seven to 10 days. When the cells are ready, they are placed on a microscope slide using a technique to make them swell, allowing easier visualization of chromosomes. The slides are stained. The stain creates a banding pattern unique to each chromosome. Under a microscope, the chromosomes are counted, identified, and analyzed based on their size, shape, and stained appearance. A scientist examines a DNA sequencing autoradiogram on a light box. Each group of four strips represents the nucleotide sequence of ACGT (Adenine-Guanine-CytosineThymine) in the DNA of the nematode worm, Onchocerca volvulus, a human parasite responsible for river blindness in tropical countries. (Photo Researchers, Inc. Reproduced by permission.)

polymorphisms and do not cause a genetic disease to occur. If a polymorphism is always present in family members with the same genetic disease, and absent in family members without the disease, it is likely that the gene responsible for the disease is near that polymorphism. The gene mutation can be indirectly detected in family members by looking for the polymorphism. To look for the polymorphism, DNA is isolated from cells in the same way it is for direct DNA mutation analysis. A restriction enzyme known to cut the DNA at the site where the polymorphism occurs is added. If the polymorphism is present, the restriction enzyme will not recognize the site and will not cut the DNA there. This results in a larger size fragment of DNA. If sufficient DNA is present, the fragments can be separated by electrophoresis, and the DNA bands are stained with ethidium bromide to visualize the position of the bands. If the amount of DNA is small, the double stranded fragments can be separated and a DNA probe can be used to determine whether the polymorphism is present. The pattern of banding of a person being tested for the disease is compared to the pattern from a family member affected by the disease. Linkage studies have disadvantages not found in direct DNA mutation analysis. These studies require multiple family members to participate in the testing. If key family members choose not to participate, the incomplete family history may make testing other members useless. The indirect method of detecting a mutated gene also causes more opportunity for error, and many disease genes are not associated with polymorphisms. CHROMOSOME ANALYSIS. Various genetic syndromes are caused by structural chromosome abnormali-

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A karyotype is the final step in the chromosome analysis. After the chromosomes are counted, a photograph is taken of the chromosomes from one or more cells as seen through a microscope. Then the chromosomes are cut out and arranged side-by-side with their partner in ascending numerical order, from largest to smallest. The karyotype is done either manually or using a computer attached to the microscope. Chromosome analysis is also called cytogenetics. Applications for genetic testing NEWBORN SCREENING. Genetic testing is used most

often for newborn screening. Every year, millions of newborn babies have their blood samples tested for potentially serious genetic diseases. Phenylketonuria is the genetic disease test most commonly performed. CARRIER TESTING. An individual who has a gene associated with a disease but never exhibits any symptoms of the disease is called a carrier. A carrier is a person who is not affected by a possessed mutated gene, but can pass the gene to an offspring. Genetic tests have been developed that tell prospective parents whether or not they are carriers of certain diseases. If one or both parents are carriers, the risk of passing the disease to a child can be predicted.

To predict the risk, it is necessary to know if the gene in question is autosomal or sex-linked. If the gene is carried on any one of chromosomes one through 22, the resulting disease is called an autosomal disease. If the gene is carried on the X or Y chromosome, it is called a sex-linked disease. Sex-linked diseases, such as the bleeding condition hemophilia, are usually carried on the X chromosome. A woman who carries a disease-associated mutated gene on one of her X chromosomes has a 50% chance of passing that gene to her son. A son who inherits that gene will develop the disease because he does not have another normal copy of the gene on a second X chromosome to

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The risk of passing an autosomal disease to a child depends on whether the gene is dominant or recessive. A prospective parent carrying a dominant gene, has a 50% chance of passing the gene to a child. A child needs to receive only one copy of the mutated gene to be affected by the disease. If the gene is recessive, a child needs to receive two copies of the mutated gene, one from each parent, to be affected by the disease. When both prospective parents are carriers, their child has a 25% chance of inheriting two copies of the mutated gene and being affected by the disease; a 50% chance of inheriting one copy of the mutated gene and being a carrier of the disease but not affected; and a 25% chance of inheriting two normal genes. When only one prospective parent is a carrier, a child has a 50% chance of inheriting one mutated gene and being an unaffected carrier of the disease, and a 50% chance of inheriting two normal genes. Cystic fibrosis is a disease that affects the lungs and pancreas and is discovered in early childhood. It is the most common autosomal recessive genetic disease found in the Caucasian population: one in 25 people of Northern European ancestry are carriers of a mutated cystic fibrosis gene. The gene, located on chromosome seven, was identified in 1989. The gene mutation for cystic fibrosis is detected by a direct DNA test. Over 600 mutations of the cystic fibrosis gene have been identified. Each of these mutations cause the same disease. Tests are available for the most common mutations. Tests that check for the 86 most common mutations in the Caucasian population will detect 90% of carriers for cystic fibrosis. The percentage of mutations detected varies according to an individual’s ethnic background. When persons test negative, it is likely, but not guaranteed that they do not have the gene. Both prospective parents must be carriers of the gene to conceive a child with cystic fibrosis.

ic mutated gene responsible for a late-onset disease has been identified, a person from an affected family can be tested before symptoms appear. Huntington’s disease is one example of a late-onset autosomal dominant disease. Its symptoms of mental confusion and abnormal body movements do not appear until middle to late adulthood. The chromosome location of the gene responsible for Huntington’s chorea was located in 1983 after studying the DNA from a large Venezuelan family affected by the disease. Ten years later, the gene was identified. A test is now available to detect the presence of the expanded base pair sequence responsible for causing the disease. The presence of this expanded sequence means a person will develop the disease. Another late onset condition, Alzheimer’s disease, is not as well understood as Huntington’s disease. The specific genetic cause of Alzheimer’s disease is not as clear. Although many cases appear to be inherited in an autosomal dominant pattern, many cases exist as single incidents in a family. Like Huntington’s disease, symptoms of mental deterioration first appear in adulthood. Genetic research has found an association between this disease and genes on four different chromosomes. The validity of looking for these genes in a person without symptoms or without family history of the disease is still being studied. CANCER SUSCEPTIBILITY TESTING. Cancer can result from an inherited (germline) mutated gene or a gene that mutated sometime during a person’s lifetime (acquired mutation). Some genes, called tumor suppressor genes, produce proteins that protect the body from cancer. If one of these genes develops a mutation, it is unable to produce the protective protein. If the second copy of the gene is normal, its action may be sufficient to continue production, but if that gene later develops a mutation, the person is vulnerable to cancer. Other genes, called oncogenes, are involved in the normal growth of cells. A mutation in an oncogene can cause too much growth, the beginning of cancer.

Tay-Sachs disease, also autosomal recessive, affects children primarily of Ashkenazi Jewish descent. Children with this disease die between the ages of two and five. This disease was previously detected by looking for a missing enzyme. The mutated gene has now been identified and can be detected using direct DNA mutation analysis.

Direct DNA tests are currently available to look for gene mutations identified and linked to several kinds of cancer. People with a family history of these cancers are those most likely to be tested. If one of these mutated genes is found, the person is more susceptible to developing the cancer. The likelihood that the person will develop the cancer, even with the mutated gene, is not always known because other genetic and environmental factors are also involved in the development of cancer.

PRESYMPTOMATIC TESTING. Not all genetic diseases show their effect immediately at birth or early in childhood. Although the gene mutation is present at birth, some diseases do not appear until adulthood. If a specif-

Cancer susceptibility tests are most useful when a positive test result can be followed with clear treatment options. In families with familial polyposis of the colon, testing a child for a mutated APC gene can reveal

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compensate for the abnormal copy. A daughter who inherits the disease associated gene from her mother, on one of her X chromosomes will become a carrier and be at risk for having a son affected with the disease.

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whether or not the child needs frequent monitoring for the disease. In families with potentially fatal familial medullary thyroid cancer or multiple endocrine neoplasia type two, finding a mutated RET gene in a child provides the opportunity for that child to have preventive removal of the thyroid gland. In the same way, MSH1 and MSH2 mutations can reveal which members in an affected family are vulnerable to familiar colorectal cancer and would benefit from aggressive monitoring.

Extra or missing chromosomes cause mental and physical abnormalities. A child born with an extra chromosome 21 (trisomy 21) has Down syndrome. An extra chromosome 13 or 18 also produces well known syndromes. A missing X chromosome causes Turner syndrome and an extra X in a male causes Klinefelter syndrome. Other abnormalities are caused by extra or missing pieces of chromosomes. Fragile X syndrome is a sex-linked disease, causing mental retardation in males.

In 1994, a mutation linked to early-onset familial breast and ovarian cancer was identified. BRCA1 is located on chromosome 17. Women with a mutated form of this gene have an increased risk of developing breast and ovarian cancer. A second related gene, BRCA2, was later discovered. Located on chromosome 13, it also carries increased risk of breast and ovarian cancer. Although both genes are rare in the general population, they are slightly more common in women of Ashkenazi Jewish descent.

Chromosome material may also be rearranged, such as the end of chromosome 1 moved to the end of chromosome 3. This is called a chromosomal translocation. If no material is added or deleted in the exchange, a person may not be affected. Such an exchange, however, can cause infertility or abnormalities if passed to children.

When a woman is found to have a mutation of one of these genes, the likelihood that she will get breast or ovarian cancer increases, but not to 100%. Other genetic and environmental factors may also influence the outcome. Testing for these genes is most valuable in families where a mutation has already been found. BRCA1 and BRCA2 are large genes; BRCA1 includes 100,000 bases. More than 120 mutations to this gene have been discovered, but a mutation could occur in any one of the bases. Studies show tests for these genes may miss 30% of existing mutations. The rate of missed mutations, the unknown disease likelihood in spite of a positive result, and the lack of a clear preventive response to a positive result, make the value of this test for the general population uncertain. PRENATAL AND POSTNATAL CHROMOSOME ANALYSIS. Chromosome analysis is usually performed on fetal

cells when a mother will be age 35 or older at the time of delivery, has experienced multiple miscarriages, or reports a family history of a genetic abnormality. Prenatal testing is done on the fetal cells from a chorionic villus sampling (from the baby’s developing placenta) at nine to 12 weeks of gestation or from the amniotic fluid (the fluid surrounding the baby) at 15-18 weeks of pregnancy. Cells from amniotic fluid usually must grow for seven to 10 days before they are ready to be analyzed. Chorionic villi cells have the potential to grow faster and can be analyzed sooner. Chromosome analysis using blood cells is performed for a child who is born with or later develops signs of mental retardation or physical malformation. In an older child, chromosome analysis may be requested to investigate developmental delays. 1060

Evaluation of a couple’s infertility or repeated miscarriages will include blood studies of both to check for a chromosome translocation. Many chromosome abnormalities are incompatible with life. Fetuses with these abnormalities often spontaneously abort during the first trimester. Cells from a fetus that died before birth can be studied to look for chromosome abnormalities that may have caused the death. CANCER DIAGNOSIS AND PROGNOSIS. Certain cancers, particularly leukemia and lymphoma, are associated with changes in chromosomes: extra or missing complete chromosomes, extra or missing portions of chromosomes, or exchanges of material (translocations) between chromosomes. Studies show that the locations of the chromosome breaks are at locations of tumor suppressor genes or oncogenes.

Chromosome analysis on cells from blood, bone marrow, or a solid tumor help to diagnose certain kinds of leukemia and lymphoma and often help predict how well a person will respond to treatment. After treatment has begun, periodic monitoring of these chromosome changes in the blood and bone marrow gives a physician information as to the effectiveness of the treatment. A well-known chromosome rearrangement is found in chronic myelogenous leukemia. This leukemia is associated with an exchange of material between chromosomes 9 and 22. The resulting smaller chromosome 22 is called the Philadelphia chromosome.

Preparation Most tests for genetic diseases of children and adults are done using blood. To collect the 5-10 mL of blood needed, a health care worker draws blood from a vein in the inner elbow region. Collection of the sample takes only a few minutes.

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Bone marrow is used for chromosome analysis in a person with leukemia or lymphoma. The person is given local anesthesia. Then the physician inserts a needle through the skin and into the bone (usually the hip bone). A sample (0.5 to 2.0 2 mL) of bone marrow is withdrawn. This procedure takes approximately 30 minutes.

KEY TERMS Autosomal disease—A disease caused by a gene located on chromosomes 1 through 22. Carrier—A person who has a disease-causing gene but does not show symptoms of that disease. Chromosome—Structures made up of DNA, on which genes are located. DNA (Deoxyribonucleic acid)—A long molecule made up of two strands of material coiled around each other in a unique double helix. DNA contains the blueprint for all of a person’s traits. Dominant gene—A gene, whose presence as a single copy, controls the expression of a trait. Enzyme—A protein produced in a cell.

Aftercare After blood collection, a person may feel discomfort or bruising at the puncture site or may become dizzy or faint. Pressure to the puncture site until the bleeding stops reduces bruising. Warm packs to the puncture site relieve discomfort. The chorionic villi sampling, amniocentesis and bone marrow procedures are all done under a physician’s supervision. A person to be tested is asked to rest after the procedure and is watched for weakness and signs of bleeding.

Complications Collection of amniotic fluid and chorionic villi share the risks of miscarriage, infection, and bleeding. The risks are higher for the chorionic villi sampling. Because of the potential risks for miscarriage, 0.5% following the amniocentesis and 1% following chorionic villi sampling procedure, both of these prenatal tests are offered to couples, but are not required. A woman should tell her physician immediately if she has cramping, bleeding, fluid loss, an increased temperature, or a change in the baby’s movement following either of these procedures. After bone marrow collection, the puncture site may become tender and a person’s temperature may rise. These are signs of a possible infection. Genetic testing involves other nonphysical risks. Many people fear the possible loss of privacy about personal health information. Results of genetic tests may be reported to insurance companies and affect a person’s insurability. Some people pay out-of-pocket for genetic tests to avoid this possibility. Laws have been proposed to deal with this problem. Other family members may be affected by the results of a person’s genetic test. Privacy of the person test-

Gene—A grouping of base pairs that give instruction for a specific trait. Karyotype—Visual comparison of chromosomes arranged side-by-side with their partner in ascending numerical order, from largest to smallest. Mutation—Any change in the sequence of DNA. Positive predictive value (PPV)—The probability that a person with a positive test result has, or will develop a disease or condition. Recessive gene—A gene that must be present in both copies of the gene pair to allow the expression of a trait. Sensitivity—The likelihood that a negative test means a person will not have the disease or a mutation. Sex-linked disorder—A disorder caused by a gene located on a sex chromosome, usually the X chromosome.

ed and the family members affected is a consideration when deciding to have a test and to share the results. A positive result carries a psychological burden, especially if the test indicates a person will develop a disease, such as Huntington’s chorea. The news that a person may be susceptible to a specific kind of cancer, while it may encourage positive preventive measures, may also negatively shadow many future decisions and activities. A genetic test result may also be inconclusive, meaning no definitive result can be given to the individual or family. This may cause an individual to feel more anxious and frustrated and experience psychological difficulties.

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Prenatal testing is done either on amniotic fluid or a chorionic villus sampling. To collect amniotic fluid, a physician performs a procedure called amniocentesis. An ultrasound is done to find the baby’s position and an area filled with amniotic fluid. The physician inserts a needle through the woman’s skin and the wall of her uterus and withdraws 5-10 mL of amniotic fluid. Placental tissue for a chorionic villus sampling is taken through the cervix. Each procedure takes approximately 30 minutes.

Genetic testing

Prior to undergoing genetic testing, genetic counselors should inform individuals to be tested about the likelihood that the test could miss a mutation or abnormality.

Results Normal results A normal result for chromosome analysis is 46, XX or 46, XY. This means there are 46 chromosomes (including two X chromosomes for a female or one X and one Y for a male) with no structural abnormalities. A normal result for a direct DNA mutation analysis or linkage study is the absence of gene mutations. There can be some benefits from genetic testing when an individual tested is not found to carry a genetic mutation. Those who learn with great certainty they are no longer at risk for a genetic disease may choose not to undergo prophylactic therapies and may feel less anxious and relieved. Abnormal results An abnormal chromosome analysis report will include the total number of chromosomes and will identify the abnormality found. Tests for gene mutations will report the mutations found. There are many ethical issues to consider with an abnormal prenatal test result. Many of the diseases tested for during a pregnancy cannot be treated or cured. In addition, some diseases tested for during pregnancy may have a late-onset of symptoms or have minimal effects on an affected individual. Before making decisions based on an abnormal test result, a person should meet again with a genetic counselor to fully understand the meaning of the results, learn what options are available based on the test result, and what are the risks and benefits of each of those options.

Resources BOOKS

Beaudet, Arthur L. “Genetics and disease.” In Harrison’s Principles of Internal Medicine, 14th ed. Edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 365-395. Gelehrter, Thomas D., Francis S. Collins, and David Ginsburg. Principles of Medical Genetics, 2nd ed. Baltimore: Williams and Wilkins, 1998. Grody, Wayne W., and Walter W. Noll. “Molecular Diagnosis of Genetic Diseases. In Clinical Diagnosis and Management by Laboratory Methods, 19th ed. Edited by John B. Henry. Philadelphia: Saunders, 1996, pp.1374-1389. Needleman, Robert D. “Fetal growth and development.” In Nelson Textbook of Pediatrics, 16th ed. Edited by Richard E. Behrman et al., Philadelphia: Saunders, 2000, pp.27-30. PERIODICALS

Brunger JW, Matthews AL, Smith RH, Robin NH. “Genetic testing and genetic counseling for deafness: the future is here.” Laryngoscope 111, no. 4 Pt 1 (2001): 715-718. D’Souza G, McCann CL, Hedrick J, Fairley C, Nagel HL, Kushner JD, Kessel R. “Tay-Sachs disease carrier screening: a 21-year experience.” Genetic Testing 4, no. 3 (2001): 257-263. Gilbert F. “Chromosome 10.” Genetic Testing 5, no.1 (2001): 69-82. Hakimian R. “Disclosure of Huntington’s disease to family members: The dilemma of known but unknowing parties.” Genetic Testing 4 no. 4 (2000): 359-364. Harris RA, Washington AE, Feeny D, Kuppermann M. “Decision analysis of prenatal testing for chromosomal disorders: what do the preferences of pregnant women tell us?” Genetic Testing 5, no. 1 (2001): 23-32. Wallerstein R, Starkman A, Jansen V. “Carrier screening for Gaucher disease in couples of mixed ethnicity.” Genetic Testing 5, no.1 (2001): 61-64. ORGANIZATIONS

Health care team roles A family physician or obstetrician often makes an initial recommendation for genetic counseling. A physician specially training in the technique will perform bone marrow aspiration, amniocentesis, or chorionic villus sampling. A nurse or phlebotomist usually collects blood samples. A cytogenetic technologist or clinical laboratory scientist/medical technologist will perform the DNA test depending upon the type of testing requested. A pathologist or geneticist processes and interprets findings of tests. Genetic counselors interpret test results and discuss options. Members of the clergy often assist people who have been tested to make decisions based on test results. 1062

American Board of Genetic Counseling, 9650 Rockville Pike, Bethesda, MD 20814-3998. (301) 571-1825. Fax: (301) 571-1895. . American College of Obstetricians and Gynecologists, 409 12th St., S.W., PO Box 96920, Washington, D.C. 200906920. . American Infertility Association, 666 Fifth Avenue, Suite 278, New York, NY 10103. (718) 621-5083. . [email protected]. American Public Health Association, 800 I Street, NW, Washington, DC 20001-3710. (202) 777-2742. Fax: (202) 777-2534. . [email protected].

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OTHER

American College of Physicians. . Lawrence Livermore Laboratory. . National Cancer Institute. and and . National Human Genome Research Institute. . National Institute of Health. and and . National Library of Medicine. and .

L. Fleming Fallon, Jr., MD, DrPH

Genital culture Definition Genital culture is the use of enrichment and selective media to isolate and identify organisms that cause genital infections such as urethritis, cervicitis, and salpingitis (pelvic inflammatory disease). The primary reason for a genital culture is to isolate Neisseria gonorrhoeae, the causative agent of gonorrhea. Other organisms that cause genital infections and can be cultured are Gardnerella vaginalis, Candida albicans, Neissria meningitidis, Haemophilus ducreyi, Mycoplasma hominis, and Ureaplasma urealyticum.

Purpose Genital culture is performed on persons who have signs of abnormal discharge or skin lesions in the genital area, or complaints such as itching or pain on urination. It is performed on persons who have evidence of other sexually transmitted diseases for which culture is not routinely performed because of the high prevalence of concomitant infection. For example, there are approximately three million new cases of Chlamydia trachomatis infection in the United States each year and many infected persons also will test positive for N. gonor-

rhoeae. Genital culture is also performed on any person who may be a victim of a sexual assault. Genital culture may be performed as a screening test on patients who have no symptoms, but are at increased risk for infection because of sexual behavior, since many sexually transmitted diseases can be carried silently. Also, pre and postnatal genital cultures for gonococcus and group B streptococcus are performed routinely on obstetrical patients. Although most genital infections are sexually transmitted, children or elderly persons are also at risk. In children, skin or wound infections may cause vaginal or urethral infections, especially when there has been physical injury to the genital area. Persons with deficient immune function and persons on prolonged antibiotic treatments are more susceptible to vaginal yeast infections (e.g., Canidida albicans or Torulopsis glabrata infection). Abscesses may form in the pelvic area and Bartholin’s gland following pregnancy, abortion, malignancy, obstetrical procedures, obstruction, and other conditions, and these often involve anaerobic bacteria.

Precautions Some infections, particularly gonorrhea, can be difficult to culture. In males it may be necessary to culture other sites that may be infected, such as the anus and mouth, if the patient has corresponding sexual habits which put him at risk. Up to 35% of males and 50% of females who are positive for gonococcal infection will test positive for Chlamydia trachomatis. This organism as well as Treponema pallidum, the causative agent of syphilis, Trichomonas vaginalis, human immunodeficiency virus, cytomegalovirus, herpes simplex 2, and human papilloma virus are not generally cultured. Because of their high prevalence, tests for these organisms (i.e., immunoassays, DNA probes, tests for antibodies) may also be performed. When performing genital cultures, universal precautions for prevention of transmission of bloodborne pathogens must be observed.

Description Neisseria gonorrhoeae causes approximately 650,000 genital infections in the United States each year. If untreated, gonorrhea can result in permanent damage to the reproductive organs (pelvic inflammatory disease), gonococcal arthritis, skin infection, and neonatal conjunctivitis (when transmitted via pregnancy). The female patient will be in the dorsal lithotomy position typical for Pap testing. A speculum is moistened with warm water (no lubricant should be used) and inserted into the vagina to secure good visualization of

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American Society for Reproductive Medicine. 1209 Montgomery Highway, Birmingham, AL 35216-2809. (205) 978-5000. .

Genital culture

KEY TERMS Group B streptococcus—A serotype of Streptococcus, Streptococcus agalactiae, which is beta hemolytic and can cause neonatal sepsis, pneumonia, or meningitis if present in the birth canal at the time of delivery especially when the delivery is difficult. Os—The opening of the cervix, which is the mouth of the uterus.

the cervix. Any excess cervical mucous should be removed with a cotton ball (held by ring forceps). A sterile cotton swab is inserted just inside the opening of the cervix (the os) and rotated gently for 30 seconds. Genital swabs are usually placed in transport media that contains charcoal to absorb toxins that inhibit the growth of gonococcus. Care should be taken not to touch the vaginal surfaces with the swab in order to avoid the transfer of normal vaginal flora. For culture, the sample is placed in Stuart’s or Amies transport medium with charcoal added and delivered to the laboratory at room temperature. For DNA probe testing (in which organisms are not cultured, but the presence or absence of their genetic material is confirmed) the swab is broken off at the top of the sterile tube provided, and the tube is capped and sent to the laboratory. For immediate viewing, a swab sample may be placed in normal saline. One drop can then be placed between a slide and coverslip, and viewed beneath the microscope. This is called a “wet prep.” A wet prep is useful for diagnosing yeast infection and trichomoniasis. Pelvic inflammatory disease samples and samples from genital lesions such as chancres are collected by aspiration. Plating for H. ducreyi should be done from the chancre aspirate and performed immediately because the organism is fastidious. In the male patient, a smaller sterile cotton swab is used to remove cells and any discharge from the last 2 cm of the urethra, and the swab is transported for culture or DNA probe testing as described for the female patient. If visible discharge is present on the surface of the penis, this should be swabbed, and it is unnecessary to enter the urethra. If prostate infection is suspected, urine culture should be performed. If infection of the prostate, epididymus or testes is suspected, seminal fluid should be cultured. All swabs or aspirates are plated on modified Thayer-Martin (MTM) agar or New York City (NYC) agar. These media are selective for the growth of N. gon1064

orrhoeae. MTM is chocolate agar (heated sheep blood agar) containing colistin to inhibit the growth of gram negative bacilli, nystatin, or anisomycin to inhibit yeast, vancomycin to inhibit growth of gram-positive bacteria, and trimethoprin to inhibit Proteus spp. NYC agar contains amphotericin B instead of nystatin and consists of clear proteose-peptone supplemented agar. In addition, the sample is plated on either 5% sheep blood agar or Columbia agar with 5% sheep blood and colistin and nalidixic acid (CNA) to isolate yeast and Gardnerella vaginalis. In addition, special selective and differential agar may be used to isolate Mycoplasma hominis and Ureaplasma urealyticum. Plates are incubated at 36°C in 5-10% carbon dioxide. MTM or NYC agar are examined for growth at 24 hours and if negative again at 48 hours. After 24 hours, any suspicious colonies are Gram-stained and tested for oxidase, which provides presumptive identification of Neisseria if positive. Further biochemical testing may be performed to differentiate N. gonorrhoeae from N. meningitides which is sometimes isolated from homosexual males. Isolated colonies should also be tested for penicillin resistance. Plates may be discarded at 48 hours if no growth is seen. Other plates are observed at 24 hours, and any suspecious colonies are isolated and tested biochemically to identify the organism. No growth or negative plates are held an additional 24 hours. Anaerobic cultures are performed on abscesses and by request. Pathogens other than N. gonorrhoeae are also tested for antibiotic susceptibility. Microscopic analysis should always be included with genital culture. Wet preparations can identify both yeast and Trichomonas vaginalis. A Gram stain of the swab material can identify gram-negative diplococci, which is presumptive evidence of gonococcal infection. In males, a positive finding on the Gram stain obviates the need for culture and the patient can begin antibiotic treatment. In females, the diplocicci must be located intracellularly in order to make a presumptive diagnosis of gonorrhea infection, and culture must be performed to confirm the diagnosis. The presence of clue cells, epithelial cells containing gram-negative or gram-variable coccobacilli, can signal the presence of Gardnerella vaginalis. In homosexual males engaging in anal intercourse, microscopic examination may reveal Giardia lamblia or Entamoeba histolytica which originated in the intestinal tract. For both male and female patients, urine tests for the DNA of Chlamydia trachomatis and Neisseria gonorrhoeae are available. These tests measure bacterial DNA that is amplified either by the ligase chain reaction (LCR) or the polymerase chain reaction (PCR). Both methods can detect the organisms within four hours, thus affording for more rapid treatment. However, the tests do not

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Preparation Male patients can improve the accuracy of test results by not urinating for one hour prior to testing. Females should avoid douching for at least 24 hours prior to testing. If one of the DNA tests is to be used, it may be preferable to collect the first urine sample of the day. Women should be informed that having cultures performed is no more uncomfortable than routine Pap testing. Men may experience some temporary discomfort. It is much preferable that these tests be done before any antibiotics are started, so that the growth of the causative agent is not suppressed.

Aftercare Patients should be instructed to have no sexual contacts until test results are back.

ior, and the opportunity should be used by staff for education to reduce risks in the future. Resources BOOKS

Fishbach, Frances Talaska. A Manual of Laboratory and Diagnostic Tests, 6th ed. Lippincott, Philadelphia, 2000. pp. 563-565. Malarky, Louise M. and Mary Ellen McMorrow. Nurses Manual of Laboratory Tests and Diagnostic Procedures. WB Saunders Co., Philadelphia, 2000. pp.177-179. Tierney, Lawrence M., Stephen J. McPhee and Maxine A. Papadakis. Current Medical Diagnosis and Treatment 2001. Lange Medical Books/McGraw-Hill, New York, 2001 p. 1309. OTHER

Centers for Disease Control. www.cdc.gov/nchstp/dstd/ disease-info.htm. National Library of Medicine. www.nlm.nih.gov/ medlineplus/ency/article/001345.htm.

Erika J. Norris

Complications The minor discomforts of genital testing are short lived, and no significant complications are common.

Genital herpes

Results A normal result would be no growth of pathologic organisms, or no evidence of infectious organisms on DNA probe or LCR assay. Any infection identified, or organisms seen, can be appropriately treated and the patient counseled regarding prevention, if the causative agent is transmitted sexually. Yeast infections and bacterial vaginosis do not generally represent sexually transmitted diseases (STDs), whereas gonorrhea, chlamydia, herpes, and trichomonas infections are classed as STDs.

Health care team roles Genital cultures are ordered by a physician and collected by a physician, nurse, or physician assistant. Culture, microscopic analysis, immunoassay, and DNA testing are performed by clinical laboratory scientists/medical technologists. Wet preparations may also be performed by the physician or physician assistant or nurse practitioner with appropriate training. Nursing staff have a very important task in educating the patient in what to expect, assisting with obtaining samples, and helping to explain test results to patients. Many patients undergoing genital testing are in need of counseling regarding the risks of careless sexual behav-

Definition Genital herpes (herpes genitalis) is a highly contagious sexually transmitted disease (STD) caused by a strain of the herpes simplex virus (HSV). Genital herpes invades the body through mucous membranes, also known as small breaks in the skin.

Description Genital herpes is characterized by pain, itching, and sores (i.e., blister-like lesions) in the genital areas of the body, including the male penis or scrotum, the female labia or vagina, or the urethra, anus, upper thighs, groin, or buttocks. Herpes simplex virus appears in two recognized forms: HSV type 1 and HSV type 2. Previously, it was believed that HSV type 1 only affected the upper body and the face, especially the mouth, appearing often as cold sores. HSV type 2 was believed to be the infecting organism in genital HSV infections. By 2001, it became known that either HSV type can cause infections in either area of the body (i.e., 15% of all genital herpes infections are caused by HSV type 1, and are believed to be the result of oral-to-genital contact). It is not spread by objects (e.g., toilet seat or doorknob), swimming pools, hot tubs, or through the air.

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detect any other genital tract pathogens that might be present in the patient.

Genital herpes

tal herpes include: early age at first sexual activity, multiple sexual partners, and other STDs. Most patients with genital herpes experience a prodrome (i.e., symptoms of oncoming disease) that includes pain, burning, itching, or tingling at the site where blisters will form. This prodromal stage may last anywhere from a few hours, to one to two days. The herpes infection prodrome can occur in both the primary infection and recurrent infections. The prodrome for recurrent infections may be intense, and cause severe burning or stabbing pain in the genital area, legs, or buttocks. Primary genital herpes Herpes simplex virus. (Photograph courtesy of the CDC.)

Herpes viruses are not new to the modern medicine. The name is derived from the Greek adjective, herpestes, which means “creeping,” and refers to the serpent-like pattern often formed by the water blisters (vesicles) of genital herpes. Other members of the herpes virus family share similar traits, also infecting human beings. These traits include varicella zoster virus, the source of both chicken pox and shingles. Epstein-Barr virus, another member of the herpes virus family, is the cause of mononucleosis. As of 2000, in the United States, there are 45 million adolescents and adults infected with HSV infection. Genital herpes is slightly more common in women, possibly because male-to-female transmission of the virus is more effective; it attacks one out of every four women. In contrast, one out of every five men contract genital herpes, and a greater percentage of black versus white males (i.e., 45.9% vs. 17.6%, respectively) become infected with the virus. According to the web site of the Centers for Disease Control, race and ethnicity in the United States are frequently associated with poverty, access to quality health care, whether health care is sought, illicit drug use, and life in communities with high incidences of STDs. Therefore, it is not surprising that HSV 2 infections are more prevalent among African-Americans (45.9%) than European-Americans (17.6%). Among teenagers, the incidence of genital herpes infections has risen steadily, at 30%, since 1970. That increase, five times higher than it was 20 years ago, is most dramatic among white teenagers in the 12–19. Young adults between the ages of 20 and 29 are now twice as likely to have HSV 2 as they were previously.

Causes and symptoms While anyone can be infected by the herpes virus, not everyone will have symptoms. Risk factors for geni1066

The first symptoms of herpes usually occur within two to seven days after contact with an infected person, but may take up to two weeks. Symptoms of the primary infection are usually more severe than those of recurrent infections. For up to 70% of patients, the primary infection presents with symptoms that affect the whole body (i.e., “constitutional symptoms”), including tiredness, headache, fever, chills, muscle aches, and loss of appetite. There may also be painful, swollen lymph nodes in the groin. These symptoms are greatest during the first three to four days of the infection and disappear within one week. Following the prodrome, herpes blisters form; they are similar in men and women. First, small red bumps appear. These bumps quickly become fluid-filled blisters. In dry areas, the blisters become filled with pus and take on a white-to-gray appearance, become covered with scabs, and heal within two to three weeks. In moist areas, the fluid-filled blisters burst, forming painful ulcers that drain before healing. New blisters may appear over a period of one week or more, and may join together to form very large ulcers. The pain is relieved within two weeks; the blisters and ulcers heal, without scarring, by the third to fourth week after the prodrome. Women may experience a very severe and painful primary infection. Herpes blisters first appear on the vagina’s entrance, labia majora (i.e., outer lips), and labia minora (i.e., inner lips). Blisters often appear on the clitoris, at the urinary opening, around the anal opening, and on the buttocks and thighs. In addition, women may get herpes blisters on the lips, breasts, and fingers, and in the eyes (due to spreading from contact with the hands). The vagina and cervix are almost always involved. This causes a watery discharge. Other symptoms that occur in women with primary infections are painful or difficult urination (83%), swelling of the urinary tube (85%), meningitis (36%), and throat infection (13%). Most women develop painful, swollen lymph nodes (i.e., lymphadenopathy) in the groin and pelvis. About one in ten

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In men, the herpes blisters usually form on the penis, but can also appear on the scrotum, thighs, and buttocks. Less than half of the men with primary herpes experience the “constitutional symptoms.” A significant percentage of men (30–40%) have a discharge from the urinary tube. Some develop lymphadenopathy in the groin and pelvis. Men, although with less frequency than women, may experience painful or difficult urination (44%), swelling of the urinary tube (27%), meningitis (13%), and throat infection (7%). Recurrent genital herpes One or more outbreaks of genital herpes per year occur in 60–90% of those infected with the herpes virus. About 40% of persons infected with herpes simplex virus type 2 will experience six or more outbreaks each year. Genital herpes recurrences are less severe than the primary infection; however, women still experience more severe symptoms and pain than men. Constitutional symptoms are not usually present. Blisters appear at the same sites during each outbreak. Usually, there are fewer blisters, less pain, and a shorter time span from symptom onset to healing than in the primary infection. One out of every four women experience painful or difficult urination during recurrent infection. Both men and women may develop lymphadenopathy. The immune system will naturally create antibodies to fight viruses; herpes viruses are no exception. Herpes viruses, however, share a survival characteristic that makes it very difficult for the immune system to actually eliminate these viruses from the body. Herpes viruses evade antibodies by traveling via nerve pathways and hiding in neurons (i.e., nerve cells). These small colonies of surviving viruses enter what is known as the latent, or dormant phase, and remain that way until reactivated. The mechanisms by which the herpes virus is reactivated are not completely understood. Reactivation, however, can cause further outbreaks of the infection. The latent phase of the herpes virus can last for days, months, or years. One of the ways that viruses differ from bacteria is in their reproductive ability. While bacteria reproduce independently, viruses require cells from their hosts to do so. When the herpes virus reactivates, it enters cells in its primary site of infection—in this case, the genital region—and causes the cells there to make more virus. Thousands of new herpes virus cells are released into the body’s system before each cell dies. This cell death and resulting tissue damage are the actual cause of the lesions that appear during an outbreak of genital herpes.

Reactivation of herpes viruses in human beings is specific to each individual, different in both triggers and severity. Evidence, however, supports the prediction that virtually all people infected with HSV type 2 will experience some form of recurrence; this averages to approximately four times per year. HSV type 1 infections are less likely to result in further symptomatic outbreaks, with an overall average recurrence rate of once per year. Rates of recurrence tend to diminish over time. Newborn babies who are infected with herpes virus experience a very severe, potentially fatal disease. This is called “neonatal herpes infection.” In the United States, one in every three women of childbearing age are infected with the herpes virus; only one in 2,000 newborns will be born infected. Newborns can be infected during passage through the birth canal or during the pregnancy, should the embryonic sac rupture early. Doctors will normally perform a cesarean section (cs) on women who go into labor with active genital herpes. All newborn infants should be checked for symptoms of neonatal herpes. Symptoms include skin lesions, listlessness, fever, and lack of appetite. Left untreated, it can cause damage to the infant’s brain and central nervous system or death. The reasons for the reactivation of herpes viruses is not yet completely understood, but research has identified some triggers that are either causative, or suspected of being causative, of recurrent outbreaks. Among these are: • prolonged exposure to ultraviolet light (i.e., sunburn), which often reactivates facial herpes infections • excessive friction or injury to genital areas • compromise of the strength of the body’s immune system, the result of herpes virus’ recurrence, and its accompanying symptoms of fatigue and illness • stress (This has also been considered a prime culprit in bringing about outbreaks. Through mid-2001, however, clinical research has not proved the a causal relationship between stress and reactivation. The investigators of one clinical study have shown a connection between decreased ability to cope with stress and recurrent infections.) • the presence of HIV (Human Immunodeficiency Virus) (Human Immunodeficieny Virus has demonstrated a weakening of the immune system, with a consequent increase in the strength and severity of genital herpes infections.) • the presence of either HSV type 1 or HSV type 2, or both, that are transmitted to others through direct bodily contact (This includes any sexual interaction [i.e.,

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women get a vaginal yeast infection as a complication of the primary herpes infection.

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• jock itch • zipper burn • hemorrhoids • acne • physical irritation from wearing tight jeans • physical irritation from sexual contact

Diagnosis Because genital herpes is so prevalent, it is diagnosed primarily by the presentation of symptoms. A diagnosis can often be made upon physical examination, and taking of a complete sexual history.

A close-up view of a penis with a blister (center of image) caused by the herpes simplex virus. (Photograph by Dr. P. Marazzi, Custom Medical Stock Photo. Reproduced by permission.)

vaginal, anal, or oral], kissing, or skin-to-skin contact. It is passed along with or without the presence of open sores or other prodromal symptoms. Notably, HSV infections are symptom free the majority of the time. For this reason, the virus is often transmitted by people infected with HSV who are not even aware that they are infected, or believe that lack of symptoms means that they are not contagious.) Interestingly, an August 2000 report in the New England Journal of Medicine stated that in a University of Washington study, the majority of people who tested positive for HSV 2 infections reported no symptoms whatsoever. Another group of researchers at the University of Washington has assembled a list of ailments about which the subjects complained; they did not know that they had genital herpes. These ailments included: For women: • hemorrhoids • physical irritation from sexual contact • heat rash • aching or itching during menses • allergy to condoms or spermicide • allergy to elastic in panty hose For men: 1068

Because a mild case of genital herpes may be overlooked during a routine physical examination, laboratory tests are very important. When possible, it is helpful to know the type of HSV with which a patient is infected. As noted previously, HSV type 2 is potentially lifethreatening to newborn infants. Viral culture is one of the most accurate and specific tests for identifying HSV type 1 or 2. As healing sores do not shed much virus, a sample from an open sore should be taken for viral culture. The doctor must determine the exact cause of the sores. The above-mentioned tests should be performed to confirm that the herpes virus is causing the genital sores. Other conditions that may produce genital sores are: • syphilis • chancroid • lymphogranuloma venereum • granuloma inguinale • herpes zoster • erythema multiform • inflammatory bowel disease • contact dermatitis • candidiasis • impetigo Because of this, a viral culture test should be performed to be absolutely certain that the sores are caused by the HSV. The results of serological tests (i.e., blood tests [either by finger-stick or blood draw] that reveal antibodies to HSV) are available within one day. They, too, are considered very accurate tests that can be performed whether open lesions are present or not. The disadvantage of this blood test is that it must be taken no earlier than 12 days post-infection; in a first infectious outbreak,

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Because most newborns who are infected with herpes virus are born to mothers with no symptoms of infection, it is important to check all newborn babies for symptoms. A culture of any skin sore should be taken to determine if it is caused by HSV. Babies should be checked for sores in their mouths and for signs of herpes infection in their eyes.

Treatment There is no cure for the herpes virus. There are, however, antiviral drugs available that have some effect in lessening the symptoms and decreasing the length of herpes outbreaks. There is evidence that some of these medications may also prevent future outbreaks. The antiviral drugs work by interfering with the replication of the viruses and are most effective when taken as early in the infection process as possible. For the best results, drug treatment should begin during the prodrome stage, before blisters are visible. Depending on the length of the outbreak, drug treatment could continue for up to 10 days. Acyclovir (Zovirax) is the drug of choice for herpes infection and can be given intravenously, taken by mouth (orally), or applied directly to sores as a topical ointment. Acyclovir has been in use for many years; only 5 out of 100 patients (5%) experience side effects. Side effects of acyclovir treatment include nausea, vomiting, itchy rash, and hives. Although acyclovir is the recommended drug for treating herpes infections, other drugs may be used. They include famciclovir (Famvir), valacyclovir (Valtrex), vidarabine (Vira-A), idoxuridine (Herplex Liquifilm, Stoxil), trifluorothymidine (Viroptic), and penciclovir (Denavir). Acyclovir is effective in reducing the severity of both the primary infection and recurrent outbreaks. When taken intravenously or orally, acyclovir reduces the healing time, virus shedding period, and duration of vesicles. The drug is taken three or five times daily depending on the dose for a period of 10 days. Recurrent herpes is treated with the same doses for a period of five days. Intravenous (IV) acyclovir is given to patients who require hospitalization because of severe primary infections or herpes complications, such as aseptic meningitis or sacral ganglionitis (i.e., inflammation of nerve bundles). Patients with frequent outbreaks (i.e., greater than six to eight per year) may benefit from long-term use of acyclovir, called “suppressive therapy.” Patients on suppressive therapy typically have longer periods between herpes outbreaks. The specific dosage used for suppres-

sion would need to be determined for each patient and should be reevaluated every few years. Alternatively, patients may use short-term suppressive therapy to lessen the chance of developing an active infection on special occasions, such as a wedding, or during holidays. There are several things that a patient may do to lessen the pain of genital sores. Wearing loose fitting clothing and cotton underwear is helpful. Removing clothing or wearing loose pajamas while at home may reduce pain, as may soaking in a tub of warm water and using a blow dryer on the “cool” setting to dry the infected area. Application of an ice pack on the affected area for 10 minutes, followed by five minutes without the ice pack, then repeating this procedure, may relieve pain. A zinc sulfate ointment may also help to heal the sores. Baking soda compresses may be soothing. Neonatal herpes Newborn babies with herpes virus infections are treated with acyclovir IV or vidarabine for 10 days. These drugs have greatly reduced neonatal deaths and increased the number of babies who appear normal at one year of age. Infected babies may be treated with longterm suppressive therapy. Alternative treatment An imbalance in the amino acids lysine and arginine is thought to be one contributing factor in herpes virus outbreaks. A ratio of lysine to arginine that is in balance (i.e., more lysine than arginine) appears to optimize the function of the immune system work. Thus, a diet that is rich in lysine may help prevent recurrences of genital herpes. Foods that contain high levels of lysine include most vegetables, legumes, fish, turkey, beef, lamb, cheese, and chicken. Patients may take 500 mg of lysine daily and increase to 1,000 mg three times a day during an outbreak. Intake of the amino acid arginine should be reduced. Foods rich in arginine that should be avoided are chocolate, peanuts, almonds, and other nuts and seeds. Since clinical experience indicates a connection between high stress and herpes outbreaks, some patients may respond well to stress-reduction and relaxation techniques. Acupressure and massage may relieve tiredness and stress. Meditation, yoga, tai chi, and hypnotherapy can also help relieve stress and promote relaxation. Some herbs, including echinacea (Echinacea spp.) and garlic (Allium sativum), are believed to strengthen the body’s defenses against viral infections. Red marine algae (family Dumontiaceae), both taken internally and applied topically, is thought to be effective in treating HSV type 1 and 2 infections. Other topical treatments may be helpful in inhibiting the growth of the herpes

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antibodies sometimes cannot be detected for three months.

Genital herpes

KEY TERMS Groin—The region of the body that lies between the abdomen and the thighs. Latent virus—A nonactive virus which is in a dormant state within a cell. Herpes virus is latent in cells of the nervous system.

time, condom use is recommended to prevent the spread of virus to uninfected partners. It is also important, however, to realize that condoms cannot stop the transmission of the herpes virus from body areas other than the sexual organs. Though research continues, there is no herpes vaccine proven effective in human beings.

Health care team roles

Prodrome—Symptoms which warn of the beginning of disease. The herpes prodrome consists of pain, burning, tingling, or itching at a site before blisters are visible.

As genital herpes infections and their consequences may dramatically vary among people, there is diverse and varied involvement of health care team members. These include:

Recurrence—The return of an active herpes infection following a period of latency.

• Primary care physicians, nurse practitioners, and alternative health care providers, all of whom will be involved in physical examinations of people complaining of symptoms. Genital herpes can be diagnosed and treated by the family doctor, dermatologist (i.e., a doctor who specialize in skin diseases), urologists (i.e., doctors who specialize in the urinary tract diseases of men and women and the genital organs of men), gynecologists (i.e., doctors who specialize in the diseases of women’s genital organs) and infectious disease specialists. Any of these may also pick up the presence of unknown genital herpes infections on routine examinations.

Lesion—A morbid, or diseased, change in tissue formation at a local site.

virus, in minimizing the damage it causes, or in helping the sores heal. Zinc sulfate ointment seems to help sores heal and to fight recurrence. Lithium succinate ointment may interfere with viral replication. An ointment made with glycyrrhizinic acid, a component of licorice (Glycyrrhiza glabra), seems to inactivate the virus. Topical applications of vitamin E or tea tree oil (Melaleuca spp.) help dry up herpes sores. Specific combinations of homeopathic remedies may also be helpful treatments for genital herpes.

Prognosis Although physically and emotionally painful, genital herpes is usually not a life-threatening disease. The primary infection can be severe and may require hospitalization for treatment. Complications of the primary infection may involve the cervix, urinary system, anal opening, and the nervous system. Persons who have a decreased ability to produce an immune response to infection (called “immunocompromised”) due to disease or medication are at risk for a very severe, possibly fatal, herpes infection. Even with antiviral treatment, neonatal herpes infections can be fatal or cause permanent nervous system damage.

Prevention The only way to prevent genital herpes is to avoid contact with infected persons. This is not an easy solution because many people aren’t aware that they are infected and can easily spread the virus to others. Avoid all sexual contact with an infected person during a herpes outbreak. Because the herpes virus can be spread at any 1070

• Physicians or nurse practitioners routinely do viral cultures. A sterile cotton swab is wiped over open sores and the sample used to infect human cells in culture. Cells killed by the herpes virus have a certain appearance under microscopic examination. The results of this test are available within two to ten days. Though it is considered quite accurate, there are estimates that up to 20% of viral culture tests give a false negative reading. Other areas that may be sampled, depending upon the disease symptoms in a particular patient, include the urinary tract, vagina, cervix, throat, eye tissues, and cerebrospinal fluid. Direct staining and microscopic examination of the lesion sample may also be used. • Finger-stick or blood-drawn laboratory tests are usually done by either nurses or laboratory technicians, but are sometimes carried out by physicians or nurse practitioners. • Obstetricians (i.e., physicians who deliver newborn babies), nurse midwives (i.e., nurses who deliver newborn babies) and obstetrical nurses (i.e., nurses who assist in the delivery of newborns and the care of mothers and infants after birth) will be involved in assuring that mothers infected with active genital herpes are provided a safe delivery (usually by cesarian section), and that newborns are thoroughly checked for signs and symptoms of the disease. As noted previously, many newborns are born infected with herpes virus to moth-

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“Some Facts About Genital Herpes.” Division of Sexually Transmitted Diseases Prevention, (August 7, 2000).

Joan M. Schonbeck

• Physicians, nurse practitioners, and alternative health practitioners will prescribe medications or herbs and diet to alleviate the symptoms of genital herpes. • Nurses will be involved in the day-to-day care, including the provision of comfort measures, such as the administration of analgesic medications, warm baths, and applying compresses and ointments to those seriously ill enough to require hospitalization or nursing home care. Many of these will be immune systemcompromised people, such as those who have AIDS.

Geriatric nutrition Definition Geriatric nutrition applies nutrition principles to delay effects of aging and disease, to aid in the management of the physical, psychological, and psychosocial changes commonly associated with growing old.

Patient education All health care providers will be involved in providing education about genital herpes. Because STDs are such a sensitive area of health care, it will be important for the health care provider to show understanding and sensitivity for health care consumers infected with HSV. Information and education, given without suggestion of judgment, can be among the most important care provided. It should emphasize that there is currently no cure for genital herpes, that the disease is extremely pervasive, and that precautions must be used during sexual contact in order to avoid infecting others. An important goal of patient education should be to make the patient aware that condoms are an excellent means of protection from HSV and pregnancy. The patients should also learn what laboratory tests will need to be done, and what medications, or treatments, can help alleviate symptoms. The diagnosis and treatment of this infectious disease should be covered by most insurance providers.

Purpose The number of people over 65 years of age jumped from 4% of the U.S. population in 1900 to 13% in 1990, and is expected to reach 20% in 2030, due primarily to advances in health care. “Elderly” was once defined as being age 65 or above, but the growing number of active and healthy older people has caused that definition to expand to “young old” (65 to 75), “old old” (75 to 85), and “oldest old” (85 and beyond). The over-85 age group is the one that is growing most rapidly. The cornerstone of geriatric nutrition is a well-balanced diet. This provides optimal nutrition to help delay the leading causes of death: heart disease, cancer, and stroke. In addition, ongoing research indicates that dietary habits, such as restricting one’s calorie intake and consuming antioxidants, may increase longevity.

Precautions Physiological changes

Resources BOOKS

Ebel, Charles. Managing Herpes: How to Live and Love With a Chronic STD. American Social Health Association, 1998. PERIODICALS

Wald, A., Zeh, J., Selke, S. “Reactivation of Genital Herpes Simplex Virus Type.” New England Journal of Medicine (August, 2000). OTHER

“Genital Herpes: A Brief Summary.” . JAMA Women’s Health Information Center. 1997. (8 April 1998).

With age comes many physical changes. Once the body reaches physiologic maturity, the rate of degenerative change exceeds the rate of cell regeneration. However, people age at different rates, so the elderly population is not a homogeneous group; there is great variability among individuals. The following are typical physiologic changes that can affect nutritional status: • Body composition changes as fat replaces muscle, in a process called sarcopenia. Research shows that exercise, particularly weight training, slows down this process. Because of the decrease in lean body mass, basal metabolic rate (BMR) declines about 5% per decade during adulthood. Total caloric needs drop, and lowered protein reserves slow the body’s ability to

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ers who had no symptoms of infection. Therefore, it is important to check all newborn babies for skin sores or lesions inside the mouth, and for signs of herpes infection in their eyes.

Geriatric nutrition

respond to injury or surgery. Body water decreases along with the decline in lean body mass. • Gastrointestinal (GI) changes include a reduction in digestion and absorption. Digestive hormones and enzymes decrease, the intestinal mucosa deteriorates, and the gastric emptying time increases. As a result, two conditions are more likely: pernicious anemia and constipation. Pernicious anemia may result because of hypochlorhydria, which decreases vitamin B12 absorption and affects approximately one third of older Americans. Constipation, despite considerable laxative use among older people, may result from slower GI motility, inadequate fluid intake, or physical inactivity. • Musculoskeletal changes occur. A progressive drop in bone mass starts when people are in their 30s or 40s; this accelerates for women during menopause, making the skeleton more vulnerable to fractures or osteoporosis. Adequate intake of calcium and vitamin D helps to retain bone. • Geriatric nutrition must take into account sensory and oral changes. Decreases in all the senses, particularly in the taste buds that affect perception of salty and sweet tastes, may affect appetite. Xerostomia, lack of salivation, affects more than 70% of the elderly. Also, denture wearers chew less efficiently than those with natural teeth. • Other organ changes may occur. Insulin secretion is decreased, which can lead to carbohydrate intolerance, and renal function deteriorates in the 40s for some people. • Cardiovascular changes may occur. Reduced sodium intakes become important, as blood pressure increases in women over age 80 (but, interestingly, it declines in older men). Serum cholesterol levels peak for men at age 60 but continue to rise in women until age 70. • Immunocompetence decreases with age. The lower immune function means less ability to fight infections and malignancies. Vitamin E, zinc, and some other supplements may increase immune function. Psychosocial changes A number of changes may occur in the aging person’s social and psychological status, potentially affecting appetite and nutrition status. These include: • Depression, the most common cause of unexplained weight loss in older adults, occurs in approximately 15% of adults over age 65, with a much higher incidence in those living in extended-care facilities. • Memory impairment caused by various types of dementia, Alzheimer’s disease, or other neurological 1072

diseases rises dramatically, with half of all persons over age 85 affected. Weight loss and improper nutrition are potential problems. • Alcohol abuse is often unreported, especially since approximately one third of alcoholics age 65 years or older begin drinking later in life. Excessive alcohol intake (over 15% of total calories) increases morbidity and mortality, and leads to both physical and psychosocial problems. • Social isolation becomes more common because of declining income, health problems, loss of spouse or friends, and assistance needs. All of these may affect appetite and possibly nutritional status.

Description Basic energy and nutrient needs Calorie requirements decrease with age, although individuals vary greatly depending on their activity level and health status. Diets that fall below 1,800 calories a day may be low in protein, calcium, iron, and vitamins, so should feature nutrient-dense foods. Protein needs of healthy older adults are the same as for other adults, with 0.8 to 1 gm of protein per kg of body weight recommended. Most older people without debilitating disease eat adequate protein, but those with infections or severe disease may become protein-malnourished due to increased protein requirements and poor appetites. Seniors do better eating more complex carbohydrates, which increase fiber, vitamins, and minerals, and help with insulin sensitivity. Lactase-treated milk or fermented dairy products are suggested if lactose intolerance develops. Because caloric needs drop and heart disease is so prevalent, reducing total dietary fat and especially the amount of saturated fats is advised. Mineral deficiencies are uncommon in older adults, and recommended amounts are the same or similar to those for younger adults. Iron-deficiency anemia related to nutrition is rare, and more likely due to blood loss. Of the vitamins, vitamin D intakes are often lower than recommended, especially among homebound or institutionalized people who lack sun exposure (the most accessible source of vitamin D). The antioxidant vitamins, vitamin E, carotenoids, and vitamin C, continue to receive attention because of their potential to improve immune function and ward off disease. Requirements for riboflavin, vitamins B6 and B12, and zinc are increased in the elderly. However, needs for vitamin A decrease. Dysphagia The incidence of dysphagia, or difficulty in swallowing, increases with age. Dysphagia results from con-

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Fluid balance Dehydration is the most common cause of fluid and electrolyte disturbances in older adults. Reduced thirst sensation and fluid intake, medications such as diuretics and laxatives, and increased fluid needs during illness contribute to dehydration. Adequate water-intake guidelines are 1 ml water/kcal energy consumed (for example, 1.8 L for an 1,800-calorie intake), or 25–30 ml/kg of weight for most individuals.

Preparation Assessment The following are used to assess nutritional needs: • A thorough medical history, physical examination, and dietary history can provide a general picture of the individual’s nutritional status. Lab values also provide valuable information. • Weight evaluation may be recommended. Normal weight status guidelines include a BMI of 21 to 27 (BMI = weight in pounds x 704.5/ht(in) squared) or Ideal Body Weight +/-10%. Guidelines for significant weight loss include 10% weight loss in six months, 5% in one month, or 2% in one week. • Dehydration evaluation involves physical assessment (poor skin turgor, dark urine, flushed skin), and assessment of recent fluid and food intake. High laboratory levels of blood urea nitrogen (BUN), albumin, serum sodium, and serum osmolality can indicate dehydration.

Skin integrity Skin breakdown is a common problem, particularly in bedridden or immunologically impaired people. The most common skin breakdown is the pressure ulcer, which occurs in 4% to 30% of hospitalized patients and 2% to 23% of residents of skilled-care nursing homes. Pressure ulcers are graded or staged to classify the degree of tissue damage. Those with more serious Stage II to Stage IV ulcers have increased nutritional needs. Protein needs increase to 1–1.5 gm protein/kg, caloric needs increase to 30–35 kcal/kg, and 25–35 cc fluid/kg is recommended. Malnutrition While most elderly people maintain adequate nutritional status, institutionalized and hospitalized older adults are at higher risk for malnutrition than individuals who are living independently. Cancer cachexia, the weak, emaciated condition resulting from cancer, accounts for about half of malnutrition cases in institutionalized adults. Two common forms of malnutrition are proteincalorie malnutrition, in which the person appears illnourished; and protein malnutrition, in which an overweight person may have depleted protein stores. Nutrition support may involve higher protein and calorie amounts, nutritional supplements such as Ensure, or enteral tube feedings that provide nutrient solutions into the GI tract.

Aftercare Laboratory values, particularly albumin for protein status and sodium and BUN for hydration status, should continue to be assessed after treatment. Tube feedings need to be continually monitored to prevent aspiration.

Results Normal laboratory values in the elderly • Protein status: albumin 4 to 6 gm/dL; prelabumin: 19 to 43 mg/dL. • Anemia status: hemoglobin: 12 to 18 gm/dL; hematocrit 33% to 49% (can be slightly lower in the elderly); MCV: 80 to 95 µm3; MCHC: 27 to 31 pg; B12: 100 to 1,300 pg/mL. • Hydration: serum sodium: 135 to 147mEq/L; serum osmolality: 285 to 295 mOsm/kg; BUN 10 to 20 mg/dL (can be slightly higher in elderly).

Health care team roles • Registered dietitians play the primary role in assessing and coordinating geriatric nutrition care. • Nursing staff also assesses patients, and physicians oversee total care and ordering of lab tests. • A speech-language therapist typically conducts a swallowing assessment and coordinates care for dysphagia.

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ditions such as stroke, Alzheimer’s or Parkinson’s disease, multiple sclerosis, or physiological changes such as loss of teeth or poorly fitting dentures. Inadequate dietary intake as a result of dysphagia can lead to weight loss, dehydration, and nutritional deficiencies. The American Dietetic Association has developed Level 1 through Level 4 dysphagia diets, which provide varying textures and liquids based on the severity of the condition.

Gestational diabetes

Description

KEY TERMS Hypochlorhydria—A deficiency of hydrochloric acid in the gastric juice. Osteoporosis—A loss of bone density leading to fractures because the skeleton is unable to sustain ordinary stresses. Pressure ulcer—Any lesion caused by unrelieved pressure resulting in damage to the underlying tissue. Sarcopenia—A deficiency of muscle or flesh that occurs in the elderly.

Resources BOOKS

Litchford, M. Clinical Geriatric Nutrition. Mary Litchford/Nutrition Dimension, Inc. 1999. Mahan, L. K., and S. Escot-Stump. Krause’s Food, Nutrition, & Diet Therapy, pp. 287-308. Philadelphia: W. B. Saunders Company, 1996. ORGANIZATIONS

American Dietetics Association. Nutrition, Aging and the Continuum of Care: Position of ADA. . OTHER

Washlien, C. Nutrition and the Elderly Course, U. of HawaiiManoa, School of Public Health, 2000.

Linda Richards, R.D., C.H.E.S.

Glucose is a form of sugar that is present in many foods, including sweets, potatoes, pasta, and breads. The body uses glucose to provide energy. It is stored in the liver, muscles, and fatty tissue. The pancreas produces a hormone (a chemical produced in one part of the body that travels to another part of the body in order to exert its effect) called insulin. Insulin is required to allow glucose to enter the liver, muscles, and fatty tissues, thus reducing the amount of glucose in the blood. In persons with diabetes, blood levels of glucose remain abnormally high. The inability of the pancreas to produce enough insulin is the cause of these high levels of glucose. In gestational diabetes, the pancreas is not at fault. The problem is in the placenta. During pregnancy, the placenta provides the baby with nourishment. It also produces a number of hormones that interfere with the body’s usual response to insulin. This condition is referred to as “insulin resistance.” The development of insulin resistance is primarily caused by a substance called lactogen, which is produced during pregnancy, and from increased blood levels of the hormones progesterone and estrogen. The blood levels of these substances tend to peak in the second and third trimester of the pregnancy, which is when GDM is most likely to occur. Most pregnant women do not develop GDM because the pancreas works to produce extra quantities of insulin to compensate for insulin resistance. However, when a woman’s pancreas cannot produce enough extra insulin, blood levels of glucose remain abnormally elevated, and the woman is considered to have GDM. It is believed that some women with borderline blood sugar problems before pregnancy are more likely to have long-term blood sugar regulation problems after developing GDM. As of January 2001, about 200,000, or 7%, of pregnant women in the United States develop GDM every year. Women at risk for GDM include those who: • are overweight

Gestational diabetes

• have immediate family members with a history of Type II diabetes

Definition Gestational diabetes mellitus (GDM) is a condition that occurs during pregnancy. Like other forms of diabetes, GDM involves a defect in the way the body processes and uses sugars (glucose) in the diet. Gestational diabetes, however, has a number of characteristics that are different from other forms of diabetes. This form of diabetes does not include women who are diabetic before they become pregnant. Gestational diabetes usually occurs in the second and third trimesters of the pregnancy. 1074

• have previously given birth to a large (over 9 lbs [4 kg]) baby • have previously had a baby who was stillborn, or born with a birth defect • have an excess amount of amniotic fluid (the cushioning fluid within the uterus that surrounds the developing fetus) • are over 25 years of age • belong to an ethnic group proved to experience higher rates of GDM. (In the United States, these groups

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Gestational diabetes

include Hispanic-Americans, American Indians, and African-Americans, as well as individuals from Asia, India, and the Pacific Islands.) • have had GDM during a previous pregnancy • have persistent evidence of excess glucose in the urine • have a history of chronic drug abuse involving agents such as corticosteroids

Causes and symptoms Most women with GDM have no recognizable symptoms. However, leaving GDM undiagnosed and untreated is dangerous to the developing fetus. Left untreated, a woman with diabetes will have consistently high blood sugar. This sugar will cross the placenta and the unborn baby’s pancreas will respond to this high level of sugar by constantly producing large amounts of insulin. The insulin will allow the cells of the fetus to take in glucose, where it will be converted to fat and stored. A fetus that has been exposed to consistently high levels of sugar may be abnormally large. Such a baby may grow so large that he or she cannot be born through the vagina, but will instead need to be born through a surgical procedure (cesarean section). Furthermore, when the baby is born, the baby will still have an abnormally large amount of insulin circulating in the blood. After birth, when the mother and baby are no longer connected via the placenta and umbilical cord, the baby will no longer be receiving the mother’s high level of sugar. The baby’s high level of insulin, however, will very quickly use up the glucose circulating in the its bloodstream, predisposing the baby to a dangerously low level of blood glucose (i.e., a condition called hypoglycemia).

Diagnosis Since GDM most often exists with no symptoms detectable by the patient, and since its existence puts the developing baby at considerable risk, screening for the disorder is a routine part of prenatal care. This screening is usually done between the 24th and 28th week of pregnancy. By this point in the pregnancy, the placental hormones have reached a sufficient level to cause insulin resistance. Screening for GDM involves the pregnant woman drinking a special solution that contains exactly 50 grams of glucose. An hour later, the woman’s blood is drawn and tested for its glucose level. A level less than 130-140 mg/dl is considered normal. When the screening glucose level is over the safe level, a special three-hour glucose tolerance test is performed. This involves following a special diet for three

A woman with gestational diabetes injects herself with insulin daily to treat her condition. (Photograph by Mark Clarke. Science Source/Photo Researchers. Reproduced by permission.)

days prior to the test. This diet is designed to contain at least 150 grams of carbohydrate each day. Just before the test, the patient is instructed to eat and drink nothing (except water) for 8–14 hours. A blood sample is then tested to determine the fasting glucose level. The patient then drinks a special solution containing exactly 100 grams of glucose, and her blood is tested every hour for the next three hours. If two or more of these levels are elevated over normal, the patient is considered to have GDM.

Treatment Treatment for GDM will depend on the severity of the diabetes. Mild forms can be treated with diet (i.e., decreasing the intake of sugars and fats). Many women are put on strict, detailed diets, and are asked to stay within a certain range of calorie intake. Exercise is sometimes used to keep blood sugar levels lower. Patients are often asked to regularly measure their blood sugar. This

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KEY TERMS Corticosteroids—Hormonal steroid substances that originate in the cortex of the adrenal gland. Estrogen—A female sex hormone responsible for secondary sexual characteristics and cyclic changes in women. Glucose—A form of sugar. The final product of the breakdown of carbohydrates (starches). Insulin—A hormone produced by the pancreas that is central to the processing of sugars and carbohydrates in the diet. Ketoacidosis—Excessive acidic condition in the body caused by excess production of ketone bodies. Lactogen—A substance that stimulates the production of milk in female animals. Placenta—An organ that is attached to the inside wall of the mother’s uterus and to the fetus via the umbilical cord. The placenta allows oxygen and nutrients from the mother’s bloodstream to pass into the unborn baby. Progesterone—A hormone that is responsible for the changes that occur in the second half of the menstrual cycle.

is done by poking a finger with a needle called a lancet, putting a drop of blood on a special type of paper, and feeding the paper into a meter that analyzes and reads the blood sugar level. When diet and exercise do not keep blood glucose levels within an acceptable range, a patient may need to take regular shots of insulin. Many babies born to women with GDM are large enough to cause more difficult deliveries, and they may require the use of cesarean section. Once the baby is born, it is important to carefully monitor its blood glucose levels. These levels may drop sharply and dangerously once the baby is no longer receiving large quantities of sugar from the mother. When this occurs, it is easily resolved by giving the baby glucose.

Prognosis Prognosis for women with GDM, and their babies, is generally good. Mothers who develop GDM need to be evaluated for glucose intolerance six to eight weeks after the birth of the baby. This evaluation usually involves a two-hour oral glucose tolerance test with 75 grams of 1076

glucose, although follow-up methods may vary. Almost all such women stop being diabetic after the baby’s birth. However, clinicians have also demonstrated that nearly 50% of these women will develop a permanent form of diabetes within 15 years. A woman who has had GDM during one pregnancy has about a 66% chance of having it again during any subsequent pregnancies. In addition, women with GDM are at increased risk for developing complications, such as infections, temporary low blood sugar, high blood pressure, and ketoacidosis.

Health care team roles Women with GDM will likely be evaluated and treated by a variety of personnel in the allied health field. The obstetric nurse, physician, or nurse midwife will gather a detailed medical history, which may provide information suggesting the patient is at increased risk for developing GDM. Laboratory technicians play an important role in the diagnosis of GDM by testing urine and blood for excessive glucose levels. An amniocentesis conducted by an imaging technician is often performed in women with GDM because of the potential abnormal growth changes in the fetus. Most patients with GDM can manage their blood sugar levels through dietary changes. A nutritional therapist plays a critical role in planning a regimen for these women. An exercise therapist can also play a significant role in the prevention and ongoing treatment of women with GDM. Exercise can help prevent excessive weight gain by the mother, which can reduce the severity of the diabetes. In addition, exercise tends to normalize blood glucose levels. If the patient requires insulin, then the nurse or physician will generally instruct the patient on how to administer the insulin. The nurse will also likely advise on how to perform blood glucose monitoring. The pharmacist can play a role in the education of the patient in this matter as well.

Prevention There is no known way to actually prevent GDM, particularly since this condition is due to the effects of normal hormones of pregnancy. However, the effects of insulin resistance can be best handled through careful attention to diet, avoiding becoming overweight throughout life, and participating in a reasonable exercise program. Resources BOOKS

Ferris, Thomas F. “Gestational Diabetes.” In Harrison’s Principles of Internal Medicine, Ed. Anthony S. Fauci, et al. New York: McGraw-Hill, 1998.

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those 1,259 between ages 13 and 15, 80% had some form of gingivitis, while 95% had gingivitis at age 60. Males were more frequently affected than females, with the overall average being 88% and 80%, respectively.

PERIODICALS

American Diabetes Association. “Gestational Diabetes Mellitus.” Diabetes Care 24, no. 1 (January 2001): S77. Tolstoi, Linda G. “Gestational Diabetes Mellitus: Etiology and Management.” Nutrition Today (September 1999). Wang, Jennifer M. “Glyburide Appears Safe for Gestational Diabetes.” Family Practice News 31, no.4 (February 15, 2001): 33+. ORGANIZATIONS

American Diabetes Association, 1660 Duke Street, Alexandria, VA 22314. (800) DIABETES (800) 3422383. .

Mark A. Mitchell

Causes and symptoms The etiology of gingivitis is especially varied and has been divided into local and systemic factors. Local factors • microorganisms • food impaction • faulty or irritating restorative orthodontic appliances • breathing through the mouth, rather than the nose • tooth malposition • chemical or drug application

GIFT see Fertility treatments

Gingivitis Definition Gingivitis is a disorder involving inflammation of the gingiva (gum tissue). It is sometimes called gum disease.

Description Periodontal disease is a worldwide problem. This mildest form of periodontal disease, gingivitis, is inflammation strictly limited to the gingiva and does not manifest changes in the underlying bone. When bony changes become evident, the condition is termed periodontitis. There is commonly little or no discomfort with gingivitis. The only people who escape gingivitis are very young infants; otherwise, it affects all age groups and people of all ethnic and racial backgrounds. A bacterial infection of the gums, it causes the gum tissues to turn red and swollen. Mild gingivitis causes little pain, and may be overlooked by the dentist; however, if left unchecked, it can turn into severe gingivitis. Many people experience varying degrees of gingivitis throughout their lives, but overlook it. It commonly develops during puberty or in early adulthood, and may persist or recur frequently. In studies cited by the American Academy of Periodontology (AAP) in Boston, Massachusetts, 1,259 patients between the ages of 13 and 65 were studied. Of

Microorganisms are the bacteria found in plaque. The bacteria that destroy living tissue release many destructive enzymes. Specific microorganisms sometimes cause inflammatory reactions in the gingiva. Streptococcal and Staphylococcal are the bacteria known to destroy tissue and cause inflammation. Food impaction, or general oral neglect, is the most common cause of gingivitis. The food impacts around the teeth and accumulation of debris on the teeth causes irritation of the gingiva by the toxins in the plaque. The byproducts of the toxins cause swelling of the tissue and redness to occur. Faulty or irritating restoration, or appliances, may act as irritants to the gum tissue and thus induce gingivitis. Overhanging margins on dental fillings may directly irritate the gingiva and cause food to become impacted; this further adds to making the gum tissue even more tender. When prosthetic or orthodontic appliances encroach on the gingival tissues, gingivitis may occur—the result of the pressure and the trapping of food and bacteria. The tissue may become inflamed, redden, and become painful to the touch. Mouth breathing (not breathing through the nose) causes drying of the oral mucous membrane and irritates the gum tissue, causing inflammation and hyperplasia of the tissue. Tooth malposition results in repeated abnormal forces during the eating and chewing of food. Calculus may be deposited on the surface of the tooth that has no force to aid in keeping it clean. Bacteria may begin to attack the tissue around the tooth, resulting in a combination of inflammation and gum recession.

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Goldman, Lee et al., ed. Cecil Textbook of Medicine. Philadelphia: W.B. Saunders, 2000. Tierney, Lawrence M. et al., ed. Current Medical Diagnosis & Treatment 2001. New York: Lange, 2001.

Gingivitis

KEY TERMS Calculus—A hard deposit that forms on the teeth, also known as hardened plaque and tartar. Edematous—An abnormal accumulation of serous fluid in the tissues. Gingiva—The gum tissue. Gum recession—The gum tissue backing away from the crown of tooth towards the root. Hyperemia—Swelling of the gum tissue. Local—Pertaining to or being in one particular place. Systemic—Pertaining to, or affecting the whole body.

Chemical or drug application may cause many gum tissue anomalies. A number of drugs are at least potentially capable of inducing gingivitis. Over-the-counter (OTC) drugs can be harmful to the gum tissue and act as an acid burn if used. Silver nitrate and general aspirin have acidic affects on the gum tissue, causing redness and tenderness to the touch. Dilantin sodium produces swelling of the gum tissue due to the chemicals in the drug. Systemic factors • nutritional disturbances • pregnancy • diabetes and other conditions that cause endocrine dysfunction Nutritional disturbances can create imbalances in the body system that effect changes in the gum tissue. Insufficient vitamin C may cause redness and swelling, along with tenderness. The inadequate intake, absorption, and utilization of some other vitamins, minerals, and food can affect the gum tissue, causing swelling and redness. Pregnancy gingivitis refers to the changes the gingiva undergoes during pregnancy. The clinical appearance of the gingiva in pregnant women may vary—from no change to a smooth, shiny, deeply reddened, marginal gingival hyperemia (swelling of the gum tissue) of the papilla on the upper roof of the mouth. Gingivitis commonly appears at the end of the first trimester of pregnancy, and may remit or even completely disappear at the termination of the pregnancy. 1078

Diabetes mellitus is also associated with severe periodontal disease. Uncontrolled diabetes can cause a metabolic change in the gum tissue and decrease an individual’s resistance to infection. Endocrine dysfunctions during puberty may lead to changes in the gum tissue (puberty gingivitis). The gingiva appears hyperemic (having an excess of blood) and edematous (swollen). Most studies have revealed that the main cause of these changes in the gingiva is caused by breathing through the mouth.

Diagnosis A patient may have gingivitis and periodontitis in different parts of the mouth at the same time. A general dentist can examine the patient and look for calculus deposits on the teeth and under the gum line. A dental explorer or a cleaning instrument will then be used by the dentist to probe the gum tissue or to check for plaque buildup. Commonly, the practitioner will ask the patient if the gums bleed while flossing and brushing. The dentist needs to be made aware of any medications being taken that might be a causative factor in the gingivitis. Information provided by the patient may lead to a gingivitis diagnosis.

Treatment The goal of treating gingivitis is for reduction of the gingival inflammation. The general dentist, or registered dental hygienist (RDH) commonly cleans the teeth. This may involve the use of various instruments or devices to loosen and remove deposits from the teeth (scaling). Gingivitis is reversible with professional treatment and good home oral hygiene care. Changing toothbrushes every three months commonly improves dental hygiene in eliminating the bacteria in the mouth. Increased intake of vitamin C may aid in the development of healthy gum tissue. It is strongly recommended that strict oral hygiene be maintained for one’s lifetime, or gingivitis will probably recur.

Prognosis The prognosis for gingivitis is excellent. Once a program of good dental hygiene, such as proper toothbrushing and frequent prophylaxis (cleaning) is implemented, the symptoms of gingivitis will begin to disappear; this can happen in as little as one week. If there is poor response to good local therapy, a search should be made for systemic factors, which might be complicating the case.

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Health care team roles An RDH is usually the first person seen by the patient when a cleaning is scheduled. The RDH role is to inform the patient of the condition of the gum tissues and consult with the general dentist about the treatment plan. After evaluating the case, ways to improve oral hygiene or to identify the irritant causing the gingivitis—such as a popcorn kernel, seed, or tartar buildup—will be suggested. Removal will then by done by the dentist. Proper brushing and flossing is usually demonstrated by the RDH. This will aid in the maintenance of oral hygiene. The front desk receptionist may be responsible for keeping track of the recall records and following up with patients, by phone, who need appointment every six months.

Prevention Prevention of gingivitis is simple and easy. Proper brushing techniques and proper flossing to remove any irritants or bacteria helps to stop gingivitis from growing. Regular dental checkups and cleanings will aid in reducing the risk of gingivitis. For people who are prone to gingivitis, it may be recommended that they brush and floss after every meal, and at bedtime. Electric toothbrushes may be recommended for patients who have problems with strength or dexterity of their hands. Special appliances or tools, such as toothpicks, special toothbrushes, and water irrigation devices may be recommended for patients who are particularly prone to plaque deposits. These supplements do not replace brushing and flossing, but are enhancements in the prevention of gingivitis. Resources ORGANIZATIONS

Adam.com Health and Medical Association Online. adam.com. 90 Tehama Street, San Francisco, CA 94105 (415) 541-9164. . American Academy of Periodontology, 4157 Mountain Road, PBN 249 Pasadena, MD 21122, (410) 437-3749. . American Dental Association, 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-2500. . InteliHealth Dental. InteliHealth Inc. 960C Harvest Drive P.O. Box 1097, Blue Bell, PA 19422(215) 775-5155. .

OTHER

ADA News Release. Silent Dental Disease is Number One Concern Among Dentists. July 1999. “Gingivitis.” Adam.com Health Issues. . “Gingivitis.” InteliHealth Dental. University of Pennsylvania School of Dental Medicine. January 2001.

Cindy F. Ovard, R.D.A

Glasses see Eye glasses

Glaucoma Definition Glaucoma is a condition where the optic nerve is subject to damage—usually, but not always, because of excessively high intraocular pressure (pressure within the eye, also called IOP). If untreated, the optic nerve damage results in progressive, permanent vision loss, starting with unnoticeable blind spots in the field of vision, progressing to tunnel vision, and then to blindness.

Description More than 2 million people in the United States have glaucoma, and 80,000 of them are legally blind as a result. It is the leading cause of preventable blindness in the United States and the most frequent cause of blindness in African-Americans, whose glaucoma risk is three times higher than the rest of the population. The risk of glaucoma increases with age, but it can strike any age group, even newborns and fetuses. Glaucoma is a class of diseases. There are at least 20 different forms that can be divided into two categories: open-angle glaucoma and narrow-angle glaucoma. To understand glaucoma, it is useful to understand eye structure. The eyes are spherical. A tough, non-leaky protective sheath (the sclera) covers the eye with the exception of the clear cornea at the front and the optic nerve at the back. Light comes into the eye through the cornea, then passes through the lens, which focuses it onto the retina (the innermost surface at the back of the eye). The rods and cones of the retina transform the light energy into electrical messages, which are transmitted to the brain by the optic nerve. The iris is located between the dome-shaped cornea and the lens. It controls the amount of light that enters the

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Regular dental cleanings and exams are recommended at least every six to twelve months.

Glaucoma

One rare form of open-angle glaucoma is different. People with normal-tension glaucoma have optic nerve damage in the presence of normal IOP. As of 2001, the mechanism of this disease is unknown. Glaucoma is also a secondary condition of over 60 widely diverse diseases and can result from injury as well.

Causes and symptoms

A close-up view of an inflamed eye in acute glaucoma, with an irregularly enlarged pupil. (Custom Medical Stock Photo. Reproduced by permission.)

eye by opening and closing the pupil. The iris, cornea, and lens are bathed in a liquid called the aqueous humor, which is similar to plasma. This liquid is continually produced by the nearby ciliary body and moved out of the eye into the bloodstream by a system of drainage canals (the trabecular meshwork). The drainage area is located in front of the iris, in the angle formed between the iris and the cornea. Glaucoma occurs if the aqueous humor is not removed rapidly enough or if it is made too rapidly, causing pressure to build up. This high pressure distorts the shape of the optic nerve and destroys nerve cells. The destruction of nerve cells results in blind spots—spots where the image from the retina is not transmitted to the brain. Open-angle glaucoma accounts for over 90% of all cases. It is called “open-angle” because the angle between the iris and the cornea is open, allowing drainage of the aqueous humor. It is usually chronic and progresses slowly. In narrow-angle glaucoma, the angle where aqueous fluid drainage occurs is narrower than normal, thus causing the fluid to drain more slowly and increasing the risk that the flow may be blocked. When the drainage area is blocked, a closed-angle glaucoma attack results. This can occur, for example, if the iris and lens suddenly adhere to each other and the iris is pushed forward. In patients with very narrow angles, this can occur when the eyes dilate (e.g., when entering a dark room or when taking certain medications). 1080

The cause of vision loss in all forms of glaucoma is optic nerve damage. There are many underlying causes and forms of glaucoma. Most causes are not known, but it is evident that different processes are involved, and a malfunction in any one of them could cause glaucoma. For example, eye trauma may result in the angle becoming blocked, or, as a person ages, the lens may become larger and push the iris forward. The cause of optic nerve damage in normal-tension glaucoma is also unknown, but there is speculation that the optic nerves of these patients are susceptible to damage at lower pressures than what is usually considered to be abnormally high. It is probable that most glaucoma is inherited. At least 10 defective genes that cause glaucoma have been identified. Initially, chronic open-angle glaucoma has no noticeable symptoms. The pressure build-up is gradual and there is no discomfort. Moreover, the vision loss is gradual and one eye fills-in the image where its partner has a blind spot. However, left untreated, vision loss becomes evident, and the condition can be painful. Acute closed-angle glaucoma is obvious from the beginning of an attack. The symptoms are blurred vision, severe pain, sensitivity to light, nausea, and halos around lights. The normally clear cornea may be hazy. This is an ocular emergency and needs to be treated immediately. Similarly, congenital glaucoma is evident at birth. Symptoms include bulging eyes, cloudy corneas, excessive tearing, and sensitivity to light.

Diagnosis The initial glaucoma diagnosis is made through an eye examination by an optometrist (O.D.) or ophthalmologist (M.D.). The examination begins with an ophthalmic assistant, technician, or scribe gathering patient information, including any family history of glaucoma. Then the ophthalmic assistant takes a reading of the patient’s intraocular pressure (IOP). IOP is measured with an instrument called a tonometer, using a technique called applanation tonometry. The test is performed after anesthetic drops are administered to the eye. The anesthetic allows the examiner to touch the patient’s eyeball without causing discomfort for the patient. Another type

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Next, an O.D., M.D., or skilled ophthalmic assistant uses an ophthalmoscope (a hand-held instrument with a light source) to examine the optic nerve, retina, and back of the eye. Other types of lenses may also be used to examine the back of the eye. A slit lamp (biomicroscope) allows the physician or assistant examine the cornea, iris, and lens. Visual field tests (perimetry), performed by an O.D., M.D., or ophthalmic assistant, can detect blind spots in a patient’s field of vision before the patient is aware of them. Certain defects may indicate glaucoma. Another test, gonioscopy, is used to distinguish between narrow-angle and open-angle glaucoma. A gonioscopy lens, which is a hand-held contact lens with a mirror, allows visualization of the angle between the iris and the cornea. Physicians may also perform a nerve fiber layer assessment which can show early damage to the eye. Fundus photography or stereoscopic photography through a dilated pupil may also be performed by an O.D., M.D., or ophthalmic assistant to document the appearance of the optic nerve so that changes may be detected on subsequent examinations. Blood pressure also is monitored, as some prescribed treatments may raise pressure and heart rate. Intraocular pressure can vary throughout the day. For that reason, patients should schedule several return visits to measure the IOP at different times of day. This yields the most accurate diagnosis.

vascular, pulmonary, and behavioral symptoms. Each medication lowers IOP by a different amount, and a combination of medications may be necessary. To ensure that IOP is lowered sufficiently, it is important that patients take their medications and be monitored regularly. IOP should be measured three to four times per year. Normal-tension glaucoma is treated by reducing IOP to less-than-normal levels, on the theory that overly susceptible optic nerves are less likely to be damaged at lower pressures. Research underway may point to better treatments for this form of glaucoma. Attacks of acute closed-angle glaucoma are medical emergencies. IOP is rapidly lowered by successive deployment of acetazolamide, hyperosmotic agents, a topical beta-blocker, and pilocarpine. Epinephrine should not be used because it exacerbates angle closure. Trabeculectomy, to open the drainage canals or make an opening in the iris, can be effective in increasing the outflow of aqueous humor. This surgery is usually successful, but the effects often last less than one year. Nevertheless, this is an effective treatment for patients whose IOP is not sufficiently lowered by drugs and for those who can’t tolerate the drugs. Laser peripheral iridotomy is a procedure used almost exclusively to treat narrow angle glaucoma. It involves creating a small opening in the peripherial iris that allows aqueous fluid to drain from behind the iris directly to the anterior chamber. This procedure typically result in “opening up” the narrow angle between the iris and the cornea, in essence converting a narrow angle into an open angle.

The first line of glaucoma treatment is the use of prescription eyedrops. Several classes of medications are effective at lowering IOP and thus preventing optic nerve damage in chronic and neonatal glaucoma. Beta blockers (e.g. timolol), carbonic anhydrase inhibitors (e.g. acetazolamide), and alpha-2 agonists (e.g. brimonidine tartrate) inhibit aqueous humor production. Miotics (e.g. pilocarpine) and prostaglandin analogues (e.g. latanoprost) increase the outflow of aqueous humor.

Argon laser trabeculoplasty is usually recommended when medications have not been able to sufficiently control IOP, although it is increasingly advocated as primary therapy for patients who are not good candidates for the use of glaucoma medications or who cannot use eyedrops. In this procedure, the beam of an argon laser is directed at the trabecular meshwork. Typically about 180° of the trabecular meshwork is treated with laser spots. As a result of this procedure, the drainage of aqueous fluid out of the eye increases, thus lowering IOP.

It is important for patients to inform their doctors of any health conditions they have or any medications they take, including over-the counter drugs. Certain drugs used to treat glaucoma are not prescribed for patients with pre-existing conditions. The drugs prescribed to treat glaucoma all have side effects, so patients taking them should be monitored closely, especially for cardio-

Gene therapy may also be part of future treatments. A mutation in the gene myocilin is believed to cause most cases of juvenile glaucoma, and 3–4% of adult glaucoma. As of 2001, researchers are investigating drugs that inhibit myocilin production. The drug therapy would not just treat IOP, but also could be used before glaucoma’s onset.

Treatment

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of tonometry called noncontact applanation shoots a puff of air into the patient’s eye. This is slightly less accurate than applanation tonometry.

Glaucoma

KEY TERMS Agonist—A drug that mimics one of the body’s own molecules. Alpha-2 agonist (alpha-2 adrenergic receptor agonist)—A class of drugs that binds to and stimulates alpha-2 adrenergic receptors, causing responses similar to those of adrenaline and noradrenaline. They inhibit aqueous humor production and have a wide variety of side effects, including dry mouth, fatigue, and drowsiness. Aqueous humor—A transparent liquid, contained in the anterior chamber (between the cornea and lens) of the eye, that is composed of water, sugars, vitamins, proteins, and other nutrients. Beta blocker (beta-adrenergic blocker)—A class of drugs that binds to beta-adrenergic receptors and thereby decreases the ability of the body’s own natural epinephrine to bind to those receptors, leading to inhibition of various processes in the body’s sympathetic system. Beta blockers can slow the heart rate, constrict airways in the lungs, lower blood pressure, and reduce aqueous secretion by ciliary tissues in the eye. Carbonic anhydrase inhibitor—A class of diuretic drugs that inhibits the enzyme carbonic anhydrase, an enzyme involved in producing bicarbonate, which is required for aqueous humor production by the ciliary tissues in the eye. Thus, inhibitors of this enzyme decrease aqueous humor production. Some side effects of these drugs are urinary frequency, kidney stones, loss of the sense of taste, depression, and anemia. Cornea—Clear, bowl-shaped structure at the front of the eye. It is located in front of the colored part of the eye (iris). The cornea lets light into the eye and partially focuses it.

Vitamin C, vitamin B1 (thiamine), chromium, zinc, and rutin may reduce IOP. Patients using alternative methods to attempt to prevent optic nerve damage should be advised they also need the care of a traditionally trained ophthalmologist or optometrist who is licensed to treat glaucoma, so that IOP and optic nerve damage can be monitored.

Prognosis About half of the people who have glaucoma are not aware of it. For them, the prognosis is not good, and 1082

Gonioscope—An instrument used to examine the trabecular meshwork. It consists of a magnifier and a lens equipped with mirrors, which sits on the patient’s cornea. Hyperosmotic drugs—A class of drugs for glaucoma that increases the osmotic pressure in the blood, which then pulls water from the eye into the blood. Iris—The colored part of the eye just behind the cornea and in front of the lens that controls the amount of light sent to the retina. Lens (the crystalline lens)—A transparent structure in the eye that focuses light onto the retina. Miotic—A drug that causes pupils to contract. Ophthalmoscope—An instrument, with special lighting, designed to view structures in the back of the eye. Optic nerve—The nerve that carries visual messages from the retina to the brain. Prostaglandin—A group of molecules that exerts local effects on a variety of processes including fluid balance, blood flow, and gastrointestinal function. Prostaglandin analogue—A class of drugs that are similar in structure and function to prostaglandin. Retina—The inner, light-sensitive layer of the eye containing rods and cones. Sclera—The tough, fibrous, white outer protective covering that surrounds the eye. Tonometry—The measurement of pressure. Trabecular meshwork—A sponge-like tissue located near the cornea and iris that functions to drain the aqueous humor from the eye into the blood.

many of them will become blind. On the other hand, the prognosis for treated glaucoma is excellent.

Health care team roles Nursing and allied health professionals play an important part in the diagnosis and treatment of glaucoma. Skilled ophthalmic technicians and assistants record the patient history and perform many of the preliminary tests. Depending on skill level, these ophthalmic assistants may perform measurement of visual acuity under both low and high illumination, assessment of ocular

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Before surgical procedures, nurses and assistants also prepare the operating room (OR). Many ophthalmologists now have their own ambulatory surgery centers where skilled technicians and ophthalmic nurses play a critical role in preparing the OR and patients for the surgery. Ophthalmic nurses also assist the ophthalmologists during surgery and discuss outcomes with patients post-operatively. Nurses and assistants assist patients by explaining the sometimes difficult regimen of glaucoma medication. In some cases, patients require several doses of a combination of medications. Ophthalmic nurses and assistants show patients the correct technique for inserting eyedrops, and reinforce the physician’s instructions for medication compliance. Patient education Ophthalmic assistants and nurses help to ensure that patients return to the physician’s office in a timely manner so that IOPs can be monitored. Nurses and assistants also emphasize the importance of adhering to the eyedrop schedule to keep IOPs at a lower level, and answer any questions concerning proper eyedrop instillation.

Prevention Because glaucoma may not initially cause symptoms, the best form of prevention is to have regular eye exams. Patients with narrow angles should avoid certain medications (including some over-the-counter medications, such as some cold or allergy medications). Patients who are glaucoma-susceptible (i.e. have narrow angles and borderline IOPs) should be advised to read the warning labels on over-the-counter medicines and inform physicians of products they are considering taking. Steroids may also raise IOP, so patients may need to be monitored more frequently if it is necessary for them to use steroids. Not enough is known about the underlying mechanisms of glaucoma to prevent the disease itself. However, prevention of optic nerve damage from glaucoma is essential and can be accomplished when glaucoma is diagnosed and treated. As more is learned about the genes that cause glaucoma, it may become possible to

test DNA and identify potential glaucoma patients, so they can be treated before IOPs become elevated. Resources BOOKS

Epstein, David L., R. Rand Allingham, and Joel S. Schuman. Chandler and Grant’s Glaucoma. 4th ed. Baltimore: Williams & Wilkins, 1997. Marks, Edith, and Rita Montauredes. Coping with Glaucoma. Garden City Park, NY: Avery, 1997. ORGANIZATIONS

American Academy of Ophthalmology. P.O. Box 7424, San Francisco, CA 94120-7424. (415) 561-8500. . American Glaucoma Society. P.O. Box 193940, San Francisco, CA 94119-3940. (415) 561-8587. Fax: (415) 561-8531. . Glaucoma Research Foundation. 490 Post Street, Suite 830, San Francisco, CA 94102. (415) 986-3162. (800) 8266693. [email protected]. . National Eye Institute. 2020 Vision Place, Bethesda, MD 20892-3655. (301) 496-5248. . Prevent Blindness America. 500 East Remington Road, Schaumburg, IL 60173. (800) 331-2020. . OTHER

“FDA Approves Two New Intraocular Pressure Lowering Drugs for the Management of Glaucoma.” FDA Online. . Hawkins, Vickey, and Larry E. Patterson. “Increasing Volume with Super Scribes.” Ophthalmology Management Online. . Helzner, Jerry. “You Can Provide Cost-Effective Glaucoma Care.” Ophthalmology Management Online. . “Optometric Clinical Practice Guideline: Care of the Patient with Open Angle Glaucoma.” American Optometric Association Online. . Ronge, Laura J. “Glaucoma: What We Know About Glaucoma Genetics.” EyeNet Magazine Online. . Titcomb, Lucy. “Treatment of Glaucoma.” Pharmacy Magazine. (29 April 1998).

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motility and binocularity, visual fields, measurement of IOPs with tonometers, evaluation of pupillary responses, and refraction.

Gliding joint

Gliding joint

KEY TERMS

Definition

Articulation—A synonym for “joint.”

A gliding joint is a synovial joint in which the bony surfaces that the joint holds together are flat, or only slightly rounded. (A synovial joint is the living material that holds two or more bones together but also permits these bones to move relative to each other.) A more precise interpretation of the international Latin anatomical term for the gliding joint would be “joint that joins flat bony surfaces.” The wrists have good examples of gliding joints (as well as joints of other types).

Description If the bony surfaces of two bones which meet at a joint actually touched each other, then motion would cause friction that would soon produce wear and tear on the touching ends of the bones. An engineer designing a mechanical counterpart would arrange for lubricating oil to prevent such wear and tear and facilitate smooth movement between the two metal “bones.” A joint thus joins bones together (indeed, it is called a “joint” because it “joins” them) but also keeps them slightly separated to prevent their damaging each other in motion. A kind of cartilage special to joints covers the ends of the bones being joined. A membrane hermetically seals two (or more) bone-ends with their cartilage, enclosing them in a kind of living capsule. For the sake of simplicity, the following example discusses a joint with only two bones. Inside this membrane capsule, there is a short distance between the cartilage of one bone and the cartilage of the other, because even cartilage rubbing directly against cartilage would produce wear and tear. But the gap between the cartilage surfaces is not a vacuum and is not filled with air. It is filled with synovial fluid. This synovial fluid is in a sense the equivalent of the motor oil which lubricates moving parts of an automobile engine. The interior of a synovial joint has negative pressure in relation to air pressure. For this reason, air pressure pushes the bones together tightly into the capsule while the fluid keeps them from actually touching. The hermetically sealed membrane capsule in this paradoxical fashion aids the tight joining while it ensures the slight separation. This negative pressure in the joint continues to work even after death. Of course, the two bones are kept together in a living body not only by the membrane capsule and the synovial fluid but also by the tissues around the bones. If in dissecting a corpse one removes the tissues leaving only the membrane capsule, the pair of 1084

Carpals—The eight small bones that form the wrist and are joined to the metacarpals of the hand and to the bones of the forearm. Metacarpals—The five bones of the hand that are joined to the carpal bones of the wrist and to the digits. Neoplasm—New and abnormal growth of tissue, which may be non-cancerous (benign) or cancerous (malignant) Synovial fluid—A transparent, sticky fluid that lubricates joints and nourishes the cartilage in a joint. (It is also found in tendons, sheaths, and bursae.) Tarsals—The seven bones located between the bones of the lower leg and the metatarsals. Vertebrae—Bones of the spine.

bones will remain tightly joined. But if one pierces the capsule and allows air to rush inside, one then has normal atmospheric pressure inside the capsule instead of the negative pressure of the interior of the joint when it is hermetically sealed by the capsule, and now the bones come easily apart. Synovial fluid has another important quality. Most bodily tissues are nourished by blood vessels, but the cartilage on bone-ends in joints does not have blood vessels. Synovial fluid provides the nutrition for the cartilage that keeps it alive, strong, and healthy. The wall of the membrane capsule has two layers. The outer layer is fibrous. The inner layer produces the synovial fluid, and hence is called the synovial layer.

Function A gliding joint allows three different kinds of motion: linear motion, such as smooth sliding of bone past bone (the bones seem to glide past each other, hence the name “gliding” joint), angular motion such as bending and stretching, and circular motion. The ends of the bones that a gliding joint joins are nearly flat or only slightly curved and thus facilitate the characteristic sliding, bending, and twisting movements.

Role in human health The role of gliding joints in human health (the same as that played by the other types of synovial joints) is to

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Common diseases and disorders The gliding joints (and the other joints) can be affected by such conditions as the following: • Ankylosis: The fusion of bones across a joint. It is often a complication of arthritis. • Ankylosing spondylitis: A type of inflammatory arthritis that progresses to ankylosis. It occurs chiefly in young men. • Capsulitis: Inflammation of the membrane capsule that produces and encloses the synovial fluid. • Dislocation: The displacing of a bone from its normal position, causing tendons to stretch and strain. • Neoplasms: Abnormal growths (neoplasms) involving the gliding joints are rare. If such growths occur, they usually involve non-cancerous (benign) growths of cartilage or of tendons and their sheaths at the joints of the wrists. Synovial sarcoma is a cancerous (malignant) growth of cells resembling those of the synovial layer of the membrane capsule. It is found at the contact surfaces of bones in a joint, usually in the larger joints of young adults. • Rheumatoid arthritis: A common form of chronic inflammation of the joints. It causes swelling, pain, stiffness, elevated temperature, and redness of the joints. It is a disease of connective tissue and leads to the destruction of bone, cartilage, and ligaments in the joint. Resources BOOKS

Dimon, Theodore, and Megan Day. Anatomy of the Moving Body: A Basic Course in Bones, Muscles, and Joints. Berkeley, CA: North Atlantic Books, 2001 Hoffmann, David. Healthy Bones and Joints: A Natural Approach to Treating Arthritis, Osteoporosis, Tendinitis, Myalgia, Bursitis. Pownal, VT: Storey Books, 2000 (A Storey Medicinal Herb Guide). OTHER

LaStayo, Paul C. Ph.D., P.T., C.H.T., Northern Arizona University, Physical Therapy Program. “Differentiating Joint and Muscle Disorders.” (29 January 2001).

Monique Laberge, Ph.D.

Glioma see Brain tumor

Glucose tests Definition Glucose tests are used to determine the concentration of glucose in blood, urine, cerebrospinal fluid, and other body fluids. These tests are used to detect an increased blood glucose (hyperglycemia), a decreased blood glucose (hypoglycemia), increased glucose in the urine (glycosuria), and a decrease in cerebrospinal, serous, and synovial fluid glucose.

Purpose Glucose tests are used in a variety of situations including: • Screening persons for diabetes mellitus. The American Diabetes Association (ADA) recommends that a fasting plasma glucose (fasting blood sugar) be used to diagnose diabetes. People without symptoms of diabetes should be tested when they are 45 years old and again every three years. People in high-risk groups should be tested before the age of 45 and tested more frequently. If the person already has symptoms of diabetes, a blood glucose test without fasting, called a casual plasma glucose test, may be performed. In difficult diagnostic cases, a glucose challenge test called a two-hour oral glucose tolerance test is recommended. If the result of any of these three tests is abnormal, it must be confirmed with a second test performed on another day. The same test or a different test can be used, but the result of the second test must be abnormal as well in order to establish a diagnosis of diabetes. • Screening for gestational diabetes. Diabetes that occurs during pregnancy is called gestational diabetes. This condition is associated with hypertension, increased birth weight, and a higher risk for preeclampsia. Women who are at risk are screened when they are 24-28 weeks pregnant. A woman is considered at risk if she is older than 25 years, is not at her normal body weight, has a parent or sibling with diabetes, or is in an ethnic group that has a high rate of diabetes (Hispanic, Native American, Asian, African-American). • Blood glucose monitoring. Daily measurement of whole blood glucose identifies diabetics who require intervention to maintain their blood glucose within an acceptable range as determined by their physician. The Diabetes Control and Complications Trial (DCCT) demonstrated that persons with diabetes who maintained blood glucose and glycated hemoglobin at or near normal decreased their risk of complications by 50-75%. Based on results of this study, the American Diabetes Association (ADA) recommends routine gly-

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allow freedom of movement and thus provide flexibility to the skeleton.

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Blood glucose (mg/dl)

300

200 Hyperglycemia, 2 h > 180 100

Normal, 2 h < 180 Hypoglycemia, 2 h < 80

Fasting

1

2 Time (hours)

3

4

Glucose Tolerance Test (GTT) Graph

Glucose tolerance test (GTT). (Delmar Publishers, Inc. Reproduced by permission.)

cated hemoglobin testing to measure long-term control of blood sugar. • Diagnosis and differentiation of hypoglycemia. Low blood glucose associated with neuroglycopenia produces symptoms such as confusion, memory loss, and seizure. Demonstration that such symptoms are the result of hypoglycemia requires evidence of a low blood glucose at the time of symptoms and reversal of the symptoms by glucose. In documented hypoglycemia, blood glucose tests are used along with measurements of insulin and C-peptide (a fragment of proinsulin) to differentiate between fasting and postprandial causes. • Analysis of glucose in body fluids. High levels of glucose in body fluids reflect a hyperglycemic state and is otherwise not clinically significant. However, low body fluid glucose levels indicate increased glucose utilization which is often caused by infection (e.g., meningitis causes a low CSF glucose); inflammatory disease (e.g., rheumatoid arthritis causes a low pleural fluid glucose); or malignancy (e.g., a leukemia or lymphoma such as Hodgkin’s disease infiltrating the central nervous system or serous cavity).

Precautions Diabetes must be diagnosed as early as possible. If left untreated, it will result in progressive vascular disease that may damage the blood vessels, nerves, kidneys, heart, and other organs. Brain damage can occur from glucose levels below 40 mg/dL and coma from levels above 450 mg/dL. For this reason, plasma glucose levels below 40 mg/dL or above 450 mg/dL are com1086

monly used as alert values. Point-of-care and home glucose monitors measure glucose in whole blood rather than plasma and are accurate generally within a range of glucose concentration between 40 and 450 mg/dL. In addition, whole blood glucose measurements are generally 10% lower than serum or plasma glucose owing to the greater water content of the red blood cells. Results are not definitive beyond the manufacturer’s stated measuring range, and should be repeated as soon as possible to avoid hypoglycemic shock, cardiac arrest, coma, and other complications of an extremely abnormal glucose result. Other endocrine disorders and several medications can cause both hyperglycemia and hypoglycemia. For this reason, abnormal glucose test results must be interpreted by a physician. A nurse or phlebotomist who collects the sample for a plasma glucose test should follow standard precautions for the prevention of transmission of bloodborne pathogens. Glucose is a labile substance; therefore, plasma or serum must be separated from the blood cells and refrigerated as soon as possible. Samples that must be transported unrefrigerated to a distant site should be collected in a tube with an additive such as sodium fluoride to inhibit glycolysis. Blood glucose methods are largely free of interferences. However, hemolysis may increase the glucose result when measured by the hexokinase method, and high levels of ascorbic acid may reduce the glucose result when measured by the glucose oxidase method. Glycated hemoglobin measurements may be affected by abnormal hemoglobin pigments, such as methemoglobin and structural hemoglobin abnormalities such as hemoglobin S. Splenectomy can result in an

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Exercise, diet, anorexia, and smoking affect the results of the oral glucose tolerance test. Drugs that decrease tolerance to glucose and affect the test include steroids, oral contraceptives, estrogens, and thiazide diuretics.

Description The body uses glucose to produce the majority of the energy it needs to function. Glucose is absorbed from the gastrointestinal tract directly and is also derived from digestion of other dietary carbohydrates. It is also produced inside cells by the processes of glycogen breakdown (glycogenolysis) and reverse glycolysis (gluconeogenesis). Insulin is made by the pancreas and facilitates the movement of glucose from the blood and extracellular fluids into the cells. Insulin also promotes cellular production of lipids and glycogen and opposes the action of glucagon which increases the formation of glucose by cells. Diabetes may result from a lack of insulin or a subnormal response to insulin. There are three forms of diabetes: Type I or insulin dependent (IDDM), type II or noninsulin dependent (NIDDM), and gestational diabetes (GDM). Type I diabetes usually occurs in childhood and is associated with low or absent blood insulin and production of ketones even in the absence of stressed metabolic conditions. It is caused by autoantibodies to the islet cells in the pancreas that produce insulin, and persons must be given insulin to control blood glucose and prevent ketosis. Type II accounts for 85% or more of persons with diabetes. It usually occurs after age 40, and is usually associated with obesity. Persons who have a deficiency of insulin may require insulin to maintain glucose, but those who have a poor response to insulin may not. Ketosis does not develop under normal metabolic conditions but may occur with stress. Gestational diabetes is a form of glucose intolerance that first appears during pregnancy. It abates after delivery, but over a 10year span approximately 30-40% of females with gestational diabetes go on to develop noninsulin dependent diabetes. There are a variety of ways to measure a person’s blood glucose. Whole blood glucose tests Whole blood glucose testing can be performed by a person in his or her home, or by a member of the health care team outside the laboratory. The test is usually performed using a drop of whole blood obtained by finger

puncture. Care must be taken to wipe away the first drop of blood because this is diluted with tissue fluid. The second drop is applied to the dry reagent test strip or device. All whole blood glucose analyzers use the glucose oxidase reaction to measure glucose concentration. In the home test kits, the enzymes glucose oxidase and peroxidase, a buffer, and dye are immobilized on the testing devise. When the blood contacts the reaction zone, it hydrates the reagents. The glucose oxidase utilizes oxygen to oxidize the glucose forming gluconic acid and hydrogen peroxide. The peroxidase enzyme catalyzes the oxidation of the dye by the hydrogen peroxide producing a colored product. The test strip or device is inserted into a portable analyzer that measures the amount of color produced. Concentration of gluocse is determined by comparing the color intensity, called the reflectance density, to that for a standard measured the same way. Pointof-care devices often utilize the same method. However, some devices employ the polarographic glucose oxidase method. In this procedure, the glucose oxidase is impregnated into a glucose permeable membrane that covers an electrode. Peroxidase and dye are not required. Glucose from the sample diffuses through the membrane and the glucose oxidase catalyzes the formation of hydrogen peroxide inside the electrode. The peroxide is unstable and reforms oxygen and water. The oxygen is reduced at the cathode of the electrode producing a current that is proportional to glucose concentration. Fasting plasma glucose test The fasting plasma glucose test requires an eighthour fast. The person must have nothing to eat or drink except water. The person’s blood is usually collected by a nurse or phlebotomist via venipuncture. Either serum, the liquid portion of the blood after it clots, or plasma may be used. Plasma is the liquid portion of unclotted blood that is collected in an anticoagulant. The glucose is measured by an enzymatic glucose method. The glucose oxidase-peroxidase or glucose oxidase-polarographic methods may be used and are similar to those described above. Two additional methods used are the hexokinase and glucose dehydrogenase methods. These methods both result in the production of NADH (NADPH) in proportion to the glucose concentration in the sample. The reaction is measured in an automated chemistry analyzer which measures light absorption. The amount of light absorbed by the NADH at 340 nm is directly proportional to the glucose in the sample. Enzymatic methods measure no sugar other than glucose, and the same normal range can be used. The ADA recommends a normal range for fasting plasma glucose of 55-109 mg/dL. A glucose level equal to greater than 126 mg/dL is indica-

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increase and hemolytic anemia a decrease in glycated hemoglobin.

Glucose tests

• fasting plasma glucose greater than 105 mg/dL Normal findings for glucose tolerance test (GTT, oral glucose tolerance test [OGTT])

• one-hour plasma glucose greater than 190 mg/dL • two-hour plasma glucose greater than 165 mg/dL • three-hour plasma glucose greater than 145 mg/dL

Blood test Fasting 30 minutes 1 hour 2 hours 3 hours 4 hours

70–115 mg/dl (. OTHER

Occupational Outlook Handbook, U.S. Department of Labor, Bureau of Labor Statistics, Division of Information Services, 2 Massachusetts Ave. NE, Room 2860, Washington, DC 20212. (202) 691-5200. .

Lisette Hilton

Ligament sprain see Sprains and strains Ligament tests see Orthopedic tests Light therapy see Phototherapy Lipase tests see Amylase and lipase tests 1404

Lipid tests Lipid tests routinely performed on plasma include measurement of total cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) cholesterol. Lipid tests may also be performed on amniotic fluid and include tests for lecithin and other pulmonary surfactants.

Purpose The purpose of blood lipid testing is to determine whether abnormally high or low concentrations of a specific lipid are present. Low levels of cholesterol are associated with liver failure and inherited disorders of cholesterol production. Cholesterol is a primary component of the plaques that form in atherosclerosis and is therefore the major risk factor for the rapid progression of coronary artery disease. High blood cholesterol may be inherited, or result from other conditions such as biliary obstruction, diabetes mellitus, hypothyroidism, and nephrotic syndrome. In addition, cholesterol may be increased in persons who have a diet rich in saturated fats and cholesterol and who lead a sedentary lifestyle. Low levels of triglyceride are seen in persons who have malnutrition or malabsorption. Increased levels are associated with diabetes mellitus, hypothyroidism, pancreatitis, glycogen storage diseases, and estrogens. Diets rich in either carbohydrates or fats may cause elevated triglycerides in some persons. Although not a component of the atherosclerotic plaque, triglycerides increase blood viscosity and promote obesity that can contribute to coronary disease. The majority of cholesterol and triglyceride testing is performed to screen persons for increased risk of coronary artery disease. Lipid tests are performed on amniotic fluid to determine the maturity of the fetal lungs. Tests are performed prior to delivery to ensure that there is sufficient pulmonary surfactant to prevent collapse of the lungs during exhalation.

Description Cholesterol screening can be performed with or without fasting and should include total and HDL cholesterol tests. The frequency of cholesterol testing depends on the patient’s risk for CAD. Adults over 20 with total cholesterol levels below 200 mg/dL need to be tested once every five years. People with higher levels should be tested for LDL cholesterol and tested at least once per year thereafter, if the LDL cholesterol is 130

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• high blood pressure • cigarette smoking • diabetes • low HDL levels • family history of CAD • age, men over 45 years and women over 55 years Measurements of cholesterol and triglycerides are routinely performed using enzymatic methods. For cholesterol, the cholesterol oxidase method is used. Plasma or serum is mixed with a reagent containing cholesterol ester hydrolyase, cholesterol oxidase, peroxidase, and a chromogen. The cholesterol ester hydrolyase converts cholesterol esters (cholesterol coupled to a fatty acid) to free cholesterol. This reacts with cholesterol oxidase forming an oxidation product and hydrogen peroxide. The peroxidase enzyme catalyzes the oxidation of the chromogen by the hydrogen peroxide. This forms a red colored product that can be measured with a spectrophotometer. The amount of light absorbed at 500 nm is directly proportional to cholesterol concentration. HDL cholesterol is usually measured by the same reaction except that the enzymes are coupled to polyethylene glycol (PEG). In the presence of sulfated cyclodextrin, these enzymes will not react with the cholesterol in LDL, VLDL, or chylomicrons. LDL cholesterol is measured by first precipitating the other lipoproteins using a mixture of antibodies to apolipoprotein C and apolipoprotein E. The LDL cholesterol can be separated by centrifugation and then measured using the cholesterol oxidase reaction. Alternatively, LDL cholesterol can be calculated using the Friedewald formula. LDL cholesterol = total cholesterol minus (HDL cholesterol + triglyceride/5). This formula will underestimate LDL cholesterol when triglycerides are above 400 mg/dL. Triglycerides are routinely measured using the glycerol kinase reaction. The reagent contains the enzymes lipase, glycerol kinase, glycerol phosphate oxidase, and peroxidase. It also contains adenosine triphosphate (ATP) and a chromogen. Triglycerides are composed of glycerol that is bound (esterified) to three long chain fatty acids. The lipase sequentially splits the fatty acids from the molecule forming glycerol and free fatty acids. The glycerol kinase catalyzes the transfer of phosphorus from ATP to the glycerol forming glycerol-phosphate. The glycerol phosphate oxidase is used to oxidize this to dihydroxyacetone phosphate. This reaction generates hydrogen peroxide. In the final step, the peroxidase

enzyme catalyzes the oxidation of the chromogen by the hydrogen peroxide. This forms a red-colored product that can be measured with a spectrophotometer. The amount of light absorbed at 500 nm is directly proportional to triglyceride concentration. An important potential interfering substance in this reaction is glycerol, which is a common additive to many medications. If the Friedewald formula is used to calculate LDL cholesterol, the triglyceride measurement must be corrected by subtracting the plasma glycerol concentration from the triglyceride result. Measurement of pulmonary surfactants During the first half of gestation, lecithin and sphingomyelin levels in amniotic fluid are approximately equal. During the second half of pregnancy, lecithin production increases, but the sphingomyelin remains constant. Lecithin is the principal pulmonary surfactant secreted by the alveolar cells (type II granular pneumocytes) of the lung. Lecithin and the other surfactants prevent collapse of the air sacs during expiration. Infants born prematurely may suffer from respiratory distress syndrome (RDS) because levels of pulmonary surfactant are insufficient to prevent collapse of the air sacs. Tests for RDS are called fetal lung maturity (FLM) tests. The reference method for determining fetal lung maturity is the amniotic fluid L/S ratio. This is measured by thin layer chromatography in which lecithin and sphingomyelin in the amniotic fluid are separated and stained to determine their relative concentrations. An L/S ratio of 2:1 or higher is consistent with fetal lung maturity. Amniotic fluid levels of other surfactants such as phosphatidyl glycerol (PG), phosphatidyl glycerol, phosphatidyl inositol, and phosphatidyl ethanolamine may be measured by high performance liquid chromatography (HPLC). PG in amniotic fluid can be detected by a latexcoated antibody (latex agglutination) test. PG is an important marker for fetal lung maturity because a falsely positive test for lecithin may occur when the fluid is contaminated with blood or meconium. Since PG is not present in blood or meconium, and is only present when lecithin is adequate, a positive test is conclusive evidence of lung maturity. Measurement of lecithin which comprises about three quarters of the total surfactant composition at birth is most often measured by fluorescence polarization. This assay has replaced the L/S ratio as the FLM test in most labs. Most of the pulmonary surfactants are present in the form of lamellar bodies. These can be counted in the amniotic fluid using an electronic cell counter at the platelet threshold. The number of lamellar bodies is proportional to the quantity of surfactant.

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mg/dL or higher. The National Cholesterol Education Program (NCEP) suggests further evaluation when the patient has any of the symptoms of CAD or if she or he has two or more of the following risk factors for CAD:

Lipid tests

Precautions

KEY TERMS Amniocentesis—A procedure to remove amniotic fluid from the womb using a fine needle. Atherosclerosis—A disease of the coronary arteries in which cholesterol is deposited in plaques on the arterial walls. The plaque narrows or blocks blood flow to the heart. Atherosclerosis is sometimes called coronary artery disease, or CAD. High-density lipoprotein (HDL)—A type of lipoprotein that protects against CAD by removing cholesterol deposits from arteries or preventing their formation. Hypercholesterolemia—The presence of excessively high levels of cholesterol in the blood. Hypertriglyceridemia—The presence of excessively high levels of TAG in the blood. Lecithin—A phospholipid found in high concentrations in surfactant. Lipid—Any organic compound that is greasy, insoluble in water, but soluble in alcohol. Fats, waxes, and oils are examples of lipids. Lipoprotein—A complex molecule that consists of a protein membrane surrounding a core of lipids. Lipoproteins carry cholesterol and other lipids from the digestive tract to the liver and other body tissues. There are five major types of lipoproteins. Low-density lipoprotein (LDL)—A type of lipoprotein that consists of about 50% cholesterol and is associated with an increased risk of CAD. Plaque—An abnormal deposit of cholesterol, TAG, dead cells, lipoproteins and calcium on the wall of an artery. Surfactant—A compound made of fats and proteins that is found in a thin film along the walls of the air sacs of the lungs. Surfactant keeps the surface pressure low so that the sacs can inflate easily and not collapse. Tocolytic drug—A compound given to women to stop the progression of labor. Triacylglyceride—A chemical compound that forms about 95% of the fats and oils stored in animal and vegetable cells. TAG levels are sometimes measured as well as cholesterol when a patient is screened for heart disease.

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Tests for triglycerides and LDL cholesterol must be performed following a 12-hour fast. The nurse or phlebotomist collecting the blood sample should observe universal precautions for the prevention of transmission of bloodborne pathogens. Acute illness, high fever, starvation, or recent surgery lowers blood cholesterol and triglyceride levels. If possible, patients should also stop taking any medications that may affect the accuracy of the test. Amniotic fluid is collected by a process called amniocentesis. This procedure is usually performed between the after the 33rd week of gestation to evaluate lung maturity. Spontaneous abortion can occur as a consequence of this procedure. Its overall incidence following amniocentesis is approximately 1%. Complications include premature labor and placental bleeding. The fluid may be contaminated with blood or meconium (intestinal contents of the fetus), which can interfere with some fetal lung maturity tests.

Preparation Patients who are scheduled for a lipid profile test should fast (except for water) for 12-14 hours before the blood sample is drawn. If the patient’s LDL cholesterol is to be measured, he or she should also avoid alcohol for 24 hours before the test. When possible, patients should also stop taking any medications that may affect the accuracy of the test results. These include corticosteroids, estrogen or androgens, oral contraceptives, some diuretics, haloperidol, some antibiotics, and niacin. Antilipemics are drugs that lower the concentration of fatty substances in the blood. When these are taken by the patient, blood testing may be done frequently to evaluate liver function as well as lipid levels.

Aftercare Aftercare with the blood lipid tests includes routine care of the skin around the needle puncture. Most patients have no aftereffects, but some may have a small bruise or swelling. A washcloth soaked in warm water usually relieves any discomfort. In addition, the patient should resume taking any prescription medications that were discontinued before the test. Care after amniocentesis requires that the clinician watch the patient for any signs of infection or possible injury to the fetus. Some things to look for are fever, vaginal bleeding, or vaginal discharge. The patient may feel sick and there may be some cramping. She should be advised to rest and to avoid strenuous activity. If labor is impending, supportive care should be provided to the

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Complications The primary risk to the patient with the lipid blood tests is a mild stinging or burning sensation during the venipuncture, with minor swelling or bruising afterward. Amniocentesis, while much safer in the third trimester, and much safer now that it is done with the guidance of ultrasound technology does present a risk of miscarriage and fetal injury. The patient should be watched for any signs of bleeding, infection, or impending labor.

Results The normal values for serum lipids depend on the patient’s age, sex, and race. Normal values for people in Western countries are usually given as 140-220 mg/dL for total cholesterol in adults, although as many as 5% of the population have a total cholesterol higher than 300 mg/dL. Among Asians, the figures are about 20% lower. As a rule, both total and LDL cholesterol levels rise as people get older. Normal values for HDL cholesterol are also age and sex dependent. The range for males between 20-29 years is approximately 30-63 mg/dL and for females of the same age group it is 33-83 mg/dL. Normal values for fasting triglycerides are also age and sex dependent. The reference range for adult males 20-29 years is 45-200 mg/dL and for females of the same age group it is 37-144 mg/dL. As with cholesterol, the normal range increases with age. Since diet and lifestyle affect normal values, which are determined by the interval between the 5th and 95th percentile of the group, it is more helpful to evaluate cholesterol and triglycerides from the perspective of desirable plasma levels. Desirable values defined by the Nation Cholesterol Education Program (NCEP) in 2001 are as follows:

FLM tests Low levels of surfactant in amniotic fluid are denoted by an L/S ratio less than 2.0 or a lecithin level less than or equal to 0.10 mg/dL. Lung development can be delayed in premature births and in babies whose mothers have diabetes.

Health care team roles Physicians will order the blood lipid tests on patients who have risk factors for heart disease or who have not been tested within the past five years. A dietician may be consulted if test results are abnormal. FLM tests are ordered by a physician, usually an obstetrician. Lipid tests are performed by clinical laboratory scientists/medical technologists or clinical laboratory technicians/medical laboratory technicians. Patient education Nurses should explain the results of abnormal blood lipid tests to patients and advise them on lifestyle changes. Patient education is important in fetal lung maturity testing. The situation faced by the expectant parents may be very critical, and the more information they can be given, the better choices they can make. Resources BOOKS

Baron, Robert B. and Warren S. Browner. “Lipid Abnormalities.” In Current Medical Diagnosis & Treatment 1998. edited by Lawrence M. Tierney et al. Stamford, CT: Appleton & Lange, 1997. Kaplan, Lawrence A. and Amadeo J. Pesce. Clinical Chemistry, Theory, Analysis and Correlation. St. Louis: Mosby Publishers, 1996. OTHER

National Cholesterol Education Program. The National Heart, Lung, and Blood Institute. National Institutes of Health. PO Box 30105, Bethesda, MD, 20824-0105. 301-2511222. . (May 2001).

• Total cholesterol: Less than 200 mg/dL; 200-239 mg/dL is borderline high and greater than 240 mg/dL is high.

Jane E. Phillips

• HDL cholesterol: Less than 40mg/dL is low. • LDL cholesterol: Less than 100 mg/dL is optimal; near optimal is 100-129 mg/dL; borderline high is 130-159 mg/dL; high is 160-189 mg/dL; and very high is anything over 190 mg/dL. • Total cholesterol: HDL ratio: Under 4.0 in males; 3.8 in females.

Lipids Definition Lipids are a wide-ranging group of organic compounds found in all living organisms, including humans,

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patient and tocolytic agents may be necessary to prevent the premature birth of the baby.

Lipids

KEY TERMS Hypercholesterolemia—An excess of cholesterol in the blood. Hyperlipidemia—A group of disorders characterized by an excess of fatty substances, such as cholesterol, triglycerides, and lipoproteins, in the blood. Protoplasmic—Relating to protoplasm, a colorless jellylike substance that is the main constituent of all human cells and tissue.

plants, and animals. Lipids are the body’s reserve supply of energy. Unlike other organic compounds, lipids are soluble in alcohol, ether, and other organic substances but not in water.

Description Lipid comes from the Greek word lipos, meaning fat. Cells make lipids in the human body and, along with carbohydrates and proteins, are components of all life. Among the major classes of lipids in humans are acids, glycerol-derived lipids (including fats and oils), and steroids. The two major lipids found in the blood are cholesterol and triglycerides.

Cholesterol Cholesterol is a lipid that is essential for repairing cell membranes, manufacturing vitamin D on the skin’s surface, and creating hormones, especially testosterone and estrogen. To circulate in the bloodstream, cholesterol must attach to proteins. The combination of cholesterol and protein is called lipoprotein. The two major lipoprotein groups are high-density lipoprotein (HDL), commonly referred to as “good” cholesterol, and low-density lipoprotein (LDL), also known as “bad” cholesterol. HDL helps prevent fat buildup throughout the body by carrying cholesterol from the arteries to the liver, where it is disposed of. LDL carries most of the cholesterol in the body, so an excess of LDL can clog the arteries with cholesterol buildup. High levels of LDL are 100 milligrams or more per deciliter (mg/dL) of blood for people with heart or vascular disease or diabetes, 160 mg/dL for people with two risk factors, and 190 mg/dL or more for people with no risk factors. A high LDL level is a primary cause of coronary heart disease (CHD) and stroke. This is because when LDL accumulates in the body, it forms a plaque 1408

that sticks to the walls of arteries, slowing or restricting blood flow and oxygen delivery to the heart and other vital organs. This causes atherosclerosis, commonly referred to as hardening of the arteries. The buildup of plaque usually occurs over a few years and without cholesterol tests the patient may not know about the problem until angina (chest pains) or an acute myocardial infarction (heart attack) occurs. Among the key risk factors for high LDL are age, gender, smoking, diabetes, and a family history of the disorder. About 25% of people with high LDL can control the disorder with a diet low in saturated fats and cholesterol, weight control, and regular exercise. About 75% of people with high LDL require lipid-lowering medications in addition to the weight, diet, and exercise guidelines. First-line drugs recommended by the National Cholesterol Education Program to treat high LDL are bile acid sequestrants such as cholestyramine (Questran) and colestipol (Colestid), niacin (either overthe-counter or time-released prescription drugs such as Niaspan, Slo-Niacin, and Nicobid), and HMG-CoA reductase inhibitors, including fluvastatin (Lescol), pravastatin (Pravachol), cervistatin (Baycol), lovastatin (Mevacor), simvastatin (Zocor), and atorvastatin (Lipitor). The second-line drug choice are fibric acid derivatives such as gemfibrozil, clofibrate, and fenofibrate (Tricor.) Estrogen replacement therapy should also be considered as complementary therapy in postmenopausal women. Levels of HDL between 30 and 75 mg/dL are associated with decreased risk of CHD and stroke. But HDL levels under 30 mg/dL are associated with a greater risk for CHD and stroke.

Triglycerides Triglycerides are another form of fat that comes from foods and is carried through the bloodstream to the tissues. High levels of triglycerides in the blood can mean that there is too much fat in the diet. Hypertriglyceridemia (high levels of triglycerides) is associated with coronary heart disease, especially since elevated triglycerides levels are usually associated with unhealthy low levels of HDL, which is necessary for good health. High triglyceride levels (more than 150 mg/dL) can be caused by excessive intake of alcohol or high-calorie foods. Other risk factors include a family history of high triglycerides, obesity, hypertension (high blood pressure), and diabetes. Treatment generally includes controlling other disorders such as diabetes and high blood pressure, proper diet and regular exercise, and fibric acid derivatives such as gemfibrozil, clofibrate, or fenofibrate.

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Lipoprotein(a) is a cholesterol-carrying molecule similar in structure to LDL and is believed to carry a protein that interferes with the body’s ability to dissolve blood clots. Elevated levels may contribute to heart attacks. Apolipoprotein A-1 is a molecule associated with healthy hearts and may lower the risk of heart disease due to high HDL. Apolipoprotein B is associated with high LDL and may be more effective in predicting heart disease in women. Remnant lipoproteins are byproducts of chylomicrons, lipid particles common in the blood during fat digestion and assimilation, and/or very low density lipoproteins. Initial research suggest they may be a risk factor for CHD.

Function Lipids manufactured by cells in the body form part of the protoplasmic structure of cells. Lipids act as a reserve source of energy. When broken down to be used as energy, lipids are converted to an energy-rich compound called adenosine triphosphate by a process known as fatty acid oxidation or beta oxidation.

Role in human health Lipids are important to the human body since they helps produce hormones, and builds cell membranes and other needed tissue. Lipids, both lipoproteins and triglycerides, are made and stored in the body and are used as energy sources. Lipids also play a major role in cardiovascular health.

Common diseases and disorders The two primary conditions associated with lipids are hyperlipidemia and hypercholesterolemia. These conditions have no overt symptoms but can lead to several serious disorders, primarily:

• Stroke, a group of brain disorders involving loss of brain functions that occur when the blood supply to any part of the brain is interrupted. Strokes are most commonly caused by atherosclerosis. Resources BOOKS

Gotto, Antonio M. and Pownall, Henry J. Manual of Lipid Disorders: Reducing the Risk for Coronary Heart Disease. New York: Lippincott Williams & Wilkins Publishers, 1999. Gurr, M. I., et al. Lipid Biochemistry. Malden, MA: Blackwell Science Inc., 2001. Pond, Caroline M. The Fats of Life. New York: Cambridge University Press, 1998. Tyman, J. H. P. Lipids in Health and Nutrition. London: Royal Society of Chemistry, 1999. PERIODICALS

Barnard, N., et al. “Does a Low-Fat Vegetarian Diet Alter Serum Lipids?” Nutrition Research Letter (Sept. 2000): 15. Bell, Stacey J., et al. “The New Dietary Fats in Health and Disease.” Journal of the American Dietary Association (March 1997): 280–286. Franklin, Deborah. “What This CEO Didn’t Know About His Cholesterol Almost Killed Him: Half of all Heart Attacks Happen to People Whose Blood Tests are Normal. New Screening May Help Reveal Who is Really at Risk.” Fortune (March 19, 2001): 154+. Mormando, Robert M. “Lipid Levels: Applying the Second National Cholesterol Education Program Report to Geriatric Medicine.” Geriatrics (Aug. 2000): 48+. Raloff, Janet. “Sphinx of Fats: Some Lipids, Wallflowers for a Century, Show Therapeutic Promise.” Science News (May 31, 1997): 342–343. Steiner, George. “The Diabetes Atherosclerosis Intervention Study (DAIS): Interim Lipid Results.” Diabetes (May 1999): SA2.

• Angina, which is chest pain that occurs when the heart does not get enough oxygen. When angina is not caused by stress or physical exertion and becomes frequent and more severe, it is called unstable angina, and may indicate an impending heart attack.

ORGANIZATIONS

• Atherosclerosis, also called hardening of the arteries, a condition in which fatty deposits called plaque build up inside the arteries, restricting blood flow.

American Heart Association. National Center, 7272 Greenville Ave., Dallas, TX 75231. (800) 242-8721. .

• Coronary heart disease, in which the arteries narrow, restricting the flow of blood and oxygen to the heart. Lack of sufficient oxygen to the heart can lead to angina or a heart attack. Most cases of CHD are due to atherosclerosis.

National Cholesterol Education Program. National Heart, Lung and Blood Institute, P.O. Box 30105, Bethesda, MD 20824. (301) 592-8573. .

Yu, Harry H., et al. “Dyslipidemia in Patients with CAD: Rational Use of Diets and Drugs.” Consultant (Sept. 2000): 1740.

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Lipids

Other lipids

Lipoproteins test

Lipoproteins test Definition Lipids are water insoluble molecules and must be transported in the plasma as macromolecular complexes containing protein called lipoproteins. The lipoproteins are large aggregates (micelles) composed of cholesterol, triglycerides, phospholipids, proteins, and small amounts of carbohydrates. Generally, the core of the lipoprotein contains hydrophobic lipids surrounded by a sheath of protein and lipids arranged with the hydrophilic ends directed outward. Carbohydrates and enzymes are present in the outer sheath. The proteins that become part of the lipoprotein are called apoproteins. Lipoproteins are grouped into four main classes depending upon their density. In order from least to greatest density these are: chylomicrons, very low density lipoprotein (VLDL), low density lipoprotein (LDL), and high density lipoprotein (HDL).

Purpose Lipoproteins are measured to classify persons with severe hyperlipoproteinemia or hypolipoproteinemia. The hyperlipoproteinemias result from increased production or decreased clearance of lipoproteins from the blood and may be inherited or secondary to other diseases or conditions. Some common causes of secondary hyperlipoproteinemia include diabetes mellitus, hypothyroidism, biliary cirrhosis, estrogens and pancreatitis. The cholesterol content of the LDL (LDL cholesterol) and HDL (HDL cholesterol) are measured, along with total cholesterol and triglycerides, to evaluate the patient’s risk for coronary heart disease. In addition, a subclass of LDL called lipoprotein(a) or Lp(a) may be measured in persons who have a family history of coronary artery disease (CAD) or predisposing risk factors for CAD.

Description Measurement Measurement of lipoproteins may be performed by ultracentrifugation of the plasma. When plasma is subjected to very high centrifugal force, the lipoproteins can be separated in a gradient salt solution on the basis of their density. Since the density is directly related to protein content, the lipoproteins can also be separated by electrophoresis. Electrophoresis is the separation of charged particles in an electrical field and is dependent on the amount and nature of the apoproteins within the lipoprotein. The 1410

electrophoretic positions of the lipoproteins are often used to describe them. Thus, HDL is also called alpha-1 lipoprotein, VLDL is called prebeta lipoprotein, and LDL is called beta lipoprotein. Chylomicrons do not migrate and are not given any designation. When one or more plasma lipid levels are extremely elevated or reduced, either of these methods may be used to determine which lipoproteins are abnormal. On the basis of these findings, abnormal lipoproteins are classified into patterns. Since severe disorders of lipoprotein metabolism are often inherited, the abnormal patterns are called phenotypes. There are five abnormal lipoprotein phenotypes (Type I through Type V), each characterized by the presence of an extremely high quantity of one or two lipoproteins. Persons with severe hyperlipoproteinemia often have skin and tissue infiltration of fat deposits, and persons with Type II and Type III are predisposed to premature atherosclerosis owing to high levels of plasma cholesterol. Lipoprotein phenotyping is not performed as a screening test to evaluate risk of coronary artery disease. Immunological methods are used to measure the quantity of specific apoproteins present in the plasma. Testing for apoA-I and apoB-100 the principal apoproteins of HDL and LDL, respectively is often performed in persons with elevated lipids who have risk factors associated with coronary artery disease. Measurement of a form of LDL, called Lp(a) is performed on these persons as well as on those who have normal lipid levels, but a family history of CAD. HDL cholesterol is routinely measured along with total cholesterol and triglycerides as a screening test for coronary artery disease. If the total cholesterol is 200 mg/dL or higher the LDL cholesterol is measured. The measurement of HDL cholesterol is based upon the measurement of cholesterol (see entry on lipid tests) under conditions that inhibit the reaction with all lipoproteins except HDL. The measurement of LDL cholesterol involves precipitating the HDL, VLDL, and cholymicrons using antibodies to apoproteins A, and E, followed by measurement of the LDL cholesterol in the supernatant. When the triglyceride concentration is below 400 mg/dL, the LDL cholesterol is often estimated using the Friedewald formula [LDL cholesterol = total cholesterol minus (HDL cholesterol + triglyceride/5)]. It should be noted that this formula will underestimate LDL cholesterol when triglycerides are above 400 mg/dL. Chylomicrons Chylomicrons are made in the intestines mainly from dietary triglycerides. They are approximately 95% triglyceride and only 2% protein by weight. The major apoproteins of chylomicrons are apoC, B, and A.

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Very low-density lipoproteins (VLDL) VLDL are formed in the liver using apoproteins partly recycled from chylomicron remnants. VLDLs are about 10% protein and 60-70% triglycerides by weight; consequently they account for only 10-15% of the plasma cholesterol. The triglycerides carried by the VLDL are derived from carbohydrate metabolism. VLDL is released into the circulation, where it is partly degraded. Excessively elevated VLDL is responsible for Type IV hyperlipoproteinemia and is most often caused by hyperinsulinemia, which promotes triglyceride production. When both chylomicrons and VLDL are greatly increased, the abnormality is defined as Type V hyperlipoproteinemia. Some free cholesterol, triglycerides, and apoproteins from VLDL are transferred to HDL in the circulation. This forms a lipoprotein of greater density and roughly equal cholesterol and triglyceride content called intermediate density lipoprotein (IDL). The IDL is converted to LDL by enzymatic removal of triglycerides and apoC. IDL is not found in significant amounts in the circulation unless there is a defect in conversion of VLDL to LDL. Such cases are caused by a deficiency of apo E-III or apo C-III activated lipase. This results in the accumulation of IDL in the plasma. This is responsible for Type III hyperlipoporteinemia. Low-density lipoprotein (LDL) The LDL is composed of about 25% protein and 4555% cholesterol by weight. LDL carries cholesterol to the cells and is then degraded by lysosomal hydrolysis. Since LDL contains the majority of the plasma cholesterol and is responsible for cholesterol transport to cells, it is positively correlated with the risk of coronary artery disease. LDL accumulates in the plasma when there is a deficiency of the apoB-100 receptor on cells. This is responsible for the Type II hyperlipoprotienimia. Low

levels of LDL occur in two inherited conditions. Abetalipoproteinemia results from a complete deficiency of apoB. This is an autosomal recessive condition associated with severe metabolic problems including intestinal malabsorption, motor nerve dysfunction, fat soluble vitamin deficiency and anemia. Hypobetalipoproteinemia is an autosomal dominant condition in which LDL levels are about 10% of normal. This condition may be associated with fat soluble vitamin deficiency that is treated by vitamin supplementation and with a very low risk for coronary artery disease. High-density lipoproteins (HDL) HDL is approximately 50% protein by weight. Phospholipids account for 25-30% of its mass and cholesterol for 15-20%. HDL is made in the liver partly from VLDL and chylomicrons. It binds to and esterifies cellular cholesterol and transports it to the liver, where it is used to make bile salts and acids. HDL provides the main route for cellular cholesterol clearance and its level is inversely related to coronary artery disease. Absent or nearly absent HDL occurs in an autosomal recessive hypolipoproteinemia called Tangier disease. This is caused by a deficiency of both apoA-I and apoA-II, the principal lipoproteins of HDL. Persons with this disease develop premature CAD. Lipoprotein a or Lp(a) Lp(a) contains apoB bound to another apoprotein that is designated apo(a). Like LDL it is about 27% protein and 65% lipid by weight and has prebata mobility on electropohoresis. The amount of Lp(a) in plasma is normally below 150 mg/dL. Elevated levels are considered to be an independent risk factor for developing coronary artery disease. High levels are inherited as an autosomal dominant trait and are not influenced by diet or exercise. It is speculated that the link betweeen Lp(a) and atherosclerosis is related to the similarity between apo(a) and plasminogen. Plasminogen is the precuror of plasmin which initiates the lysis of blood clots. Measurement guidelines The Expert Panel of the National Cholesterol Education Program (NCEP) sponsored by the National Institutes of Health has published guidelines for the detection of high cholesterol in adults which are listed below. The NCEP panel recommends that adults over the age of 20 be tested for cholesterol and HDL every five years. If the cholesterol is high, the HDL is low (below 40 mg/dl), or other risk factors are present, a complete lipoprotein profile that includes total cholesterol, triglyc-

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Chylomicrons are degraded in the plasma by the enzyme lipoprotein lipase, which splits the triglycerides into glycerides, and fatty acids, which are mainly absorbed by cells. Smaller chylomicron remnants are returned to the liver, where they are degraded by hepatic lipase. In the blood, some of the apoprotein A and C from chylomicrons are transferred to HDL. The chylomicrons are lighter than water and will float to the top of the plasma when it is stored overnight in the refrigerator. Since plasma from a fasting specimen should not contain chylomicrons, the observation of this floating layer is significant and indicates a deficiency of peripheral lipase activity. Chylomicrons are found in the fasting plasma of persons with Type I and Type V hyperlipoproteinemia.

Lipoproteins test

High density lipoprotein guidelines reflect the fact that this lipoprotein is inversely related to risk for CAD.

KEY TERMS

LDL cholesterol guidelines are: Atherosclerosis—Disease of blood vessels caused by deposits of cholesterol, fats, lipoproteins, cells and calcium on the inside walls of the vessels.

• low: < 40 mg/dL • desirable: < 130 mg/dL (deciliter)

Cardiovascular disease—Disease that affects the heart and blood vessels.

• optimal: < 100 mg/dL

Cholesterol—A fat-like substance called a lipid. It is used to build cell membranes, hormones and bile acids. The body makes cholesterol and gets it from food.

• borderline high: 130-159 mg/dL

Lipoproteins—The packages in which cholesterol and TAGs travel throughout the body.

The NCEP also identified factors that patients may have that make the risk of heart disease higher. Health care professionals are advised to help the patient lower their cholesterol as much as possible, if they have two or more of these risk factors:

erides, HDL cholesterol, and LDL cholesterol should be performed.

Preparation Initial screening for total cholesterol and HDL cholesterol may be performed on nonfasting persons. The tests require a blood specimen usually collected by venipuncture or fingerstick. The nurse or phlebotomist performing the test should observe universal precautions for the prevention of transmission of bloodborne pathogens. If results require follow-up testing, the patient must fast for 12 hours before the test, eating nothing and drinking only water. The person should not have alcohol for 24 hours before the test. There should be a stable diet and no illnesses occurring in the preceding two weeks. A test for lipoprotein electrophoresis requires a 12-hour fast and a blood sample collected in EDTA.

Complications

Results

• borderline high: 200-239 mg/dL • high: > 240 mg/dL 1412

• very high: > 190 mg/dL

• Cigarette smoking. • High blood pressure, with a measurement of > 140/90 mm Hg (millimeters of mercury). In addition, it is considered a risk factor if the patient is on blood pressure lowering medications, even if they have achieved a normal blood pressure. • Age, over 45 years in men and over 55 years in women. Estrogen, a sex hormone in women protects against heart disease. The levels of estrogen are lower after a woman goes through menopause, roughly after the age of 55. • Low HDL cholesterol (less than 35 mg/dL). Note that HDL > 60 mg/dL is a negative risk factor for CAD. • Family history of premature heart disease. Premature heart disease is defined as heart disease seen before age 55 in a male relative or before age 65 in a female relative. Some people have normal variations in their lipoprotein and total cholesterol levels. Repeat testing may be necessary, especially if a value is at a borderline risk category point.

Health care team roles

In April 2001, the NIH released new NCEP guidelines to assist doctors and nurses in identifying who is at risk for CAD. • desirable: < 200 mg/dL

• high: 160-189 mg/dL

• Diabetes mellitus.

Discomfort or bruising may occur at the puncture site or the person may feel dizzy or faint. Pressure to the puncture site until the bleeding stops reduces bruising. Warm packs to the puncture site relieve discomfort.

Total cholesterol guidelines are:

• near optimal: 100-129 mg/dL

Lipoprotein testing is ordered by a physician. A nurse or phlebotomist usually collects the blood sample for the tests. Testing is most often performed by clinical laboratory scientists/medical technologists or clinical laboratory technicians/medical laboratory technicians. All clinicians should be well versed in the NCEP guidelines and treatment recommendations including both dietary and drug interventions. Patient’s with high cho-

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Resources BOOKS

Burtix, Carl A. and Edward R. Ashwood. Tietz Textbook of Clinical Chemistry, Third ed., Philadelphia, W.B. Saunders Company, 1999. Rifai, Nader, G. Russell Warnick, and Marek H. Dominiczak. Handbook of Lipoprotein Testing. Washington, D.C.: American Association of Clinical Chemistry (AACC) Press, 1997. ORGANIZATIONS

American Heart Association. 7272 Greenville Avenue, Dallas, TX, 75231-4596. 214-706-1220. . National Cholesterol Education Program. The National Heart, Lung, and Blood Institute. National Institutes of Health. PO Box 30105, Bethesda, MD, 20824-0105. 301-2511222. May 2001.

Jane E. Phillips

Liquid diets see Fad diets

Lithotripsy Definition Lithotripsy is a therapeutic medical procedure used to disintegrate stones (calculi) in the urinary tract and kidneys. Extracorporeal shock wave lithotripsy (ESWL) uses shock waves generated outside the body and is noninvasive. Intracorporeal shock wave lithotripsy (ISWL) delivers shock waves through a specially designed scope used for the urinary tract (ureteroscope) and kidneys (nephroscope) and is a minimally invasive procedure. Ultrasound lithotripsy also uses a scope to deliver ultrasonic waves (mechanical vibrations) and is minimally invasive.

Purpose Lithotripsy is used when a kidney stone is too large to pass on its own, or when a stone becomes stuck in a ureter (a tube which carries urine from the kidney to the bladder) and will not pass. Kidney stones are extremely painful and can cause serious medical complications,

such as kidney damage, if not removed. Usually, stones smaller than 5 mm in diameter can pass without intervention, while stones larger than 7 mm in diameter require lithotripsy or the placement of a urethral or ureteral stent to help them pass. Stones larger than 10 mm require lithotripsy or surgery. ESWL is a noninvasive alternative to open surgery (which is only very rarely performed for stones now) or percutaneous nephrolithotomy. ESWL is used in patients with stones less than or equal to 1 cm located in the kidneys or ureters. ISWL is a minimally invasive endoscopic technique that is used in patients with stones over 1 cm, with stones in the lower urinary tract, with impacted stones, and when ESWL is unsuccessful. Both ESWL and ISWL can also be used to fragment gallbladder and bile duct stones.

Precautions ESWL should not be considered for patients with severe skeletal deformities, patients weighing over 300 lbs (136 kg), patients with abdominal aortic aneurysms, or patients with uncontrollable bleeding disorders. Patients who are pregnant should not be treated with ESWL. Patients with cardiac pacemakers should be evaluated by a cardiologist familiar with lithotripsy. Lithotripsy may temporarily inhibit the pacemaker or cause circuit damage leading to erratic functioning or cessation of the pacemaker. The cardiologist should be present during the lithotripsy procedure in the event there are problems with the pacemaker.

Description Lithotripsy uses focused shock waves to fragment a stone in the kidney or the ureter. In ESWL, the patient is placed on a table in contact with a water-filled cushion; and a shock wave is generated, travels through the water, and shatters and fragments the stone. Older ESWL systems involved immersing the patient in a tub of water; but this space-consuming, awkward method has been replaced by water-filled cushions. Once the stone is fragmented, the resulting gravel is left to pass on its own; the patient may have been stented prior to the procedure to widen the urethra and or ureters to allow the fragments to pass easily and with less pain. In ISWL, a ureteroscope is inserted through the urethra and bladder and into the ureters, or a nephroscope is inserted, usually through an incision in the patient’s back. Once the stone is located using the endoscope, an electrohydraulic, laser, or ultrasound lithotripter can be used to fragment the stone. In ISWL using an electrohydraulic lithotripter, a probe is inserted through the endoscope and against the stone, and shock waves are delivered by a generator. In laser ISWL,

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lesterol levels may be requested to consult a dietician in order to evaluate their meal plans, and learn how to follow the Step 1 or 2 diets that may be needed to lower the LDL cholesterol.

Lithotripsy A lithotriptor in use by patient in tub. This noninvasive method crushes kidney stones through shock waves. (Photo Researchers, Inc. Reproduced by permission.)

a pulsed-dye laser is used to deliver laser energy through a fiber inserted through the endoscope and into the stone. Ultrasound ISWL uses a generator to produce mechanical vibrations delivered to the stone via a probe tip inserted through the generator. In ISWL, after the stone is fragmented, the pieces can be removed using a grasper or basket or left to pass on their own if they are small enough.

Preparation Prior to the lithotripsy procedure, a complete physical examination is done, including a urine analysis, followed by imaging tests to determine the number, location, and size of the stone or stones. A test called an intravenous pyelogram, or IVP, is often used to locate the stones and determine the degree of obstruction (blockage). An IVP involves injecting a dye (contrast medium) into a vein in the arm. This dye, which shows up on x ray, travels through the bloodstream and is excreted by the kidneys. The dye then flows down the ureters and into the bladder. The dye surrounds the stones, and x rays are then used to evaluate the stones and the anatomy of the urinary system. For those patients who are allergic to the dye, ultrasound, which uses focused sound waves, or 1414

computed tomography without contrast dye is performed. Blood tests are done to determine if any potential bleeding problems exist. For women of childbearing age, a pregnancy test is done to make sure the patient isn’t pregnant; and elderly patients have an elctrocardiogram (ECG) done to make sure no potential heart problems exist. Some patients may have a stent placed prior to the lithotripsy procedure. A stent is a plastic tube placed in the ureter which allows the passage of gravel and urine after the procedure is completed.

Aftercare Most patients have a lot of blood in their urine after the lithotripsy procedure. This is normal and should clear after several days to a week or so. Lots of fluids should be taken to encourage the flushing of any gravel remaining in the urinary system. The patient may be asked to urinate through a strainer and collect any stone fragments that pass for examination by the physician. Patients with stents may experience some discomfort during urination or during certain movements; this is normal. The patient should follow up with the urologist in about two weeks to make sure that everything is going as planned. If a stent

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Aneurysm—A dilation of the wall of an artery which causes a weak area prone to rupturing. Bladder—Organ in which urine is stored prior to urination. Bleeding disorder—Problems with the clotting mechanism of the blood. Cardiologist—A physician who specializes in problems with the heart and its vessels. Computed tomography—An imaging examination that uses x-rays to produce a cross-sectional image of the anatomical area of interest; used to image the urinary tract and kidneys to detect kidney stones. ECG—Electrocardiogram; a tracing of the electrical activity of the heart. Gravel—The debris which is formed from a fragmented kidney stone. IVP (Intravenous pyelogram)—The use of a dye, injected into the veins, used to locate kidney stones. Also used to determine the anatomy of the urinary system. Kidney stones—Also called calculi; hard masses that form in the urinary tract and which can cause pain, bleeding, obstruction, or infection. Stones are primarily made up of calcium and can vary in size from a few millimeters to over a centimeter and more in diameter.

has been inserted, it is normally removed at this time. Patients may return to work whenever they feel able. Occasionally, the ESWL procedure does not break stones into pieces small enough to pass. In these cases, an endoscope may be used to remove the pieces after the ESWL procedure.

Nephroscope—An endoscope, a thin flexible tube with optics, used to examine the kidneys and through which intracorporeal lithotripsy can be performed. Percutaneous nephrolithotomy—A minimally invasive endoscopic procedure involving a small incision in the back through which a nephroscope is inserted to remove stones from the kidney; used in conjunction with ISWL and after unsuccessful ESWL. Stent—A small, short plastic tubular device placed in the urethra or ureters to widen them in order for stones and stone fragments to pass easily. Ultrasound—Sound waves used to determine the internal structures of the body. Ureter—A tube which carries urine from the kidney to the bladder. Ureteroscope—An endoscope, a thin flexible tube with optics, used to examine the ureters and through which intracorporeal lithotripsy can be performed. Urethra—A tube through which urine passes during urination. Urologist—A physician who specializes in problems of the urinary system.

prior to the procedure due to obstruction by stones. Prophylactic antibiotics are administered to treat infection. Other postprocedural complications sometimes associated with the administration of anesthetics include nausea, vomiting, and allergic reaction.

Health care team roles Complications Abdominal pain is not uncommon after lithotripsy, but it is usually not cause to worry. However, persistent or severe abdominal pain may imply unexpected internal injury. Colicky renal pain is very common as gravel is still passing. Other problems may include perirenal hematomas (blood clots around the kidneys); hemorrhage; pancreatitis (inflammation of the pancreas); damage to nearby organs and tissues (during ISWL); and obstruction by stone fragments. The most common complication is urinary tract infection, sometimes present

Lithotripsy is performed by a urologist or urologic surgeon, sometimes in conjunction with a radiologist, and with assistance from nursing staff for patient monitoring and medication administration during the procedure. The procedure may also be performed by a uroradiologist. If ISWL requires general anesthesia or conscious sedation, an anesthesiologist and/or nurse anesthetist may need to be present for the procedure. Because ESWL uses x rays to locate the stones, a radiologic technologist may be required to assist with operating the x-ray equipment.

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KEY TERMS

Liver

Resources BOOKS

Tanagho, Emil, and Jack McAninch, eds. Smith’s General Urology. 14th ed. Norwalk, CT: Appleton and Lange Publishers, 1995.

Function

PERIODICALS

Portis, Andrew J. and Chandru P. Sundaram. “Diagnosis and Initial Management of Kidney Stones.” American Family Physician 63, no. 7 (April 1, 2001): 1329-1338. Shagam, Janet Yagoda. “Extracorporeal Shock Wave Lithotripsy.” Radiologic Technology 72, no. 2 (November-December 2000): 145-163. ORGANIZATIONS

American Urological Association. 1120 North Charles Street, Baltimore, MD 21201. 410-727-1100. . National Kidney Foundation. 30 East 33rd Street, Suite 1100, New York, NY 10016. (800) 622-9010. . Society of Urologic Nurses and Associates. East Holly Avenue, Box 56, Pitman, NJ 08071-0056. 609-256-2335. .

Jennifer E. Sisk, M.A.

Liver-spleen scan see Liver radionuclide scan

Liver Definition The liver is the largest gland and largest internal organ in the human body (the skin is the largest organ overall).

Description Weighing 3-3.5 lbs (1.4-1.6 kg), the liver is a dark red, wedge-shaped gland approximately eight and a half inches long (roughly the size of a football). It is located in the right side of the abdominal area just below the diaphragm and above the stomach. Approximately 1.5 qts (1.5 L) of blood flow through the liver each minute. The liver holds about 13% of the body’s blood supply. It is furnished with blood from two large vessels, the portal vein and the hepatic artery (hepatic means liver). Blood that has circulated through the stomach, spleen, and intestine enters the liver through the portal vein as part of the portal circulation system. 1416

The liver extracts nutrients and toxins from this blood, which is then returned through the hepatic vein to the right side of the heart. The hepatic artery supplies oxygenated blood directly from the heart to the liver.

Some of the liver’s many important functions include: • Production of bile which is stored in the gall bladder and used to digest fats. If the excretion of bile is blocked, the stools become pale and retain fat. As a result, fat-soluble vitamins (vitamins A,D, E, and K) are not properly absorbed and levels of bilirubin, the main component of bile, rises in the blood. Once bilirubin levels reach a certain level, jaundice or yellowing of the skin and eyes occurs. • Synthesis of proteins, including albumin. Albumin is the predominant protein in blood plasma and helps to retain fluid within the blood vessels. The loss of albumin results in fluid shifting from blood vessels to the surrounding tissue. The result is swelling of tissue, a condition called edema. • Production of blood-clotting factors that control bleeding. Loss of clotting factors leads to increased chance of hemorrhage. • Metabolism of hormones and medications, such as estrogen and acetominophen (Tylenol). When the liver is damaged, its ability to metabolize hormones decreases. This can result in changes to estrogen and testosterone levels in the body. Symptoms of these changes include loss of pubic hair and the development of spider angiomas, small clusters of red blood vessels on the skin of the upper body, in both males and females. Men sometimes experience a decrease of testicular size and development of breast tissue (a condition called gynecomastia). A decline in the body’s ability to metabolize medications means that normal doses can turn into toxic levels. Therefore, doses of medicines are often reduced for people who have liver disease. • Regulation of glucose levels. Loss of liver cells leads to poorly controlled glucose levels. Glucose levels may soar after eating (hyperglycemia) or fall dangerously low between meals (hypoglycemia). This poor regulation of blood sugar is due to a different mechanism than the mechanisms that lead to diabetes types I and II. • Conversion of ammonia, a by-product of metabolism, into a less toxic form called urea. Inability to convert ammonia to urea results in elevated ammonia levels in the blood. This can result in a condition called hepatic encephalopathy, which is a neurological syndrome characterized by alterations in mental status and behav-

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• sleep disturbances, mental confusion, and coma that may result from an accumulation of toxic substances that impair brain function • fatigue or loss of stamina

Role in human health A healthy liver enables the human body to: • produce energy when needed • manufacture new proteins • store certain vitamins, minerals, and sugars • regulate transport of fat stores

• loss of sexual drive or diminished performance The most common liver diseases are as follows: Viral hepatitis • Hepatitis A spreads through contaminated water and food.

• facilitate the digestive process by producing bile

• Hepatitis B may be transmitted through transfusions, cuts, kissing, tooth brushing, ear piercing, tattooing, dental work, or during sexual contact.

• control the production and excretion of cholesterol

• Hepatitis C primarily spreads through infected blood.

• neutralize and destroy toxic substances

The liver often becomes tender and enlarged, and the patient usually experiences fever, weakness, nausea, vomiting, jaundice, and aversion to food. The virus may be present in the bloodstream, intestines, feces, saliva, and other body secretions. Hepatitis is common in the United States and some forms of it can be extremely infectious. Most people recover from viral forms of the disease without treatment, but some die and others may develop a chronic, disabling illness. In the United States there are more than four million hepatitis carriers.

• regulate blood clotting

• metabolize alcohol • monitor proper chemical and drug blood levels • cleanse the blood and discharging waste products into the bile • maintain hormone balance • serve as the main fetal blood forming organ • resist infection • regenerate its damaged tissue • store iron

Common diseases and disorders Symptoms and signs of liver disease: • jaundice, or abnormal yellowing of the skin and eyes (often the first, and may be the only, sign of liver disease) • dark urine • gray, yellow, or light colored stools • nausea, vomiting, and/or loss of appetite • intestinal bleeding due to liver diseases obstructing blood flow. (Bleeding may result in vomiting of blood, and bloody or black stools.) • abdominal swelling (Liver disease may cause ascites, an accumulation of fluid in the abdominal cavity.) • prolonged generalized itching • an increase or decrease of more than 5% body weight in two months • abdominal pain

Alcohol-related liver disorders Liver disorders related to alcohol include fatty liver, alcoholic hepatitis, and alcoholic cirrhosis. Fatty liver, the most common alcohol-related liver disorder, causes liver enlargement and abdominal discomfort. Swollen livers are often tender or painful, and may cause jaundice and liver function abnormalities. Alcoholic hepatitis often results in nausea, vomiting, abdominal pain, fever, jaundice, liver enlargement and tenderness, and white blood cell count elevation. At times alcoholic hepatitis may be asymptomatic. Cirrhosis Over 25,000 Americans die from cirrhosis each year. It is the seventh leading cause of death. Among those 2544, it is the fourth disease-related cause of death. Cirrhosis of the liver occurs when damaged liver cells are replaced by scar tissue causing diminished blood flow, which causes additional liver cell death. Loss of liver function results in gastrointestinal disturbances, emaciation, liver and spleen enlargement, jaundice, fluid accumulation in the abdomen and other tissues. Obstructed circulation often causes massive vomiting of blood.

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ior. Although acute episodes can be reversible, severe cases of hepatic encephalopathy can lead to coma and death.

Liver biopsy

Reyes syndrome is a fatal disorder in which fat accumulates in the liver.

KEY TERMS

Cirrhosis may result from extensive liver injury. Ascites—Accumulation of fluid in the abdominal cavity. Bile—Yellowish substance released by the liver into the intestines to digest fats.

Liver cancer Most liver cancer results from the spread of cancer from other organs to the liver (metastasis). Resources

Any severe liver injury may cause cirrhosis. Over half of the deaths from cirrhosis result from alcohol abuse, hepatitis, and other viruses. Toxins, chemicals, excessive iron or copper, severe drug reactions, and bile duct obstruction may also cause cirrhosis.

BOOKS

Cotran, Ramzi, S. Robbins Pathologic Basis of Disease. 6th ed. Philadelphia: W.B. Saunders Company, 1999. Guyton, Arthur C. Textbook of Medical Physiology. 10th ed. Philadelphia: W.B. Saunders Company, 2000. PERIODICALS

Gallstones Gallstones form when cholesterol and/or pigment in bile crystallize into gall stones. Gall stones vary in size from small pebbles to golf balls. Occasionally gallstones become lodged in the bile ducts leading from the gallbladder to the duodenum (first part of the small intestine). This may cause extreme abdominal pain. When gall stones block bile ducts, bile cannot flow into the intestines, and backs up into the bloodstream causing jaundice. Gallstones are more common in people over 40, especially among women and the obese. Each year in the United States, 400-500,000 gallbladders are surgically removed. Children’s liver disorders Tens of thousands of American children contract liver diseases causing hundreds of deaths each year. The most common of these diseases are: Biliary atresia is caused by the lack, or inadequate size, of bile ducts connecting the liver to the intestine. Unable to excrete bile, death results from cirrhosis and bleeding by two years of age. Chronic active hepatitis destroys liver cells replacing them with scar tissue. It is caused by an unknown process that resembles an allergy to the child’s own liver tissue. Galactosemia, an inherited disease, is caused by the lack of an enzyme needed to digest milk sugar. As a result, milk sugar accumulates in the liver and other organs, leading to cirrhosis of the liver, cataracts, and brain damage. Wilson’s disease occurs when copper accumulates in the liver due to an inherited abnormality, causing cirrhosis and brain damage. 1418

Smales, Caroline. “Hepatitis: Symptoms, Treatments, and Prevention.” Nursing Times (4 November 1998): 58-60. ORGANIZATIONS

American Liver Foundation. 75 Maiden Lane, Suite 603, New York, NY 10038. 1-800-GOLIVER (1-800) 465-4837) .

Bill Asenjo, MS, CRC

Liver biopsy Definition A liver biopsy is a medical procedure performed to obtain a small piece of liver tissue for diagnostic testing. The sample is examined under a microscope by a doctor who specializes in the effects of disease on body tissues (a pathologist) to detect abnormalities of the liver. Liver biopsies are sometimes called percutaneous liver biopsies, because the tissue sample is obtained by going through the patient’s skin. This is a useful diagnostic procedure with very low risk and little discomfort to the patient.

Purpose A liver biopsy is usually done to evaluate the extent of damage that has occurred to the liver because of chronic and acute disease processes or toxic injury. Biopsies are often performed to identify abnormalities in liver tissues after imaging studies and radiopharmaceutical scans have failed to yield clear results. A liver biopsy may be ordered to diagnose or stage any of the following conditions or disorders:

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• cirrhosis • repeated abnormal results from liver function tests • alcoholic liver disease • unexplained swelling or enlargement of the liver (hepatomegaly) • suspected drug-related liver damage such as acetaminophen poisoning • hemochromatosis, a condition of excess iron in the liver • intrahepatic cholestasis, the build up of bile in the liver • hepatitis • primary cancers of the liver, such as hepatomas, cholangiocarcinomas, and angiosarcomas • metastatic cancers of the liver (These are over 20 times as common in the United States as primary cancers.) • post liver transplant to measure graft rejection • fever of unknown origin • suspected tuberculosis, sarcoidosis, or amyloidosis

Precautions When performing the liver biopsy and blood collection that precedes it, the physician and other health care providers should follow universal precautions for the prevention of transmission of bloodborne pathogens. Some patients should not have percutaneous liver biopsies. They include those with any of the following conditions: • a platelet count below 100,000 • a prothrombin test time greater than three seconds over the reference interval • a liver tumor with a large number of veins • a large amount of abdominal fluid (ascites) • infection anywhere in the lungs, the lining of the chest or abdominal wall, the biliary tract, or the liver • benign tumors (angiomas) of the liver (These tumors consist mostly of enlarged or newly formed blood vessels and may bleed heavily.) • biliary obstruction

Description Percutaneous liver biopsy is sometimes called aspiration biopsy or fine needle aspiration (FNA) because it is done with a hollow needle attached to a suction syringe. The special needles that are used to perform a

liver biopsy are called Menghini or Jamshedi needles. The amount of specimen collected should be about 1-2 cc. In many cases the biopsy is done by a doctor who specializes in x rays and imaging studies (a radiologist). The radiologist will use computed tomography scan (CT scan) or ultrasound to guide the needle to the target site for the biopsy. Some ultrasound guided biopsies are performed using a biopsy gun which has a spring mechanism which contains a cutting sheath. This type of procedure gives a greater yield of tissue. An hour or so before the biopsy, the patient will be given a sedative to aid in relaxation. The patient is then asked to lie on the back with the right elbow to the side and the right hand under the head. The patient is instructed to lie as still as possible during the procedure. He or she is warned to expect a sensation resembling a punch in the right shoulder when the needle passes a certain nerve (the phrenic nerve) but to hold still in spite of the momentary feeling. Following these instructions to the patient, the doctor marks a spot on the skin where the needle will be inserted. The right side of the upper abdomen is thoroughly cleansed with an antiseptic solution, generally iodine. The patient is then given a local anesthetic at the biopsy site. The doctor prepares the needle by drawing sterile saline solution into a syringe. The syringe is then attached to the biopsy needle, which is inserted into the patient’s chest wall. The doctor then draws the plunger of the syringe back to create a vacuum. At this point the patient is asked to take a deep breath and hold it. The needle is inserted into the liver and withdrawn quickly, usually within two seconds or less. The negative pressure in the syringe draws or pulls a sample of liver tissue into the biopsy needle. As soon as the needle is withdrawn, the patient can breathe normally. This step takes only a few seconds. Pressure is applied at the biopsy site to stop any bleeding and a bandage is placed over it. The liver tissue sample is placed in a cup with a 10% formalin solution and sent to the laboratory immediately. The entire procedure takes 10 to 15 minutes. Test results are usually available within a day. Most patients experience minor discomfort during the procedure, but not severe pain. Mild medications of a non-aspirin type can be given after the biopsy if the pain lasts for several hours.

Preparation Liver biopsies require some preparation of the patient. Since aspirin and ibuprofen (Advil, Motrin) are known to inhibit platelets and lessen clotting function, it is best to avoid these medications for at least a week

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• jaundice

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KEY TERMS Aspiration—The technique of removing a tissue sample for biopsy through a hollow needle attached to a suction syringe. Bile—Liquid produced by the liver that is excreted into the intestine to aid in the digestion of fats. Biliary—Relating to bile. Biopsy—The surgical removal and microscopic examination of living tissue for diagnostic purposes. Cholestasis—A blockage in the flow of bile. Cirrhosis—A progressive disease of the liver characterized by the death of liver cells and their replacement with fibrous tissue. Formalin—A clear solution of diluted formaldehyde that is used to preserve liver biopsy specimens until they can be examined in the laboratory. Gross inspection—A visual examination of the tissue with the unaided eye performed by a pathologist. Hepatitis—Inflammation of the liver, caused by infection or toxic injury. Jaundice—Also termed icterus. An increase in blood bile pigments that are deposited in the skin, eyes, deeper tissue and excretions. The skin and whites of the eye will appear yellow. Menghini needle/Jamshedi needle—Special needles used to obtain a sample of liver tissue by aspiration. Percutaneous biopsy—A biopsy in which the needle is inserted and the sample removed through the skin. Prothrombin test—A common test to measure the amount of time it takes for a patient’s blood to clot. Units are in seconds. Vital signs—A person’s essential body functions, usually defined as the pulse, body temperature, and breathing rate. Vital signs are checked periodically during procedures like liver biopsies to make sure that the patient is not having physical problems as a result of the procedure.

before the biopsy. The doctor should check the patient’s records to see whether he or she is taking any other medications that may affect blood clotting. A platelet count 1420

(or complete blood count) and prothrombin time are performed prior to the biopsy. These tests determine whether there is an abnormally high risk of uncontrolled bleeding from the biopsy site which may contraindicate the procedure. The patient should limit food or drink for a period of four to eight hours before the biopsy. Before the procedure, the patient or family member should sign a consent form. The patient will be questioned for any history of allergy to the local anesthetic and asked to empty the bladder so that he or she will be more comfortable during the procedure. His or her pulse rate, temperature, and breathing rate (vital signs) will be noted so that the doctor can tell during the procedure if he or she is having any physical problems.

Aftercare Liver biopsies are now considered outpatient procedures in most hospitals. Patients are asked to lie on their right sides for one hour and then to rest quietly for three more. At regular intervals, a nurse checks the patient’s vital signs. If there are no complications, the patient is sent home but is asked to stay within an hour from the hospital since delayed bleeding may occur. Patients should arrange to have a friend or relative take them home after discharge. Bed rest for a day is recommended, followed by a week of avoiding heavy work or strenuous exercise. The patient can resume eating a normal diet. Some mild soreness in the area of the biopsy is normal after the anesthetic wears off. Irritation of the muscle that lies over the liver can also cause mild discomfort in the shoulder for some patients. Acetaminophen can be taken for minor soreness, but aspirin and ibuprofen products are best avoided. The patient should, however, call the doctor if there is severe pain in the abdomen, chest, or shoulder; difficulty breathing; or persistent bleeding. These signs may indicate that there has been leakage of bile into the abdominal cavity, or that air has been introduced into the cavity around the lungs.

Complications The complications associated with a liver biopsy are usually very small. The most significant risk is prolonged internal bleeding. In about 0.4% of cases, a patient with liver cancer will develop a fatal hemorrhage from a percutaneous biopsy. These fatalities result because some liver tumors are supplied with a large number of blood vessels and bleed very easily. Other complications from percutaneous liver biopsies include the leakage of bile or the introduction of air into the chest cavity (pneumothorax). There is also a small chance that an infection may

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Results After the biopsy, the liver sample is sent to the pathology laboratory and examined. A normal (negative) result would find no evidence of pathology in the tissue sample. It should be noted that many diseases of the liver are focal and not diffuse; an abnormality may not be detected, if the sample was taken from an unaffected site. If symptoms persist, the patient may need to undergo a repeat biopsy. The pathologist will perform a gross inspection of the sample to note any changes in appearance. In cirrhosis, the sample will be fragmented and hard. Fatty liver, seen in heavy drinkers, will float in the formalin solution and will be yellow. Carcinomas are white. The pathologist will also look for deposition of bile pigments (green) indicating cholestasis (obstruction of bile flow). In preparation for microscopic examination, the tissue will be frozen and cut into thin sections. These will be mounted on glass slides and stained with various dyes to aid in identifying microscopic structures. Using the microscope, the pathologist will examine the tissue samples, and identify abnormal cells or microarchitecture and any deposited substances such as iron or copper. In liver cancer, small dark malignant cells will be visible within the liver tissue. An infiltration of white blood cells may signal infection. The pathologist also checks for the number of bile ducts and whether they are dilated. He or she also looks at the health of the small arteries and portal veins. Fibrosis will appear as scar tissue and fatty changes are diagnosed by the presence of lipid droplets. Many different findings may be noted and a differential diagnosis (one out of many possibilities) can often be made. In difficult cases, other laboratory tests such as liver function enzymes, will aid the clinician in determining the final diagnosis.

Health care team roles The liver biopsy requires the skill of many clinicians including the radiologist, hepatologist and pathologist in order to make the diagnosis. Nurses will assist the physician during the biopsy procedure and in caring for the patient after the procedure. Tissues are prepared for microscopic evaluation by a histologic technician. Patient education Patients should be told what to expect in the way of discomfort pre- and post-procedure. In addition, they

should be advised about what medications they should not take before or after the biopsy. It is important for the clinician to reassure the patient concerning the safety of the procedure. Resources BOOKS

“Hepatobiliary Disorders: Introduction.” In Professional Guide to Diseases, edited by Stanley Loeb, et al. Springhouse, PA: Springhouse Corporation, 2001. Kanel, Gary C. and Jacob Korula. Liver Biopsy Evaluation, Histologic Diagnosis and Clinical Correlations. Philadelphia, PA: W.B. Saunders Company, 2000. “Screening and Diagnostic Evaluation.” In The Merck Manual of Diagnosis and Therapy, 17th Edition, edited by Robert Berkow, et al. Whitehouse Station, NJ: Merck Research Laboratories, 1999. ORGANIZATIONS

American Liver Foundation. 1425 Pompton Avenue, Cedar Grove, NJ 07009. (800) 465-4837. .

Jane E. Phillips, PhD

Liver cancer Definition Liver cancer is a form of cancer with a high mortality rate. Liver cancers are classified into two types. They are either primary, when the cancer starts in the liver itself; or metastatic, when the cancer has metastasized (spread) to the liver from some other part of the body.

Description Primary liver cancer Primary liver cancer is a relatively rare disease in the United States, representing about 2% of all malignancies. It is much more common in other parts of the world, representing from 10-50% of malignancies in Africa and parts of Asia. According to the American Cancer Society, in the United States during 1998, more than 14,000 new cases of primary liver cancer were diagnosed, and approximately 13,000 deaths were attributable to it. TYPES OF PRIMARY LIVER CANCER. In adults, most primary liver cancers belong to one of two types: hepatomas, also known as hepatocellular carcinomas, which start in the liver tissue itself; and cholangiocarcinomas, which are cancers that develop in the bile ducts

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occur, or an internal organ such as the lung, gall bladder, or kidney could be punctured. This risk is decreased when using the ultrasound or CT guided procedure.

Liver cancer

to place some individuals at higher risk of developing liver cancer. These factors include: • Gender. The male/female ratio for hepatoma is 4:1. • Age over 60 years. • Environmental exposure to carcinogens (cancer causing substances). Examples of environmental carcinogens are aflatoxin, substance produced by a mold that grows on rice and peanuts; thorium dioxide, used at one time as a contrast dye for x rays of the liver; and vinyl chloride, used in manufacturing plastics. • Use of oral estrogens for contraception (birth control). A three-dimensional computed tomography (CAT) scan of a patient’s abdomen showing a malignant tumor (upper right) in the liver. (Photo Researchers, Inc. Reproduced by permission.)

inside the liver. About 90% of primary liver cancers are hepatomas. In the United States, about one person in every 40,000 will develop a hepatoma; in Africa and Asia, over 8 persons in 40,000 will develop this form of cancer. Two rare types of primary liver cancer are mixedcell tumors and Kupffer cell sarcomas. There is one type of primary liver cancer that usually occurs in children younger than four years of age and between the ages of 12-15. This type of childhood liver cancer is called a hepatoblastoma. Unlike liver cancers in adults, hepatoblastomas have a good chance of being treated successfully. Approximately 70% of children with hepatoblastomas experience complete cures. When the tumor is detected early, the survival rate is over 90%. Metastatic liver cancer The second major category of liver cancer, metastatic liver cancer, is about 20 times as common in the United States as primary liver cancer. Because blood from all parts of the body must pass through the liver for filtration, cancer cells from other organs and tissues easily reach the liver, where they can lodge and grow into secondary tumors. Primary cancers in the colon, stomach, pancreas, rectum, esophagus, breast, lung, or skin are the most likely to metastasize to the liver. It is not unusual for the metastatic cancer in the liver to be the first noticeable sign of a cancer that started in another organ. Second only to cirrhosis, metastatic liver cancer is the most common cause of fatal liver disease.

Causes and symptoms Risk factors for primary liver cancer The exact cause of primary liver cancer is still unknown. In adults, however, certain factors are known 1422

• Hereditary hemochromatosis. Hemochromatosis is a disorder characterized by abnormally high levels of iron storage in the body. It often progresses to cirrhosis. • Cirrhosis. Hepatomas appear to be a frequent complication of cirrhosis of the liver. Between 30-70% of hepatoma patients also have cirrhosis. It is estimated that a patient with cirrhosis has 40 times the chance of developing a hepatoma than a person with a healthy liver. Cirrhosis usually results from alcohol abuse or chronic viral hepatitis. • Exposure to hepatitis B (HBV) or hepatitis C (HBC) viruses. In Africa and most of Asia, exposure to hepatitis B is an important factor; in Japan and some Western countries, exposure to hepatitis C is associated with a higher risk of developing liver cancer. In the United States, nearly 25% of patients with liver cancer have evidence of HBV infection. Hepatitis B and C are commonly found among intravenous drug abusers. Symptoms of liver cancer The early symptoms of primary, as well as metastatic, liver cancer are often vague and not specific to liver disorders. The long delay between the beginning of the tumor’s growth and signs of illness is the major reason the disease has such a high mortality rate. At the time of diagnosis, patients are often tired, with fever, abdominal pain, and loss of appetite. They may look emaciated and generally ill. As the tumor grows bigger, it stretches the membrane surrounding the liver (the capsule), causing pain in the upper abdomen on the right side. The pain may extend into the back and shoulder. Some patients develop ascites (a collection of fluid) in the abdominal cavity. Others may have gastrointestinal bleeding. In addition, the tumor may block the ducts of the liver or the gall bladder, leading to jaundice. In patients with jaundice, the whites of the eyes and the skin may turn yellow, and the urine becomes dark-colored.

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Physical examination When a diagnosis of primary liver cancer is suspected, the physician will scrutinize the patient’s history for risk factors and pay close attention to the condition of the abdomen during the physical examination. Masses or lumps in the liver and ascites can often be felt while the patient is lying flat on the examination table. The liver is usually swollen and hard in patients with liver cancer; it may be sore when the physician presses on it. In some cases, the patient’s spleen is also enlarged. The physician may be able to hear a bruit (an abnormal sound) or friction rub when a stethoscope is used to listen to the blood vessels that lie near the liver. These abnormal sounds are caused by the pressure of the tumor on the blood vessels. Laboratory tests Blood tests, performed by a laboratory technologist or technician, may be used to evaluate liver function or to confirm risk factors, such as hepatitis B or C infection. About 75% of patients with liver cancer show evidence of hepatitis infection. Between 50-75% of primary liver cancer patients have abnormally high blood serum levels of alpha-fetoprotein (AFP). The AFP test, however, cannot be used by itself to confirm a diagnosis of liver cancer, because cirrhosis or chronic hepatitis can also produce high alpha-fetoprotein levels. Tests for alkaline phosphatase, bilirubin, lactic dehydrogenase, and other chemicals indicate that the liver is not functioning normally. Though useful, abnormal liver function test results can not alone establish the diagnosis of liver cancer. Imaging studies Imaging studies are used to locate specific areas of abnormal tissue in the liver. Liver tumors as small as an inch across can be detected by ultrasound or computed tomography scan (CT scan). Imaging studies, however, cannot tell the difference between a hepatoma and other abnormal masses or nodules in the liver. A sample of liver tissue for biopsy is needed to make the definitive diagnosis of a primary liver cancer. CT or ultrasound may be used to guide the physician in selecting the best location for obtaining the biopsy sample. Chest x rays may be used to see whether the liver tumor is primary or has metastasized from a primary tumor in the lungs. Imaging studies, including chest x rays, are usually performed by a radiology technician.

Liver biopsy Liver biopsy provides the definite diagnosis of liver cancer. A sample of the liver or tissue fluid is removed with a fine needle and is examined by a pathologist, under a microscope, for the presence of cancer cells. In about 70% of cases, the biopsy is positive for cancer. In most cases, there is little risk to the patient from the biopsy procedure. In about 0.4% of cases, however, the patient develops a fatal hemorrhage from the biopsy because some tumors are supplied with a large number of blood vessels and bleed very easily. Laparoscopy The physician also may perform a laparoscopy to assist in the diagnosis of liver cancer. A laparoscope is a small tube-shaped instrument with a light at one end that is inserted into the patient’s abdomen. A small piece of liver tissue is removed and sent for biopsy (microscopic examination for the presence of cancer cells).

Treatment Treatment of liver cancer is based on several factors, including the type of cancer (primary or metastatic); stage (early or advanced); the location of other primary cancers or metastases; the patient’s age; and other coexisting diseases, including cirrhosis. For many patients, treatment of liver cancer is primarily intended to relieve the pain caused by the cancer; it aims to relieve symptoms but not to cure the disease. Surgery Few liver cancers in adults can be cured surgically because they are usually too advanced by the time they are discovered. If the cancer is contained within one lobe of the liver, and if the patient does not have cirrhosis, jaundice, or ascites, then surgery is the best treatment option. Patients who can have their entire tumors removed have the best chances for survival. Unfortunately, only about 5% of patients with metastatic cancer (from primary tumors in the colon or rectum) fall into this group. If the entire visible tumor can be removed, about 25% of patients will be cured. The surgical procedure that is performed is called a partial hepatectomy, or partial removal of the liver. The surgeon will remove either an entire lobe of the liver (a lobectomy) or cut out the area around the tumor (a wedge resection). Chemotherapy Some patients with metastatic cancer of the liver may have their lives prolonged for a few months by chemotherapy, although cure is not possible. If the

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no suitable donors. Further research in the field of transplant immunology may make liver transplantation a viable treatment modality.

KEY TERMS Aflatoxin—A substance produced by molds that grow on rice and peanuts. Exposure to aflatoxin is thought to explain the high rates of primary liver cancer in Africa and parts of Asia. Alpha-fetoprotein—A protein in blood serum that is found in abnormally high concentrations in most patients with primary liver cancer. Cirrhosis—A chronic degenerative disease of the liver, in which normal cells are replaced by fibrous tissue. Cirrhosis is a major risk factor for the later development of liver cancer. Hepatitis—A viral disease characterized by inflammation of the liver cells (hepatocytes). People infected with hepatitis B or hepatitis C virus are at an increased risk for developing liver cancer.

tumor cannot be removed by surgery, then a catheter may be placed in the main artery (hepatic artery) of the liver and an implantable infusion pump can be installed. The pump allows much higher concentrations of the anticancer drug to be carried to the tumor than is possible with chemotherapy carried through the bloodstream. The drug used for infusion pump therapy is usually floxuridine (FUDR), given for 14-day periods alternating with 14-day rests. Systemic chemotherapy, given through a peripheral vein, can also be used to treat liver cancer. The drugs usually used are 5-fluorouracil (Adrucil, Efudex) or methotrexate (MTX, Mexate). Systemic chemotherapy does not, however, significantly increase survival time. Radiation therapy Radiation therapy may be used to relieve some symptoms of the disease. In general, radiation therapy will not prolong survival. Radioimmunotherapy is an experimental form of radiation therapy used to treat some types of liver cancer. A radioactive isotope is given intravenously and concentrates in the liver, where it radiates the tumor internally. Liver transplantation Since 1998, removal of the entire liver (total hepatectomy) and liver transplantation have very rarely been used to treat liver cancer. This is because very few patients are eligible for this procedure, either because the cancer has spread beyond the liver or because there are 1424

Prognosis Liver cancer has a very poor prognosis because it is often not diagnosed until it has metastasized. Fewer than 10% of patients survive three years after the initial diagnosis; the overall five-year survival rate for patients with hepatomas is around 4%. Most patients with primary liver cancer die within several months of diagnosis. Patients with liver cancers that metastasized from cancers in the colon live slightly longer than those whose cancers spread from cancers in the stomach or pancreas.

Health care team roles Like other cancer patients, patients with liver cancer are usually cared for by a multidisciplinary team of health professionals. The patient’s family physician or primary care physician collaborates with other physician specialists, such as surgeons and oncologists. Radiologic technicians perform x ray, CT and MRI scans and nurses and laboratory technicians may obtain samples of blood, urine and other laboratory tests. Nurses also perform patient and family education. Before and after any surgical procedures, including biopsies, nurses explain the procedures and help to prepare patients and families. Patients may also benefit from counseling from social workers, other mental health professionals or pastoral counselors.

Prevention Presently, there are no useful strategies for preventing metastatic cancers of the liver. Primary liver cancers, however, are 75-80% preventable. Current strategies focus on widespread vaccination for hepatitis B; early treatment of hereditary hemochromatosis; and screening of high-risk patients with alpha-fetoprotein testing and ultrasound examinations. Lifestyle factors that may be modified in order to prevent liver cancer include avoidance of exposure to environmental carcinogens, toxic chemicals, and foods harboring molds that produce aflatoxin. Most important, however, is avoidance of alcohol and drug abuse. Alcohol abuse is responsible for 60-75% of cases of cirrhosis, which is a major risk factor for eventual development of primary liver cancer. Hepatitis is a widespread disease among persons who abuse intravenous drugs.

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BOOKS

Friedman, Lawrence S. “Liver, Biliary Tract, & Pancreas.” In Current Medical Diagnosis & Treatment 1998, edited by Lawrence M. Tierney, Jr., et al. Stamford, CT: Appleton & Lange, 1997. Murphy, Gerald P. et al. American Cancer Society Textbook of Clinical Oncology Second Edition Atlanta, GA: The American Cancer Society, Inc. 1995. Rudolph, Rebecca E., and Kris V. Kowdley. “Cirrhosis of the Liver.” In Current Diagnosis 9, edited by Rex B. Conn, et al. Philadelphia: W. B. Saunders Company, 1997. Way, Lawrence W. “Liver.” In Current Surgical Diagnosis & Treatment, edited by Lawrence W. Way. Stamford, CT: Appleton & Lange, 1994. ORGANIZATIONS

American Cancer Society. 1599 Clifton Road, N.E., Atlanta, GA 30329. (800)227-2345. American Liver Foundation. 1425 Pompton Avenue, Cedar Grove, NJ 07009. (800)465-4837. Cancer Research Institute. 681 Fifth Avenue, New York, NY 10022. (800)992-2623. National Cancer Institute (National Institutes of Health). 9000 Rockville Pike, Bethesda, MD 20892. (800)422-6237.

Barbara Wexler

Liver function tests Definition Liver function tests, or LFTs, include tests that are routinely measured in all clinical laboratories. LFTs include bilirubin, a compound formed by the catabolism of hemoglobin; ammonia, a product of protein catabolism that is normally converted into urea by the liver before being excreted by the kidneys; proteins that are made by the liver including total protein, albumin, prothrombin, and fibrinogen; cholesterol and triglycerides, which are made and excreted via the liver; and the enzymes alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), and lactate dehydrogenase (LDH). Other liver function tests include serological (tests to demonstrate antibodies) and DNA tests for hepatitis and other viruses, tests for antimitochondrial and smooth muscle antibodies, transthyretin (prealbumin), protein electrophoresis, bile acids, alpha-fetoprotein, and a constellation of other enzymes that help differentiate necrotic versus obstructive liver disease.

Liver function tests done individually do not give the physician very much information, but used in combination along with a careful history, physical examination, and imaging studies they contribute to making an accurate diagnosis of the specific liver disorder. Different tests will show abnormalities in response to liver inflammation, liver injury due to drugs, alcohol, toxins or viruses, liver malfunction due to blockage of the flow of bile, and liver cancers.

Precautions Blood for LFTs is collected by venipuncture. The nurse or phlebotomist performing the procedure must be careful to observe universal precautions for the prevention of transmission of bloodborne pathogens. Blood for ammonia testing should be iced immediately after collection, stored anaerobically until measured, and assayed within 30 minutes to prevent an increase in ammonia caused by deamination of amino acids in the blood. Hemolysis will falsely increase tests for LD, AST, and ALT. Bilirubin: Drugs that may cause increased blood levels of total bilirubin include anabolic steroids, antibiotics, antimalarials, ascorbic acid, Diabinese, codeine, diuretics, epinephrine, oral contraceptives, and vitamin A. Ammonia: Muscular exertion can increase ammonia levels, while cigarette smoking produces significant increases within one hour of inhalation. Drugs that may cause increased levels include alcohol, barbiturates, narcotics, and diuretics. Drugs that may decrease levels include broad-spectrum antibiotics, levodopa, lactobacillus, and potassium salts. ALT: Drugs that may increase ALT levels include acetaminophen, ampicillin, codeine, dicumarol, indomethacin, methotrexate, oral contraceptives, tetracyclines, and verapamil. Previous intramuscular injections may cause elevated levels. GGT: Drugs that may cause increased GGT levels include alcohol, phenytoin, and phenobarbital. Drugs that may cause decreased levels include oral contraceptives. LD: Strenous activity may raise levels of LDH. Alcohol, anesthetics, aspirin, narcotics, procainamide, and fluoride may also raise levels. Ascorbic acid (vitamin C) can lower levels of LDH.

Description The liver is the largest and one of the most important organs in the body. As the body’s “chemical factory,” it regulates the levels of most of the biomolecules found in

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Resources

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the blood, and acts with the kidneys to clear the blood of drugs and toxic substances. The liver metabolizes these products, alters their chemical structure, makes them water soluble, and excretes them in bile. Laboratory tests for total protein, albumin, ammonia, transthyretin, and cholesterol are markers for the synthetic function of the liver. Tests for cholesterol, bilirubin, ALP, and bile salts are measures of the secretory (excretory) function of the liver. The enzymes ALT, AST, GGT, LD, and tests for viruses are markers for liver injury. Some liver function tests are used to determine if the liver has been damaged or its function impaired. Elevations of these markers for liver injury or disease tell the physician that something is wrong with the liver. ALT and bilirubin are the two primary tests used largely used for this purpose. Bilirubin is measured by two tests, called total and direct bilirubin. The total bilirubin measures both conjugated and unconjugated bilirubin while direct bilirubin measures only the conjugated bilirubin fraction in the blood. Unconjugated bilirubin is formed from heme in the reticuloendothelial cells in the spleen that remove old red blood cells from the circulation. The RE cells release the bilirubin into the blood where it is bound by albumin and transported to the liver. The bilirubin is taken up by liver cells and conjugated to glucuronic acid, which makes the bilirubin water soluble. This form will react directly with a Ehrlich’s diazo reagent, hence the name direct bilirubin. While total bilirubin is elevated in various liver diseases, it is also increased in certain (hemolytic) anemias caused by increased red blood cell turnover. Neonatal hyperbilirubinemia is a condition caused by an immature liver than cannot conjugate the bilirubin. The level of total bilirubin in the blood becomes elevated, and must be monitored closely in order to prevent damage to the brain caused by unconjugated bilirubin, which has a high affinity for brain tissue. Bilirubin levels can be decreased by exposing the baby to UV light. Direct bilirubin is formed only by the liver, and therefore, it is specific for hepatic or biliary disease. Its concentration in the blood is very low (0-0.2 mg/dL) and therefore, even slight increases are significant. Highest levels of direct bilirubin are seen in obstructive liver diseases. However, direct biliruibn is not sensitive to all forms of liver disease (e.g., focal intrahepatic obstruction) and is not always elevated in the earliest stages of disease, and therefore, ALT is needed to exclude a diagnosis. ALT is an enzyme that transfers an amino group from the amino acid alanine to a ketoacid acceptor (oxaloacetate). The enzyme was formerly called serum glutamic pyruvic transaminase (SGPT) after the products formed by this reaction. Although ALT is present in other tissues besides liver, its concentration in liver is far 1426

greater than any other tissue, and blood levels in nonhepatic conditions rarely produce levels of a magnitude seen in liver disease. The enzyme is very sensitive to necrotic or inflammatory liver injury. Consequently, if ALT or direct bilirubin are increased, then some form of liver disease is likely. If both are normal, then liver disease is unlikely. These two tests along with others are used to help determine what is wrong. The most useful tests for this purpose are the liver function enzymes and the ratio of direct to total bilirubin. These tests are used to differentiate diseases characterized primarily by hepatocellular damage (necrosis) from those characterized by obstructive damage (cholestasis or blockage of bile flow). In hepatocellular damage, the transaminases, ALT and AST, are increased to a greater extent than alkaline phosphatase. This includes viral hepatitis, which gives the greatest increase in transaminases (10-50 fold normal), hepatitis induced by drugs or poisons (toxic hepatitis), alcoholic hepatitis, hypoxic necrosis (a consequence of congestive heart failure), chronic hepatitis, and cirrhosis of the liver. In obstructive liver diseases, the alkaline phosphatase is increased to a greater extent than the transaminases (ALP>ALT). This includes diffuse intrahepatic obstructive disease which may be caused by some drugs or biliary cirrhosis, focal obstruction that may be caused by malignancy, granuloma, or stones in the intrahepatic bile ducts, or extrahepatic obstruction such as gall bladder or common bile duct stones, or pancreatic or bile duct cancer. In both diffuse intrahepatic obstruction and extrahepatic obstruction, the direct bilirubin is often greatly elevated because the liver can conjugate the bilirubin, but this direct bilirubin cannot be excreted via the bile. In such cases the ratio of direct to total bilirubin is greater than 0.4. Aspartate aminotransferase, formerly called serum glutamic oxaloacetic transaminase (SGOT), is not as specific for liver disease as is ALT, which is increased in myocardial infarction, pancreatitis, muscle wasting diseases, and many other conditions. However, differentiation of acute and chronic forms of hepatocellular injury are aided by examining the ratio of ALT to AST, called the DeRitis ratio. In acute hepatitis, Reye’s syndrome, and infectious mononucleosis the ALT predominates. However, in alcoholic liver disease, chronic hepatitis, and cirrhosis the AST predominates. Alkaline phosphatase is increased in obstructive liver diseases, but it is not specific for the liver. Increases of a similar magnitude (three- to five-fold normal) are commonly seen in bone diseases, late pregnancy, leukemia, and some other malignancies. The enzyme gamma-glutamyl transferase (GGT) is used to help differentiate the source of an elevated ALP. GGT is greatly increased in

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Lactate dehydrogenase (LD) is found in almost all cells in the body. Different forms of the enzyme (isoenzymes) exist in different tissues, especially in heart, liver, red blood cells, brain, kidney and muscles. LD is increased in megaloblastic and hemolytic anemias, leukemias and lymphomas, myocardial infarction, infectious mononucleosis, muscle wasting diseases, and both necrotic and obstructive jaundice. While LD is not specific for any one disorder, the enzyme is elevated (two- to five-fold normal) along with liver function enzymes in both necrotic and obstructive liver diseases. LD is markedly increased in most cases of liver cancer. An enzyme pattern showing a marked increase in LD and to a lesser degree ALP with only slightly increased transaminases (AST and ALT) is seen in cancer of the liver (space occupying disease). Such findings should be followed-up with imaging studies and measurement of alpha-fetoprotein and carcinoembryonic antigen, two tumor markers prevalent in hepatic cancers. Some liver function tests are not sensitive enough to be used for diagnostic purposes, but are elevated in severe or chronic liver diseases. These tests are used primarily to indicate the extent of damage to the liver. Tests falling into this category are ammonia, total protein, albumin, cholesterol, transthyretin, fibrinogen, and the prothrombin time. Analysis of blood ammonia aids in the diagnosis of severe liver diseases and helps to monitor the course of these diseases. Together with the AST and the ALT, ammonia levels are used to confirm a diagnosis of Reye’s syndrome, a rare disorder usually seen in children and associated with infection and aspirin intake. Reye’s syndrome is characterized by brain and liver damage following an upper respiratory tract infection, chickenpox, or influenza. Ammonia levels are also helpful in the diagnosis and treatment of hepatic encephalopathy, a serious brain condition caused by the accumulated toxins that result from liver disease and liver failure. Ammonia levels in the blood are normally very low. Ammonia produced by the breakdown of amino acids is converted by the liver to urea. When liver disease becomes severe, failure of the urea cycle results in elevated blood ammonia

and decreased urea (or blood urea nitrogen, BUN). Increasing ammonia signals end-stage liver disease and a high risk of hepatic coma. Albumin is the protein found in the highest concentration in blood, making up over half of the protein mass. Albumin has a half-life in blood of about three weeks and decreased levels are not seen in the early stages of liver disease. A persistently low albumin in liver disease signals reduced synthetic capacity of the liver and is a sign of progressive liver failure. In the acute stages of liver disease, proteins such as transthyretin (prealbumin) with a shorter half-life may be measured to give an indication of the severity of the disease. Cholesterol is synthesized by the liver and cholesterol balance is maintained by the liver’s ability to remove cholesterol from lipoproteins, and use it to produce bile acids and salts that it excretes into the bile ducts. In obstructive jaundice caused by stones, biliary tract scarring, or cancer, the bile cannot be eliminated and cholesterol and triglycerides may accumulate in the blood as low-density lipoprotein cholesterol. In acute necrotic liver diseases triglycerides may be elevated due to hepatic lipase deficiency. In liver failure caused by necrosis, the liver’s ability to synthesize cholesterol is reduced and blood levels may be low. The liver is responsible for production of the vitamin K clotting factors. In obstructive liver diseases a deficiency of vitamin K-derived clotting factors results from failure to absorb vitamin K. In obstructive jaundice, intramuscular injection of vitamin K will correct the prolonged prothrombin time. In severe necrotic disease, the liver cannot synthesize factors I (fibrinogen) or factors II, VII, IX, and X from vitamin K. When attributable to hepatic necrosis, an increase in the prothrombin time by more than two seconds indicates severe liver disease. Serum protein electrophoresis patterns will be abnormal in both necrotic and obstructive liver diseases. In the acute stages of hepatitis, the albumin will be low and the gamma globulin fraction will be elevated owing to a large increase in the production of antibodies. The alpha-1 globulin and alpha-2 globulin fractions will be elevated owing to production of acute phase proteins. In biliary cirrhosis the beta globulin may be elevated owing to an increase in beta lipoprotein. In hepatic cirrhosis the albumin will be greatly decreased, and the pattern will show bridging between the beta and gamma globulins owing to production of IgA. The albumin to globulin ratio (A/G) ratio will fall below one. The most prevalent liver disease is viral hepatitis. Tests for this condition include a variety of antigen and antibody markers and nucleic acid tests that are discussed in detail elsewhere (see entry on hepatitis tests). Acute

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obstructive jaundice, alcoholic liver disease, and hepatic cancer. When the increase in GGT is two or more times greater than the increase in ALP, the source of the ALP is considered to be from the liver. When the increase in GGT is five or more times the increase in ALP, this points to a diagnosis of alcoholic hepatitis. GGT, but not AST and ALT, is elevated in the first stages of liver inflammation due to alcohol consumption, and GGT is useful as a marker for excessive drinking. GGT has been shown to rise after acute persistent alcohol ingestion and then fall when alcohol is avoided.

Liver function tests

iary cirrhosis, and those with M2 specificity are considered specific for this disease.

KEY TERMS Bile acid—A detergent that is made in the liver and excreted into the intestine to aid in the absorption of fats. Biliary—Relating to bile. Cirrhosis—A liver disease where there is a loss of normal liver tissues, replaced by scar tissue. This is usually caused by chronic alcohol abuse but can be caused by blockage of the bile ducts. Detoxification—A process of altering the chemical struction of a compound to make it less toxic. Hepatitis—Inflammation of the liver. Hepatocyte—Liver cell. Isoenzyme—One of a group of enzymes that brings about the same reactions on the same chemicals, but are different in their physical properties. Jaundice—Hyperbilirubinemia or too much bilirubin in the blood. Bilirubin will be deposited in the skin and the mucosal membranes. The whites of the eyes and the skin appear yellow. Neonatal jaundice—A disorder in newborns where the liver is too premature to conjugate bilirubin which builds up in the blood.

viral hepatitis is associated initially with 20 to 100 fold increases in transaminases and is followed shortly afterward by jaundice. Such patients should be tested for hepatitis B surface antigen (HbsAg) and IgM antibodies to hepatitis B core antigen (anti-HBc IgM), and anti-hepatitis C virus (anti-HVC) to identify these causes. In addition to hepatitis A-G, viral hepatitis may be caused by Epstein-Barr virus (EBV) and cytomegalovirus (CMV) infections of the liver. Tests for these viruses such as the infectious mononucleosis antibody test, anti- viral capsid antigen test (anti-VCA), and anti-CMV test are useful in diagnosing these infections. Liver disease may be caused by autoimmune mechanisms in which autoantibodies destroy liver cells. Autoimmune necrosis is associated with systemic lupus erythematosus and chronic viral hepatitis usually caused by hepatitis B and hepatitis C virus infections. These conditions give rise to anti-smooth muscle antibodies and anti-nuclear antibodies, and tests for these are useful markers for chronic hepatitis. Antibodies to mitochondrial antigens (antimitochondrial antibodies) are found in the blood of more than 90% of persons with primary bil1428

Preparation Patients are asked to fast and to inform clinicians of all drugs, even over the counter drugs, that they are taking. Many times liver function tests are done on an emergency basis and fasting and obtaining a medical history are not possible.

Aftercare Patients will have blood drawn into a vacuum tube and may experience some pain and burning at the site of injection. A gauze bandage may be placed over the site to prevent further bleeding. If the person is suffering from severe liver disease, they may lack clotting factors. The nurse should be careful to monitor bleeding in these patients after obtaining blood.

Results Reference ranges vary from laboratory to laboratory and also depend upon the method used. However, normal values are generally framed by the ranges shown below. Values for enzymes are based upon measurement at 37°C. • ALT: 5-35 IU/L (values for the elderly may be slightly higher, and values also may be higher in men and in African-Americans). • AST: 0-35 IU/L. • ALP: 30-120 IU/LALP is higher in children, older adults and pregnant females. • GGT: males 2-30 U/L; females 1-24 U/L. • LD: 0-4 days old: 290-775 U/L; 4-10 days: 545-2000 U/L; 10 days-24 months:180-430 U/L; 24 months-12 years:110-295 U/L; 12-60 years:100-190 U/L; 60 years: >110-210 U/L. • Bilirubin: (Adult, elderly, and child) Total bilirubin: 0.1-1.0 mg/dL; indirect bilirubin: 0.2-0.8 mg/dL; direct bilirubin: 0.0-0.3 mg/dL. (Newborn) Total bilirubin: 112 mg/dL. Note: critical values for adult: greater than 1.2 mg/dL. Critical values for newborn (requiring immediate treatment): greater than 15 mg/dL. • Ammonia: 10-70 micrograms per dL (heparinized plasma). Normal values for this test vary widely, depending upon the age of the patient and the type of specimen. • Albumin: 3.2-5.4 g/L.

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ALT: Values are significantly increased in cases of hepatitis, and moderately increased in cirrhosis, liver tumor, obstructive jaundice, and severe burns. Values are mildly increased in pancreatitis, heart attack, infectious mononucleosis, and shock. Most useful when compared with ALP levels. AST: High levels may indicate liver cell damage, hepatitis, heart attack, heart failure, or gall stones. ALP: Elevated levels occur in diseases that impair bile formation (cholestasis). ALP may also be elevated in many other liver disorders, as well as some lung cancers (bronchogenic carcinoma) and Hodgkin’s lymphoma. However, elevated ALP levels may also occur in otherwise healthy people, especially among older people. GGT: Increased levels are diagnostic of hepatitis, cirrhosis, liver tumor or metastasis, as well as injury from drugs toxic to the liver. GGT levels may increase with alcohol ingestion, heart attack, pancreatitis, infectious mononucleosis, and Reye’s syndrome.

are performed by clinical laboratory scientists/medical technologists or clinical laboratory technicians/medical laboratory technicians. Patient education Health care providers should inform the patient of any abnormal results and explain how these values reflect the status of their liver disease. It is important to guide the patient in ways to stop behaviors such as taking drugs or drinking alcohol, if these are the causes of the illness. Resources BOOKS

Burtis, Carl A., and Edward R. Ashwood. Tietz Textbook of Clinical Chemistry. Philadelphia: W.B. Saunders, 1999. Cahill, Matthew. Handbook of Diagnostic Tests, 2nd ed. Springhouse, PA: Springhouse Corporation, 1999. Pagana, Kathleen Deska, and Timothy James Pagana. Mosby’s Manual of Diagnostic and Laboratory Tests. Philadelphia: Mosby, Inc., 1998.

LD: Elevated LD is seen with heart attack, kidney disease, hemolysis, viral hepatitis, infectious mononucleosis, Hodgkin’s disease, abdominal and lung cancers, germ cell tumors, progressive muscular dystrophy and pulmonary embolism. LD is not normally elevated in cirrhosis. Bilirubin: Increased indirect or total bilirubin levels can indicate various serious anemias, including hemolytic disease of the newborn and transfusion reaction. Increased direct bilirubin levels can be diagnostic of bile duct obstruction, gallstones, cirrhosis, or hepatitis. It is important to note that if total bilirubin levels in the newborn reach or exceed critical levels, exchange transfusion is necessary to avoid kernicterus, a condition that causes brain damage. Ammonia: Increased levels are seen in primary liver cell disease, Reye’s syndrome, severe heart failure, hemolytic disease of the newborn, and hepatic encephalopathy. Albumin: Albumin levels are increased due to dehydration. They are decreased due to a decrease in synthesis of the protein which is seen in severe liver failure and in conditions such as burns or renal disease that cause loss of albumin from the blood.

Health care team roles A physician will order the liver function tests that he or she feels are necessary, and the nurse or phlebotomist will draw the blood. Patients will probably be referred to an internist or hepatologist if results are abnormal. LFTs

Jane E. Phillips, PhD

Liver radionuclide scan Definition A liver scan, also known as a liver-spleen scan, is a diagnostic imaging procedure to evaluate the liver and spleen for suspected disease.

Purpose A liver scan is performed to determine the size, configuration, relative function of the liver and spleen, and to detect space occupying lesions such as, cysts, an abscess, and tumors. Liver scans are indicated if a patient has abdominal pain, if a patient’s liver enzymes (determined by blood tests) are abnormal, if the patient is jaundiced, and to detect and monitor metastatic disease. A liver scan may also be helpful in diagnosing specific disorders, by detecting features which are characteristic of a disorder, such as cirrhosis of the liver. This study may also be part of the battery of tests used to evaluate potential candidates for liver transplant.

Precautions Women who are pregnant are cautioned against having this test unless the benefit of having the test out-

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Abnormal results

Long-term insurance

KEY TERMS Radionuclide—A substance which emits radiation that can be detected by a scanner as the substance disintegrates.

weighs the risks. If a woman is breast feeding, she will be required to stop for a specified period of time, depending on the dose given.

tumor and therefore other imaging tests such as ultrasound or CT may be required to assess the nature of the abnormality. Too much radioisotope in the spleen and bones compared to the liver, known as “colloid shift,” can indicate portal hypertension or cirrhosis. Liver diseases such as hepatitis may also cause an abnormal scan, but is rarely diagnosed from the information revealed by this study alone. Again, other diagnostic tests are performed along with a liver scan to evaluate specific abnormalities and to arrive at a diagnosis.

Health care team roles Description This test is be performed in an out-patient facility or a hospital x-ray or nuclear medicine department. The patient is injected intravenously with a radioactive tracer, or radionuclide, that accumulates in certain cells of the liver, spleen, and bone marrow. Approximately 15 minutes after the injection, the patient is asked to lie down on a bed. A gamma camera or scintillation camera is positioned above the upper abdomen and may lightly touch the patient. It is important for the patient to lie quietly. Position changes and brief periods of breath holding may be required. The test usually takes approximately 30 minutes. Occasionally, a SPECT (Single Photon Emission Computed Tomography) study is indicated to further pinpoint an area of abnormality. The SPECT procedure is the same, but the camera will circle around the patient, in order to provide a cross sectional image of the liver.

Preparation

Resources BOOKS

Klingensmith III, M.D., Wm. C., Dennis Eshima, Ph.D., John Goddard, Ph.D. Nuclear Medicine Procedure Manual 2000-2001. Vitti, Richard A., and Leon S. Malmud. “Gastrointestinal System.” In Nuclear Medicine, edited by Donald R. Bernier, et al. St. Louis: Mosby, 1997. PERIODICALS

No physical preparation is required. The patient will be asked to remove metal objects from the area to be imaged. If the patient has had other recent nuclear scans, a waiting period may be necessary so that any residual radiation in the body will not interfere. The patients should understand that there is no danger of significant radioactive exposure to themselves or others. Only small amounts of radionuclide are used. The total amount of radiation absorbed is often less than the dose received from ordinary x rays.

Drane, Walter E. “Scintigraphic Techniques for Hepatic Imaging.” Radiologic Clinics of North America, 36 (March 1998): 309-318.

Christine Miner Minderovic, B.S., R.T., R.D.M.S.

Local anesthetic see Anesthesia, local

Long-term insurance

Aftercare

Definition

No special aftercare is necessary.

Results A normal scan will show a liver of normal size, shape, and position. It is expected that the liver will accumulate the radioactive tracer in a uniform fashion. Areas that appear absent may represent a cyst, abscess, or a 1430

The injection and scan are performed by a nuclear medicine technologist, who will also obtain pertinent medical history from the patient and explain the test. The technologist is trained to handle radioactive materials, operate the scanner, and to process the data. The images are interpreted by a medical doctor who is a radiologist or nuclear medicine specialist. The patient received the results of the scan from their personal physician or doctor who ordered the test.

Long-term insurance provides for a person’s care in cases of chronic illness or disability. Policies are available with a wide range of coverage options. Long-term insurance refers to coverage of health services, which may include community health care, nursing home care, and home support. Long-term health

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Description A major health care challenge looms over America as the population ages and people live longer. The country lacks a comprehensive health system that serves the needs of millions of older persons and individuals with long-term disabilities. Long-term care options are often fragmented, uncoordinated, and costly for patients, their families and, in some instances, public coffers. Millions of Americans, according to the American Association of Retired Persons (AARP), are denied access to long-term care services because they cannot pay for services, do not qualify for public funding or cannot access the types of services that they need and can afford. People of all ages usually prefer to receive long-term care in their own homes, or in home-like assisted-living facilities. More than three-quarters of older Americans in need of long-term care live in the community, with most receiving no paid services. The majority of long-term care is provided by unpaid, informal caregivers, such as family and friends. In 1996, more than 22 million households in the United States included a caregiver who was age 50 or older. About 73% of unpaid caregivers were women, nearly one-third of whom were over age 65. Many caregivers, especially women, balance multiple caregiving roles by providing for both their parents and their children. Medicare does not cover most long-term care services. In 1997, 68% of nursing home residents were dependent on Medicaid to finance at least some of their care. For many, long-term insurance is unaffordable, and many cannot qualify because of pre-existing conditions. Long-term insurance policies are often complex. People who purchase them may not read the fine print, then are forced to cancel the policy later because it does not fit their needs. Increasing rates factored into some long-term policies, known as “climbing premiums,” may also become prohibitively expensive. Long-term care insurance can benefit the consumer, provided that such items as affordability, coverage gaps, and timing of purchase are carefully considered. It may be advisable to check the financial stability and the claims ratio of the insurance company. Long-term insurance is a serious financial investment and should be considered a part of estate planning. A qualified, independent professional should be consulted to review the policy before purchase. The state health insurance assistance program (SHIP) is also available to answer questions.

The type of care that a client seeks is another important consideration before purchasing a policy. There is as yet no universal standard for defining long-term care facilities. A placement that is covered under one company’s policy may not be covered under another’s. Physicians can also play a part in denial of a placement by stating that the facility of choice is either not adequate or too advanced for the patient’s needs. When to buy a policy is another important consideration. Individuals with a pre-existing diagnosis for a debilitating condition or illness may not be eligible for coverage. This clause is common in most insurance policies of any type. But purchasing a policy too far in advance of an anticipated need can work against a buyer. The health care industry is currently in a state of flux, and technological advances are rapid. The benefits provided in a policy that is purchased at one point in time may not match the care available in the distant future, giving the company reason to deny benefits. Generally, long-term insurance operates as an indemnity program for potential nursing home and/or home health-care costs. Additionally, many policies provide coverage for adult daycare, for care delivered in an assisted-living facility, and for hospice care. Rarely are all costs covered. Some long-term care policies are pure indemnity programs which pay the insured a daily benefit contracted for by the insured. The pure indemnity program pays the full daily benefit regardless of the amount of care that the insured receives per diem. Other long-term care policies pay for covered losses, or the cost of care actually received each day, up to the selected daily benefit level. This type of policy is also referred to as a “pool-of-money” contract. Long-term insurance is available either as part of a group or individual coverage, although most are currently purchased by individuals. Most policies cover skilled, custodial and intermediate long-term care services. A purchaser is wise not to consider a contract that does not cover each level of long-term care services. A recent change in the U.S. federal tax law allows for a portion of a long-term insurance premium to be taxdeductible. This deduction increases with the insured’s age. Benefits under a long-term care contract are triggered in a tax-qualified policy when the insured becomes unable to perform a number of activities associated with normal daily living or suffers from a cognitive impairment that requires supervision. Non tax-qualified policies usually offer more liberal eligibility criteria, which includes long-term benefits because of a medical necessity.

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insurance is normally for the elderly, but is sometimes also applicable to younger individuals with disabilities.

Lower limb orthoses

Low-cholesterol diet see Diet therapy

KEY TERMS

Low-fat diet see Diet therapy

Indemnity—Protection, as by insurance, against damage or loss.

Low-phenylalanine diet see Diet therapy Low-purine diet see Diet therapy Low-salt diet see Diet therapy

Long-term insurance can help pay for needed services, as well as protect against the risk of significant financial loss. It may also provide choices about services and where they are received. Normally, neither employer health insurance nor Medicare pays for significant longterm care expenses, although Medicare does pay for short-term skilled care. Medicaid, the federal/state health insurance for those with limited assets and income, does pay for long-term care, but patients must use most of their savings or assets before these benefits can be realized.

Lower gastrointestinal exam see Barium enema

Lower limb orthoses Definition

Viewpoints Long-term insurance policies can be expensive and may be restrictive in what they provide. Before purchasing a policy, individuals should make certain that it is within their means and will meet their anticipated needs. Some policies allow policy holders to tap into survivor death benefits to use for health care needs. Several different policies should be compared in detail. Recommendations from elderly advocate organizations can be helpful. Young people with disabilities have fewer options for long-term insurance because many policies exempt individuals with a pre-existing condition.

Professional implications Health care professionals should be aware of the pros and cons of long-term insurance and be able to answer patients’ questions. Long-term insurance may involve special billing procedures. Resources Shelton, Phyllis. Long-Term Care Planning Guide Version 2000. Shelton Marketing Services, 2000. PERIODICALS

Bern-Klug, Mercedes. “Health Insurance for People with Medicare.” Clinical Reference Systems Annual 2000, p. 781. Norrgard, Carolyn. “Long-term care insurance.” Clinical Reference Systems Annual 2000, p. 988. OTHER

American Association for Retired Persons (AARP) 601 E St., NW, Washington DC 20049. (800) 424-3410. .

Jacqueline N. Martin, M.S. 1432

Low back pain, physical therapy for see Back and neck pain, physical therapy for

A lower limb orthosis is an external force system used to compensate or control for decreased or abnormal forces in the hip, knee, ankle, or foot.

Purpose Orthoses may be used for any of the following reasons: to lend stability to a weak joint, correct or maintain alignment, control motion in the presence of abnormal tone, immobilize a body part, protect an inflamed joint, or provide proprioceptive feedback. Individuals who have upper or lower motor neuron dysfunction, inflammatory joint diseases, sports injuries, or skeletal deformities may use orthoses.

Description Foot orthoses Foot orthoses are fabricated for individuals who have abnormal joint alignment in the foot, causing inappropriate motion during stance and gait. Abnormal mechanics may lead to pain and increased stress in the joints of the foot, leg and even back. Custom foot orthoses are made based upon a cast of the individual’s foot, following a thorough biomechanical assessment of stance and gait. Based on the findings, rigid, semi-rigid, or soft inserts are fabricated to fit into the client’s shoe to provide support where needed, for example, under the arch, the metatarsals, and/or the heel. The University of California Biomechanics Laboratory (UCBL) orthosis is a specific custom-molded orthosis that snugly holds the heel and midfoot in optimal alignment with regards to mediolateral stability.

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Lower limb orthoses

Ankle-foot orthoses (AFOs) In adults and children with neuromotor dysfunction, AFOs can be used to maintain appropriate alignment, provide mediolateral stability, and help with toe clearance or heel rise during the gait cycle. The supramalleolar orthosis (SMO) evolved from the UCBL orthosis to address not only mediolateral stability, but also anteriorposterior issues, including foot clearance. It extends to the area above the malleoli, and may be solid or include a mechanical ankle joint. Ankle-foot orthoses that extend to the area just below the knee provide more stability than the SMO, and may be either static or dynamic. Static AFOs prohibit ankle motion; the most common is the solid AFO. The solid AFO prevents foot drop during gait and also can help to control knee extension or hyperextension, depending on how the ankle is set. Dynamic AFOs may allow for plantarflexion and/or dorsiflexion of the ankle through the use of either a mechanical joint or the location of trimlines. Various methods, such as pin stops and check straps, can be used to limit the amount of plantarflexion or dorsiflexion allowed as well. These options provide versatility in setting the range of ankle motion for individuals who have some control and/or expected return of function. A variety of ankle supports are also available for individuals with musculoskeletal function. Air casts provide stability to those rehabilitating from ankle sprains, while Achilles straps may be used for tendonitis. Night splints and arch straps may help with positioning in those with plantar fasciitis. Knee-ankle-foot-orthoses (KAFOs) A KAFO is used when the knee needs to be stabilized and an AFO is insufficient. For example, KAFOs may be used in patients who have had a stroke, spinal cord injury or traumatic injury to the limbs. A conventional KAFO consists of double metal uprights connected to the shoe via a stirrup. A thermoplastic KAFO is custom-formed for total contact to the patient’s thigh and calf. A variety of knee joints are available to allow for or restrict flexion and extension movement. Knee orthoses There are three categories of orthoses that address musculoskeletal impairments at the knee joint. Athletes use prophylactic orthoses in hopes of preventing knee injury. Rehabilitative orthoses are used post-operatively to allow protected motion to occur at the knee joint.

A girl with rheumatoid arthritis walks with the aid of braces. (Photograph by John Moss. Photo Researchers, Inc. Reproduced by permission.)

Functional orthoses are designed to provide stability and proprioceptive input to a patient returning to daily activities. Research is inconclusive on the effectiveness of prophylactic orthoses; however, studies do indicate that functional orthoses may be helpful in preventing further injuries in individuals who have already sustained an injury. Hip-knee-ankle-foot orthoses (HKAFOs) The hip guidance orthosis (HGO) and the reciprocating guidance orthosis (RGO) are two types of lumbosacral HKAFOs that can be used by adults or children to produce a reciprocal gait pattern. In both types, the user is braced from mid-trunk to the feet. These orthoses are most commonly used in children with myelomeningocele, but are also used by patients with traumatic spinal cord injury, muscular dystrophy, cerebral palsy, and multiple sclerosis.

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KEY TERMS Donning and doffing—Putting on and taking off an orthosis or prosthesis. Legg-Calve-Perthes disease—Flattening of the femoral head in children, related to avascular necrosis. Myelomeningocele—A neural tube defect causing herniation of the spinal cord, its meninges and cerebrospinal fluid, often leading to paraplegia. Plantar fasciitis—Inflammation of the layer of fascia surrounding the muscles of the soles of the feet. Proprioceptive input—Sensations of body movement and position without the use of visual cues. Thermoplastic—A material used in orthosis fabrication that is formable when heated and rigid when cooled. Trimline—The border of the orthosis, the location of which is a factor in determining the level of support or flexibility available.

er at home with directions from the orthotist. As with operation, maintenance may vary depending on the type of orthosis, and users should follow the instructions of their orthotists.

Health care team roles The patient, family, physician, orthotist and physical therapist all play important roles in orthotic intervention. The patient and family provide information about their lifestyles, home environment, and support network that allow for a realistic assessment of the ability to don, doff, care for and use an orthosis. The physician often plays an important role in identifying the need for an orthosis and preliminarily educating the patient about goals of orthotic intervention. The physical therapist and orthotist often cooperate in performing the preorthotic assessment. The physical therapist usually has important information regarding the patient’s impairments and functional abilities, and may have an idea about what type of orthosis may be appropriate. The orthotist assesses limb function, takes necessary measurements for fabrication, and has extensive, up-to-date knowledge about what types of orthoses and components may best fit the patient’s needs.

Training

Hip orthoses Postoperative total hip orthoses sometimes are used after a total hip replacement in order to prevent the motions of hip flexion, adduction and internal rotation that can cause dislocation. In infants with developmental dysplasia of the hip, which causes hip instability, a Pavlik harness or hip abduction orthosis is used to position the hips in flexion and abduction to encourage desired bone development and prevent dislocation. Hip abduction orthoses are also used to treat children with Legg-CalvePerthes disease.

Operation Donning and doffing an orthosis can be a challenge at first, especially for children or for individuals with upper extremity impairments. The orthotist provides specific instructions for donning and doffing with the least difficulty. In addition, he or she provides instructions regarding the need to monitor skin for possible breakdown.

Maintenance

The orthotist educates the patient about donning, doffing, caring for and using the orthosis. A wearing schedule is often provided for the patient to gradually grow accustomed to the orthosis. Because the physical therapist usually sees the patient regularly, he or she monitors the patient’s progress with all aspects of orthotic intervention. Resources BOOKS

Lusaradi, Michelle M., and Caroline C. Nielsen. Orthotics and Prosthetics in Rehabilitation. Boston: ButterworthHeinemann, 2000. Nawoczenski, Deborah A. and Marcia E. Epler. Orthotics in Functional Rehabilitation of the Lower Limb. Philadelphia: W. B. Saunders Company, 1997. PERIODICALS

Andrews, Karen L., and Kimberly A. Bouvette. “Anatomy for Management and Fitting of Prosthetics and Orthotics.” Physical Medicine and Rehabilitation: State of the Art Reviews 10 (October 1996): 502-507. ORGANIZATIONS

Orthotic maintenance may include resetting joint angles, which is usually done by an orthotist or a physical therapist under the direction of an orthotist. Screws in joint mechanisms also may loosen occasionally, and tightening can usually be done by the patient or caregiv1434

American Academy of Orthotists and Prosthetists. 526 King Street, Suite 201, Alexandria, VA 22314. (703) 836-0788. .

Peggy Campbell Torpey, MPT

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Definition A lower limb prosthesis is an artificial replacement for any or all parts of the lower extremity (leg).

Purpose A prosthesis is used to provide an individual who has an amputated limb with the opportunity to perform functional tasks, particularly ambulation (walking), which may not be possible without the limb. In 2000, there were more than 1.5 million people in the United States with amputations. Amputation surgery most often is performed due to complications of peripheral vascular disease or neuropathy; trauma is the second leading cause of amputation. Amputations performed because of tumor or congenital limb deficiency are less common.

Description There are several levels of lower limb amputation, including partial foot, ankle disarticulation, transtibial (below the knee), knee disarticulation, transfemoral (above the knee), and hip disarticulation. The most common are transtibial (mid-calf) and transfemoral (midthigh). The basic components of these lower limb prostheses are the foot-ankle assembly, shank, socket, and suspension system. Foot-ankle assembly The foot-ankle assembly is designed to provide a base of support during standing and walking, in addition to providing shock absorption and push-off during walking on even and uneven terrain. Four general categories of foot-ankle assemblies are non-articulated, articulated, elastic keel, and dynamic-response. One of the most widely prescribed foot is the solid-ankle-cushion-heel (SACH) foot, due to its simplicity, low cost, and durability. It may be inappropriate, however, for active community ambulators and sports participants. Articulated assemblies allow motion at the level of the human ankle; this motion may occur in one or more planes, depending on whether it is a single-axis or multi-axis foot. These assemblies offer more mobility at the cost of less stability and increased weight. The elastic keel foot is designed to mimic the human foot without the use of mechanical joints; the dynamic-response foot is designed to meet the demands of running and jumping in athletic users.

The shank corresponds to the anatomical lower leg, and is used to connect the socket to the ankle-foot assembly. In an endoskeletal shank, a central pylon, which is a narrow vertical support, rests inside a foam cosmetic cover. Endoskeletal systems allow for adjustment and realignment of prosthetic components. In an exoskeletal shank, the strength of the shank is provided by a hard outer shell that is either hollow or filled with lightweight material. Exoskeletal systems are more durable than endoskeletal systems; however, they may be heavier and have a fixed alignment, making adjustments difficult. Socket The socket contacts the residual limb and disperses pressure around it. A hard socket offers direct contact between the limb and the socket, resulting in decreased friction, no liner bulk, easy cleaning, and increased durability. It is, however, difficult to fit and adjust in response to residual limb changes. A soft socket includes a liner as a cushion between the socket and residual limb. This provides additional protection for the limb but may increase friction and bulk. Transtibial socket types include: patellar tendon-bearing (PTB), silicone suction, energy-storing, or bent-knee designs. Transfemoral socket types include: quadrilateral, ischial containment, and contoured adducted trochanteric-controlled alignment method (CAT-CAM) designs. A prosthetic sock is usually worn to help cushion the limb from forces and accommodate for volume changes. Prosthetic socks are available in a variety of materials and thickness, and may be worn in layers to achieve the most comfortable fit. Suspension Suspension devices should keep the prosthesis firmly in place during use and allow comfortable sitting. Several types of suspension exist, both for the transtibial and transfemoral amputation. Common transtibial suspensions include sleeve, supracondylar, cuff, belt and strap, thigh-lacer, and suction styles. Sleeves are made of neoprene, urethane, or latex and are used over the shank, socket and thigh. Supracondylar and cuff suspensions are used to capture the femoral condyles and hold the prosthesis on the residual limb. The belt and strap method uses a waist belt with an anterior elastic strap to suspend the prosthesis, while the thigh-lacer method uses a snugfitting corset around the thigh. The suction method consists of a silicone sleeve with a short pin at the end. The sleeve fits over the residual limb and the pin locks into the socket. With a transfemoral prosthesis, suction and several types of belt suspension also are available.

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Shank

Lower limb prostheses

Lower limb prostheses

limb ambulation. Many individuals will be fitted with a temporary prosthesis when the wound has healed. A temporary prosthesis allows for ambulation and continued shrinkage of the residual limb until a definitive prosthesis is fit. When evaluating a prosthesis before use, the prosthetist and physical therapist should ensure that the inside of the socket is smooth and that all joints move freely. The socket should fit securely on the residual limb, and the overall prosthesis length should match the length of the intact leg. The patient must learn how to properly put on the residual limb sock and the prosthesis itself. A variety of techniques are used, depending on the type of socket and suspension system.

Maintenance The user should be aware of how to properly care for and maintain the prosthesis, liner, and socks. Most plastic sockets and liners can be wiped with a damp cloth and dried. Socks should be washed and changed daily. Due to the wide variety of componentry and materials used in the fabrication of prostheses, the prosthetist should be the source for instructions regarding proper care and maintenance for each individual. In general, the patient should return to the prosthetist for any repairs, adjustments or realignments.

Health care team roles A man wears an artificial leg. (Photograph by Andrew Holbrooke. Stock Market. Reproduced by permission.)

Transfemoral amputations also provide the additional challenge of incorporating a prosthetic knee unit. The knee unit must be able to bend and straighten smoothly during ambulation, in addition to providing stability during weightbearing on that limb. Knees are available as single-axis, polycentric, weight-activated, manual-locking, hydraulic, and pneumatic units. Technology using microprocessors in knee units is becoming a reality, although costs can be prohibitive.

Operation Use of an actual prosthesis usually follows a period of postoperative management that includes addressing issues of pain, swelling, and proper positioning. In addition, physical therapy for range of motion, strength, bed mobility, transfers, and single limb ambulation often takes place during the initial rehabilitation period. In some cases, an individual may be fitted with an immediate post-operative prosthesis to allow for early double1436

The patient’s primary care physician, surgeon, neurologist, prosthetist, physical and occupational therapists, nurses, and social worker are all important players in the multidisciplinary health care team. Surveys of patients with amputations have shown that the physical therapist, along with the physician and prosthetist, plays one of the most valued roles in providing information and help both at the time of amputation and following amputation. The entire team’s input, along with the patient’s input, is vital in determining whether a prosthesis should be fit and the specific prescription for the prosthesis. Input should be provided regarding the patient’s medical history, premorbid level of function, present level of function, body build, range of motion, strength, motivation, and availability of familial and social support. The physical therapist usually plays a major role in training an individual to walk with a prosthesis, and also is the health care professional who can evaluate prosthetic function immediately and over time. The physical therapist is trained in gait assessment and should watch for compensations and gait deviations that may indicate a problem with the prosthesis.

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The main goal of prosthetic training usually is smooth, energy-efficient gait. This includes the ability of the individual to accept weight on either leg, balance on one foot, advance each leg forward and adjust to different types of terrain or environmental conditions. Principles of motor learning often are used in training, progressing from simple to complex tasks. Individuals begin with learning to keep their bodies stable in a closed environment with no manipulation or variability. An example may be practicing standing balance on one or both legs. Mobility, environmental changes, and task variability are added slowly to further challenge the individual as tasks are mastered. In the end, an example of a more complex task practiced may be the ability walk in a crowded hallway while carrying an object in one hand. In addition to ambulation training, the patient also should be taught how to transfer to and from surfaces, assume a variety of positions such as kneeling or squatting, and manage falls. Depending upon the individual’s previous and present level of function, use of a traditional cane, quad cane, or crutches may be indicated. Patient motivation, comorbidity, level of amputation and level of function are all factors in determining the outcome of rehabilitation. Resources BOOKS

Gailey, Robert S. One Step Ahead: An Integrated Approach to Lower Extremity Prosthetics and Amputee Rehabilitation. Miami: Advanced Rehabilitation Therapy, Inc., 1994. Lusardi, Michelle M., and Caroline C. Nielsen. Orthotics and Prosthetics in Rehabilitation. Boston: ButterworthHeinemann, 2000. May, Bella J. Amputations and Prosthetics: A Case Study Approach. Philadelphia: F.A. Davis Company, 1996. PERIODICALS

Hsu, Miao-Ju, et al. “Physiological Measurements of Walking and Running in People with Transtibial Amputations with 3 Different Prostheses.” Journal of Orthopedic and Sports Physical Therapy 29 (Sept. 1999): 526-33.

Peggy Campbell Torpey, MPT

Lumbar puncture see Cerebrospinal fluid (CSF) analysis Lumbosacral radiculopathy see Sciatica

Lung biopsy Definition Lung biopsy is a procedure by which a small sample of lung tissue is obtained for examination. Usually, it is examined under the microscope and also may be sent to the microbiological laboratory for culture. Microscopic examination is performed by pathologists.

Purpose A lung biopsy is usually ordered to determine the cause of abnormalities that appear on chest x rays, such as nodules or infiltrates. Lung biopsies are performed to confirm a diagnosis of cancer, especially if malignant cells are detected in the patient’s sputum or bronchial washing. In addition to evaluating lung tumors and their associated symptoms, lung biopsies may be used in the diagnosis of lung infections, especially tuberculosis and Pneumocystis pneumonia, drug reactions, and chronic diseases of the lung such as sarcoidosis. A lung biopsy can be used for treatment as well as diagnosis. Bronchoscopy, a type of lung biopsy performed with a long slender instrument called a bronchoscope, can be used to clear a patient’s air passages of secretions and to remove blockages from the airways. Today, flexible fiberoptic bronchoscopes, which are easier to use than rigid scopes, are used to perform most biopsies.

Precautions As with any other biopsy, lung biopsies should not be performed on patients who have a tendency to bleed or abnormal blood clotting because of low platelet counts or prolonged prothrombin time (PT) or partial thromboplastin time (PTT). Platelets are small blood cells that play a role in the blood clotting process. PT and PTT measure how well blood clots. If they are prolonged, it might be unsafe to perform a biopsy because of the risk of bleeding. If the platelet count is lower than 50,000/cubic mm, the patient may be given a platelet transfusion as a temporary relief measure, and a biopsy can then be performed.

Description Overview The mediastinum separates the right and the left lungs from each other. The heart, the trachea, the lymph nodes, and the esophagus lie in the mediastinum. Lung

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Training

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biopsies may involve mediastinoscopy, as well as the lungs themselves. Types of lung biopsies Lung biopsies can be performed using a variety of techniques. A bronchoscopy is ordered if a lesion identified on the x ray seems to be located in the periphery of the chest. If the suspicious area lies close to the chest wall, a needle biopsy can be done. If both these methods fail to diagnose the problem, an open lung biopsy may be performed. When there is a question about whether the lung cancer has spread to the lymph nodes in the mediastinum, a mediastinoscopy is performed. NEEDLE BIOPSY. About an hour before the needle biopsy procedure, a sedative is administered to the patient. The patient is mildly sedated but fully awake. An X ray technician takes a computerized axial tomography (CT) scan to identify the location of the suspicious areas. Markers are placed on the overlying skin to mark the biopsy site. The skin is thoroughly cleansed with an antiseptic solution, and a local anesthetic is injected to numb the area.

The physician then makes a small incision, about half an inch (1.25 cm) in length. The patient is asked to take a deep breath and hold it while the physician inserts the biopsy needle through the incision into the lung. When enough tissue has been obtained, the needle is withdrawn. Pressure is applied at the biopsy site and a sterile bandage is placed over the cut. The entire procedure takes between 30 and 45 minutes. The patient may feel a brief sharp pain or some pressure as the biopsy needle is inserted. Most do not experience severe pain.

A chest x ray is done following an open biopsy, to check for a pneumothorax (lung collapse). The patient may experience some grogginess for a few hours after the procedure. Patients also may experience tiredness and muscle aches for a day or two, because of the general anesthesia. The throat may be sore because of the placement of the endotracheal tube. The patient may also have some pain or discomfort at the incision site, which can be relieved by pain medication. VIDEO-ASSISTED THORASCOPIC SURGERY. A new technique, video-assisted thorascopic surgery (VATS), also can be used to biopsy lung and mediastinal lesions. VATS may be performed on selected patients in place of open lung biopsy. To perform a VATS procedure, the surgeon makes several small incisions in the patient’s chest wall. A thorascope, a thin, hollow, lighted tube with a tiny video camera mounted on it, is inserted through one of the small incisions. The other incisions allow the surgeon to insert surgical instruments to retrieve tissue for biopsy. MEDIASTINOSCOPY. The preparation for a mediastinoscopy is similar to that for an open biopsy. The patient is sedated and prepared for general anesthesia. The neck and the chest are cleansed with an antiseptic solution.

After the patient is anesthetized, an incision about two or three inches long is made at the base of the neck. A thin, hollow, lighted tube, called a mediastinoscope, is inserted through the incision into the space between the right and the left lungs. The surgeon removes any lymph nodes or tissues that look abnormal. The mediastinoscope is then removed, and the incision is sutured and bandaged. A mediastinoscopy takes about an hour.

Preparation

OPEN BIOPSY. Open biopsies are performed in a hospital operating room under general anesthesia. As with needle biopsies, patients are sedated before the procedure. An intravenous line is placed to give medications or fluids as necessary. A hollow tube, called an endotracheal tube, is passed through the mouth, into the airway leading to the lungs. It is used to convey the general anesthetic.

Before scheduling a lung biopsy, the physician performs a preoperative history and physical examination. An electrocardiogram (EKG) and laboratory tests may be performed before the procedure to check for clotting problems, anemia, and blood type, in case a transfusion becomes necessary.

Once the patient is anesthetized, the surgeon makes an incision over the lung area, a procedure called a thoracotomy. Some lung tissue is removed and the incision is closed with sutures. The entire procedure usually takes about an hour. A chest tube is sometimes placed with one end inside the lung and the other end protruding through the closed incision. Chest tube placement is done to prevent the lungs from collapsing by removing the air from the lungs. The tube is removed a few days after the biopsy.

Patients who will undergo surgical diagnostic and treatment procedures should be encouraged to stop smoking. Patients able to stop smoking several weeks before surgical procedures have fewer postoperative complications.

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Before any procedure is performed, the patient is asked to sign a consent form. The nurse may review the procedure and answer questions about the consent form or procedure. The nurse will advise the patient preparing

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Aftercare Needle biopsy Following a needle biopsy, the patient is allowed to rest comfortably. The nurse checks the patient’s status at two-hour intervals. If there are no complications after four hours, then the patient can go home. Patient education Prior to discharge to home, the nurse instructs the patient about resuming normal activities. Patients are advised to rest at home for a day or two before resuming regular activities, and to avoid strenuous activities for a week after the biopsy. Open biopsy, VATS, or mediastinoscopy After an open biopsy, VATS, or mediastinoscopy, patients are taken to the recovery room for observation. If no complications develop, they are returned to the hospital room. Nursing care includes monitoring temperature, pulse blood pressure and respiration. Fever may indicate infection, and decreased breath sounds may be symptoms of pneumothorax. Sutures are usually removed after seven to 14 days. If the patient has extreme pain, light-headedness, or difficulty breathing after an open biopsy, the physician should be notified immediately. The sputum may be slightly bloody for a day or two after the procedure. Heavy or persistent bleeding requires evaluation by the physician.

Complications Needle biopsy Needle biopsy is associated with fewer risks than open biopsy, because it does not involve general anesthesia. Rarely, the lung may collapse because of air that leaks in through the hole made by the biopsy needle. If a pneumothorax (lung collapse) occurs, a chest tube is inserted into the pleural cavity to re-expand the lung. Some hemoptysis (coughing up of blood) occurs in 5% of needle biopsies. Prolonged bleeding or infection may also occur, although these are very rare. Open biopsy Possible complications of an open biopsy include infection or pneumothorax. Death occurs in about 1 in 3000 cases. If the patient has very severe breathing problems before the biopsy, then breathing may be further

KEY TERMS Bronchoscopy—A medical test that enables the physician to see the breathing passages and the lungs through a hollow, lighted tube. Endotracheal tube—A hollow tube that is inserted into the windpipe to administer anesthesia. Lymph nodes—Small, bean-shaped structures scattered along the lymphatic vessels which serve as filters. Lymph nodes trap bacteria or cancer cells that are traveling through the lymphatic system. Mediastinoscopy—A procedure that allows the physician to see the organs in the mediastinal space using a thin, lighted, hollow tube (a mediastinoscope). Mediastinum—The area between the lungs, bounded by the spine, breastbone, and diaphragm. Pneumothorax—A condition in which air or gas enters the pleura (area around the lungs) and causes a collapse of the lung. Sputum—A mucus-rich secretion that is coughed up from the passageways (bronchial tubes) and the lungs.

impaired following the operation. For patients with normal lung function before the biopsy, the risk of respiratory problems resulting from or following the procedure is very small. Mediastinoscopy Complications due to mediastinoscopy are rare; death occurs in fewer than one in 3000 cases. More common complications include pneumothorax or bleeding caused by damage to the blood vessels near the heart. Mediastinitis, infection of the mediastinum, may develop. Injury to the esophagus or larynx may occur. If the nerves leading to the larynx are injured, the patient may be left with a permanently hoarse voice. All of these complications are rare.

Results Abnormal results of needle biopsy, VATS, and open biopsy may be associated with diseases other than cancer. Nodular lesions, while frequently cancerous, can also be the result of active infections such as tuberculosis, or may be healed scars from a previous infection. In a third

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for general anesthesia to refrain from eating or drinking anything for at least 12 hours before the biopsy.

Lung cancer

of biopsies using a mediastinoscope, the lymph nodes that are biopsied prove to be cancerous. Abnormal results should always be considered in the context of the patient’s medical history, physical examination, and other tests such as sputum examination, chest x rays, etc. before a definitive diagnosis is made.

Health care team roles

Description Types of lung cancer

Fiberoptic bronchoscopy is performed by pulmonologists, physician specialists in pulmonary medicine. CT guided needle biopsy is done by interventional radiologists, physician specialists in radiological procedures. Thoracic surgeons perform open biopsy and VATS. Specially trained nurses, x ray, and laboratory technicians assist during the procedures and provide pre and postoperative education and supportive care. Resources BOOKS

“Bronchoscopy.” In The Merck Manual of Diagnosis and Therapy, edited by Robert Berkow, et al. Rahway, NJ: Merck Research Laboratories, 1992. Groenwald, S.L. et al. Cancer Nursing Principles and Practice. Sudbury, MA: Jones and Bartlett Publishers, 1997, pp.1273-1275. Murphy, Gerald P., et al. American Cancer Society Textbook of Clinical Oncology Second Edition Atlanta, GA: The American Cancer Society, Inc., 1995, pp.223-234. Otto, S.E. Oncology Nursing. St. Louis, MO: Mosby, 1997, pp. 317-318. ORGANIZATIONS

American Cancer Society. 1599 Clifton Road, N.E., Atlanta, GA 30329. (800)227-2345. American Lung Association. 1740 Broadway, New York, NY 10019-4374. (800)586-4872. Cancer Research Institute. 681 Fifth Avenue, New York, NY 10022. (800)992-2623. National Cancer Institute (National Institutes of Health). 9000 Rockville Pike, Bethesda, MD 20892. (800) 422-6237.

Barbara Wexler

Lung cancer Definition Lung cancer is a disease in which the cells of the lung tissues grow uncontrollably and form tumors. It is the leading cause of death from cancer among both men and women in the United States. The American Cancer 1440

Society estimates that in 2001 at least 169,500 new cases of lung cancer will be diagnosed, and that lung cancer will account for 28% of all cancer deaths—approximately 157,400 people.

There are two kinds of lung cancers, primary and secondary. Primary lung cancer starts in the lung itself. Primary lung cancer is divided into small cell lung cancer and non-small cell lung cancer, depending on how the cells look under the microscope. Secondary lung cancer is cancer that starts somewhere else in the body (for example, the breast or urinary bladder) and metastasizes (spreads) to the lungs. Identifying the type of lung cancer is important because treatment varies by type. For example, small cell cancers generally are treated with surgery. On the other hand, surgery is not generally considered beneficial for non-small cell cancers; they are treated with chemotherapy. Small cell cancer was formerly called oat cell cancer, because the cells resemble oats in their shape. About a fourth of all lung cancers are small cell cancers. This is a very aggressive cancer and spreads to other organs within a short time. It is generally diagnosed in people who are heavy smokers. Non-small cell cancers account for the remaining 75% of primary lung cancers. They can be further subdivided into three categories. Nearly 30% of non-small cell cancers are squamous cell carcinomas. Squamous cell carcinoma is most often found near the bronchi of patients with a history of smoking. Forty percent of non-small cell cancers are adenocarcinomas, most often found in the outer region of the lung. The remaining 10% are large-cell undifferentiated carcinomas. These rapidly spreading carcinomas may be found throughout the lung. Incidence of lung cancer Lung cancer is rare among young adults. It is usually found in people who are 50 years of age or older, the average age at diagnosis is 60. While the incidence of the disease is decreasing among white men, it is steadily rising among African-American men, and among both white and African-American women. This change is probably due to the increase in the number of smokers in these groups. In 1987, lung cancer replaced breast cancer as the number one cancer killer among women. Lung cancer is responsible for more deaths than the combined totals for cancers of the colon, breast, and prostate.

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• shortness of breath

Causes

• persistent hoarseness

SMOKING. Tobacco smoking is the leading cause of

• swelling of the neck and face

lung cancer. Ninety percent of lung cancers can be prevented by giving up tobacco. Smoking marijuana cigarettes is considered yet another risk factor for cancer of the lung. These cigarettes have a higher tar content than tobacco cigarettes. In addition, they are inhaled very deeply—as a result, the carcinogens in the smoke are held in the lungs for a longer time.

• significant weight loss that is not due to dieting or vigorous exercise; fatigue and loss of appetite

EXPOSURE TO ASBESTOS AND TOXIC CHEMICALS.

Diseases other than lung cancer may cause these symptoms. It is vital, however, for patients to consult a physician to rule out the possibility that they are the presenting symptoms of lung cancer.

Exposure to asbestos fibers, either at home or in the workplace, is also considered a risk factor for lung cancer. Studies show that compared to the general population, asbestos workers are seven times more likely to die from lung cancer. Asbestos workers who smoke increase their risk of getting lung cancer by 50-100 times. Besides asbestos, mining industry workers exposed to coal products or radioactive substances such as uranium, and workers exposed to chemicals such as arsenic, vinyl chloride, mustard gas, and other carcinogens also have a higher than average risk of contracting lung cancer. ENVIRONMENTAL CONTAMINATION. High levels of

radon, a radioactive gas that cannot be seen or smelled, pose a risk for lung cancer. This gas is produced by the breakdown of uranium, and does not present any problem outdoors. In the basements of some houses that are built over soil containing natural uranium deposits, however, radon may accumulate to dangerous levels. Other forms of environmental pollution (e.g., auto exhaust fumes) may also slightly increase the risk of lung cancer. CHRONIC LUNG INFLAMMATION AND SCARRING.

Inflammation and scar tissue are sometimes produced in the lung by diseases such as silicosis and berylliosis, which are caused by inhalation of certain minerals; tuberculosis; and certain types of pneumonia. This scarring may increase the risk of developing lung cancer. FAMILY HISTORY. Although the exact cause of lung cancer is not known, people with a family history of lung cancer appear to have a slightly higher risk of contracting the disease.

Symptoms Because lung cancers tend to spread very early, only 15% are detected in their early stages. The chances of early detection, however, can be improved by seeking medical care at once if any of the following symptoms appear: • a cough that does not go away • chest pain

• bloody or brown-colored phlegm (sputum) • unexplained fever • recurrent lung infections, such as bronchitis or pneumonia

If the lung cancer has spread to other organs, the patient may have other symptoms such as headaches, bone fractures, pain, bleeding, or blood clots. Early detection and treatment can increase the chances of a cure for some patients; for others, it can at least prolong life.

Diagnosis Physical examination and initial tests If lung cancer is suspected, the physician will take a detailed medical history to document the symptoms and assess the risk factors. The history is followed by a complete physical examination. The physician will examine the patient’s throat to rule out other possible causes of hoarseness or coughing, and listen to the patient’s breathing and the sounds made when the patient’s chest and upper back are percussed (tapped). The physical examination, however, is not conclusive. If there is reason to suspect lung cancer—such as a history of heavy smoking or occupational exposure to substances known to irritate the lungs—the physician may order a chest x ray to see if there are any masses in the lungs. Special imaging techniques, such as PET scans (positron emission tomography), CT (computerized axial tomography) scans or MRI (magnetic resonance imaging) may provide more precise information about the size, shape, and location of any tumors. X ray and other imaging techniques may be performed by a radiologic technician. Sputum analysis Sputum analysis involves microscopic examination of the cells that are either coughed up from the lungs, or are collected through a bronchoscope. Sputum analyses can diagnose at least 30% of lung cancers, some of which do not show up even on chest x rays. In addition, this lab-

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oratory test can help detect cancer in its very early stages, before it metastasizes (spreads) to other regions. The sputum test does not, however, provide any information about the location of the tumor and must be followed by other diagnostic tests. Lung biopsy Lung biopsy is the definitive diagnostic tool for cancer. It can be performed in several different ways. The physician can perform a bronchoscopy, which involves the insertion of a slender, lighted tube, called a bronchoscope, down the patient’s throat and into the lungs. In addition to viewing the passageways of the lungs, the physician can use the bronchoscope to obtain samples of the lung tissue. In another procedure known as a needle biopsy, the location of the tumor is first identified using a CT scan or MRI. The physician then inserts a needle through the chest wall and collects a sample of tissue from the tumor. In the third procedure, known as surgical biopsy, the chest wall is opened up and a part of the tumor, or all of it, is removed. A pathologist, a physician who specializes in the study of diseased tissue, examines the tumor samples to identify the cancer type and stage. Patient education Patients who will undergo surgical diagnostic and treatment procedures should be encouraged to stop smoking. Patients able to stop smoking several weeks before surgical procedures have fewer postoperative complications.

Treatment Treatment for lung cancer depends on the type of cancer, its location, and its stage. Staging is a process that describes if the cancer has metastasized and the extent of its spread. Lung cancer is staged at the time of diagnosis; this is called clinical staging. It usually is staged again following surgical intervention; this is called pathologic staging. When determining a course of treatment, the patient’s age, medical history, and general state of health are taken into account. The most commonly used modes of treatment are surgery, radiation therapy, and chemotherapy. Surgery Surgery is not usually an option for small cell lung cancers, because they have usually spread beyond the lung by the time they are diagnosed. Because non-small cell lung cancers are less aggressive, however, surgery can be used to treat them. The surgeon determines the type of surgery, depending on how much of the lung is 1442

affected. Surgery may be the primary method of treatment, or radiation therapy and/or chemotherapy may be used to shrink the tumor before surgery is attempted. Not all patients are candidates for surgery, especially the removal of an entire lung (pneumonectomy). For example, many smokers suffer from emphysema as well as lung cancer, and as a result have sharply reduced lung capacity. Spirometric testing may be performed to assess lung capacity. The forced expiratory volume in one second (FEV1) is a laboratory test that helps to determine whether patients will have adequate pulmonary function after resection. There are three different types of surgical operations: • Wedge resection. This procedure involves removing a small part of the lung. A wedge resection is done when the cancer is in a very small area and has not metastasized to any other chest tissues or other parts of the body. • Lobectomy. A lobectomy is the removal of one lobe of the lung. The right lung has three lobes and the left lung has two lobes. If the cancer is limited to one part of the lung, the surgeon will perform a lobectomy. • Pneumonectomy. A pneumonectomy is the removal of an entire lung. If the cancer cells have spread throughout the lung, and if the surgeon feels that removal of the entire lung is the best option for curing the cancer, a pneumonectomy will be performed. Postoperative surgical nursing care includes monitoring temperature, pulse blood pressure and respiration. Fever may indicate infection; patients are vulnerable to bacterial and viral infections. Decreased breath sounds may be symptoms of pneumothorax. The pain that follows surgery can be relieved by medications. The tendency of surgical stress to weaken the patient’s immune system is treatable with antibiotics, anti-viral medicines, and vaccines. Patient education Postoperative patient teaching encourages ambulation (walking), and reinforces patient and family understanding of surgical results and necessary follow-up. Radiotherapy Radiotherapy involves the use of high-energy rays to kill cancer cells. It is used either by itself or in combination with surgery or chemotherapy. Radiotherapy can be used to treat all types of cancer. The amount of radiation used depends on the size and the location of the tumor. There are two types of radiotherapy treatments, external beam radiation therapy and internal (or interstitial) radiotherapy. In external radiation therapy, the radi-

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A normal lung (left) and the lung of a cigarette smoker (right). (Photograph by A. Glauberman, Photo Researchers, Inc. Reproduced by permission.)

ation is delivered from a machine positioned outside the body. Internal radiotherapy uses a small pellet of radioactive materials placed inside the body in the area of the cancer. Radiation therapy may produce such side effects as tiredness, skin rashes, upset stomach, and diarrhea. Dry or sore throats, difficulty in swallowing, and loss of hair in the treated area are all minor side effects of radiation. Some side effects diminish or disappear either during the course of the treatment or after the treatment is over. Patient education Patient education by nurses and radiologic technicians includes measures to identify and manage side effects such as fatigue or radiodermatitis (skin condition resulting from radiotherapy). Chemotherapy Chemotherapy uses anti-cancer medications that are either given intravenously or taken by mouth. These drugs enter the bloodstream and travel throughout the body, killing cancer cells that have spread to different organs. Chemotherapy is used as the primary treatment

for cancers that have spread beyond the lung and cannot be removed by surgery. It may also be used in addition to surgery or radiation therapy. Chemotherapy is tailored to each patient’s needs. The prescribed regimen depends on the type of cancer, the extent of its spread, and the patient’s general state of health. Most patients are given a combination of several different drugs. Besides killing the cancer cells, these drugs also harm normal cells. Hence, the dose has to be carefully adjusted to minimize damage to normal cells. Chemotherapy often has severe side effects, including nausea, vomiting, hair loss, anemia, weakening of the immune system, and sometimes infertility. Most of these side effects end when the treatment is over. Other medications can be given to lessen the unpleasant side effects of chemotherapy. Patient education Patient teaching helps patients and families to distinguish between anticipated side effects such as alopecia (hair loss), nausea, and constipation and the more serious side effects that require medical attention. Examples of

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Slightly more than 40% of patients survive for at least a year after diagnosis, as opposed to 30% 25 years ago. The five-year survival rate for all stages of lung cancer is 14%.

KEY TERMS Alopecia—Hair loss. Biopsy—The surgical removal and microscopic examination of living tissue for diagnostic purposes. Bronchoscope—A thin, flexible, lighted tube that is used to view the air passages in the lungs. Carcinogen—Any substance capable of causing cancer. Chemotherapy—Treatment of cancer with synthetic drugs that destroy the tumor either by inhibiting the growth of cancerous cells or by killing them. Lobectomy—Surgical removal of an entire lobe of the lung. Metastasize—The spread of cancer cells from a primary site to distant parts of the body. Pathologist—A physician who specializes in the diagnosis of disease by studying cells and tissues under a microscope. Pneumonectomy—Surgical removal of an entire lung.

Lung cancer treatment involves an multidisciplinary team of health care professionals. In addition to primary care physicians, such as a family practitioner or an internist, the treatment team may include a pulmonologist, pathologist, radiologist, and thoracic surgeon as well as specialized nurses, radiologic and laboratory technicians, respiratory therapists, and dieticians. Patient education Before, during and after treatment, nurses and allied health professionals should inform and educate patients and families about the risks and complications of any planned diagnostic test, intervention, or treatment. Patients and families should be taught about some of the common side effects of treatment, including weight loss, malnutrition, increased risk of infection, pain, fatigue, and depression.

Prevention

Pneumothorax—Collapse of the lung. Radiation therapy—Treatment using high energy radiation from X-ray machines, cobalt, radium, or other sources. Sputum—Mucus or phlegm that is coughed up from the passageways of the lungs. Stage—A term used to describe the size and extent of spread of cancer. Wedge resection—Removal of only a small portion of a cancerous lung.

side effects that can not be managed at home include bleeding, fever, and confusion or hallucinations.

Prognosis If the lung cancer is detected before it has had a chance to spread to other organs, and if it is treated appropriately, at least 49% of patients can survive five years or longer after the initial diagnosis. Only 15% of lung cancers, however, are found at this early stage. Improvements in surgical technique and the development of new approaches to treatment have markedly improved the one-year survival rate for lung cancer. 1444

Health care team roles

The best way to prevent lung cancer is never to smoke or to quit smoking if one has already started. Secondhand smoke from tobacco should be avoided. Appropriate precautions should be taken when working with carcinogens (cancer-causing substances). Promoting healthy lifestyles, testing houses for the presence of radon gas, and asbestos abatement are also useful preventive strategies. Patient education The objectives of education are to prevent patients, especially children and adolescents, from smoking, and to encourage smokers to quit. Participation in smoking cessation programs should be encouraged and patients should be informed about the health risks of passive (secondhand) smoking. Patient education also should describe the role of environmental carcinogens such as asbestos and radon in the development of lung cancer. Resources BOOKS

Groenwald, S.L. et al. Cancer Nursing Principles and Practice. Sudbury, MA: Jones and Bartlett Publishers, 1997, pp.1260-1287.

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ORGANIZATIONS

American Cancer Society. 1599 Clifton Road, N.E., Atlanta, GA 30329. (800)227-2345. American Lung Association. 1740 Broadway, New York, NY 10019-4374. (800)586-4872. Cancer Research Institute. 681 Fifth Avenue, New York, NY 10022. (800)992-2623. National Cancer Institute (National Institutes of Health). 9000 Rockville Pike, Bethesda, MD 20892. (800)422-6237.

Barbara Wexler

Lung function tests see Pulmonary function test

Lung perfusion and ventilation scan Definition A lung perfusion scan and ventilation study are two diagnostic imaging studies. A lung perfusion scan assesses blood flow to the lungs. A lung ventilation study reveals the distribution of air space within the lungs. These are two separate studies that are often performed sequentially. The tests are called by different names, including perfusion lung scan, aerosol lung scan, ventilation lung scan, xenon lung scan, ventilation/perfusion scanning (VPS), pulmonary scintiphotography, or most commonly, V/Q scan.

Purpose Lung scans may be performed for patients with chest pain, for those coughing up blood (hemoptysis), or for those having difficulty breathing (dyspnea). A perfusion scan alone or both tests are frequently performed for patients with a suspected pulmonary embolism (blood clot in the lung) or for follow-up in patients with known pulmonary embolism. Lung scans are a sensitive method for demonstrating the presence of pulmonary disease but are not often specific for a certain disease. For example,

an abnormal scan may also be caused by chronic obstructive pulmonary disease (COPD), asthma, pneumonia, venous hypertension, pleural effusion, and cardiomegaly.

Precautions The amount of radioactivity a person is exposed to during these tests is very low and is not harmful. However, if the patient has had other recent nuclear medicine tests, it may be necessary to wait until other radiopharmaceuticals have been cleared from the body so that they do not interfere with these tests.

Description These tests are typically done in a hospital nuclear medicine department or out-patient radiology facility. Scans to diagnose pulmonary embolism are often done on an emergency basis. Most often, both studies are needed. Sometimes a perfusion scan is done without a ventilation scan. Rarely, a ventilation scan is done alone. For a lung perfusion scan, the patient is injected intravenously with radioactive particles, known as Tc 99m MAA (macroaggregated albumin). The particles pass through the larger blood vessels and become temporarily trapped in small blood vessels. The images thus reflect blood perfusion in the lungs. Images are obtained anteriorly, posteriorly, laterally, and obliquely. For a lung ventilation scan, the patient inhales a radioactive gas through a mask placed over the nose and mouth. Images of the ventilation lung scan show the distribution of the gas in the lungs. The test typically consists of three phases. The first stage is the initial, or ventilation stage, which reflects the rate of ventilation of the different lung segments. Second is the equilibrium stage, which represents gas volume of the lungs. The third stage is the wash-out phase, which demonstrates any gas trapping that may occur in obstructive diseases. Images are typically obtained posteriorly, although additional views may also be performed. Each test takes approximately 15 to 30 minutes. If possible, the patient usually sits up while the images are taken.

Preparation To accompany the lung scan, the patient should have a chest x ray within 12 to 24 hours of the study. Otherwise, there is no special preparation needed for these tests. The patient may eat and drink normally before the procedure.

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Murphy, Gerald P., et al. American Cancer Society Textbook of Clinical Oncology, Second Edition. Atlanta, GA: The American Cancer Society, Inc., 1995, pp.220-234. Otto, S.E. Oncology Nursing. St. Louis, MO: Mosby, 1997, pp. 312-343. “Pulmonary Disorders: Tumors of the Lung.” In The Merck Manual of Diagnosis and Therapy, edited by Robert Berkow, et al. Rahway, NJ: Merck Research Laboratories, 1992.

Lungs

Resources

KEY TERMS

BOOKS

Pulmonary embolism—A blood clot or other blockage in the arteries leading to the lungs.

Aftercare No special aftercare is needed. The patient may resume normal activities immediately.

Complications There are no complications associated with these tests.

Klingensmith III, M.D., Wm. C., Dennis Eshima, Ph.D., John Goddard, Ph.D. Nuclear Medicine Procedure Manual 2000-2001. Pagana, Kathleen, and James Pagana. “Lung Scan.” In Mosby’s Diagnostic and Laboratory Test Reference, 2nd ed. St. Louis: Mosby, 1995, pp. 533-34. “Scanning Tests.” In Illustrated Guide to Diagnostic Tests. Springhouse: Springhouse Corp., 1996, pp. 679-82. Zaret, Barry, ed. “Lung Scan.” In The Patient’s Guide to Medical Tests. New York: Houghton Mifflin, 1997, pp.138-40.

Christine Miner Minderovic, B.S., R.T., R.D.M.S.

Results Normally, there is a physiological relationship between the perfusion of the pulmonary blood vessels and their regional alveolar ventilation. An imbalance of this relationship as demonstrated by these studies reflect various respiratory diseases. Other diagnostic tests are often required to confirm a diagnosis. Normal results for both tests show an even distribution of radioactive material in all parts of the lungs. For the lung perfusion scan, diminished or absent perfusion suggests decreased blood flow to that part of the lung, and possibly a pulmonary embolism. However, pneumonia, emphysema, or lung tumors can create readings on the lung perfusion scan that falsely suggest a pulmonary embolism is present. For the ventilation study, areas that show an increased accumulation of radioactive gas, particularly after the wash-out phase, suggests obstructive lung disease. Areas where there is decreased or absent radioactive gas flow suggests mechanical obstruction of air flow, such as an embolus. Certain combinations of abnormalities in lung perfusion and ventilation scans suggest pulmonary embolism.

Health care team roles Both the lung perfusion and ventilation scans are performed by a nuclear medicine technologist. The technologist is trained to handle radioactive materials, operate the equipment, and process the data. The tests are interpreted by a radiologist who may specialize in nuclear medicine. Patients receive the results from their personal physician or the doctor who ordered the test. 1446

Lungs Definition The two lungs are spongy and highly elastic organs of respiration in the pulmonary cavities of the thorax, where the aeration of blood occurs.

Description Each lung has an irregular conical shape with a blunt top, called the apex, extending into the root of the neck. They have concave bottoms resting on the arc of the diaphragm, a mostly concave inner mediastinal surface that follows the lines of the pericardium, and a convex outer (costal) surface. The right lung is larger than the left, and consists of three lobes (upper, middle, and basal or lower). The left lung consists of two lobes, an upper and a basal, or lower, lobe. Each lung consists of an exterior plasma coat comprised of an organ coat which folds back to make an interior lining for the chest cavity. The inner lung contains sub-serous areolar tissue with elastic fibers interspersed over the surface of the organ. The parenchyma, or functional part of the organ, is composed of secondary lobules (alveolar ducts) that differentiate into primary lobules (alveoli) consisting of blood vessels, lymphatics, nerves, and an alveolar duct that connects with air space. The lung, as it relates to inspiration and expiration, has two distinct zones in which the lung passages convey air to the alveolar sacs. The zones relate to the two functions of these passages. One is for conducting air, and the other is for respiration. The parts of the conducting zone do not participate in gas transfer, rather they convey air

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The conducting zone starts at the trachea and branches out to the bronchi. The bronchi differentiate into bronchioles and then into terminal bronchioles. The respiratory zone starts after the terminal bronchioles at the respiratory bronchioles. These differentiate into the alveolar ducts, which terminate at the alveolar sacs. The lungs consist mainly of the tiny air containing alveolar sacs.

Function The lung is the sole means of gas exchange in respiration. Air is brought into the body through the mouth or nose and trachea to the lung. There oxygen diffuses from the airspace of the alveoli into the blood stream and carbon dioxide diffuses from the blood into the alveoli’s airspace. The alveoli are small hollow sacs. Their ends connect to the lumens of the airways. The air adjacent to surfaces of the alveolar wall are lined by a single cell layer of flat epithelial cells called type I alveolar cells. In between type I cells are type II cells. They are thicker, and secrete a fluid called surfactant. In the alveolar walls this fluid and connective tissue fills the interstitial space and is interspersed with capillaries. In some places the interstitial space is nonexistent and the epithelial cell membranes are in direct contact with the capillaries. The blood in the capillaries is separated from the air by a single layer of flat epithelial cells. The surface area in a single alveoli is roughly the size of a small basketball court due to the undulating terrain of the type I and II epithelial cells. There are around 300 million alveoli in the adult male. Thus, there is a large surface area where the air and the blood stream are in close proximity. This large surface area is necessary for gas exchange to easily occur. The respiratory system also needs a continual supply of fresh air, which is supplied by the process of breathing. The process of breathing is aided by the position of the lungs in the thorax (chest). The thorax is a closed chamber that extends from the neck muscles to the diaphragm. The diaphragm is a dome shaped sheet of skeletal muscle that separates the thorax from the abdomen. The sides of the thorax are bounded by connective tissue around the spine, ribs, intercostal muscles, and sternum. A completely enclosed sac consisting of a thin sheet of cells, called the pleura, surround each lung. Between the pleura and the lung is interstitial fluid. As the

diaphragm expands and contracts the intra-pleural pressure placed on the lungs causes the lung to inflate and deflate. Breathing allows a fresh supply of air and oxygen to enter the lung upon inflation and carbon dioxide to exit the lung upon deflation. It also causes a change in the pressure of the lung. The epithelial surface from the conducting zone to the respiratory bronchioles is lined with cilia that continually beat in the direction of the pharynx. There are epithelial cells and glands on this surface that secrete mucus. This mucus catches particulate and bacterial matter, and the material (and mucus) is slowly moved by the cilia toward the pharynx. There it is either swallowed or coughed up as sputum. The epithelial layer also secretes another viscous fluid that allows the cilia to move mucus easily out of the lung. Toxic substances can inhibit ciliary action. Agents like cigarette smoke can paralyze the cilia for extended periods of time. This inhibits the movement of mucus and particles out of the lungs. The suspension of this process can inhibit gas exchange and eventually cause prolonged oxygen deficiency. Respiration Respiration is the process by which the body takes in oxygen and emits carbon dioxide. The following is a summary of the steps of respiration: • ventilation • interchange of CO2 and O2 between alveolar air and blood in lung capillaries • transport of CO2 and O2 through the bloodstream • interchange of CO2 and O2 between blood in lung capillaries and alveolar air by diffusion • use of O2 and production of CO2 by cells in metabolism Ventilation is the interchange of air between the atmosphere and the alveoli by bulk flow. Bulk flow is the movement of air from a region of high pressure to one of low pressure. Bulk flow may be thought of as occurring between the outside air, the air in most of the lung, and the air in the alveolar sacs. Flow of some gases (especially oxygen and carbon dioxide) also occurs between the alveolar air and the blood. It is important to note that the pressure of individual gases is different in different types of air. For example, air going into the lungs is rich in oxygen and low in carbon dioxide. Air leaving the lungs is rich in carbon dioxide and low in oxygen. The different concentrations (or pressures) of individual gases are known as the partial pressures, and the partial

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to and from the respiratory zone. All of the parts of the respiratory zone can take part in gas transfer. However, the uppermost branches, such as the respiratory bronchioles, participate in respiration only in times of exertion.

Lungs

KEY TERMS Interstitial space—The spaces found within organs and tissues. Metabolism—A series of chemical and physiological changes in the body that either build larger molecules out of smaller molecules (anabolism) or break down larger molecules into smaller ones (catabolism). Parenchyma—The active portion of an organ that fulfills its function (as opposed to purely structural portions of the organ). Proteolysis—The breaking down of proteins by cleaving or hydrolyzing peptide bonds (the bonds connecting amino acids within the protein).

pressure of each individual gas adds up to the total pressure of the gas. When air is inspired (taken in), it has a higher partial pressure of oxygen than the air already in the lung, and a lower partial pressure of carbon dioxide. Therefore, inspired air allows oxygen to flow from the area of highest pressure (inspired air) to the alveolar sacs (that have a lower partial pressure of oxygen), and into the bloodstream. The same inspired air has a low partial pressure of carbon dioxide, so carbon dioxide leaves the bloodstream (where it has a high partial pressure), enters the alveolar air (where the pressure is lower), and is passed onto the inspired air (where the partial pressure is even lower). Thus, carbon dioxide gas and oxygen gas both move from areas of highest pressure to lowest pressure in an attempt to reach a pressure (or concentration) equilibrium. This process is called gas exchange. After gas exchange has taken place, the air is expired, or expelled to rid the body of air that has a high concentration (partial pressure) of carbon dioxide gas. Then the process begins again. Lung expansion and contraction The concept of bulk flow (explained above) and Boyle’s law explain the expansion and contraction of the lung. Boyle’s law states that, at constant temperature, an increase in the volume of a container (lung) lowers the pressure of a gas, and a decrease in the container (lung) volume raises the pressure. Thus, when the volume of the lung expands, the pressure inside the lung is lowered, and when the volume of the lung contracts, the pressure inside the lung rises. 1448

Inspiration occurs when the muscles of inspiration increase the volume of the thoracic cavity. The decrease in pressure in the cavity causes the lungs to expand to fill the cavity, which lowers the pressure inside the lung. Since air flows from areas of high pressure to low pressure, air fills the lungs to equalize the air pressure inside the lungs with the outside air, and inspiration occurs. The difference between the internal pressure in the lung and the pressure of the outside air is called the transpulmonary pressure. During expiration, the muscles of inspiration relax, and the lung contracts. The decreased volume causes increased pressure inside the lungs, which results in air being expired, or expelled. In normal adults, expiration does not require any effort.

Role in human health The lungs ability to extract oxygen from the atmosphere and supply it to the body’s tissues is essential for metabolism and therefore for life. Disease and disorder can interfere with the body’s normal function and slow a normally healthy person. Serious interference with the lung’s function can cause hypoxia and even death.

Common diseases and disorders Asthma is an intermittent disease characterized by a chronic inflammation of the airways, causing smooth muscle contraction in the airway. The causes vary from person to person and can include allergies, viral infections, environmental pollutants, mold, dust, dander, cigarette smoke, overexertion, and naturally released bronchiorestrictors. Ingested items such as food coloring, preservatives, and medications can trigger an attack. Chronic obstructive pulmonary disease (COPD) refers to emphysema, chronic bronchitis, or a combination of the two. This category of disease is one of the major causes of death and disability in the world. These diseases restrict ventilation and the oxygenation of the blood. Chronic bronchitis is characterized by excessive mucus production in the bronchi and chronic inflammatory changes in the small airways. The accumulation of mucus and thickening of inflamed airways obstruct the flow of air. It is primarily a result of cigarette smoking, although pollution may also play a role. Emphysema is a major cause of hypoxia and is characterized by the destruction of the alveolar walls, and the atrophy and collapse of the lower airways. The lungs self-destruct through the secretion of proteolytic enzymes by white blood cells. Cigarette smoke stimulates the release of harmful enzymes and destroys the

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Pneumonia is normally caused by bacterial or viral infection. It can be triggered by the inhalation of toxic chemicals, chest trauma, yeast, rickettsiae, and fungi. It is the inflammation and compaction of the lung parenchyma. The alveolar spaces fill with mucus, inflammatory cells, and fibrin. Tuberculosis is caused by the infection of Mycobacterium tuberculosis. It can affect most organs but is most commonly found in the lungs. The bacteria cause lesions to be formed on the lungs and spread to other tissues. Pulmonary tissue in motion will be chronically affected and may eventually be destroyed, if left untreated. The erosion of lung tissue into the blood vessels can result in life-threatening hemorrhages. Other less common diseases of the lung include Legionnaire’s disease, cystic fibrosis, histoplasmosis, coccidiomycosis, and Mycobacterium avium complex. Resources BOOKS

Bullock, John, et. al. National Medical Series for Independent Study—Physiology. Third ed. Williams & Wilkins, 1995. Vander, Arthur et. al. Human Physiology—the Mechanisms of Body Function. Eighth ed. McGraw-Hill, 2001. ORGANIZATIONS

The American Lung Association. 1740 Broadway, New York, NY, 10019. 212-315-8700. . OTHER

Thompson, B.H., W.J. Lee, J.R. Galvin, and J. S. Wilson. “Lung Anatomy.” Virtual Hospital. University of Iowa Health Care. .

Sally C. McFarlane-Parrott

Luteinizing hormone test see Pituitary hormone tests

Lymphatic system Definition The lymphatic system is composed of a network of vessels that collects fluid and plasma proteins that leak out of capillaries and into the interstitial space. Lymphatic vessels return the lymph (fluid and plasma protein) back to the circulatory system through the veins.

Description The lymphatic system is a secondary system of vessels that is distinct both in anatomy and function from the blood vessel capillaries of the circulatory system. Small lymphatic vessels (or “lymphatics”) called lymphatic capillaries are found in almost all organs of the body except superficial layers of the skin, the central nervous system, endomysium of muscles, and the bone. These exceptions have a system of smaller vessels called prelymphatics. Fluid from prelymphatics returns to nearby lymphatic vessels, or the cerebral spinal fluid in the case of the central nervous system. Lymphatic capillaries are made up of a single layer of endothelial cells. They are anchored to the surrounding connective tissue by special filaments called anchoring filaments. The system begins as a series of sacs. Each sac has a low hydrostatic pressure relative to the outside of the sac. At the end of the lymphatic capillaries there are endothelial valves. The valves form as a result of the slight overlap of the endothelial cells, and the overlapping edge has the ability to open inward. The valves open enough to allow fluid and plasma protein to pass into the lymphatic capillary. Inside the lymph vessels are valves that prevent the backflow of lymph, a general name for the slightly opalescent fluid picked up by the lymphatics. Surrounding the lymphatics are smooth muscles that contract involuntarily to assist in the movement of lymph through the system. The lymphatic capillaries converge into larger lymph vessels. The larger lymph vessels pass through swellings called lymph nodes and then empty into one of two large lymph ducts. The lymph ducts empty into the venous circulatory system through either the right or left subclavian veins. Lymph from the right side of the head, arm and chest empties into the right subclavian vein. Lymph collected from the lower part of the body, and lymph from the left side of the head, arm and chest empties into the left subclavian vein. Both subclavian veins are located within the thorax underneath the clavicles, the thin bones located on the top part of the chest.

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enzymes that normally protect against proteolysis. The proteolytic enzymes cause the breakdown of the alveolar walls. The damaged alveoli fuse and a gradual decrease in the surface area available for gas exchange results. Emphysema increases the work of breathing and, when severe enough, causes hypoventilation (inadequate ventilation). The obstruction caused by the collapse of the lower airways is accompanied with destruction of the lung’s elastic tissues and the eventual collapse of the airways.

Lymphatic system Lymph nodes filter the flow of lymph in the lymphatic system. (National Institutes of Health. Reproduced by permission.)

At approximately 600 sites in the human body, lymphatic vessels converge into bundles of tissue called lymph nodes. The shape of a lymph node resembles a kidney bean and ranges in size from a few millimeters to a few centimeters. They are mostly found at the base of extremities such as the arms, legs and head. Many afferent lymphatics or vessels lead the lymph into the node at the larger curve of the bean shape and efferent lymphatics, fewer in number, take the lymph away from the node at the hilum, the depressed region of the bean shape. All nodes have a blood supply from the circulatory system running through them. The blood vessels enter and exit at the hilum. Inside the nodes are a honeycomb of lymphfilled sinuses that have macrophages and groupings of lymphocytes that produce antibodies. As mentioned, lymph is the fluid flowing through the lymphatic system and originates from the interstitial spaces of the organs and tissues. Another element of the lymph is a type of cell of the immune system called a lymphocyte, which is a type of white blood cell. Lymphocytes mature in either the thymus (T-lymphocytes) or the bone marrow (B-lymphocytes), which are primary lymphoid organs The blood supply transports lymphocytes from their site of maturation (the thymus or 1450

bone marrow) to secondary lymphoid organs such as the lymph nodes, spleen, and tonsils. All lymphocytes in the adult originate in the bone marrow.

Function Fluid enters organs and tissues from the arterial capillaries, and is eventually reabsorbed by the venous capillaries. However, not all of the fluid is reabsorbed by blood capillaries. About one tenth of the fluid is returned to the blood vessels via the lymphatic system. The lymphatic system reabsorbs about 2–4 qt (l) of fluid per day. Lymph composition is different depending on the site of origin. For example lymph collected from the gastrointestinal tract is high in fat that has been absorbed during digestion, and lymph collected from the bone marrow and thymus is high in lymphocyte concentration. Lymph is collected when the pressure of the interstitial fluid and plasma proteins increases in the organs and tissues. Lymph pushes against the outside of the lymphatic valves and flows into the lymphatic capillary. This is called bulk flow. Valves are located throughout the lymphatic system approximately 0.15 in (38 mm) apart. Backflow is not possible in the lymphatics because the

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Lymphatic system

The lymph collected from the body’s tissues is carried through the lymphatic vessels and lymph nodes. This illustration shows lymph nodes and vessels in the groin. (National Institutes of Health. Reproduced by permission.)

valves open in only one direction. Therefore, the lymphatic system runs in only one direction. There are several factors the affect the rate at which lymph is collected. Interstitial fluid pressure affects the rate of flow of fluid into the lymphatic capillaries. Elevated capillary pressure, increased interstitial fluid pressure, and increased capillary permeability all contribute to an increase in the amount of interstitial pressure and the rate of lymph flow. Smooth muscles around the lymphatic vessels act as lymphatic pumps, and their involuntary contractions affect the rate of lymph flow. As the lymphatic vessel swells with fluid, the smooth muscle around that portion senses the stretch and automatically contracts, pushing the lymph through the valve to the next chamber. The valve prevents backwards flow as the smooth muscle in the chamber contracts to send the lymph through the next valve into the next chamber. This process continues along the entire vessel until the lymph passes through the lymph nodes and into the subclavian vein. Factors outside of the lymphatic system can also affect the rate of lymph flow by assisting in the pumping of lymph through the system. The following eternal fac-

tors can increase lymph flow: contraction of close skeletal muscles, movements made by other parts of the body, nearby arterial pulses, and compression of tissues by items outside of the body. Therefore, during periods of exercise, the lymphatic system is extremely active and the flow rate is high. The terminal end of the lymphatic capillary also has a pump that can affect the rate of lymph flow. When the interstitial fluid pressure is high, the surrounding tissue expands. The anchoring filaments that are attached to the endothelial cells at the terminal end of the lymphatic capillary and to the connective tissue pull the capillary valves open, allowing inward flow of interstitial fluid. Then the internal lymphatic capillary pressure causes the valves to close and the smooth muscle in the first compartment to contract and push the lymph into the next chamber. Contractile actomyosin filaments are also present in the end terminal of the lymphatic vessels. These filaments cause the rhythmic contraction of the terminal end of the lymphatic capillary. Therefore, they contribute to part of the initial pumping of lymph through the system.

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KEY TERMS B-lymphocytes (B-cells)—A type of white blood cell that originates in the bone marrow and recognizes foreign antigens (or proteins), secreting antibodies in an immune response. Interstitial space—The spaces found within organs and tissues. Lymph—The slightly opalescent fluid found within the lymphatic system. Lymph nodes—Bean shaped swellings along the lymphatic vessels that contain macrophages and lymphocytes. Lymphatics—The system of lymphatic vessels. T-lymphocytes (T-cells)—A type of white blood cell that originates in the thymus and attaches themselves to foreign organisms, secreting lymphokines that kill the foreign organisms. Tonsil—A collection of lymphocytes that form a mass in the back of the pharynx.

Role in human health The lymphatic system has a variety of roles in human health ranging from returning fluid from organs back to the circulatory system, to an important part in the human immune response, to absorbing lipids from the intestines. The defining role of the lymphatic vessels is to return any fluid that has leaked from the capillaries and into the interstitial space back to the circulatory system through the veins. This is important because if fluid was retained in the tissues, the result in reduced blood volume and swelling of the tissues. Another important role of the lymphatic system is the ability of plasma proteins to fit through the lymphatic valves and into the lymphatic capillary. Since most proteins have such a high molecular weight, they are unable to be reabsorbed by venous capillaries. With out the reabsorption of the plasma proteins, humans can die within 24 hours. The lymphatic system also has an essential role in the process of digestion. Primarily, the lymphatic capillaries in the gastrointestinal tract are one of the main routes for fats to be absorbed. Fats enter the lymphatics before entering the blood stream. High molecular weight proteins are not the only large substances that are absorbed. Microorganisms such as bacteria can also fit between the endothelial cells of 1452

the terminal end of the lymphatic capillary. As this occurs and the bacteria are transported to the next lymph node, the meshwork of the node and sinuses with in the node act as a filter, catching and trapping the foreign organisms. Once trapped, microorganisms can be attacked by the concentrated cells of the immune system. Macrophages may consume disease-causing bacteria, Blymphocytes may come into contact with the antigens on the surface of the microorganism and stimulate antibodies, and T-lymphocytes called “killer” cells that attach themselves to the foreign organism and release a substance to destroy the organism. The destructive nature of the “killer” cells is enhanced by another T-lymphocyte called “helper” cells (T-helper cells also assist B-cells). If this system fails, then microorganisms are not destroyed, resulting in the spread of infection though the lymphatic system and extreme infection possibly leading to death. Cancer cells that have lost adherence to, and break away from, the primary tumor are collected by the lymphatic system and filtered by latticework within the lymph nodes. Within the lymph node T-cells release substances called lymphokine (e.g. gamma interferor and interleukin 2) that may help destroy the cancer cells. Doctors use the lymph nodes as one factor of evaluation when determining the stage of the cancer. In other words, when determining how far the cancer has progressed at the time of diagnosis, the lymph nodes can be dissected to determine if cancer has spread (metastisized) from the original tumor or not. If cancer cells are present in the lymph nodes, then the cancer receives a higher stage and a less-optimistic diagnosis. In cancers that metastasize via the lymphatics, the lymph nodes where cancer cells are present are often removed. This is even more common when the lymph nodes in question are adjacent to the tumor, when the lymph nodes are located on the only lymphatic vessel present in the area of the tumor, or if no other lymphatics will be damaged during the removal.

Common diseases and disorders Since the lymphatic system is responsible for draining excess fluid from tissues and organs, the most common symptom of diseases and disorders of the lymphatic system is swelling. For example, a disease known as elephantiasis, which is caused by a filarial worm infestation, involves the blockage of the lymphatics. When the lymphatics are blocked, fluid cannot be drained and swelling occurs in the affected areas. Administering ethyl-carbamazine drugs, elevating the area and wearing a compression stocking can treat elephantiasis. Tonsillitis is another disease of the lymphatic system. Tonsillitis usually involves a bacterial or viral infec-

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A condition common among individuals following surgery for breast cancer or prostate cancer is lymphedema. It is caused by blockage of lymph vessels or lymph nodes located near the surgical site and can result in swollen arms or legs. If microorganisms cause the swelling, then antibiotics are used as treatment. If microorganisms are not the cause, then compression garments and message therapy are used as treatment. There are also cancers called lymphosarcomas and cancers of the lymph nodes that can affect the lymphatic system. The causes of these cancers are not known and there is not a consensus on what preventative measures can be taken to reduce the risk of developing these cancers. Symptoms of cancers affecting the lymphatic system include loss of appetite, energy, and weight, as well as swelling of the glands. As with many cancers, treat-

ment includes surgical removal followed by adjuvant radiation and chemotherapy. Resources BOOKS

Braunwald, Eugene, et al. Harrison’s Principles of Internal Medicine, 15th ed. New York: McGraw-Hill, 2001. Lee, Richard G. M.D., et al. Wintrob’s Clinical Hematology, 10th ed. Philadelphia: Lippincott Williams & Wilkins, 1999. Vander, Arthur. Human Physiology: The Mechanisms of Body Function, Seventh ed. New York: WBC McGraw-Hill, 1998. ORGANIZATIONS

Lymphatic Research Foundation. 941 N.E. 19th Avenue, Suite 305, Ft. Lauderdale, Florida, 33304-3071. (954)5253510. .

Sally C. McFarlane-Parrott

Lymphocyte typing see Flow cytometry analysis Lymphomas see Malignant lymphomas

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tion located within the tonsils. The tonsils are swollen, and the patient experiences a fever, sore throat, and difficulty swallowing. This can be treated by the use of antibiotics or through a surgical procedure called a tonsillectomy.

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M Macular degeneration Definition Macular degeneration is the progressive deterioration of a critical region of the retina called the macula. The macula is 3–5 mm and is responsible for central vision. This disorder leads to irreversible loss of central vision, although peripheral vision is retained. In the early stages, vision may be gray, hazy, or distorted.

Description Macular degeneration is the most common cause of legal blindness in people over 60, and accounts for approximately 11.7% of blindness in the United States. About 28% of the population over age 74 is affected by this disease. Age-related macular degeneration (ARMD) is the most common form of macular degeneration. It is also known as age-related maculopathy (ARM), aged macular degeneration, and senile macular degeneration. Approximately ten million Americans have some vision loss due to ARMD. ARMD is subdivided into a dry (atrophic) and a wet (exudative) form. The dry form is more common and accounts for 70–90% of cases of ARMD. It progresses more slowly than the wet form and vision loss is less severe. In the dry form, the macula thins over time as part of the aging process and the pigmented retinal epithelium (a dark-colored cell layer at the back of the eye) is gradually lost. Words may appear blurred or hazy, and colors may appear dim or gray. With wet ARMD, new blood vessels grow underneath the retina and distort the retina. These blood vessels can leak, causing scar tissue to form on the retina. The wet form may cause visual distortion and make straight lines appear wavy. A central blind spot develops.

The wet type progresses more rapidly and vision loss is more pronounced. Less common forms of macular degeneration include: • Cystoid macular degeneration: Vision loss in the macula due to fluid-filled areas (cysts) in the macular region. This may be a result of other disorders, such as aging, inflammation, or high myopia. • Diabetic macular degeneration: Deterioration of the macula due to diabetes. • Senile disciform degeneration (Kuhnt-Junius macular degeneration): A severe type of wet ARMD that involves hemorrhaging in the macular region. It usually occurs in people over 40 years old.

Causes and symptoms Age-related macular degeneration is intrinsic to aging for some individuals, but not all. People with an ARMD-affected family member have an increased the risk for its development. A slightly higher incidence occurs in females, although males and females are considered to be equally at risk. Whites and Asians are more susceptible to developing ARMD than blacks, in whom the disorder is rare. The cause of ARMD is thought to be arteriosclerosis in the blood vessels supplying the retina. Certain risks for the heart are considered similar risks to those that contribute to the development of macular degeneration. Smoking increases the risk of developing wet-type ARMD, and may increase the risk of developing dry-type as well. Dietary fat also increases the risk. In one study of older (age 45–84) Americans, signs of early ARMD were 80% more common in the group who ate the most saturated fat compared to those who ate the least. Low consumption of antioxidants, such as foods rich in vitamin A, is associated with a higher risk. It is generally believed that exposure to ultraviolet (UV) light may con-

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tribute to disease development, but this has not been proven conclusively. A study reported in Ophthalmology in 2000 concluded that hypertension, thyroid hormones, and antacids are associated with certain types of ARMD. The issue of antacids is not widely recognized since no determination has yet been made regarding whether the antacids themselves lead to the disease, or whether it is the stomach problems that are a contributing factor. Obesity was also found to be a factor in this study. The main symptom of macular degeneration is a central vision change. The patient may experience blurred central vision or a blank spot on the page when reading, visual distortion such as bending of straight lines, and images might appear smaller than is the actual object. Some patients notice a change in color perception, or abnormal light sensations. These symptoms can emerge suddenly and become progressively worse. Patients should be advised that a sudden onset of symptoms, particularly vision distortion, is an indication for immediate evaluation.

search for blank spots in the central vision. The doctor might order fluorescein angiography (intravenous injection of fluorescent dye followed by visual examination and photography of the back of the eye) to determine if blood vessels in the retina are leaking. Retinal pigmented epithelium (RPE) mottling that occurs, like the drusen, due to ateriorsclerotic changes of the macula decreasing the blood supply, can also be indicated through a thorough examination. A central visual field test called an Amsler grid is usually given to patients who are suspected of having ARMD. It is a grid printed on a sheet of paper (also presented for home use every week). When viewing a central dot on the page, the patient should note if any of the lines appear to be wavy or missing. This could be an indication of fluid and the onset of wet ARMD. High-risk patients particularly will be urged to schedule more frequent checkups. Although ophthalmologists and optometrists can accurately diagnose macular degeneration, attending physicians may want to consult with a retinal specialist for the best treatment protocols.

Diagnosis Optometrists and ophthalmologists, with assistance from ophthalmic assistants, technicians and nurses, should carefully screen patients who are at risk for macular degeneration. These include patients older than 60; patients with hypertension or cardiovascular disease; cigarette smokers; patients with a first-degree family (sibling or maternal) history of vision loss from ARMD regardless of age; patients with aphakia or pseudophakia; or someone with a cataract, and patients with a history that indicates significant cumulative light exposure. The ophthalmic assistant will take a careful history and log these risk factors. The patient then should have a complete ocular examination. Vision tests, performed by the physician or a skilled ophthalmic assistant, examine best corrected visual acuity, as well as near monocular visual acuity; refraction; biomicroscopy; tonometry; and stereoscopic fundus examination with pupillary dilation. Though rarely used even if ARMD is suspected, a central 10-degree computerized automated perimetry might be utilized along with fundus photography and laser ophthalmoscope scanning. After preliminary testing, specific tests are performed to determine macular degeneration. To make the diagnosis, the doctor dilates the pupil with eye drops and examines the interior of the eye, examining the retina for the presence of drusen, small white-yellow spots in the macular area, and for gross changes in the macula such as thinning. The doctor also administers a visual field test to 1456

Treatment While vision loss cannot be reversed, early detection is important because treatments are available that may halt or slow the progression of the wet form of ARMD. Some treatments for the dry form were still in early clinical trials in 2001. In wet-type ARMD and in senile disciform macular degeneration, new capillaries grow in the macular region and leak. This leaking of blood and fluid causes a portion of the retina to detach. Blood vessel growth, called neovascularization, can be treated with laser photocoagulation in some cases, depending upon the location and extent of the growth. Argon or krypton lasers can destroy the new tissue and flatten the retina. This treatment is effective in about half the cases but results may be temporary. A concern exists that laser therapy causes the laser to destroy the photoreceptors in the treated area. If the blood vessels have grown into the fovea (a region of the macula responsible for fine vision), treatment may be impossible. Because capillaries can grow quickly, this form of macular degeneration should be handled as an emergency and treated immediately. Photodynamic therapy (PDT) is a promising new treatment approved by the Food and Drug Administration in 2000. With PDT, the patient is given a light-activated drug intravenously with no damage to the retina. The drug, Visudyne, is absorbed by the damaged blood vessels. The affected area on the retina is exposed to a non-

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Another form of treatment for the wet form of ARMD is radiation therapy with either x rays, or a proton beam. Growing blood vessels are sensitive to treatment with low doses of ionizing radiation. The growth of nerve cells in the retina is stunted. They are insensitive and thus are not harmed by this treatment. External beam radiation treatment has shown promising results at slowing progression in limited, early trials. Other therapies that are under study include treatment with alpha-interferon, thalidomide, and other drugs that slow the growth of blood vessels. Subretinal surgery also has shown promise in rapid-onset cases of wet ARMD. This surgery carries the risk of retinal detachment, hemorrhage, and acceleration of cataract formation. A controversial treatment called rheotherapy involves pumping the patient’s blood through a device that removes some proteins and fats. As of 2001, this had not been proven to be safe or effective. Consumption of a diet rich in antioxidants (beta carotene and the mixed carotenoids that are precursors of vitamin A, vitamins C and E, selenium, and zinc), or antioxidant nutritional supplements, may help prevent macular degeneration, particularly if started early in life. Research has shown that nutritional therapy can prevent ARMD or slow its progression once established. Researchers also are working on therapies to treat the dry form of macular degeneration. Low-energy laser treatment for drusen is currently in clinical trials as of 2001. In this treatment the ophthalmologist uses a diode laser to reduce the drusen level. Some ophthalmologists were already performing this procedure “off-label,” without FDA approval. Another treatment, approved overseas but not in the United States, treats dry ARMD by implanting a miniaturized telescope to magnify objects in the central field of vision. This does not treat the disease, but aids the patient’s vision in only the very severe cases of ARMD.

Prognosis The dry form of ARMD is self-limiting and eventually stabilizes, with permanent vision loss. The vision of patients with the wet form of ARMD often stabilizes or improves even without treatment, at least temporarily.

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thermal laser light that activates the drug exactly 15 minutes after the infusion begins. It must be exactly 15 minutes for the treatment to be successful. The light chemically alters the drug, and any leakage from choroidal neovascularization (CNV) ceases. Patients require treatment every three months during the first year of therapy, and should be advised to avoid bright light or sun exposure for several days after therapy.

A slit-lamp view showing macular degeneration of the eye. (Custom Medical Stock Photo. Reproduced by permission.)

However, after a few years, patients with this type are usually left without acute central vision. Many macular degeneration patients lose their central vision permanently and may become legally blind. However, macular degeneration rarely causes total vision loss. Peripheral vision is retained. Patients can compensate for central vision loss, even when macular degeneration renders them legally blind. Improved lighting and low-vision aids can help even if visual acuity is poor. Vision aids include special magnifiersallowing patients to read, and provide telescopic aids for long-distance vision. The use of these visual aids plus the retained peripheral vision assist in maintaining patient independence.

Health care team roles Ophthalmic assistants, technicians, and nurses assist optometrists and ophthalmologists in testing for macular degeneration. Skilled ophthalmic staff take patient history and perform refraction; biomicroscopy; tonometry; stereoscopic fundus examination with pupillary dilation, only rarely; computerized automated perimetry; and fundus photography. Registered ophthalmic nurses also play an important role in preparing patients for PDT. Only registered nurses and physicians are allowed to mix the drug used for PDT. RNs familiar with infusion are best-suited for this task. Nurses and ophthalmic staff also play an important role in PDT follow-up care. They are critical in issuing patient instructions to stay out of bright light and sunlight after treatment, and to wear sun-protective clothing for each treatment. Patient education Ophthalmic staff should reinforce the physician’s instructions when assessing macular degeneration. They

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Treatment, 37th ed. Stamford, CT: Appleton and Lange, 1998.

KEY TERMS

ORGANIZATIONS

Drusen—Tiny yellow dots on the retina that can be soft or hard and that usually do not interfere with vision. Fovea—A tiny pit in the macula that is responsible for sharp vision. Neovascularization—Growth of new capillaries. Photoreceptors—Specialized nerve cells (rods and cones) in the retina that are responsible for vision. Retina—The light-sensitive membrane at the back of the eye that images are focused on. The retina sends the images to the brain via the optic nerve.

should emphasize the importance of the Amsler grid and regular check-ups to monitor the progression of the disease. Staff should also reaffirm doctor’s orders with patients being treated with PDT. They should review that PDT is not a cure, but a slowing of the disease, and that retreatment is necessary for its success. Staff should also reinforce restrictions on patients’ activities, such as staying out of direct sunlight or bright light for several days after PDT. They should also make follow-up calls to patients to ensure they are returning for PDT on time and to see if they have any questions about retreatment. Ophthalmic personnel should also be considerate of the age of most macular degeneration patients and provide large, easy-to-read instructions, and not rush them through the therapy or aftercare.

OTHER

Angelucci, Diane. “Managing PDT.” Ophthalmology Management Online . Kent, Christopher. “AMD Therapy New Hope for Treating Macular Degeneration” Optometric Management Online . “Macular Degeneration: A New Approach to Treating the Dry Form” Ophthalmology Management Online . “National Study Finds Smoking, Hypertension, Antacid Use Associated with Macular Degeneration” American Academy of Ophthalmology Online. . Roach, Linda. “Retina/Vitreous: Laser to Drusen Offers Hope for Dry AMD” EyeNet Magazine Online. .

Mary Bekker

Mad cow disease see Creutzfeldt-Jakob disease

Prevention Avoiding the risk factors for macular degeneration may help prevent it. This includes avoiding tobacco smoke and eating a diet low in saturated fat and rich in antioxidants. Some doctors suggest that wearing UVblocking sunglasses reduces risk. Use of estrogen in postmenopausal women is associated with a lower risk of developing ARMD. Resources

Magnesium hydroxide see Antacids Magnetic resonance angiography see Magnetic resonance imaging

Magnetic resonance imaging

BOOKS

Norris, June, ed. Professional Guide to Diseases, 5th ed. Springhouse, PA: Springhouse Corporation, 1995. Tierney, Lawrence M. Jr., Stephen J. McPhee, and Maxine A. Papadakis, eds. Current Medical Diagnosis and

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American Academy of Ophthalmology (National Eyecare Project). P.O. Box 429098, San Francisco, CA. 941429098. (800)222-EYES. . American Optometric Association. 243 North Lindbergh Blvd., St. Louis, MO 63141. (314) 991-4100. . National Eye Institute. National Institutes of Health. Bethesda, Maryland. . Prevent Blindness America. 500 East Remington Road, Schaumburg, IL 60173. (800) 331-2020. .

Definition Magnetic resonance imaging (MRI) is a unique and versatile medical imaging modality. Doctors can obtain highly refined images of the body’s interior using MRI.

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Purpose MRI was developed in the 1980s. The latest additions to MRI technology are angiography (MRA) and spectroscopy (MRS). MRA was developed to study blood flow, while MRS can identify the chemical composition of diseased tissue and produce color images of brain function. The many advantages of MRI include: • Detail. MRI creates precise images of the body based on the varying proportions of magnetically polarizable elements in different tissues. Very minor fluctuations in chemical composition can be determined. MRI images have greater subject contrast than those produced with standard x rays, computed tomography (CT), or ultrasound, all of which depend on the differing physical properties of tissues. This contrast sensitivity lets MRI distinguish fine variations in tissues deep within the body. It also is particularly useful for spotting and distinguishing diseased tissues (tumors and other lesions) early in their development. Often, doctors prescribe an MRI scan to more fully investigate earlier findings of the other imaging techniques. • Scope. The entire body can be scanned, from head to toe and from the skin to the deepest recesses of the brain. Moreover, MRI scans are not adversely affected by bone, gas, or body waste, which can hinder other imaging techniques. (Although the scans can be degraded by motion such as breathing, heartbeat, and normal bowel activity.) MRI process produces crosssectional images of the body that are as sharp in the middle as on the edges, even of the brain through the skull. A close series of these two-dimensional images can provide a three-dimensional view of a targeted area. • Safety. MRI does not depend on potentially harmful ionizing radiation, as do standard x-ray and CT scans. There are no known risks specific to the procedure, other than for people who might have metal objects in their bodies. Given all the advantages, doctors would undoubtedly prescribe MRI as frequently as ultrasound scanning, but the MRI process is complex and costly. The process requires large, expensive, and complicated equipment; a

highly trained operator; and a doctor specializing in radiology. Generally, MRI is prescribed only when serious symptoms and/or negative results from other tests indicate a need. Many times an alternative imaging procedure is more appropriate for the type of diagnosis needed. Doctors may prescribe an MRI scan of different areas of the body. • Brain and head. MRI technology was developed because of the need for brain imaging. It is one of the few imaging tools that can see through bone (the skull) and deliver high quality pictures of the brain’s delicate soft tissue structures. MRI may be needed for patients with symptoms of a brain tumor, stroke, or infection (like meningitis). MRI also may be needed when cognitive and/or psychological symptoms suggest brain disease (like Alzheimer’s or Huntington’s diseases, or multiple sclerosis), or when developmental retardation suggests a birth defect. MRI can also provide pictures of the sinuses and other areas of the head beneath the face. • Spine. Spinal problems can create a host of seemingly unrelated symptoms. MRI is particularly useful for identifying and evaluating degenerated or herniated intervertebral discs. It can also be used to determine the condition of nerve tissue within the spinal cord. • Joint. MRI scanning is often used to diagnose and assess joint problems. MRI can provide clear images of the bone, cartilage, ligaments, and tendons that comprise a joint. MRI can be used to diagnose joint injuries due to sports, advancing age, or arthritis. It can also be used to diagnose shoulder problems, like a torn rotator cuff. MRI can detect the presence of an otherwise hidden tumor or infection in a joint, and can be used to diagnose the nature of developmental joint abnormalities in children. • Skeleton. The properties of MRI that allow it to see though the skull also allow it to view the interior of bones. It can be used to detect bone cancer, inspect the marrow for leukemia and other diseases, assess bone loss (osteoporosis), and examine complex fractures. • The rest of the body. While CT and ultrasound satisfy most chest, abdominal, and general body imaging needs, MRI may be needed in certain circumstances to provide more detailed images or when repeated scanning is required. The progress of some therapies, like liver cancer therapy, need to be monitored, and the effect of repeated x-ray exposure is a concern.

Precautions MRI scanning should not be used when there is the potential for an interaction between the strong MRI mag-

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By using strong magnetic fields and pulses of radio waves to manipulate the natural magnetic properties in the body, this technique produces images not possible with other diagnostic imaging methods. MRI is particularly useful for imaging the brain and spine, as well as the soft tissues of joints and the interior structure of bones. The entire body can be imaged using MRI, and the technology poses few known health risks.

Magnetic resonance imaging Magnetic resonance imaging (MRI) uses magnets and radio waves to make images of the body’s organs, soft tissue, bone, and even blood flow. (Jon Meyer/Custom Medical Stock Photo. Reproduced by permission.)

netic field and metal objects that might be imbedded in a patient’s body. The force of magnetic attraction on certain types of metal objects (including surgical steel and clips used to pinch off blood vessels) could move them within the body and cause serious injury. The movement would occur when the patient is moved into and out of the magnetic field. Metal may be imbedded in a person’s body for several reasons. • Medical. People with implanted cardiac pacemakers, metal aneurysm clips, or who have had broken bones repaired with metal pins, screws, rods, or plates must tell their radiologist prior to having an MRI scan. In some cases (like a metal rod in a reconstructed leg) the difficulty may be overcome. • Injury. Patients must tell their doctors if they have bullet fragments or other metal pieces in their body from old wounds. The suspected presence of metal, whether from an old or recent wound, should be confirmed before scanning. • Occupational. People with significant work exposure to metal particles (working with a metal grinder, for example) should discuss this with their doctor and radiologist. The patient may need prescan testing—usually 1460

a single, standard x ray of the eyes to see if any metal is present. Chemical agents designed to improve the image and/or allow for the imaging of blood or other fluid flow during MRA may be injected. In rare cases, patients may be allergic to or intolerant of these agents, and these patients should not receive them. If these chemical agents are to be used, patients should discuss any concerns they have with their doctor and radiologist. The potential side effects of magnetic and electric fields on human health remain a source of debate. In particular, the possible effects on an unborn baby are not well known. Any woman who is, or may be, pregnant should carefully discuss this issue with her doctor and radiologist before undergoing a scan. As with all medical imaging techniques, obesity greatly interferes with the quality of MRI.

Description In essence, MRI produces a map of hydrogen atoms distributed in the body. Hydrogen is the simplest element known, the most abundant in biological tissue, and one

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Once a patient’s hydrogen atoms have been aligned in the magnet, pulses of very specific radio wave frequencies are used to jolt them out of alignment. The hydrogen atoms alternately absorb and emit radio wave energy, vibrating back and forth between their resting (polarized) state and their agitated (radio pulse) state. This comprises the “resonance” part of MRI. The MRI equipment detects the duration, strength, and source location of the signals emitted by the atoms as they relax and translates the data into an image on a television monitor. The amount of hydrogen in diseased tissue differs from the amount in healthy tissue of the same type, making MRI particularly good at identifying tumors and other lesions. In some cases, chemical agents such as gadolinium can be injected to improve the contrast between healthy and diseased tissue. A single MRI exposure produces a two-dimensional image of a slice through the entire target area. A series of these image slices closely spaced (usually less than half an inch) makes a virtual three-dimensional view of the area. Magnetic resonance spectroscopy (MRS) is different from MRI because MRS uses a continuous band of radio wave frequencies to excite hydrogen atoms in a variety of chemical compounds other than water. These compounds absorb and emit radio energy at characteristic frequencies, or spectra, which can be used to identify them. Generally, a color image is created by assigning a color to each distinctive spectral emission. This comprises the “spectroscopy” part of MRS. MRS is still experimental and is available in only a few research centers. Doctors primarily use MRS to study the brain and disorders, like epilepsy, Alzheimer’s disease, brain tumors, and the effects of drugs on brain growth and metabolism. The technique is also useful in evaluating metabolic disorders of the muscles and nervous system. Magnetic resonance angiography (MRA) is a variation on standard MRI. MRA, like other types of angiography, looks specifically at blood flow within vascular system, but does so without the injection of contrast agents or radioactive tracers. Standard MRI cannot detect blood flow, but MRA uses specific radio pulse sequences

to capture usable signals. The technique is generally used in combination with MRI to obtain images that show both vascular structure and flow within the brain and head in cases of stroke, or when a blood clot or aneurysm is suspected. Regardless of the exact type of MRI planned, or area of the body targeted, the procedure involved is basically the same and occurs in a special MRI suite. The patient lies back on a narrow table and is made as comfortable as possible. Transmitters are positioned on the body and the cushioned table that the patient is lying on moves into a long tube that houses the magnet. The tube is as long as an average adult lying down, and the tube is narrow and open at both ends. Once the area to be examined has been properly positioned, a radio pulse is applied. Then a twodimensional image corresponding to one slice through the area is made. The table then moves a fraction of an inch and the next image is made. Each image exposure takes several seconds and the entire exam will last anywhere from 30-90 minutes. During this time, the patient is not allowed to move. If the patient moves during the scan, the picture will not be clear. Depending on the area to be imaged, the radio-wave transmitters will be positioned in different locations. • For the head and neck, a helmet-like hat is worn. • For the spine, chest, and abdomen, the patient will be lying on the transmitters. • For the knee, shoulder, or other joint, the transmitters will be applied directly to the joint. Additional probes will monitor vital signs (like pulse, respiration, etc.). The process is very noisy and confining. The patient hears a thumping sound for the duration of the procedure. Since the procedure is noisy, music supplied via earphones is often provided. Some patients get anxious or panic because they are in the small, enclosed tube. This is why vital signs are monitored and the patient and medical team can communicate between each other. If the chest or abdomen are to be imaged, the patient will be asked to hold his/her breath as each exposure is made. Other instructions may be given to the patient, as needed. In many cases, the entire examination will be performed by an MRI operator who is not a doctor. However, the supervising radiologist should be available to consult as necessary during the exam, and will view and interpret the results sometime later. Open MRI units Many adult patients and, especially children, become extremely claustrophobic when placed inside the confines of a full strength (1.5 Tesla) superconducting

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that can be magnetically polarized. It will align itself within a strong magnetic field, like the needle of a compass. The earth’s magnetic field is not strong enough to polarize a person’s hydrogen atoms, but the superconducting magnet of an MRI machine can. The strength of the Earth’s magnetic field is approximately 1 gauss. Typical field strength of an MRI unit, with a superconducting magnet is 1,500 gauss expressed as 1.5 kilogauss or 1.5 Tesla units. This comprises the “magnetic” part of MRI.

Magnetic resonance imaging

motion artifacts because patients need to remain still for longer periods of time.

KEY TERMS Angiography—Any of the different methods for investigating the condition of blood vessels, usually via a combination of radiological imaging and injections of chemical tracing and contrasting agents. Gadolinium—A very rare metallic element useful for its sensitivity to electromagnetic resonance, among other things. Traces of it can be injected into the body to enhance the MRI pictures. Hydrogen—The simplest, most common element known in the universe. It is composed of a single electron (negatively charged particle) circling a nucleus consisting of a single proton (positively charged particle). It is the nuclear proton of hydrogen that makes MRI possible by reacting resonantly to radio waves while aligned in a magnetic field. Ionizing radiation—Electromagnetic radiation that can damage living tissue by disrupting and destroying individual cells. All types of nuclear decay radiation (including x rays) are potentially ionizing. Radio waves do not damage organic tissues they pass through. Magnetic field—The three-dimensional area surrounding a magnet, in which its force is active. During MRI, the patient’s body is permeated by the force field of a superconducting magnet. Radio waves—Electromagnetic energy of the frequency range corresponding to that used in radio communications, usually 10,000 cycles per second to 300 billion cycles per second. Radio waves are the same as visible light, x rays, and all other types of electromagnetic radiation, but are of a higher frequency.

Preparation In some cases (such as for MRI brain scanning or an MRA), a chemical designed to increase image contrast may be given by the radiologist immediately before the exam. If a patient suffers from anxiety or claustrophobia, drugs may be given to help the patient relax. The patient must remove all metal objects (watches, jewelry, eye glasses, hair clips, etc). Any magnetized objects (like credit and bank machine cards, audio tapes, etc.) should be kept far away from the MRI equipment because they can be erased. The patient cannnot bring their wallet or keys into the MRI machine. The patient may be asked to wear clothing without metal snaps, buckles, or zippers, unless a medical gown is worn during the procedure. The patient may be asked to remove any hair spray, hair gel, or cosmetics that may interfere with the scan.

Aftercare No aftercare is necessary, unless the patient received medication or had a reaction to a contrast agent. Normally, patients can immediately return to their daily activities. If the exam reveals a serious condition that requires more testing and/or treatment, appropriate information and counseling will be needed.

Complications MRI poses no known health risks to the patient and produces no physical side effects. Again, the potential effects of MRI on an unborn baby are not well known. Any woman who is, or may be, pregnant, should carefully discuss this issue with her doctor and radiologist before undergoing a scan.

Results magnet. This problem is often severe enough to prevent them from having an MRI scan performed. An alternative design, to the standard MRI unit is one where the magnet is comprised of two opposed halves with a large space in between. Units designed this way are known as open MRI machines. The advantage is, they can be used for patients who are claustrophobic. The disadvantage is, the field strength of the magnets is lower than with standard full strength machines, usually somewhere in the range of 0.2–0.5 Tesla. Lower strength magnetic fields require more time for image acquisition increasing the risks of 1462

A normal MRI, MRA, or MRS result is one that shows the patient’s physical condition to fall within normal ranges for the target area scanned. Generally, MRI is prescribed only when serious symptoms and/or negative results from other tests indicate a need. There often exists strong evidence of a condition that the scan is designed to detect and assess. Thus, the results will often be abnormal, confirming the earlier diagnosis. At that point, further testing and appropriate medical treatment is needed. For example, if the MRI indicates the presence of a brain tumor, an MRS may be prescribed to determine the type of tumor so that aggres-

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Magnetic resonance imaging unit

Health care team roles The MRI examination is conducted by an MRI technologist and a radiologist. The MRI technologist is responsible for preparing the patient for the examination by making sure that all metallic objects have been removed and that the patient does not have any metallic implants that will be affected by the examination. It is recommended that a prescreening MRI questionnaire be developed and that all patients be required to complete the form prior to having an MRI. If necessary for the area being imaged, an intravenous contrast agent will be administered by either the technologist or a nurse. Nursing staff may also be present during the examination, depending on the medical condition of the patient. The radiologist oversees the selection of MRI imaging sequences and protocols and reviews the acquired images to be sure image quality is appropriate for diagnosis. The radiologist also provides the final interpretation of images and provides a report for any referring physicians.

Definition A magnetic resonance imaging (MRI) unit uses a magnetic field, radiofrequency waves, and computerized image processing to produce cross-sectional images of the anatomy.

Purpose An MRI unit has several diagnostic clinical applications, including: • diagnosing diseases of the central nervous system, brain, and spine • detecting musculoskeletal disorders and injuries • identifying infectious diseases such as those associated with acquired immunodeficiency syndrome (AIDS) • detecting metastatic liver disease

Resources

• imaging the cardiovascular system

BOOKS

• staging prostate, bladder, and uterine cancers

Haaga, John R., et al., eds. Computed Tomography and Magnetic Resonance Imaging of the Whole Body. St. Louis, MO: Mosby, 1994. Kevles, Bettyann Holtzmann. Naked to the Bone: Medical Imaging in the Twentieth Century. New Brunswick, NJ: Rutgers University Press, 1997. Zaret, Barry L., et al., eds. The Patient’s Guide to Medical Tests. Boston: Houghton Mifflin Company, 1997. PERIODICALS

The Basics of MRI. Joseph P. Hornak, Ph.D., http//www.cis.rit.edu/htbooks/mri/. Brief Introduction to FMRI. Copyright 1998, Steve Smith, FMRIB, . Kevles, Bettyann. “Body Imaging.” Newsweek (Winter 97/98 Extra Millennium Issue): 74-76. ORGANIZATIONS

American College of Radiology. 1891 Preston White Dr., Reston, VA 22091. (703) 648-8900. . American Society of Radiologic Technologists. 15000 Central Ave. SE, Albuquerque, NM 87123-3917. (505) 298-4500. . Center for Devices and Radiological Health. United States Food and Drug Administration. 1901 Chapman Ave., Rockville, MD 20857. (301) 443-4109. .

Stephen John Hage, AAAS, RT-R, FAHRA

• studying bone marrow diseases • imaging the breast adjunctive to conventional mammography Some MRI units can perform magnetic resonance angiography (MRA), which is used to image vascular and arteriovenous malformations, thromboses, stenoses, and other vascular abnormalities. In particular, MRA is used for evaluating the carotid artery and cerebral vasculature in patients with suspected or known stroke. An MRI unit can also be used in conjunction with other imaging modalities such as computed tomography (CT) for localizing the treatment target for radiation treatment planning and prior to surgical treatment of tumors, including stereotactic radiosurgery and image-guided surgery. It is also possible to evaluate brain function associated with certain tasks such as language or vision using functional MRI. MRI provides images with excellent contrast that allow clinicians to clearly see details of soft tissue, bone, joints, and ligaments. Because MRI does not use ionizing radiation to produce images, like radiography and CT, it is often the examination of choice for imaging the male and female reproductive systems, pelvis and hips, and urinary tract and bladder.

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sive treatment can begin immediately without the need for a surgical biopsy.

Magnetic resonance imaging unit Magnetic resonance imaging system. (Photograph by Mason Morfit. FPG International Corp. Reproduced by permission.)

Description MRI units are used in the radiology department and outpatient imaging centers for diagnostic imaging, in the emergency care and critical care settings to diagnose acute conditions such as stroke in the clinical research setting (especially for brain research), and in orthopedic practices. Large hospitals usually have one or more MRI units that are typically located in the radiology department or in a separate annex near the radiology and emergency departments.

the magnetic field when a radiofrequency pulse is added. When the pulse is terminated, protons relax back into alignment with the magnetic field, and this generates a radiofrequency signal that is received by the antenna coil. Different tissues such as those high in water and in fat will produce different signals that are then processed by the computer and converted into anatomical images. MRI protocols and imaging sequences are based on the different signals produced by different types and physiologic states of tissue.

An MRI unit consists of a magnet system, a radiofrequency (RF) transmitter/receiver system, a gradient system, a patient table, a computer workstation, and operator console. The magnetic strength of the magnet is measured in teslas (T), a unit of magnetic field strength, and ranges from 0.064–4 T, depending on the type of system. The magnetic field generated during an MRI examination is approximately 8,000 times stronger than the Earth’s magnetic field. Principles of image production are based on the magnetic spin properties of hydrogen atoms in the body’s tissues and fluids and how they behave in a magnetic field. Basically, hydrogen protons (particles located in the atom’s nucleus) will align with an applied magnetic field and will spin perpendicular to

The magnet system is contained in the gantry, which is a large square or round unit with a hole in the center (the bore) through which the patient table is moved. Magnets may be of three types: permanent magnet, resistive or superconducting electromagnet, and iron-core electromagnet. Permanent magnets are extremely heavy and thus require special construction; however, they do not require electrical power or cooling because they are constructed of magnetic alloys. They also have almost no fringe field (the magnetic field outside the magnet itself). Permanent magnets are limited to field strengths of 0.3 T or less. Resistive electromagnets use electrical coils to generate a magnetic field and thus require cooling water. Resistive magnets are limited to field strengths of 0.5 T.

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An MRI unit with a field strength less than 0.2 T is considered low field, an MRI unit with a field strength of 0.2 T to 1 T is considered mid field, and an MRI unit with a field strength greater than 1 T is considered high field. In general, high-field MRI units are capable of shorter imaging times and higher image quality and are preferred for many clinical applications. The radiofrequency system transmits and receives signals using a coil that acts as an antenna. Separate coils are used for head and body imaging, and specially designed coils are used for imaging the spine, face, knee, breast, shoulder, and extremities. The gradient system produces magnetic fields in the direction of the primary field and perpendicular to the primary field in order to select the area for imaging and to register the location of signals received from the area imaged. The radiofrequency and gradient systems are turned on and off (pulsed) to control image contrast; these pulse patterns are called a pulse sequence. There are several different types of pulse sequences used, and they vary according to the duration, frequency, and timing of the pulses. Different pulse sequences are used to image different anatomic areas, and the pulse sequence is chosen based on the characteristics of the tissue being imaged such as fat content, water content, and anatomic area. There are several different types of MRI units and MRI imaging methods: • Conventional MRI units have long, closed bores that surround most of the patient’s body during imaging. • Short-bore MRI units were developed in response to patient claustrophobia and to retain the image-quality benefits of conventional systems, and have bore lengths that allow patients of average height to have much of their body outside the bore during imaging. The patient’s head can then be outside the bore for exams not involving the brain and neck, thereby reducing claustrophobic reactions. • Open MRI units were also developed in response to patient claustrophobia and to facilitate interventional procedures. They have bores that are open on most sides (sometimes columns are used to support the gantry). Open MRI units usually have low-field strengths. • Dedicated extremity/head/breast MRI units have very small bores designed to accommodate imaging of

limbs, joints, or the head, and are primarily used for orthopedic applications. A dedicated breast MRI system is also available. • Mobile MRI units are installed in a specially designed trailer and driven to hospitals that do not have an MRI unit. Mobile MRI services are used frequently in rural areas. • Functional MRI is an imaging technique that rapidly acquires images that display changes in cerebral blood flow in response to visual or auditory stimuli or motor tasks. This technique is used primarily for research to map the functional organization of the brain. • Interventional and intraoperative MRI is a developing field that involves performing interventional procedures such as catheterization or guidewire insertion, and intraoperative guidance such as during neurosurgery, using a specially designed MRI unit. Open MRI units are being used for these applications due to their open-bore design, which facilitates patient access. • MRI spectroscopy is an imaging technique used primarily in research that measures metabolites in the brain to evaluate brain tissue. • Echoplanar MRI is an imaging technique that uses rapidly oscillating magnetic field gradients for image acquisition in less than 30 milliseconds. It is used to evaluate real-time cardiac and brain function, as well as muscle activity. • MRI angiography is an imaging technique used to evaluate the blood vessels, for example, to detect aneurysms or atherosclerosis. Injection of a contrast agent is required. • Diffusion tensor MRI is a relatively new imaging technique that tracks water molecules in the brain to detect abnormalities associated with stroke, multiple sclerosis, and other conditions.

Operation An MRI unit is operated by the MRI technologist who prepares the patient for the examination, including administering any necessary intravenous contrast agents and positioning the patient on the table. Some examinations require the use of special surface coils (e.g., for head, knee, etc.) to focus the radiofrequency pulses on the area of interest. The MRI technologist places or attaches the appropriate coil and helps the patient onto the table. After the patient is properly positioned, the MRI technologist goes to the control room, which is adjacent to but separated from the MRI unit by a window, and initiates the imaging sequences selected by the radiologist. Usually, two to six imaging sequences are per-

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Superconducting magnets use titanium alloy coils that require cooling with liquid helium or liquid nitrogen (cryogens). They can have field strengths of up to 2 T. Iron-core electromagnets use a combination of permanent and electromagnet technology, and require cooling water for operation. Field strengths are usually 0.3 or 0.4 T.

Magnetic resonance imaging unit

formed, each lasting approximately two to 15 minutes. The technologist instructs the patient via an intercom system when the scanning sequence is to begin and whether holding of breath or stillness is required. While the images are being acquired, the MRI technologist and radiologist review them on the computer workstation to make sure the image quality is sufficient for diagnosis. Image artifacts may occur during image acquisition, and the technologist and radiologist should monitor acquired images for artifacts. Patient motion, respiratory motion, implants, signal loss, and improper unit settings can all cause artifacts to occur. Constantly occurring artifacts related to the unit’s operation or magnetic field may require a service call from the manufacturer or testing by a medical physicist. With regard to patient safety, there are no side effects associated with the magnetic field during an MRI examination, but, in general, MRI is not recommended for pregnant women. Patients with a pacemaker, cochlear implants, aneurysm clips, and other metallic implants must check with a physician before undergoing MRI due to the possible effects of the magnetic field on the implants. Patients who have been exposed to shrapnel or metal shavings (especially in the eye) may not be able to have an MRI; instances where the magnetic field caused movement of metal fragments in the body and subsequent patient injury have been reported. Because eyeshadow may contain metallic substances, patients undergoing MRI should not wear make-up during the examination. Several incidents have occurred where patients undergoing MRI examinations received serious skin burns from contact with surface coils or monitoring cables. Therefore, the United States Food and Drug Administration (FDA) has issued precautions to prevent burns during MRI, including removal of unnecessary coils, cables, and leads before the scan is begun; frequent checking of coils, cables, and leads for frayed insulation or exposed wires; and a thorough check that cables and leads do not form loops, touch the sides of the magnet bore, or directly touch the patient. The magnetic field requires that all medical equipment used in the MRI suite be MRI-compatible. For example, patient monitoring equipment, intravenous poles, ventilators, and contrast media injectors should have been tested and certified by the manufacturer as MRI-compatible. If interventional procedures are performed in the MRI suite, anesthesia units, surgical instrumentation, patient monitoring systems, and resuscitation equipment should all be MRI-compatible. The operation and performance of equipment that is not MRI-compatible may be affected by the magnetic field, or if the equip1466

ment contains certain metals, it may be attracted to the magnet, causing equipment damage and presenting a safety problem. Because patients may be brought into the MRI suite on wheelchairs or with oxygen canisters, MRI staff should be sure that the magnetic field is not on during patient transfer. There have been several hazard reports of injury to patients and staff by oxygen canisters, wheelchairs, and other metal items when they were rapidly drawn to the magnet. During the MRI examination, all patients, but particularly those under sedation or anesthesia or in critical condition, should be monitored using physiologic monitoring equipment, intercom systems, and video. Some patients may be claustrophobic during the examination or may experience anxiety. To alleviate these discomforts, an MRI-compatible music system and increased ventilation in the magnet bore can be installed. Depending on the type of magnet, different types of shielding are required for the MRI suite. The performance of the MRI unit depends on the homogeneity, or uniformity, of the magnetic field, which may be disturbed by surrounding hospital equipment, metallic structures, and environmental factors. A process called shimming is used to improve the uniformity of the magnetic field, and is accomplished by using shim coils or ferromagnetic materials around the magnet. Shimming is usually done during installation or testing by physicists. The entire MRI suite may need to be shielded with different materials to insulate the magnet from outside interference or to prevent the magnet’s fringe field from interfering with the operation of medical equipment in adjacent areas.

Maintenance Because of the complexity of an MRI unit, a service contract covering parts replacement, preventive maintenance, and emergency repairs is usually purchased from the manufacturer or a third-party service organization. The biomedical engineering staff and/or the MRI technologist conduct periodic performance testing of image quality and other parameters. Surface coils should be cleaned and maintained according to manufacturer instructions. Many MRI units have special cooling system requirements, and storage and replenishment of cryogens (chemicals used for cooling the magnet system) is necessary. This is generally performed by the service provider or biomedical engineering staff.

Health care team roles The MRI examination is conducted by an MRI technologist and a radiologist. The MRI technologist is responsible for preparing the patient for the examination

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Training MRI technologists have completed special education programs in MRI physics, operation, and safety. All manufacturers of MRI units provide on-site, and sometimes off-site, training on the technical features and clinical applications of their systems. The American College of Radiology has developed an MRI site accreditation program, which requires that the MRI system, quality control procedures, MRI technologists, and radiologists be evaluated according to certain standards of performance. As of 2001, this accreditation was not mandatory, but many facilities undergo the process to demonstrate quality performance. Resources BOOKS

Dendy, P.P., and B. Heaton. Physics for Diagnostic Radiology, 2nd ed. Philadelphia, PA: Institute of Physics Publishing, 1999. NessAiver, Moriel. All You Really Need to Know about MRI Physics. Baltimore, MD: Simply Physics, 1997. PERIODICALS

Kanal, Emanual, ed. “MRI Safety.” Magnetic Resonance Imaging Clinics of North America 6, no. 4 (November 1998). Ladd, Mark E., Harald H. Quick, and Jorg R. Debatin. “Interventional MRA and Intravascular Imaging.” Journal of Magnetic Resonance Imaging 12 (2000): 524-46. Lewin, Jonathan S., Andrew Metzger, and Warren R. Selman. “Intraoperative Magnetic Resonance Image Guidance in

KEY TERMS Aneurysm—Localized enlargement of an artery or vein. Artifact—An artificial feature in an acquired MRI image. Atherosclerosis—Hardening of the arteries, a form of heart disease. Metabolites—Byproducts of metabolism that accumulate in brain tissue that is measured by MRI spectroscopy. Teslas (T)—A unit of magnetic field strength.

Neurosurgery. Journal of Magnetic Resonance Imaging 12 (2000):512-24. Sawyer-Glover, Anne M., and Frank G. Shellock. “Pre-MRI Procedure Screening: Recommendations and Safety Considerations for Biomedical Implants and Devices.” Journal of Magnetic Resonance Imaging 12 (2000): 92-106. Tempany, Clare M.C., and Barbara J. McNeil. “Advances in Biomedical Imaging.” Journal of the American Medical Association 285, no. 5 (February 7, 2001): 562-67. ORGANIZATIONS

American College of Radiology. 1891 Preston White Drive, Reston, VA 20191-4397. (800)227-5463. . American Society of Radiologic Technologists (ASRT). 15000 Central Avenue SE, Albuquerque, NM 87123-2778. (800) 444-2778. . Clinical Magnetic Resonance Society. 2825 Burnet Avenue, Suite 2, Cincinnati, OH 45219. (800) 823-2677. . International Society for Magnetic Resonance in Medicine. 2118 Milvia Street, Suite 201, Berkeley, CA 94704. (510) 841-1899. . Radiological Society of North America. 820 Jorie Boulevard, Oak Brook, IL 60523-2251. (630) 571-2670. . OTHER

“Magnetic Resonance Imaging.” American Society of Radiologic Technologists. . “MR Imaging (MRI)—Body.” .

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by making sure that all metallic objects have been removed and that the patient does not have any metallic implants that will be affected by the examination. It is recommended that a prescreening MRI questionnaire be developed and that all patients be required to complete the form prior to having an MRI. If necessary for the area being imaged, an intravenous contrast agent will be administered by either the technologist or a nurse. Nursing staff may also be present during the examination, depending on the medical condition of the patient. The radiologist oversees the selection of MRI imaging sequences and protocols and reviews the acquired images to be sure image quality is appropriate for diagnosis. The radiologist also provides the final interpretation of images and provides a report for any referring physicians. For cancer cases, oncologists may also be involved in image review for treatment planning purposes. If interventional MRI procedures are performed, specialists such as a gastroenterologist, orthopedic surgeon, neurologist, or neurosurgeon may perform the procedures while the MRI unit is operated by the technologist.

Malabsorption syndrome

drate absorption, and irritation from unabsorbed fatty acids

Magnetic resonance spectroscopy see Magnetic resonance imaging

• edema (fluid retention in the body’s tissues) due to decreased protein absorption • malnutrition and weight loss due to decreased fat, carbohydrate, and protein absorption; weight may be 80–90% of usual weight despite increased oral intake of nutrients

Malabsorption syndrome Definition Malabsorption syndrome is an alteration in the ability of the intestine to absorb nutrients adequately into the bloodstream.

• muscle wasting and atrophy due to decreased protein absorption and metabolism • perianal skin burning, itching, or soreness due to frequent loose stools

Causes and symptoms Protein, fats, and carbohydrates (macronutrients) normally are absorbed in the small intestine; the small bowel also absorbs about 80% of the 8.4–10.5 qt (8–10 l) of fluid ingested daily. There are many different conditions that affect fluid and nutrient absorption by the intestine. A fault in the digestive process may result from failure of the body to produce the enzymes needed to digest certain foods. Congenital structural defects or diseases of the pancreas, gall bladder, or liver may alter the digestive process. Inflammation, infection, injury, or surgical removal of portions of the intestine may also result in absorption problems; reduced length or surface area of intestine available for fluid and nutrient absorption can result in malabsorption. Radiation therapy may injure the mucosal lining of the intestine, resulting in diarrhea that may not become evident until several years later. The use of some antibiotics can also affect the bacteria that normally live in the intestine and affect intestinal function. Risk factors for malabsorption syndrome include: • family history of malabsorption or cystic fibrosis • use of certain drugs such as mineral oil or other laxatives • travel to foreign countries, which may introduce parasites into the body • intestinal surgery • excess alcohol consumption Individuals may experience symptoms of malabsorption, the most common of which include: • anemia, with weakness and fatigue due to inadequate absorption of vitamin B12, iron, and folic acid • diarrhea (sometimes explosive diarrhea with greasy, foul-smelling stools), steatorrhea (excessive amount of fat in the stool), and abdominal distention with cramps, bloating, and gas due to impaired water and carbohy1468

• muscle cramping due to decreased vitamin D, calcium, and potassium levels

Irregular heart rhythms may also result from inadequate levels of potassium and other electrolytes. Blood clotting disorders may occur due to a vitamin K deficiency. Children with malabsorption syndrome often exhibit a failure to grow and thrive. Several disorders can lead to malabsorption syndrome, including cystic fibrosis, chronic pancreatitis, lactose intolerance, and celiac disease (gluten enteropathy, non-tropical sprue). Tropical sprue is a malabsorptive disorder that is uncommon in the United States, but seen more often in people from the Caribbean, India, or southeast Asia. Although its cause is unknown, the disorder is thought to be related to environmental factors, including infection, intestinal parasites, or possibly the consumption of certain food toxins. Symptoms often include a sore tongue, anemia, weight loss, along with diarrhea and passage of fatty stools. Celiac disease, also known as non-tropical sprue, gluten enteropathy, or celiac sprue, is an inherited disorder resulting in malabsorption because of an allergic reaction after consumption of a protein called gluten. Gluten is found in wheat, rye, barley, and oats. Whipple’s disease is a relatively rare malabsorptive disorder that affects mostly middle-aged men. The cause of the disorder is possibly related to bacterial infection, resulting in nutritional deficiencies, chronic low-grade fever, diarrhea, joint pain, weight loss, and darkening of the skin’s pigmentation. Other organs of the body may be affected, including the brain, heart, lungs, and eyes. Short bowel syndromes—which may be present at birth (congenital) or the result of surgery—reduce the surface area of the bowel available to absorb nutrients and can also result in malabsorption syndrome. Bacterial overgrowth that is triggered by intestinal diverticulosis, intestinal disorders, blind loops, fistulas,

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• Serum calcium: May be low due to vitamin D and amino acid malabsorption.

Intestinal lymphangiectasia, also called idiopathic hypoproteinemia, is a disorder affecting children and young adults in which the lymph vessels supplying the lining of the small intestine become enlarged. Lymph vessel enlargement may be a birth defect or may have been due to inflammation of the pancreas, called pancreatitis or a condition called constrictive pericarditis, which is characterized by a stiffening of the sac around the heart (constrictive pericarditis). These conditions increase pressure on the lymphatic system. Symptoms of intestinal lymphangiectasia are severe edema, and perhaps nausea, vomiting, mild diarrhea, fatty stools, and abdominal pain. The number of lymphocytes in the blood may decrease. As well, cholesterol and protein levels in the blood are low.

• Serum protein and albumin: May be low due to protein losses.

Diagnosis Doctors often suspect malabsorption syndromes when weight loss, diarrhea, and nutritional deficiencies occur despite eating a healthy and adequate diet. The diagnosis of malabsorption syndrome and identification of the underlying cause can require extensive diagnostic testing. The first phase of diagnosis involves a thorough medical history and physical examination by a physician, who will then determine the appropriate laboratory studies and x rays. A 72-hour stool collection may be ordered for fecal fat measurement; increased fecal fat in the stool indicates malabsorption. A biopsy of the small intestine may be done to assist in differentiating between malabsorption syndrome and small bowel disease. Pancreatic function tests are often conducted since pancreatic disorders are a common cause of malabsorption syndromes. Ultrasound, computed tomography scan (CT scan), magnetic resonance imaging (MRI), barium enema, or other x rays to identify abnormalities of the gastrointestinal tract and pancreas may also be ordered. To diagnose intestinal lymphangiectasia, an intravenous injection of radioactive-labeled albumin may be ordered. Excessive protein is lost if abnormal amounts of the radioactive substance appear in the stool. Enlarged lymph vessels are indicated by a biopsy of the small intestine. Laboratory studies of the blood may include: • Serum cholesterol: May be low due to decreased fat absorption and digestion. • Serum sodium, potassium, and chloride: May be low due to electrolyte losses with diarrhea.

• Serum vitamin A and carotene: May be low due to bile salt deficiency and impaired fat absorption. • D-xylose test: Decreased excretion may indicate malabsorption. • Schilling test: May indicate malabsorption of vitamin B12.

Treatment Fluid and nutrient monitoring and replacement is essential for any individual with malabsorption syndrome. Hospitalization may be required when severe fluid and electrolyte imbalances occur. Consultation with a dietitian to assist with nutritional support and meal planning is helpful. If the patient is able to eat, the diet and supplements should provide bulk and be rich in carbohydrates, proteins, fats, minerals, and vitamins. The patient should be encouraged to eat several small meals throughout the day, avoiding fluids and foods that promote diarrhea. Intake and output should be monitored, along with the number, color, and consistency of stools. The individual with malabsorption syndrome must be monitored for dehydration, including dry tongue, mouth, and skin; increased thirst; low, concentrated urine output; or feeling weak or dizzy when standing. Pulse and blood pressure should be monitored for increased or irregular pulse rate, or hypotension (low blood pressure). The individual should also be alert for signs of nutrient, vitamin, and mineral depletion, including nausea or vomiting; fissures at corner of mouth; fatigue or weakness; dry, thinning hair; easy bruising; tingling in fingers or toes; and numbness or burning sensation in legs or feet. Fluid volume excess, as a result of diminished protein stores, may require fluid intake restrictions. The physician should also be notified of any shortness of breath. Other specific medical management for malabsorption syndrome is dependent upon the cause. Treatment for tropical sprue consists of folic acid supplements and long-term antibiotics. Depending on the severity of the disorder, this treatment may be continued for six months or longer. Whipple’s disease also may require long-term use of antibiotics such as tetracycline. Management of some individuals with malabsorption syndrome may require injections of vitamin B12 and oral iron supplements. The doctor may also prescribe enzymes to replace missing intestinal enzymes, or antispasmodics to reduce abdominal cramping and associated diarrhea. People with cystic fibrosis and chronic pancreatitis require pan-

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and strictures may cause malabsorption, resulting in fat malabsorption and flatulence.

Malabsorption syndrome

KEY TERMS Anemia—A decrease in the number of red blood cells in the bloodstream, characterized by pallor, loss of energy, and generalized weakness. Atrophy—A wasting away of a tissue or organ, often caused by insufficient nutrition. Biopsy—A tissue sample removed from the body for examination under the microscope. Constrictive pericarditis—A condition that is characterized by a stiffening of the sac around the heart, which leads to increased pressure on the lymphatic system. Cystic fibrosis—A hereditary genetic disorder that occurs most often in Caucasians. Thick, sticky secretions from mucus-producing glands cause blockages in the pancreatic ducts and the airways. Edema—An excessive accumulation of fluid in the tissue spaces.

onset of symptoms may be slow and difficult to diagnose. Treatment may be long, complicated, and changed often for optimal effectiveness. Patience and a positive attitude are important in controlling or curing the disorder.

Health care team roles The health care team should familiarize patients with their condition and the methods of dealing most effectively with their malabsorption syndrome. Physicians will typically take charge of the patient’s care, ordering tests and medications. Nurses are involved in the daily care of the patient, including administering medicines. Clinical laboratory scientists and medical technologists peform laboratory tests on blood or fecal samples. Radiologic technologists perform many of the imaging studies used in diagnosis.

Prevention

Short bowel syndrome—A condition in which the bowel is not as long as normal, either because of surgery or because of a congenital defect.

Many malabsorption syndromes are hereditary. Genetic screening may prevent passing on the genes to unborn children. For infants or children, the best means of prevention of some of these hereditary conditions are by early detection at routine well-baby examinations and periodic follow-ups with school-aged and adolescent children. In some cases, however, prevention of malabsorption syndromes can consist of simply avoiding foods or substances that cause the patient an allergic reaction and/or gastrointestinal distress. Careful monitoring is necessary to prevent additional illnesses caused by nutritional deficiencies. Impure water sources should be avoided when traveling to prevent parasitic infection.

Steatorrhea—An excessive amount of fat in the stool.

Resources

Gluten enteropathy—A hereditary malabsorption disorder caused by sensitivity to gluten, a protein found in wheat, rye, barley, and oats; also called non-tropical sprue or celiac disease. Intestines—Also known as the bowels; intestines are divided into the large and small intestines, extending from the stomach to the anus.

BOOKS

creatic supplements. Those with lactose intolerance or gluten enteropathy will have to modify their diets to avoid foods that they cannot properly digest. Intestinal lymphangiectasia is treated by correcting the cause of the lymph vessel enlargement. For instance, treating constrictive pericarditis may relieve pressure on the lymph vessels. Some people improve by eating a lowfat diet and taking supplements of certain triglycerides, which are absorbed directly into the blood and not through the lymph vessels. If only a small part of the intestine is affected, it can be removed surgically.

Prognosis The expected course for the individual with malabsorption syndrome varies, depending on the cause. The 1470

Institute of Medicine. Dietary Reference Intakes: Applications in Dietary Assessment. Washington, D.C.: National Academy Press, 2001. Institute of Medicine. Dietary Reference Intakes: Risk Assessment (Compass Series). Washington, D.C.: National Academy Press, 1999. Larson-Duyff, Roberta. The American Dietetic Association’s Complete Food & Nutrition Guide. New York: John Wiley & Sons, 1998. Kelsen, David, Bernard Levin, and Joel Tepper. Principles and Practice of Gastrointestinal Oncology. Philadelphia: Lippincott Williams & Wilkins Publishers, 2001. Mahan, L. Kathleen, and Sylvia Escott-Stump. Krause’s Food, Nutrition, & Diet Therapy. London: W. B. Saunders Co., 2000. Monahan, Frances, and Marianne Neighbors. MedicalSurgical Nursing: Foundations for Clinical Practice. Philadelphia: W. B. Saunders Co., 1998.

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PERIODICALS

Jeppesen, Palle B., et al. “Differences in Essential Fatty Acid Requirements by Enteral and Parenteral Routes of Administration in Patients with Fat Malabsorption.” American Journal of Clinical Nutrition (1999): 70: 78-84. Misbah, S.A., and N. P. Mapstone. “Whipple’s Disease Revisited.” Journal of Clinical Pathology (2000): 53: 750-55. Murphy, Jane, et al. “Fat Malabsorption in Cystic Fibrosis Patients.” American Journal of Clinical Nutrition (1999): 70: a943-a944. ORGANIZATIONS

American Dietetic Association. 216 W. Jackson Blvd., Chicago, IL 60606-6995. (312) 899-0040. . Food and Nutrition Information Center Agricultural Research Service, USDA. National Agricultural Library, Room 304, 10301 Baltimore Avenue, Beltsville, MD 207052351. (301) 504-5719. (301) 504-6409. . [email protected]. OTHER

“Malabsorption.” 2001. .

Crystal Heather Kaczkowski, M.Sc.

Malabsorption tests Definition Malabsorption tests are done to determine if a patient has dietary malabsorption or maldigestion and to help differentiate between these two conditions. Malabsorption occurs when the gastrointestinal (GI) tract cannot take up a dietary compound. This is caused by the loss of function of the cells responsible for absorption. Maldigestion occurs when an important digestive enzyme or tissue is lacking or not functioning correctly. This may be caused by genetic disorders, injury to the tissue that provides the enzyme (i.e. the pancreas), alterations in pH that make the enzymes inactive, or to surgery. In general, clinicians speak of both disorders as malabsorption disorders since they both result in a lack of absorption of nutrients.

Purpose Malabsorption tests are generally used to determine why someone is malnourished or is experiencing gastrointestinal upset. Some malabsorption tests are used as a last resort because the testing procedures are complicated. The physician first needs to rule out other disorders such as ulcers in the stomach and intestine. In the population, the elderly are at the greatest risk for developing malabsorption disorders. Before ordering malabsorption tests, physicians may do a general screen for malnutrition. This can include tests for proteins that reflect nutritional status such as serum albumin and prealbumin (transthyretin); tests for serum calcium, vitamin B12, folate, iron, and vitamin D to detect a deficiency of vitamins or minerals; and a peripheral blood smear to detect anemia, which may have a related cause. The absorptive capacity of the gastrointestinal tract is staggering. In general, we absorb hundreds of grams of carbohydrates, over 100 grams of fat and 50-100 grams of amino acids per 24-hour period. This is accomplished by the mucosal cells lining the intestine. These surfaces contain many villi, small projections that increase the surface area of the intestinal wall. It is estimated the average adult human intestine has the absorptive surface area of a tennis court. Different parts of the GI tract have different functions and nutrients are broken down and absorbed in different parts. Carbohydrate digestion begins in the mouth with salivary amylase and continues in the stomach via the action of the stomach and low pH. In the small intestine, pancreatic amylase and intestinal enzymes such as lactase complete carbohydrate hydrolysis, forming simple sugars that are absorbed. Any undigestible carbohydrate (fiber) is excreted in the feces. Fat digestion and absorption is very efficient, with very little fat found in the feces. Pancreatic and gastric lipases are the enzymes most responsible for the breakdown of triacylglycerides (triglycerides) into small glycerides and free fatty acids. The action of lipase requires bile salts and bile acids that are also needed to emulsify the fats. The free fatty acids and small glycerides produced by the hydrolysis of triglycerides are absorbed in the intestine and converted by the mucosal cells into chlyomicrons. Protein digestion begins in the stomach with the action of hydrochloric acid and pepsin, and continues in the intestine via the activity of pancreatic and intestinal proteases such as trypsin, chymotrypsin, and carboxypeptidase. The dipeptides and amino acids produced from protein hydrolysis are absorbed via complex mechanisms by the intestinal epithelial cells. Malabsorption of nutrients can cause painful GI symptoms and over time cause malnutrition. Patients lose

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Rodwell-Williams, Sue. Essentials of Nutrition and Diet Therapy.) London: Mosby-Year Book, 1999. Speakman, Elizabeth, and Norma Jean Weldy. Body Fluids and Electrolytes, 8th ed. London: Mosby Incorporated, 2001.

Malabsorption tests

vitamins and minerals along with basic nutrients. Some malabsorption syndromes can cause dehydration since they produce diarrhea. Diagnosing the cause of malabsorption is difficult, and doctors will try many different testing approaches. Malabsorption can be caused by many things including: • Pancreatic insufficiency, caused by inflammation of the pancreas (pancreatitis), obstruction of the pancreatic duct, pancreatic cancer, inherited deficiency of pancreatic enzymes. • Defective stimulation of the stomach due to illness or surgery. Muscles in the stomach need to contract to mix up the food with digestive enzymes and acid. • Elevated pH of stomach acid (hypoacidity or achlorhydria). • Lack of bile acids due to obstruction (gallstones or tumors) or due to liver disease. • Bacterial overgrowth in the lower intestine. • Food allergies such as celiac disease. • Inflammation of the intestines or colon, such as colitis, Crohn’s disease, inflammatory bowel syndrome. • Parasitic infections, such as Whipple’s disease or tropical sprue. • Lack of enzymes in the intestine. For example, lactase deficiency causes lactose intolerance, a very common cause of malabsorption in adults. • Surgical removal of parts of the intestine due to disease, or surgery to decrease the size of the stomach to promote weight loss. • Diseases such as diabetes, AIDS, cystic fibrosis, thyroid disease, and alcoholism. Symptoms of malabsorption are varied because the disorder effects so many systems. General symptoms may include loss of appetite (anorexia), weight loss, fatigue, shortness of breath, dehydration, low blood pressure, and swelling (edema). Nutritional disorders may cause anemia (lack of iron, folate and vitamin B12), bleeding tendency (lack of vitamin K), or bone disease (lack of vitamin D). Gastrointestinal symptoms include flatulence, stomach distention, borborygmi (rumbling in the bowels), discomfort, diarrhea, steatorrhea (excessive fat in stool) and frequent bowel movements.

Precautions Most malabsorption tests require a blood sample collected by venipuncture. The nurse or phlebotomist must follow universal precautions for the prevention of transmission of bloodborne pathogens. Most of the tests done to measure malabsorption are relatively safe but do 1472

require some effort on the patient’s part. Many require an overnight fast. Some patients who need malabsorption tests may be malnurished or dehydrated. Clinicians should watch for low blood pressure, weakness, thirst, concentrated urine (dehydration), and dizziness. Some tests require ingestion of highly concentrated nutrients that may be difficult for the patient to digest. Asking patients to collect urine or feces over a long time period can cause problems with compliance. It is important to make sure the patient understands the test and why he or she must comply. Clinical laboratories will reject any samples that appear to have been collected or stored incorrectly.

Description Breath hydrogen test The breath hydrogen test is used to measure two things, carbohydrate malabsorption such as lactose intolerance and bacterial overgrowth. Hydrogen is produced by bacterial fermentation of unabsorbed carbohydrates in the intestines. Bacterial overgrowth can occur in this situation because there is a large food supply. The hydrogen produced goes into the blood stream and is excreted through the lungs. The test is done using a gas chromatograph, an apparatus that can separate compounds from one another based on their chemical composition. The patient is asked to fast overnight, and his or her breath is collected in a plastic syringe at the start of the test. The patient is then given something to eat depending on what is being evaluated. If the doctor suspects that the patient has trouble absorbing carbohydrates, then he or she may be given rice, glucose or fructose. If lactose intolerance is suspected, the patient is given a food containing lactose such as milk. For general bacterial overgrowth tests, the patient will be given glucose. The patient’s breath will be collected in a plastic syringe every thirty minutes for the next two to five hours, depending on the test. The syringe will be capped and sent to the laboratory for analysis. The test is simple and non-invasive and while not diagnostic, it gives the doctor an idea of what may be wrong. D-xylose absorption test D-xylose is a sugar that is not normally found in the blood. It can be easily absorbed by healthy intestinal cells without the aid of pancreatic enzymes, and is poorly metabolized so that at least 50% of the dose is excreted in the urine within 24 hours. This test is a good general screen for malfunction of absorption, and helps to differentiate intestinal malabsorption syndromes (reduced Dxylose absorption) from pancreatitis (normal D-xylose absorption). Adults are given an oral dose (usually 25

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Tests for celiac disease Celiac disease is a disorder characterized by antibodies to gluten, a protein found in wheat. The disease produces lesions in the intestine and decreases the tissue’s ability to absorb many different nutrients. Patients have diarrhea and lose weight over time. The lesions will improve when foods containing gluten are removed from the diet. Tests for this disease involve drawing the patient’s blood and testing for the presence of three antibodies, antigliadin, antiendomysium, and antireticulin antibodies. Patients with celiac disease are followed closely by their doctors, even after dietary changes, because they are more prone to developing intestinal cancers and intestinal ulcerations. Stool fat testing Stool fat testing, measuring fats in the feces, is a sensitive way to determine if the patient has fat malabsorption but the test does not differentiate between pancreatic and intestinal causes. Fat is normally absorbed very efficiently by the intestinal cells. High levels of fat in the feces causes steatorrhea, a type of feces that appears pale in color and greasy. Before the test, the patient is put on a high fat diet, consuming between 50-150 g/day of fat for three days. The patient must collect their feces over the next 72 hours using a 1-gallon paint can that can be well sealed. The fecal sample must be refrigerated to prevent any bacterial action. Fecal fat analysis is performed by first weighing the sample and then extracting the lipids with an organic solvent. The extraction solvent is evaporated and the dry weight of the fat that remains is measured. Normal absorption of fat is indicated by a fecal fat level of less than or equal to 7 grams per day. A more simple but less accurate way to measure fat absorption is to count the fat droplets in a well mixed sample of the stool specimen using a microscope and a neutral fat stain. Another simplified screening test is the fat tolerance test called the butterfat or the fatty meal test.

The patient is asked to fast overnight and is given 1 gram of fat per kg of body weight. This is a substantial amount of fat and usually is given as 1 gram of butter per Kg spread on a piece of toast or as 6 ounces of corn oil. Blood is drawn before the dose and again three and six hours afterwards. The fasting, three-hour and six-hour plasma samples are analyzed for triglyceride concentration. Normal absorption is indicated by at least a 50% increase in triglycerides over the fasting level.

Preparation The patient should be advised about the test he or she is taking and what the testing procedure involves. It is important with all tests, except the celiac antibody tests, that the patient fasts overnight. This allows the clinician to determine a “baseline” or starting value. Patients who are required to collect a 72-hour fecal sample must seal the sample well and keep it refrigerated to prevent any degradation.

Aftercare Some patients may feel sick after the procedures since they are being exposed to compounds that they may have trouble absorbing. Nurses should be careful to discuss any side effects with the patient beforehand, and the patient should be given the smallest amount of substance possible to avoid problems. In addition, patients may be malnourished and need something to eat and drink once the procedure is over.

Complications The hydrogen breath test may not be accurate if the patient is a smoker, has pulmonary disease, is not fasting or is hyperventilating. Patients being measured for bacterial overgrowth must not only fast overnight, but avoid fiber-rich foods for three days before the test. Patients taking the fecal fat test must remain on a high fat diet before and during the test. Falsely low results with the D-xylose test will be seen if the pateint has been vomiting, has gastric stasis, fluid build up (ascites), fluid retention (edema) or bacterial overgrowth. There is a decrease in urinary excretion of D-xylose with aspirin, colchicine, digitalis, MAO inhibitors, food consumption, neomycin and opiates. In addition, excretion is lower in those with impaired renal function and in elderly patients.

Results D-xylose absorption should be greater than 1.2 g/5 hours with a 5 g dose of D-xylose and 4.0 g/5 hours in an

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grams) of D-xylose. A five-hour timed urine sample is collected, and a blood sample is collected two hours after the dose is given. Children are given a 5 gram dose of Dxylose, and a blood sample is collected one hour after the dose is given. Adults should excrete at least 25% of the dose in the five-hour urine sample, and have a two-hour blood level of at least 25 mg/dL. Children should have a one-hour blood level of at least 20 mg/dL. The D-xylose test will be normal if the patient has normal absorptive capacity in the intestine, or if the patient has malabsorption that is caused by a pancreatic problem. It will be low if the patient has celiac disease, tropical sprue, Crohn’s disease, advanced AIDs, or pellegra (niacin deficiency).

Malaria

Resources

KEY TERMS

BOOKS

Absorption—Process of taking up digested food substances into the cells and blood stream of the body. Carbohydrate—A macromolecule (large molecule) that is made of sugars or starch.

Burtis, Carl A. and Edward R. Ashwood. Tietz Textbook of Clinical Chemistry. Philadelphia: W.B. Saunders Company, 1999. Kaplan, Lawrence A. and Amadeo J. Pesce. Clinical Chemistry Theory, Analysis and Correlation. St. Louis: Mosby Publishing, 1996.

Diarrhea—Excessive production of feces. This is usually due to a large amount of water in the stool.

Jane E. Phillips, Ph.D.

Fats—A macromolecule that is not soluble in water. Fats are also called lipids. Gastrointestinal—Having to do with the stomach and intestines. Gluten—One of the proteins found in wheat products. Lactase—An enzyme that breaks down lactose. Lipase—An enzyme that breaks down fats. Mucosa—The cells lining the digestive tract. These cells secrete mucus to protect themselves from digestion. Protease—An enzyme that breaks down proteins. Protein—A macromolecule that is made of amino acids. Steatorhhea—Feces that contain a high level of fat due to poor fat absorption in the GI tract. Villi—Projections of tissue into the intestine that increase the surface area.

adult given a 25 g dose of D-xylose. Fecal fat should be less than 7 g/day in adults and less than 2 g/day in a child. Hydrogen breath test results are based on the baseline value, which in most people should be extremely low. The results are measured in parts per million and the actual numbers depend on the sugar or carbohydrate given. Abnormal results with the celiac tests are any antibodies measured since healthy people do not generate antibodies to gluten protein.

Health care team roles Malabsorption tests are ordered by a physician. The malabsorption tests call for a skilled team of nurses and dieticians who administer the tests. Clinical laboratory scientists/medical technologists perform malabsorption tests, and the physician interprets the result. 1474

Malaria Definition Malaria is a serious, infectious disease spread by certain mosquitoes. It is most common in tropical climates. It is characterized by recurrent symptoms of chills, fever, and an enlarged spleen. The disease can be treated with medication, but it often recurs. Malaria is endemic (occurs frequently in a particular locality) in many third world countries. Isolated, small outbreaks sometimes occur within the boundaries of the United States.

Description Malaria is not a serious problem in the United States. Within the last decade, only about 1,200 cases have been reported each year in this country, mostly by people who were infected elsewhere. Locally transmitted malaria has occurred in California, Florida, Texas, Michigan, New Jersey, and New York City. While malaria can be transmitted in blood, the American blood supply is not screened for malaria. Widespread malarial epidemics are far less likely to occur in the United States, but small, localized epidemics could return to the western world. The picture is far more bleak outside the territorial boundaries of the United States. A recent government panel warned that disaster looms over Africa from the disease. Malaria infects between 300 and 500 million people every year in Africa, India, southeast Asia, the Middle East, Oceania, and Central and South America. About 2 million of the infected die each year. Most of the cases and almost all of the deaths occur in sub-Saharan Africa. At the present time, malaria kills about twice as many people each year as does AIDS. As many as half a billion people worldwide are left with chronic anemia due to malaria infection. In some parts of Africa, people battle up to 40 or more separate episodes of malaria in their lifetimes. The spread of malaria is becoming even

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Causes and symptoms Human malaria is caused by four different species of a parasite called plasmodium: Plasmodium falciparum (the most deadly), P. vivax, P. malariae, and P. ovale. The last two are fairly uncommon. Many animals can get malaria but human malaria does not spread to animals. In turn, animal malaria does not spread to humans. A person gets malaria when bitten by a female mosquito who is looking for a blood meal and is infected with the malaria parasite. The parasites enter the blood stream and travel to the liver, where they multiply. When they re-emerge into the blood, symptoms appear. By the time a person shows symptoms, the parasites have reproduced very rapidly, clogging blood vessels and rupturing blood cells. Malaria cannot be casually transmitted directly from one person to another. Instead, a mosquito bites an infected person and then passes the infection on to the next human it bites. It is also possible to spread malaria via contaminated needles or in blood transfusions. This is why all blood donors are carefully screened with questionnaires for possible exposure to malaria. The amount of time between the mosquito bite and the appearance of symptoms varies, depending on the strain of parasite involved. The incubation period is usually between eight and 12 days for falciparum malaria, but it can be as long as a month for the other types. Symptoms from some strains of P. vivax may not appear until eight to 10 months after the mosquito bite occurred. The primary symptom of all types of malaria is the “malaria ague” (chills and fever). In most cases, the fever has three stages, beginning with uncontrollable shivering for an hour or two, followed by a rapid spike in temperature (as high as 106°F, or 41.1°C), which lasts for three to six hours. Then, just as suddenly, the affected person begins to sweat profusely, which will quickly bring down the fever. Other symptoms may include fatigue, severe headache, or nausea, and vomiting. As the sweating subsides, an individual typically feels exhausted and falls asleep. In many cases, this cycle of chills, fever, and sweating occurs every other day, or every third day, and may last for between a week and a month. Those with the chronic form of malaria may have a relapse as long as 50 years after the initial infection. Falciparum malaria is far more severe than other types of malaria because the parasite attacks all red blood cells, not just the young or old cells, as do other types. It causes the red blood cells to become very “sticky.” A per-

son with this type of malaria can die within hours of the first symptoms. The fever is prolonged. So many red blood cells are destroyed that they block the blood vessels in vital organs (especially the kidneys), and the spleen becomes enlarged. There may be brain damage, leading to coma and convulsions. The kidneys and liver may fail. Malaria in pregnancy can lead to premature delivery, miscarriage, or stillbirth. Certain kinds of mosquitoes (called anopheles) can pick up the parasite by biting an infected human. (The more common kinds of mosquitoes in the United States do not transmit the infection.) This is true for as long as that human has parasites in the blood. Since strains of malaria do not protect against each other, it is possible to be re-infected with the parasites again and again. It is also possible to develop a chronic infection without developing an effective immune response.

Diagnosis Malaria is diagnosed by examining blood under a microscope. The parasite can be seen in the blood smears on a slide. These blood smears may need to be repeated over a 72-hour period to make an accurate diagnosis. Antibody tests are not usually helpful because many people developed antibodies from past infections, and the tests may not be readily available. Anyone who becomes ill with chills and fever after being in an area where malaria exists must see a doctor and mention the recent travel to endemic areas. A person with the above symptoms who has been in a high-risk area should insist on a blood test for malaria. The doctor may believe the symptoms are just the common flu virus. Malaria is often misdiagnosed by North American doctors who are not used to seeing the disease. Delaying treatment of falciparum malaria can be fatal.

Treatment Falciparum malaria is a medical emergency that must be treated in a hospital. The type of drugs, the method of giving them, and the length of the treatment depend on where the malaria was contracted and how sick is the affected person. For all strains except falciparum, the treatment for malaria is usually chloroquine (Aralen) by mouth for three days. Those falciparum strains suspected to be resistant to chloroquine are usually treated with a combination of quinine and tetracycline. In countries where quinine resistance is developing, other treatments may include clindamycin (Cleocin), mefloquin (Lariam), or sulfadoxone/pyrimethamine (Fansidar). Most persons

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more serious as the parasites that cause malaria develop resistance to the drugs used to treat the condition.

Malaria

Zygote

Stomach

Fertilization

Gametocytes become differentiated into egg and sperm

MOSQUITO

Salivary gland

Sporozoites released and migrate to salivary gland

Oocyst Sporogony occurs Sporozoites develop

Sporozoite

HUMAN

Blood vessel of human host Sporozoite entering liver cell

Liver

Trophozoite

Gametocytes

Sporozoite becomes merozoite

CYCLE IN LIVER CELLS

Infect other liver cells or enter red blood cells

Ameboid form CYCLE IN BLOOD CELLS

Liberation of merozoites

Merozoite entering red cell INCUBATION PERIOD

CHILLS AND FEVER STAGE

The life cycle of Plasmodium vivax, the parasite that causes malaria. (Illustration by Hans & Cassidy.)

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Anyone who acquired falciparum malaria in the Dominican Republic, Haiti, Central America west of the Panama Canal, the Middle East, or Egypt can still be cured with chloroquine. Almost all strains of falciparum malaria in Africa, South Africa, India, and southeast Asia are now resistant to chloroquine. In Thailand and Cambodia, there are strains of falciparum malaria that have some resistance to almost all known drugs. A person with falciparum malaria needs to be hospitalized and given antimalarial drugs in different combinations and doses depending on the resistance of the strain. The individual may need IV fluids, red blood cell transfusions, kidney dialysis, and assistance breathing. A drug called primaquine may prevent relapses after recovery from P. vivax or P. ovale. These relapses are caused by a form of the parasite that remains in the liver and can reactivate months or years later. Another new drug, halofantrine, is available abroad. While it is licensed in the United States, it is not marketed in this country and it is not recommended by the Centers for Disease Control and Prevention in Atlanta, Georgia. Preventing mosquito bites while in the tropics is an important way to avoid malaria. Alternative treatment The Chinese herb qiinghaosu (the western name is artemisinin) has been used in China and southeast Asia to fight severe malaria, and became available in Europe in 1994. Because this treatment often fails, it is usually combined with another antimalarial drug (mefloquine) to boost its effectiveness. It is not available in the United States and other parts of the developed world due to fears of its toxicity, in addition to licensing and other issues. A western herb called wormwood (Artemesia annua) that is taken as a daily dose can be effective against malaria. Protecting the liver with herbs like goldenseal (Hydrastis canadensis), Chinese goldenthread (Coptis chinensis), and milk thistle (Silybum marianum) can be used as preventive treatment.

Prognosis If treated in the early stages, malaria can be cured. Those who live in areas where malaria is epidemic, however, can contract the disease repeatedly, never fully recovering between bouts of acute infection.

Health care team roles Physicians, assisted by laboratory technicians, usually make a diagnosis of malaria. Nurses may provide prevention education and support during recovery from malaria ague.

Prevention Several researchers are currently working on a malarial vaccine, but the complex life cycle of the malaria parasite makes it difficult. A parasite has much more genetic material than a virus or bacterium. For this reason, a successful vaccine has not yet been developed. Malaria is an especially difficult disease to vaccinate against because the parasite goes through several separate stages. One recent, promising vaccine appears to have protected up to 60% of people exposed to malaria. This was evident during field trials for the drug that were conducted in South America and Africa. It is not yet commercially available. The World Health Association (WHO) has been trying to eliminate malaria for the past 30 years by controlling mosquitoes. Their efforts were successful as long as the pesticide DDT killed mosquitoes and antimalarial drugs cured those who were infected. Today, however, the problem has returned a hundredfold, especially in Africa. Because both the mosquito and parasite are now extremely resistant to the insecticides designed to kill them, governments are now trying to teach people to take antimalarial drugs as a preventive medicine and avoid being bitten by mosquitoes. Travelers to high-risk areas should use insect repellent containing DEET for exposed skin. Because DEET is toxic in large amounts, children should not use a concentration higher than 35%. DEET should not be inhaled. It should not be rubbed onto the eye area, on any broken or irritated skin, or on children’s hands. It should be thoroughly washed off after coming indoors. Individuals who use the following preventive measures get fewer infections than those who do not: • Between dusk and dawn, remain indoors in wellscreened areas. • Sleep inside pyrethrin or permethrin repellent-soaked mosquito nets. • Wear clothes over the entire body. Anyone visiting endemic areas should take antimalarial drugs starting a day or two before leaving the United States. The drugs used are usually chloroquine or mefloquine. This treatment is continued through at least four weeks after leaving the endemic area. However,

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receive an antibiotic for seven days. Those who are very ill may need intensive care and intravenous (IV) malaria treatment for the first three days.

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Resources

KEY TERMS

BOOKS

Arteminisinins—An antimalarial family of products derived from an ancient Chinese herbal remedy. Two of the most popular varieties are artemether and artesunate, used mainly in southeast Asia in combination with mefloquine. Chloroquine—This antimalarial drug was first used in the 1940s, until the first evidence of quinine resistance appeared in the 1960s. It is now ineffective against falciparum malaria almost everywhere. However, because it is inexpensive, it is still the antimalarial drug most widely used in Africa. Native individuals with partial immunity may have better results with chloroquine than a traveler with no previous exposure. Mefloquine—An antimalarial drug that was developed by the United States Army in the early 1980s. Today, malaria resistance to this drug has become a problem in some parts of Asia (especially Thailand and Cambodia). Quinine—One of the first treatments for malaria, quinine is a natural product made from the bark of the Cinchona tree. It was popular until being superseded by the development of chloroquine in the 1940s. In the wake of widespread chloroquine resistance, however, it has become popular again. It or its close relative quinidine can be given intravenously to treat severe falciparum malaria. Sulfadoxone/pyrimethamine (Fansidar)—This antimalarial drug developed in the 1960s is the first drug tried in some parts of the world where chloroquine resistance is widespread. It has been associated with severe allergic reactions due to its sulfa component.

even those who take antimalarial drugs and are careful to avoid mosquito bites can still contract malaria. International travelers are at risk for becoming infected. Most Americans who have acquired falciparum malaria were visiting sub-Saharan Africa. Travelers in Asia and South America are less at risk. Travelers who stay in air conditioned hotels on tourist itineraries in urban or resort areas are at lower risk than backpackers, missionaries, and Peace Corps volunteers. Some people in western cities where malaria does not usually exist may acquire the infection from a mosquito carried onto a jet. This is called airport or runway malaria. 1478

Humphreys, Margaret. Malaria in the United States: Poverty, Race, and Public Health. Baltimore: Johns Hopkins University Press, 2001. Krause, Peter J. “Malaria.” In Nelson Textbook of Pediatrics, 16th ed., edited by Richard E. Behrman et al. Philadelphia: Saunders, 2000, 1049-1052. Krogstad, Donald J. “Malaria.” In Cecil Textbook of Medicine, 21st ed., edited by Goldman, Lee and Bennett, J. Claude. Philadelphia: W.B. Saunders, 2000, 1947-1951. Poser, Charles M. and Bruyn, G.W. An Illustrated History of Malaria. New York: Parthenon Publishing Group, 1999. White, Nicholas J. and Bremen, Joel G. “Malaria and Other Diseases Caused by Red Blood Cell Parasites.” In Harrison’s Principles of Internal Medicine, 14th ed., edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 1180-1189. PERIODICALS

Albrecht, H., Lennox, J., del Rio, C. “Quinidine and malaria.” Archives of Internal Medicine 161, no. 8 (2001): 1118-1119. Arya, S.C. “Limitations of Rapid Tests for Malaria Diagnosis by Travelers.” Journal of Travel Medicine 7, no. 6 (2000): 340-342. Etchegorry, M.G., Matthys F., Galinski M., White N.J., Nosten F. “Malaria Epidemic in Burundi.” Lancet 357, no. 9261 (2001): 1046-1047. Kerr, C. “Malaria Vaccine News.” Trends in Microbiology 9, no. 5 (2001): 202-207. Lawler, S. “Boost for Development of Malaria Vaccine.” Trends in Cellular Biology 11, no. 4 (2001): 151-157. Marshall, H. “Vaccine Prevents Malaria Parasite from Infecting Mosquitoes.” Trends in Immunology 22, no. 3 (2001): 125-132. Smith, T.A., Leuenberger, R., Lengeler, C. “Child Mortality and Malaria Transmission Intensity in Africa.” Trends in Parasitology 17, no. 3 (2001): 145-149. Taverne, J. “Malaria, HIV and Mosquito Control on the Web.” Trends in Parasitology 17, no. 3 (2001): 155-156. Taylor-Robinson, A. “Immunity to Malaria Increases During puberty.” Trends in Parasitology 17, no. 5 (2001): 213-215. Taylor-Robinson, A. “Rationale for Malaria Anti-toxin Therapy.” Trends in Parasitology 17, no. 3 (2001): 119124. ORGANIZATIONS

Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30333. (404) 639-3534 or (800) 3113435. ; . Pan American Health Organization, 525 Twenty-third Street, NW, Washington, D.C. 20037. (202)974-3000. Fax: (202)974-3663. ; [email protected].

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OTHER

Centers for Disease Control and Prevention. and . Malaria Foundation International. . Malaria Vaccine Initiative. . Medical Research Programme of South Africa. . National Institutes of Health. . World Health Organization Malaria Fact Sheets. and . World Health Organization Tropical Disease Research. .

L. Fleming Fallon, Jr., M.D., Dr.P.H.

Male infertility see Infertility Male reproductive system see Reproductive system, male

Malignant lymphomas Definition Malignant lymphomas are a group of cancers in which cells of the lymphatic system become abnormal and start to grow uncontrollably and spread (metastasize) throughout the body. Because lymph tissue is in many parts of the body, lymphomas can start in almost any organ of the body. Lymphomas are classified as being either non-Hodgkin’s lymphoma or Hodgkin’s disease.

Description The lymph system is made up of ducts or tubules that carry lymph to all parts of the body. Lymph is a milky fluid that contains the lymphocytes or white blood cells, as well as protein and waste products. These are the infection-fighting cells of the blood. Small pea-shaped organs are found along the network of lymph vessels. These are called the lymph nodes, and their main function is to make and store lymphocytes. Clusters of lymph nodes are found in the pelvis region, underarm, neck, chest, and abdomen. The spleen, the tonsils, and the thymus are part of the lymphatic system.

The lymphocyte is the main cell of the lymphoid tissue. There are two main types of lymphocytes: the T lymphocyte and the B lymphocyte. Lymphomas develop from these two cell types. B cell lymphomas are more common among adults; while among children, the incidence of T and B cell lymphomas is almost equal. The T and the B cell perform different jobs within the immune system. When an infectious bacterium enters the body, the B cell makes proteins called “antibodies.” These antibodies attach themselves to the bacteria and flag them for destruction by other immune cells. The T cells help protect the body against viruses. When a virus enters the cell, it generally produces certain proteins that are projected on the surface of the infected cell. T cells recognize these proteins and produce certain substances (cytokines) that destroy the infected cells. Some of the cytokines made by the T cells attract other cell types, which are capable of digesting the virusinfected cell. The T cells can also destroy some types of cancerous cells. Lymphomas can be divided into two main types: Hodgkin’s lymphoma or Hodgkin’s disease, and nonHodgkin’s lymphomas. The two are distinguished by cell type and have similar symptoms. Non-Hodgkin’s lymphomas are more common, with at least 30 different types. Hodgkin’s primarily affects individuals 15–40 years of age, while Non-Hodgkin’s occurs mainly in persons between the ages of 30–70. Lymphomas are grouped (staged) by how aggressively they grow—slow growing (low grade, mostly found in B-cell types), intermediate growing (seen in both B-cell and T-cell types), and rapidly growing (high grade, seen in both B-cell and T-cell types)—and how far they spread. Lymphomas are also staged by the Roman numerals I, II, III, and IV. These stages indicate the following: • Stage I. There is only one cancer site. No bone marrow involvement found. • Stage II. Two sites are found, either above or below the diaphragm. There is no bone marrow involvement. • Stage III. Sites are found above and below the diaphragm, but there is still no bone marrow involvement. • Stage IV. The bone marrow is involved and the cancer cells have metastasized beyond the lymphatic system. A majority of non-Hodgkin’s lymphomas begin in the lymph nodes. About 20% start in other organs, such as the lungs, liver, or the gastrointestinal tract. Malignant lymphocytes multiply uncontrollably and do not perform their normal functions. Hence, the body’s ability to fight infections is affected. In addition, these malignant cells may crowd the bone marrow and, depending on the stage,

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World Health Organization, Communicable Diseases, 20 Avenue Appia, 1211 Geneva 27, Switzerland. +41 (22) 791 4140. Fax: +41 (22) 791 4268. , [email protected].

Malignant lymphomas

fer from immune-deficient (immunodeficiency) disorders and those who have been treated with immune suppressive drugs for transplants or for conditions such as rheumatoid arthritis and autoimmune diseases are at an increased risk for this disease. Some studies have shown a loose association between retroviruses, such as HTLV-I, and some rare forms of lymphoma. The Epstein-Barr virus has been linked to Burkitt’s lymphoma in African countries. However, a direct cause-and-effect relationship has not been established.

A close-up view of a malignant lymph cell. (Custom Medical Stock Photo. Reproduced by permission.)

prevent the production of normal red blood cells, white blood cells, and platelets. A low red blood cell count causes anemia, while a reduction in the number of platelets makes the person susceptible to excessive bleeding. Cancerous cells can also invade other organs through the circulatory system of the lymph, causing those organs to malfunction. In 2001, an estimated 56,200 Americans received a diagnosis of non-Hodgkin’s lymphoma, and approximately 16,300 people died from malignant lymphomas. It is the fifth most common cancer in the country (not including nonmelanoma skin cancers). The incidence of non-Hodgkin’s lymphoma has nearly doubled since the 1970s; however, during the 1990s the rate began to decline. The increase was related both to an actual increase in the number of cases as well as improved methods of detecting the disease. Over 95% of nonHodgkin’s lymphomas occur in adults, with the average age at diagnosis being in the early 40s. The disease more commonly occurs in men than women, and whites are affected to a greater extent than Asian Americans or African Americans.

Causes and symptoms The exact cause of non-Hodgkin’s lymphomas is not known. However, the incidence has increased significantly in recent years. Part of the increase is due to the AIDS epidemic. Individuals infected with the AIDS virus have a higher likelihood of developing non-Hodgkin’s lymphomas. People exposed to certain pesticides and ionizing radiation have a higher than average chance of developing this disease. For example, an increased incidence of lymphomas has been seen in survivors of the atomic bomb explosion in Hiroshima, and in people who have undergone aggressive radiation therapy. People who suf1480

The symptoms of lymphomas are often vague and non-specific. The signs and symptoms may differ, depending on the location of the involvement. Patients may experience loss of appetite, weight loss, nausea, vomiting, abdominal discomfort, and indigestion. The patient may complain of a feeling of fullness, which is a result of enlarged lymph nodes in the abdomen. Sometimes the abdomen can become so swollen it may resemble pregnancy in a woman. Pressure or pain in the lower back is another symptom. In the advanced stages, the patient may have bone pain, headaches, constant coughing, and abnormal pressure and congestion in the face, neck, and upper chest. Some may have fevers and night sweats. In most cases, patients go to the doctor because of the presence of swollen glands in the neck, armpits, or groin area. Since all the symptoms are common to many other illnesses, it is essential to seek medical attention if any of the conditions persist for two weeks or more. Only a qualified physician can correctly diagnose whether the symptoms are due to lymphoma or some other ailment.

Diagnosis Like all cancers, lymphomas are best treated when found early. However, it is often difficult to diagnose lymphomas. There are no screening tests available; and, since the symptoms are non-specific, lymphomas are rarely recognized in their early stages. Detection often occurs by chance during a routine physical examination. When the doctor suspects lymphoma, a complete medical history is taken and a thorough physical examination is performed. Enlargement of the lymph nodes, liver, or spleen may suggest lymphomas. Blood tests will determine the cell counts and obtain information on how well the organs, such as the kidney and liver, are functioning. A biopsy of the enlarged lymph node is the most definitive diagnostic tool for staging purposes. The doctor may perform a bone marrow biopsy. During the biop-

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Once the exact form of lymphoma is known, it is then staged to determine how aggressive it is, and how far it has spread. Staging is necessary to plan appropriate treatment. Conventional imaging tests, such as x rays, computed tomography scans (CT scans), magnetic resonance imaging (MRI), and abdominal sonograms, are used to determine how far the disease has spread. Rarely, a lumbar puncture or a spinal tap is performed to check if malignant cells are present in the fluid surrounding the brain. In this test, the physician inserts a needle into the epidural space at the base of the spine and collects a small amount of spinal fluid for microscopic examination.

Treatment Much progress has been made in the treatment of non-Hodgkin’s lymphoma. Treatment options for lymphomas depend on the type of lymphoma and its present stage. In most cases, treatment consists of chemotherapy, radiotherapy, or a combination of the two methods. Chemotherapy is the use of anti-cancer drugs to kill cancer cells. In non-Hodgkin’s lymphomas, combination therapy, which involves the use of multiple drugs, has been found more effective than single drug use. The treatment may last about six months, but in some cases may last as long as a year. The drugs may either be administered intravenously or given orally in the form of pills. If cancer cells have invaded the central nervous system, then chemotherapeutic drugs may be injected, through a needle in the brain or back, into the fluid that surrounds the brain. This procedure is known as intrathecal chemotherapy. Radiation therapy, where high-energy ionizing rays are directed at specific portions of the body, such as the upper chest, abdomen, pelvis, or neck, is often used for treatment of lymphomas. External radiation therapy, where the rays are directed from a source outside the body, is the most common mode of radiation treatment. Stem cell transplantation is used in cases where the lymphomas do not respond to conventional therapy, or in cases where the patient has had a relapse or suffers from recurrent lymphomas. However, one study done in the Netherlands suggested that patients may do just as well

with a standard chemotherapy regimen rather than the transplant. There are two ways of performing stem cell transplantation. In a procedure called “allogeneic stem cell transplant,” a donor is found whose cells match that of the patient. The donor can be a twin (best match), a sibling, or a person who is not related at all. High-dose chemotherapy or radiation therapy is given to eradicate the lymphoma. The donor stem cells are then given to replace those destroyed by the therapy. In “autologous stem cell transplantation,” some of the patient’s own stem cells are collected, “purged” of lymphoma cells, and frozen. High-dose chemotherapy and radiation therapy are given. The stem cells that were taken and frozen are then thawed and put back into the patient’s body to replace the destroyed marrow. One of the serious risks of autologous stem cell transplants is that it is possible for some of the lymphoma cells to remain even after purging the stem cells. There are no proven alternative treatments for nonHodgkin’s lymphoma. However, many complementary therapies, including vitamins and herbal remedies, massage, and acupuncture, may help persons going through treatment to better cope with the side effects they might experience. Because many of these therapies have not been studied thoroughly, it is not known which ones may be potentially harmful or helpful. Therefore, the patient with lymphoma should be advised to speak with their health care professional prior to trying any alternative or complementary treatment.

Prognosis Like all cancers, the prognosis for lymphoma depends on the stage of the cancer, and the patient’s age and general health. When all the different types and stages of lymphoma are considered together, only 50% of patients survive five years or more after initial diagnosis. This is because some types of lymphoma are more aggressive than others. Patients with T-cell lymphomas generally have a worse prognosis than those with B-cell types. The five-year survival rate for those with nonHodgkin’s lymphoma rose from 31% in 1960 to 51% in 1994. The overall survival rate among children, 78%, is definitely better than among older people. About 90% of the children diagnosed with early stage disease survive five years or more, while only 60%–70% of adults diagnosed with low grade lymphomas survive for five years or more.

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sy, a cylindrical piece of bone and marrow fluid is removed. They are generally taken out of the hipbone. These samples are sent to the laboratory for examination. In addition to diagnosis, the biopsy may also be repeated during the treatment phase of the disease to see if the lymphoma is responding to therapy.

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Resources

KEY TERMS

BOOKS

Antibodies—Proteins made by the B lymphocytes in response to the presence of infectious agents such as bacteria or viruses in the body. Autoimmune disease—A disease caused by a person’s own antibodies or T cells that attack molecules, cells, or tissues. Biopsy—The surgical removal and microscopic examination of living tissue for diagnostic purposes. Growth factors (cytokines)—Chemicals made by the cells that act on other cells to stimulate or inhibit their function. Cytokines that stimulate growth are called “growth factors.” Metastasize—The spread of a disease, such as a cancer, from its original site to another part of the body.

Health care team roles Many members of the health care team will work with the lymphoma patient. The primary physician may initially suspect lymphoma and order the appropriate diagnostic workup. The surgeon performs the biopsy, and the pathologist confirms the cellular diagnosis. Various x-ray and lab technicians will perform other imaging studies. Specially trained nurses administer chemotherapy and will instruct the patient on all aspects of his diagnosis and treatment. The patient may see both a medical and radiation oncologist, depending upon the specifics of the treatment ordered. Registered nurses also provide part-time family education.

Beers, Mark H. and Robert Berkow, eds. The Merck Manual of Diagnosis and Therapy. 17th ed. Whitehouse Station, NJ: Merck and Company, Inc., 1999. PERIODICALS

“Bexxar Highly Effective First-Line Treatment” Vaccine Weekly (June 7, 2000). Gottlieb, Scott. “Bone Marrow Transplants Show No Benefit For Non-Hodgkin’s Lymphoma” British Medical Journal (January 20, 2001): 127. ORGANIZATIONS

American Cancer Society. (800) ACS-2345. . The Leukemia and Lymphoma Society of America, Inc. 1311 Mamaroneck Ave, White Plains, NY 10605. (914)9495213. . Lymphoma Research Foundation. 8800 Venice Boulevard, Suite 207, Los Angeles, CA 90034. (310)204-7040. . National Cancer Institute. Building 31, Room 10A31, 31 Center Drive, MSC 2580, Bethesda, MD 20892-2580. (800)4CANCER. .

Deanna Swartout-Corbeil, R.N.

Malignant melanoma Definition Malignant melanoma is a type of skin tumor that is characterized by the cancerous growth of melanocytes, which are cells that produce a dark pigment called melanin.

Prevention Although many cancers may be prevented by making diet and life style changes which reduce risk factors, there is currently no known way to prevent lymphomas. Protecting oneself from developing AIDS, which may be a risk factor for lymphomas, is the only preventive measure that can be practiced. No special tests are available for early detection of non-Hodgkin’s lymphomas. Paying prompt attention to the signs and symptoms of this disease and seeing a doctor if the symptoms persist are the best strategies for an early diagnosis of lymphoma. Early detection affords the best chance for a cure. 1482

Description Overview Cancer of the skin is the most common type of cancer and continues to grow in incidence. Skin cancer starts in the top layer of skin (the epidermis) but can grow down into the lower layers, the dermis and the subcutaneous layer. There are three main types of cells located in the epidermis, each of which can become cancerous. Melanocytes are the pigmented cells that are scattered throughout the skin, providing protection from ultraviolet (UV) light. Basal cells rest near the bottom of the epidermis and the layer of cells that continually grow to replace skin. The third type of epidermal cell is the squa-

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Melanoma Malignant melanoma is the most serious type of skin cancer. It develops from melanocytes. Although melanoma is the least common skin cancer, it is the most aggressive. It spreads (metastasizes) to other parts of the body—especially the lungs and liver—as well as invading surrounding tissues. Melanomas in their early stages resemble moles. In Caucasians, melanomas appear most often on the trunk, head, and neck in men and on the arms and legs in women. Melanomas in African Americans, however, occur primarily on the palms of the hand, soles of the feet, and under the nails. Melanomas appear only rarely in the eyes, mouth, vagina, or digestive tract. Although melanomas are associated with exposure to the sun, the greatest risk factor for developing melanoma may be genetic. People who have a first-degree relative (parent, sibling or child) with melanoma have an increased risk up to eight times greater of developing the disease. Basal cell cancer Basal cell cancer is the most common type of skin cancer, accounting for about 75% of all skin cancers. It occurs primarily on the parts of the skin exposed to the sun and is most common in people living in equatorial regions or areas of high ozone depletion. Light-skinned people are more at risk of developing basal cell cancer than dark-skinned people. This form of skin cancer is primarily a disease of adults; it appears most often after age 30, peaking around age 70. Basal cell cancer grows very slowly. If it is not treated, however, it can invade deeper skin layers and cause disfigurement. This type of cancer can appear as a shiny, translucent nodule on the skin or as a red, wrinkled and scaly area. Squamous cell cancer Squamous cell cancer is the second most frequent type of skin cancer. It arises from the outer keratinizing layer of skin, so named because it contains a tough protein called keratin. Squamous cell cancer grows faster than basal cell cancer; it is more likely to metastasize to the lymph nodes as well as to distant sites. Squamous cell cancer most often appears on the arms, head, and neck. Fair-skinned people of Celtic descent are at high risk for developing squamous cell cancer. This type of cancer is rarely life-threatening but can cause serious problems if it spreads and can also cause disfigurement. Squamous cell cancer usually appears as a scaly, slightly elevated area of damaged skin.

Other skin cancers Besides the three major types of skin cancer, there are a few other relatively rare forms. The most serious of these is Kaposi’s sarcoma (KS), which occurs primarily in persons who have AIDS or older males of Mediterranean descent. When KS occurs with AIDS it is usually more aggressive. Other types of skin tumors are usually nonmalignant and grow slowly. These include: • Bowen’s disease. This is a type of skin inflammation (dermatitis) that sometimes looks like squamous cell cancer. • Actinic or solar keratosis. This is a sunlight-damaged area of skin that sometimes develops into cancer. • Keratoacanthoma. A keratoacanthoma is a domeshaped tumor that can grow quickly and appear like squamous cell cancer. Although it is usually benign, it should be removed. Risk factors SUN EXPOSURE. Most skin cancers are associated with the amount of time that a person spends in the sun and the number of sunburns received, especially if they occurred at an early age. Skin cancer typically does not appear for 10-20 years after the sun damage has occurred. Because of this time lag, skin cancer rarely occurs before puberty and occurs more frequently with age. MOLES. The number of moles (nevi) on a person’s skin is related to the likelihood of developing melanoma. There are three types of nevi: not cancerous (benign); atypical (dysplastic); or birthmark (congenital). All three types of nevi have been associated with a higher risk of developing melanoma. Sometimes the moles themselves can become cancerous. Usually, however, the cancer is a new growth that occurs on normal skin. HEREDITY. The tendency to develop skin cancer also tends to run in families. As has already been mentioned, there appears to be a significant genetic factor in the development of melanoma.

Causes and symptoms Skin cancer begins to develop when a change or mutation occurs in one of the cells of the skin, causing it to grow without control. This mutation can be caused by ultraviolet (UV) light; most skin cancers are thought to be caused by overexposure to UV light from the sun. The incidence of severe, blistering sunburns is particularly closely related to skin cancer, more so when these burns occur during childhood. Exposure to ionizing radiation, arsenic, or polycyclic hydrocarbons in the workplace also

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mous cells which make up most of the cells in human skin.

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• Asymmetry. A normal mole is round, whereas a suspicious mole is unevenly shaped. • Border. A normal mole has a clear-cut border with the surrounding skin, whereas the edges of a suspect mole are often irregular. • Color. Normal moles are uniformly tan or brown, but cancerous moles may appear as mixtures of red, white, blue, brown, purple, or black. • Diameter. Normal moles are usually less than 0.20 in (5 mm) in diameter. A skin lesion greater than 0.25 in (0.6 cm) across may be suspected as cancerous. There are two systems used in staging melanomas. The first is Clark’s, which bases staging on the level of invasion, or which tissues the tumor has penetrated (i.e. which skin layer). The other is the American Joint Committee on Cancer. The second system is sometimes called the TNM system, which stands for tumor-nodesmetastasis, after the three major phases in cancer progression. Most experts generally agree that the thickness of the tumor is more accurate than the level of invasion for predicting prognosis (the outcome of the disease and estimated chance of recovery) and choosing an appropriate treatment.

Diagnosis

A close-up image of a malignant melanoma on patient’s back. (Custom Medical Stock Photo. Reproduced by permission.)

appears to stimulate the development of skin cancers. The use of psoralen for treatment of psoriasis may be associated with the development of squamous cell cancer. Skin cancers are also more common in immunocompromised persons, such individuals with AIDS or those who have undergone organ transplants. The first sign of skin cancer is usually a change in an existing mole, the presence of a new mole, or a change in a specific area of skin. Any change in a mole or skin lesion, including changes in color, size, or shape, tenderness, scaliness, or itching should be suspected of being skin cancer. Areas that bleed or are ulcerated may be signs of more advanced skin cancer. By doing a monthly self-examination, a person can identify abnormal moles or areas of skin and seek evaluation from a qualified health professional. The ABCD rule provides an easy way to remember the important characteristics of moles when one is examining the skin: 1484

A person who has a suspicious-looking mole or area of skin should consult a doctor. In many cases, the person’s primary care physician will make a referral to a doctor who specializes in skin diseases (a dermatologist). The dermatologist will carefully examine the lesion for the characteristic features of skin cancer. If further testing seems necessary, the dermatologist will perform a skin biopsy by removing the lesion under local anesthesia. Because melanomas tend to grow in diameter, as well as downwards into the epidermis and fatty layers of skin, a biopsy sample that is larger than the mole will be taken. This tissue is then analyzed under a microscope by a specialist in diseased organs and tissues (a pathologist). The pathologist makes the diagnosis of cancer and determines how far the tumor has grown into the skin. The evaluation of the progression of the cancer is called staging. Staging refers to how advanced the cancer is and is determined by the thickness and size of the tumor. Additional tests will also be done to determine if the cancer has moved into the lymph nodes or other areas of the body. These tests might include chest x ray, computed tomography scan (CT scan), magnetic resonance imaging (MRI), and blood tests.

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Surgery The primary treatment for skin cancer is to cut out (excise) the tumor or diseased area of skin. Surgery usually involves a simple excision using a scalpel to remove the lesion and a small amount of normal surrounding tissue. A procedure known as microscopically controlled excision can be used to examine each layer of skin as it is removed to ensure that the proper amount is taken. Depending on the amount of skin removed, the cut is either closed with stitches or covered with a skin graft. When surgical excision is performed on visible areas, such as the face, cosmetic surgery may also be performed to minimize the scar. Other techniques for removing skin tumors include burning, freezing with dry ice (cryosurgery), or laser surgery. For skin cancer that is localized and has not spread to other areas of the body, excision may be the only treatment needed. Nonsurgical approaches Although chemotherapy is the normal course of therapy for most other types of advanced cancer, it is not usually effective and not usually used for advanced skin cancer. For advanced melanoma that has moved beyond the original tumor site, the local lymph nodes may be surgically removed. Immunotherapy in the form of interferon or interleukin is being used more often with success for advanced melanoma. There is growing evidence that radiation therapy may be useful for advanced melanoma. Other treatments under investigation for melanoma include gene therapy and vaccination. Recent studies have shown that the use of a vaccine prepared from a person’s own cancer cells may be useful in treating advanced melanoma. For people previously diagnosed with skin cancers, the chances of getting additional skin cancers are high. Therefore, regular monthly self-examination, as well as frequent examinations by a dermatologist, are essential. Alternative treatment There are no established alternative treatments for skin cancer. Immunotherapy, which strengthens the immune system, is an approach that may prove valuable in the future. Preventive measures that can be helpful include minimizing exposure to the sun and sunburn, eating a diet high in antioxidants and supplementation with antioxidant nutrients.

Prognosis The prognosis for skin cancer depends on several factors, the most important of which are the invasiveness

of the tumor and its location. The prognosis is good for localized skin cancers that are diagnosed and treated early. For basal cell cancer and squamous cell cancer, the cure rate is close to 100%, although most people with these forms will have recurrent skin cancer. For localized melanoma, the cure rate is approximately 95%. The prognosis worsens with larger tumors. Melanoma that has spread to the lymph nodes has a 5-year survival rate of 54%; advanced melanoma has a survival rate of only 13%. When melanoma has spread to other parts of the body, it is generally considered incurable. The median length of survival is six months.

Health care team roles A physician makes an initial diagnosis. A dermatologist and pathologist may confirm the diagnosis. A surgeon removes most lesions. A plastic and reconstructive surgeon may repair or minimize surgical scars. Nurses and nurse practitioners will participate in prevention education with patients.

Prevention Prevention is the best way to approach skin cancer. Avoiding unnecessary sun exposure, from such sources as sun lamps and tanning salons, is relatively simple. Parents of small children should protect them against the risk of sunburn. Precautions include avoiding high sun, when the rays of the sun are most intense (between 11 A.M. and 1 P.M.). In addition, persons living at high elevations need to take extra precautions because the intensity of UV radiation increases by 4% with every 1,000-ft (305-m) rise above sea level. When outdoors protective clothing should be worn, covering exposed skin. Sunglasses with UV protective coating should also be worn. There is presently some debate about the ability of sunscreen to protect against skin cancer. Some scientists believe that gradual exposure to the sun, in order to develop a mild tan, may offer the best protection from skin cancer. Skin cancer has also been related to diets that are high in fat. Decreasing the amount of fat consumed may also help to decrease the risk of skin cancer. Resources BOOKS

Balch, Charles M. Cutaneous Melanoma, 3rd ed. St. Louis, Quality Medical Publishing, 1998. Buchan, John and Roberts, Daffyd Lloyd. Pocket Guide to Malignant Melanoma. New York, Blackwell Science, 2000.

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Treatment

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KEY TERMS Biopsy—Removal of a small piece of tissue for examination. This is done under local anesthesia and removed by either using a scalpel or a punch, which removes a small cylindrical portion of tissue. Cryosurgery—The use of extreme cold to destroy tissue in treating skin cancer. Dermatologist—A doctor who specializes in skin diseases. Epidermis—The outermost layer of skin. Interferon—A group of proteins that have an effect on immune function and appear to have an anti- tumor effect in some persons. Melanin—A dark pigment that is found in certain skin cells and helps to protect the skin from ultraviolet light. Melanocyte—A specialized skin cell that produces melanin. Metastasis—The movement of cancer cells from one area of the body to another through the blood or the lymph vessels. Pathologist—A specialist in diseased organs and tissues. Staging—The process of classifying and evaluating the progression of a cancer. TNM staging—A staging system for classifying cancers developed by the American Joint Committee on Cancer. The initials stand for tumor, nodes, and metastasis.

Darmstadt, Gary L. “Tumors of the skin.” In Nelson Textbook of Pediatrics, 16th ed., edited by Richard E. Behrman et al. Philadelphia: W.B. Saunders, 2000, 2051-2053. Parker, Frank. “Skin diseases of general importance.” In Cecil Textbook of Medicine, 21st ed., edited by Goldman, Lee and Bennett, J. Claude. Philadelphia: W.B. Saunders, 2000, 2276-2298. Poole, Catherine M. and Guerry, DuPont. New Haven, CT, Yale University Press, 1998. Schofield, Jill R. and Robinson, William A. What You Really Need to Know About Moles and Melanoma. Baltimore: Johns Hopkins University Press, 2000. Smithson, William A. “Cancer of the skin.” In Nelson Textbook of Pediatrics, 16th ed., edited by Richard E. Behrman et al. Philadelphia: Saunders, 2000, 1566-1567.

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Sober, Arthur J., Koh, Howard K., Tran, N-LT and Washington, Carl V. “Melanoma and other skin cancers.” In Harrison’s Principles of Internal Medicine, 14th ed., edited by Anthony S. Fauci, et al. New York: McGrawHill, 1998, 543-549. PERIODICALS

Bedikian A.Y., Plager C., Stewart J.R., O’Brian C.A., Herdman S.K., Ross M., Papadopoulos N., Eton O., Ellerhorst J., Smith T. “Phase II evaluation of bryostatin1 in metastatic melanoma.” Melanoma Research 11, no. 2 (2001): 183-188. Hillner B.E., Kirkwood J.M., Agarwala S.S. “Burden of illness associated with metastatic melanoma.” Cancer 91, no. 9 (2001): 1814-1821. Lucci A., Citro H.W., Wilson L. “Assessment of knowledge of melanoma risk factors, prevention, and detection principles in Texas teenagers.” Journal of Surgical Research 97, no. 2 (2001): 179-183. Naylor M.F. “Melanoma vaccines.” Dermatology Online Journal 6, no. 1 (2000): 5-9. Shore R.E. “Radiation-induced skin cancer in humans.” Medical and Pediatric Oncology 36, no. 5 (2001): 549-554. Taran J.M., Heenan P.J. “Clinical and histologic features of level 2 cutaneous malignant melanoma associated with metastasis.” Cancer 91, no. 9 (2001): 1822-1825. ORGANIZATIONS

American Academy of Dermatology, 930 N. Meacham Road, PO Box 4014, Schaumburg, IL 60168-4014. (847) 3300230. Fax: (847) 330-0050. . American Melanoma Foundation, 3914 Murphy Canyon Road, Suite A132, San Diego, CA 92123. (858) 2774426. . [email protected]. Melanoma Education Foundation, 7 Jones Road, Peabody, MA 01960. . [email protected]. Melanoma Research Foundation, 23704-5 El Toro Rd., #206, Lake Forest, CA 92630. Phone/Fax: (800) 673-1290. [email protected]. National Cancer Institute, Building 31, Room 10A31, 31 Center Drive, MSC 2580, Bethesda, MD 20892-2580. (800) 422-6237 or (301) 435-3848. ttp://www.nci.nih.gov/. Skin Cancer Foundation, 245 5th Avenue Suite 1403, New York, NY 10016. (800) 754-6490. Fax: (212) 725-5751. , [email protected]. OTHER

American Academy of Dermatology. . Melanoma Foundation of Australia. .

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Malocclusion

National Library of Medicine. . National Melanoma Foundation. . University of California-Davis. . University of Maryland. . University of Pennsylvania. .

L. Fleming Fallon, Jr., M.D., Dr.P.H.

Malocclusion Definition Malocclusion is an abnormality in the way the upper and lower teeth fit together in biting or chewing. The word malocclusion literally means “bad bite.” The condition may also be referred to as an irregular bite, crossbite, or overbite.

Description Malocclusion may be seen as crooked, crowded, or protruding teeth, or disproportionately smaller or larger jaws. Malocclusion can affect a person’s appearance, speech, and ability to eat. Usually by age seven, enough of the permanent teeth have come in for dentists to identify current malocclusion and anticipate future problems if teeth and bone are left untreated. Adults and children can be successfully treated for most problems related to malocclusion.

Causes and symptoms Malocclusions are most often inherited, but may be acquired. Inherited conditions include too many or too few teeth; too much or too little space between teeth; irregular mouth, jaw size, and shape; and atypical formations of the jaws and face, such as a cleft palate. Malocclusions may be acquired from habits like finger or thumb sucking, tongue thrusting, premature loss of teeth from an accident or dental disease, and medical conditions such as enlarged tonsils and adenoids that lead to mouth breathing. Malocclusions may not have symptoms, or they may produce pain from increased stress on the oral structures.

A close-up of person’s mouth and teeth. The teeth are misarranged due to excessive thumb sucking. (Custom Medical Stock Photo. Reproduced by permission.)

Teeth may show abnormal signs of wear on the chewing surfaces or decay in areas of tight overlap. Chewing may be difficult. Left untreated, crooked or crowded teeth can become worse, sometimes requiring costly treatment to correct serious problems that develop over time. Orthodontic problems can contribute to conditions that cause tooth decay and gum disease. They can also help cause abnormal wear of tooth surfaces, inefficient chewing function, excessive stress on gum tissue and supporting bone, as well as jaw misalignment, resulting in headaches and face or neck pain.

Diagnosis Malocclusion is most often found during a dental examination or screening. A dentist or dental hygienist checks a patient’s occlusion by watching how the teeth make contact when the patient bites down normally. The dentist asks the patient to bite down on a piece of coated paper placed between the upper and lower teeth; this paper will leave colored marks at the points of contact. When malocclusion is suspected, photographs and x rays of the face and mouth may be taken for further study. To confirm the presence and extent of malocclusion, the dentist makes a plaster study model of the patient’s teeth from impressions. These models duplicate the fit of the teeth and are very useful in treatment planning.

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KEY TERMS Braces—An orthodontic appliance consisting of brackets cemented to the surface of each tooth and wires of stainless steel or nickel titanium alloy. Braces treat malocclusion by gradually changing the position of the teeth. Impression—An imprint of the upper or lower teeth made in a pliable material that sets. When this material has hardened, it may be filled with plaster, plastic, or artificial stone to make an exact model of the teeth. Occlusion—The way the upper and lower teeth fit together in biting or chewing. Retainer—An orthodontic appliance worn to stabilize teeth in a new position. Space maintainer—An orthodontic appliance worn to prevent adjacent teeth from moving into the space left by an unerupted or prematurely lost tooth.

Treatment Malocclusion may be remedied by orthodontic treatment. Orthodontics is a specialty of dentistry that manages the growth, prevention, and correction of abnormal dental and facial relationships. Braces are the most commonly used orthodontic appliances in the treatment of malocclusion. Braces apply constant gentle force to slowly change the position of the teeth, straightening them and properly aligning them with the opposing teeth. Braces consist of removable or fixed (cemented or bonded to the teeth) brackets, made of metal, ceramic, or plastic. In most cases, braces are not removable for daily tooth brushing, so the patient must be especially diligent about keeping the mouth clean and removing bacterial plaque that is easily trapped, in order to prevent tooth decay. Foods that are crunchy should be avoided to minimize the risk of breaking the appliance. Hard fruits, vegetables, and breads must be cut into bite-sized pieces before eating. Foods that are sticky, including chewing gum, should be avoided because they may pull off the brackets or weaken the cement. Carbonated beverages may also weaken the cement, as well as contribute to tooth decay. Teeth should be brushed immediately after eating sweet foods. Special floss threaders are available to make flossing easier. 1488

If overcrowding is creating malocclusion, one or more teeth may be extracted (surgically removed), giving other teeth room to move. If a tooth has not yet erupted or is prematurely lost, the orthodontist may insert an appliance called a space maintainer to keep the other teeth from moving out of their natural position. In severe cases of malocclusion, surgery may be necessary and the patient would be referred to yet another specialist, an oral or maxillofacial surgeon. Once the teeth have been moved into their new position, the braces are removed and a retainer is worn until the teeth stabilize in that position. Retainers do not move teeth, they only hold them in place. Orthodontic treatment is the only effective treatment for malocclusion not requiring surgery. However, depending on the cause and severity of the condition, an orthodontist may be able to suggest other appliances as alternatives to braces. Experts recommend early treatment, which can help to guide the growth of the jaw, regulate the widths of the dental arches, correct thumb, finger, and other sucking habits, enhance swallowing and speech, and improve personal appearance and selfesteem. Adults are candidates for orthodontics to correct malocclusion, as well. Healthy teeth can be moved to more desirable positions at any age. Alternative treatment There are some techniques of craniosacral therapy that can alter structure. This therapy may allow correction of some cases of malocclusion. If surgery is required, pre- and post-surgical care with natural remedies, as well as vitamin and mineral supplements, may enhance recovery. Night guards and stress management are sometimes recommended to ease the strain on the jaw and to limit teeth grinding.

Prognosis Depending on the cause and severity of the malocclusion and the appliance used in treatment, a patient should expect correction of the condition to take one to three years. Interceptive, or early treatment procedures, might take months or more. The time required to correct malocclusion depends on the growth of the patient’s mouth and face, patient cooperation, and the extent of the problem.

Health care team roles The general dentist or dental hygienist, during preventive oral care, is often the first health professional to see evidence of a malocclusion. The general dentist usually determines a patient’s need to have the problem

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Prevention Malocclusion is preventable at times. It can be prevented by space maintenance and may be minimized by controlling habits such as finger or thumb sucking. Initial consultation with an orthodontist before a child is seven years old may lead to appropriate management of the growth and development of the child’s dental and facial structures, circumventing many of the factors contributing to malocclusion.

Negligence can result from a lack of knowledge or skill, or from failure to exercise reasonable judgment in the application of professional knowledge or skill. Lack or failure is determined by comparing the action in question with what a similar practitioner would reasonably be expected to do in the same circumstances. In law, malpractice is classified as a tort, which is a wrongful act resulting in injury to another’s person, property, or reputation. In a tort, the injured party is entitled to seek compensation for the injury. All torts, including malpractice, have three features: • a person who has a duty of care toward others • a failure to exercise due care • an injury or financial damages caused by the failure

Resources ORGANIZATIONS

Academy of General Dentistry. 211 East Chicago Ave., Chicago, IL 600611. (312) 440-4800. . American Association of Oral and Maxillofacial Surgeons. 9700 West Bryn Mawr Avenue, Rosemont, IL 600185701. (847) 678-6200. . American Association of Orthodontists. 401 N. Lindbergh Blvd. St. Louis, MO 63141-7816. (314) 993-1700. . OTHER

OrthoFind. (310) 328-2020. . Interview with Dr. Leslie Seldin, practicing general dentist and spokesperson for the American Dental Association. Office address: 40 Central Park. New York, NY 100191413. (212) 246-2398.

Lisette Hilton

Malpractice Definition Malpractice is defined as improper or negligent practice by a lawyer, physician, or other professional who injures a client or patient. The fields in which a judgment of malpractice can be made are those that require training and skills beyond the level of most people’s abilities. Medical malpractice is defined as a wrongful act by a physician, nurse, or other medical professional in the administration of treatment— or at times, the omission of medical treatment, to a patient under his or her care. Although dentists, architects, accountants, and engineers are also liable to malpractice suits, most lawsuits of this type in the United States involve medical malpractice.

Description The American Nurses Association estimates that there are 1–3 million health care errors in United States hospitals per year. In the past, only physicians were sued for malpractice, but as of 2001, nurses and other allied health professionals are being named with increasing frequency as defendants in lawsuits. This focus on shared responsibility can be attributed to a number of factors. The responsibilities of nurses and allied health professionals are continually expanding to include more risk and more patient contact without a physician present. In some clinic settings, advanced practice nurses have prescriptive authority and can perform many of the same functions as a physician. This expansion increases the liklihood of lawsuits against nonphysician health care providers. In 2001, limits on staffing and a shortage of qualified nurses have increased demands on the time and attention of health care professionals. Even conscientious workers may find themselves making mistakes when under increased pressure to do more with fewer resources. This pressure leads to errors resulting from breakdowns in communication as well. In addition, the advent of the Internet has produced a patient population that is more knowledgeable about health care and more aware of the risks and benefits of treatment. Health care providers are no longer regarded as “always knowing what’s best.” Easy access to health care information enables patients to judge for themselves if they are receiving reasonable care or not. The legal process of malpractice suits When a patient wishes to sue a medical professional for malpractice, he or she must first consult an attorney. Most malpractice attorneys work on a contingent fee

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looked at by a specialist, such as an orthodontist. Dental assistants are ancillary personnel used in dentists’ or orthodontists’ offices to assist in the procedures.

Malpractice

KEY TERMS Contingent fee—A method of compensation in which an attorney is paid only if damages are awarded to the client. Contingent fees are usually a percentage of the gross amount of the award. Defendant—The party sued or accused in a court of law. Plaintiff—The party initiating a lawsuit in a court of law. Prescriptive authority—Legal authority granted to advanced practice nurses to prescribe medication. Tort—A wrongful act that causes injury to another person’s body, property, or reputation, for which the injured party is entitled to seek compensation. Malpractice is classified as a tort in the legal system of the United States.

basis. This term means that the attorney is paid only if the patient recovers damages from the professional. The attorney usually receives a percentage of the gross award—sometimes as high as 30–40%. The attorney will obtain a detailed medical history from the patient, including the names of all physicians and hospitals who have treated him or her. The most important step is securing a medical expert. The attorney will consult someone certified in the relevant medical specialty in order to determine whether there is sufficient evidence that the defendant medical professional did indeed injure the patient. If the medical expert concludes that there is evidence of malpractice, a lawsuit is filed. If the plaintiff and the defendant cannot resolve their differences outside of court, the case will go to trial before a judge and jury.

Breach of duty is determined by comparing the action in question with the established standard of care. These standards are developed by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) and State Nurse Practice Acts, and are communicated by professional associations, professional journals and textbooks, job descriptions, and organization policies and procedures. Proving causation requires evidence that the health care provider’s negligence directly caused injury or harm to the patient. Even if breach of duty can be established, malpractice is not proven unless causation is confirmed. The last step in proving malpractice is verifying that the patient suffered disability, disfigurement, pain, suffering, or financial loss as a result of negligence. In some states, any of the defendants may be required to pay 100% of the award, even if they were only slightly negligent in comparison to the other defendants. This rule is gradually being abolished, however, and usually liability is distributed based on degree of fault.

Viewpoints Since there has been a trend to include nurses and allied health professionals in medical malpractice suits, the question of liability insurance must be addressed. Nurses and allied health professionals are usually covered by liability insurance provided by their employer, and many professionals consider this coverage sufficient. Others, however, encourage purchasing a personal policy as well for the following reasons: • The employer’s policy may not cover the total award. • Employer coverage may not apply after job termination.

Proving medical malpractice Four elements must be proven in court in order for a verdict of malpractice, or negligence, to be issued. These include legal duty; breach of duty; causation; and damages. Legal duty to the patient is initiated upon establishment of a provider-patient relationship. For example, if treatment is begun, a contract is implied to exist between the health care provider and the patient. If health care professionals assist at the scene of an accident, they are covered under Good Samaritan law if the assistance is given freely and in a situation where other medical personnel and equipment are not immediately available. In most states, there is no legal duty to assist in such a situ1490

ation, although there may be an ethical or moral duty. Good Samaritan law offers protection against litigation for simple negligence in order to encourage health care professionals to stop at accident scenes, but any action considered gross negligence is not protected.

• Agency workers are not usually covered by hospital policies. • Personal policies may also cover attorney fees, transportation, and paid time off from work. Some professionals may think that having personal liability insurance makes them more likely to be sued; however, this is not true. If a health care worker is involved in a negligent situation in any way, they can be named in the lawsuit. The plaintiff’s lawyer may not investigate the defendants for personal insurance; and even if the lawyer does make an investigation, the jury is not allowed to have that information.

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Professional implications The obvious professional implications of malpractice include the reasons for lawsuits against nurses and allied health professionals; and ways to avoid being named in a suit. Reasons for lawsuits against nurses and allied health professionals Nurses and allied health care professionals have a duty to question physician orders that are inappropriate or unclear. If they do not ask such questions, and a patient is harmed as a result of an inappropriate order, the nurse or allied health professional is just as liable for damages as the physician. The same is true for verbal orders. Verbal orders should be accepted only in emergency situations, and the physician should write and sign the order immediately afterwards. Telephone orders can be accepted by a registered nurse or pharmacist, but should be signed by the physician as soon as possible. If a patient’s status changes and the physician is not notified, the nurse is liable for damages that may occur. These changes include change in physical status, critical laboratory values, and critical information that the physician should ask for but doesn’t. If a medical resident is managing the patient, the attending physician must still be notified. Documentation is crucial. Specifics should be documented about the patient’s condition, who was notified and what was said, the interventions implemented, and the outcomes of care. A favorite phrase in health care is “If it wasn’t documented, it wasn’t done,” and that’s exactly how the court will view the patient’s chart in a lawsuit. Other common reasons for lawsuits against nurses include: • failure to secure the patient’s safety • failure to properly assess the patient • failure to perform a procedure according to established standards of care • failure to administer medication properly

Ways to avoid being named in a lawsuit Nurses and allied health care professionals who are conscientious and who exercise good judgment are usually successful at avoiding negligent practice. Not every situation can be completely controlled, however, especially when other physicians or health care professionals are involved. The American Nurses Association is a strong advocate for patient safety and has proposed whistle-blower protection for nurses and allied health care professionals who report unsafe patient care practices. Whistle-blower protection legislation has been addressed at the state and federal levels. There is another simple way to lessen the chance of being included in a lawsuit: give compassionate care. It’s been established that patients who file lawsuits tend to sue people who have made them angry. Often, the real issue for patients is that they feel they have not been heard or treated with respect. One study (Beckman, et al., 1994) reviewed 45 malpractice cases against a large medical center and found that in 71%of the cases, plaintiffs stated that they had a negative relationship with the caregivers. The issues included feelings of abandonment; feeling that discomfort had been ignored; not receiving explanations about the care given or expected outcomes; and feeling that the patient’s or family’s opinions were discounted. In another situation, a defense attorney for health care providers found that a plaintiff refused to name a certain nurse in the lawsuit, even though the nurse was clearly negligent. The plaintiff felt that this nurse was the only one who gave compassionate care. Effective communication, compassionate care, and treating patients with dignity increases both patient and professional satisfaction. The end result is patients who are less likely to initiate lawsuits, and health care workers who are less likely to end up in court. Resources PERIODICALS

Beckman, H.B., et al. “The Doctor-Patient Relationship and Malpractice: Lessons from Plaintiff’s Depositions.” Archives of Internal Medicine 154, no.12 (1994): 1365. Calloway, S. “Preventing Communication Breakdowns.” RN 64, no. 1(2001): 71-72, 74. Crane, Mark. “NPs and PAs: What’s the malpractice risk?” Medical Economics 77, no. 6 (March 20, 2000). Helm, A., and N. Kihm. “Is Professional Liability Insurance for You?” Nursing 31, no. 1 (2001): 48. Martin, G.A. “ARNA Workplace Advocacy Newsletter. TortsR-Us.” Arkansas Nursing News 17, no. 4 (2001): 16-18. Mock, K. “Keep Lawsuits at Bay with Compassionate Care.” RN 64, no. 5 (2001): 83-84, 86.

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Some nurses and allied health professionals may decide not to have personal liability insurance “because it costs too much.” The average yearly cost of a nursing policy with a liability limit of $1,000,000 is approximately $90. That’s relatively inexpensive protection from having to pay out of one’s own pocket for damages awarded in a lawsuit.

Mammography

ORGANIZATIONS

American Bar Association (ABA). 750 North Lake Shore Drive, Chicago, IL 60611. (312) 988-5000 or (800) 964-4253. American Nurses Association. 600 Maryland Ave. SW, 100 W., Washington, DC 20024. (800) 274-4ANA. . OTHER

Allied Health Professionals Policy.HCPro. 2001. (July 28, 2001).

Abby Wojahn, R.N.,B.S.N.,C.C.R.N.

breast cancer, such as those with a positive family history of the disease. Beginning screening mammography at a younger age may be recommended for these women. Diagnostic mammography is used to evaluate an existing problem, such as a lump, discharge from the nipple, or unusual tenderness in one area. It is also done to evaluate further abnormalities that have been seen on screening mammograms. The radiologist normally views the films immediately and may ask for additional views such as a magnification view of one specific area. Additional studies such as an ultrasound of the breast may be performed as well to determine if the lesion is cystic or solid. Breast-specific positron emission tomography (PET) scans as well as in MRI (magnetic resonance imaging) may be ordered to further evaluate a tumor, but mammography is still the first choice in detecting small tumors on a screening basis.

Mammography Precautions

Definition Mammography is the study of the breast using xrays. The actual test is called a mammogram. It is an xray of the breast which shows the fatty, fibrous and glandular tissues. There are two types of mammograms. A screening mammogram is ordered for women who have no problems with their breasts. It consists of two x-ray views of each breast: a craniocaudal (from above) and a mediolateral oblique (from the sides). A diagnostic mammogram is for evaluation of abnormalities in either men or women. Additional x rays from other angles, or special coned views of certain areas are taken.

Description

Purpose The purpose of screening mammography is breast cancer detection. A screening test, by definition, is used for patients without any signs or symptoms, in order to detect disease as early as possible. Many studies have shown that having regular mammograms increases a woman’s chances of finding breast cancer in an early stage, when it is more likely to be curable. It has been estimated that a mammogram may find a cancer as much as two or three years before it can be felt. The American Cancer Society (ACS) guidelines recommend an annual screening mammogram for every woman of average risk beginning at age 40. Radiologists look specifically for the presence of microcalcifications and other abnormalities that can be associated with malignancy. New digital mammography and computer aided reporting can automatically enhance and magnify the mammograms for easier finding of these tiny calcifications. The highest risk factor for developing cancer is age. Some women are at an increased risk for developing 1492

Screening mammograms are not usually recommended for women under age 40 who have no special risk factors and a normal physical breast examination. A mammogram may be useful if a lump or other problem is discovered in a woman aged 30-40. Below age 30, breasts tend to be “radiographically dense,” which means the breasts contain a large amount of glandular tissue which is difficult to image in fine detail. Mammograms for this age group are controversial. An ultrasound of the breasts is usually done instead since it gives no radiation to the patient.

A mammogram may be offered in a variety of settings. Hospitals, outpatient clinics, physician’s offices, or other facilities may have mammography equipment. In the United States only places certified by the Food and Drug Administration (FDA) are legally permitted to perform, interpret, or develop mammograms. Mammograms are taken with dedicated machines using high frequency generators, low kvp, molybdenum targets and specialized x-ray beam filtration. Sensitive high contrast film and screen combinations along with prolonged developing enable the visualization of minute breast detail. In addition to the usual paperwork, a woman will be asked to fill out a questionaire asking for information on her current medical history. Beyond her personal and family history of cancer, details about menstruation, previous breast surgeries, child bearing, birth control, and hormone replacement therapy are recorded. Information about breast self-examination (BSE) and other breast health issues are usually available at no charge.

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Mammography

At some centers, a technologist may perform a physical examination of the breasts before the mammogram. Whether or not this is done, it is essential for the technologist to record any lumps, nipple discharge, breast pain or other concerns of the patient. All visible scars, tattoos and nipple alterations must be carefully noted as well. Clothing from the waist up is removed, along with necklaces and dangling earrings. A hospital gown or similar covering is put on. A small self-adhesive metal marker may be placed on each nipple by the x-ray technologist. This allows the nipple to be viewed as a reference point on the film for concise tumor location and easier centering for additional views. Patients are positioned for mammograms differently, depending on the type of mammogram being performed: • Craniocaudal position (CC): The woman stands or sits facing the mammogram machine. One breast is exposed and raised to a level position while the height of the cassette-holder is adjusted to the same level. The breast is placed mid-film with the nipple in profile and the head turned away from the side being x-rayed. The shoulder is relaxed and pulled slightly backward while the breast is pulled as far forward as possible. The technologist holds the breast in place and slowly lowers the compression with a foot pedal. The breast is compressed between the film holder and a rectangle of plastic (called a paddle). The breast is compressed until the skin is taut and the breast tissue firm when touched on the lateral side. The exposure is taken immediately and the compression released. Good compression can be uncomfortable, but it is very necessary. Compression reduces the thickness of the breast, creates a uniform density and separates over-lying tissues. This allows for a detailed image with a lower exposure time and decreased radiation dose to the patient. The same view is repeated on the opposite breast. • Mediolateral oblique position (MLO): The woman is positioned with her side towards the mammography unit. The film holder is angled parallel to the pectoral muscle, anywhere from 30-60 degrees depending on the size and height of the patient. The taller and thinner the patient the higher the angle. The height of the machine is level with the axilla (armpit). The arm is placed at the top of the cassette-holder with a corner touching the armpit. The breast is lifted forward and upward and compression is applied until the breast is held firmly in place by the paddle. The nipple should be in profile and the opposite breast held away if necessary by the patient. This procedure is repeated for the

Mammography can detect breast cancer before it can be felt, increasing the chances that it can be treated successfully. (D. Weinstein/Custom Medical Stock Photo. Reproduced by permission.)

other breast. A total of four x-rays, two of each breast, are taken for a screening mammogram. Additional xrays, using special paddles, different breast positions, or other techniques may be taken for a diagnostic mammogram. The mammogram may be seen and interpreted by a radiologist right away, or it may not be reviewed until later. If there is any questionable area or abnormality, extra x-rays may be recommended. These may be taken during the same appointment. More commonly, especially for screening mammograms, the woman is called back on another day for these additional films. A screening mammogram usually takes approximately 15-30 minutes. A woman having a diagnostic mammogram can expect to spend up to an hour for the procedure. The cost of mammography varies widely. Many mammography facilities accept “self referral.” This means women can schedule themselves without a physician’s referral. However, some insurance policies do require a doctor’s prescription to ensure payment. Medicare will pay for annual screening mammograms for all women over age 39.

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P.A. chest x-rays travel from posterior to anterior (P.A. projection)

Posteroanterior (P.A.) projection

A.P. chest x-rays travel from anterior to posterior (A.P. projection)

Anteroposterior (A.P.) projection

Lateral (Lat.) position

Left posterior oblique (L.P.O.) position

Radiographic Projection Positions

Positioning for breast x rays. (Delmar Publishers, Inc. Reproduced by permission.)

Aftercare

Preparation The compression or squeezing of the breast necessary for a mammogram is a concern of many women. Mammograms should be scheduled when a woman’s breasts are least likely to be tender. One to two weeks after the first day of the menstrual period is usually best. Some women with sensitive breasts also find that stopping or decreasing caffeine intake from coffee, tea, colas, and chocolate for a week or two before the examination decreases any discomfort. Women receiving hormone therapy may also have sensitive breasts. Over-thecounter pain relievers are recommended an hour before the mammogram appointment when pain is a significant problem. Women should not put deodorant, powder, or lotion on their upper body on the day the mammogram is performed. Particles from these products can get on the breast or film holder and may show up as abnormalities on the mammogram. Most facilities will have special wipes available for those patients who need to wash before the mammogram. 1494

No special aftercare is required.

Complications The risk of radiation exposure from a mammogram is considered minimal and not significant. Experts are unanimous that any negligible risk is by far outweighed by the potential benefits of mammography. Patients who have breast implants must be x-rayed with caution and compression is minimally applied so that the sac is not ruptured. Special techniques and positioning skills must be learned before a technologist can x-ray a patient with breast implants. Some breast cancers do not show up on mammograms, or “hide” in dense breast tissue. A normal (or negative) study is not a guarantee that a woman is cancerfree. The false-negative rate is estimated to be 15-20%, higher in younger women and women with dense breasts. False positive readings are also possible. Breast biopsies may be recommended on the basis of a mammogram, and find no cancer. It is estimated that 75-80% of all breast biopsies resulted in benign (no cancer pres-

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Results A mammography report describes details about the x ray appearance of the breasts. It also rates the mammogram according to standardized categories, as part of the Breast Imaging Reporting and Data System (BIRADS) created by the American College of Radiology (ACR). A normal mammogram may be rated as BIRADS 1 or negative, which means no abnormalities were seen. A normal mammogram may also be rated as BIRADS 2 or benign findings. This means there are one or more abnormalities but they are clearly benign (not cancerous), or variations of normal. Some kinds of calcifications, enlarged lymph nodes or obvious cysts might generate a BIRADS 2 rating. Many mammograms are considered borderline or indeterminate in their findings. BIRADS 3 means either additional images are needed, or an abnormality is seen and is probably (but not definitely) benign. A follow-up mammogram within a short interval of six to twelve months is suggested. This helps to ensure that the abnormality is not changing, or is “stable.” Only the affected side will be x-rayed at this time. Some women are uncomfortable or anxious about waiting, and may want to consult with their doctor about having a biopsy. BIRADS 4 means suspicious for cancer. A biopsy is usually recommended in this case. BIRADS 5 means an abnormality is highly suggestive of cancer. A biopsy or other appropriate action should be taken.

Health care team roles The mammographic x-ray technologist works closely with the radiologist. Films of high quality must be taken so the radiologist can make an accurate diagnosis. The technologist also assists the radiologist when performing biopsies or fine needle aspirations. Analysis of the specimen will be carried out in the laboratory by the medical laboratory technician. It is important for the technologist to fill out the proper laboratory forms. Biopsies performed in the operating room will sometimes require a magnified x-ray of the specimen itself. The technologist must work in conjunction with the surgeon and operating room nurses to make sure the specimen is x-rayed immediately and than returned for further analysis. All radiology technologists must be certified according to a recognized standard such as that of the American Society of Registered Radiology Technologists. The MQSA, or Mammography Quality Standards Act,

KEY TERMS Breast biopsy—A procedure where suspicious tissue is removed and examined by a pathologist for cancer or other disease. The breast tissue may be obtained by open surgery, or through a needle. Craniocaudal—Head to tail, x-ray beam directly overhead the part being examined. Radiographically dense—An abundance of glandular tissue, which results in diminished film detail.

enforced by the FDA, ensures that all mammographic xray technologists receive adequate training and continued education to perform special techniques such as mammography of patients with breast implants. It is also part of the technologist’s or nurse’s job to perform quality assurance and to keep statistics to ensure FDA compliance. Patient education The mammography technologist must be empathetic to the patient’s modesty and anxiety. He or she must explain that compression is necessary to improve the quality of the image but does not harm the breasts. Patients will be very anxious when additional films are requested. Explaining that an extra view will give the radiologist more information will help to eases the patient’s tension. One in eight women in North America will develop breast cancer. Educating the public on monthly breast self-examinations and yearly mammograms will help in achieving an early diagnosis and therefore a better cure. Resources PERIODICALS

Carmen, Ricard, R. T. R. Mammography: Techniques and Difficulties. O.T.R.Q., 1999. Gagnon, Gilbert. Radioprotection in Mammography. O.T.R.Q., 1999. Ouimet, Guylaine, R. T. R. Mammography: Quality Control. O.T.R.Q., 1999. ORGANIZATIONS

American Cancer Society (ACS), 1599 Clifton Rd., Atlanta, GA 30329. (800) ACS-2345. . Federal Drug Administration (FDA), 5600 Fishers Ln., Rockville, MD 20857. (800) 532-4440. . National Cancer Institute (NCI) and Cancer Information Service (CIS), Office of Cancer Communications, Bldg.

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ent) findings. This is considered an acceptable rate, because recommending fewer biopsies would result in too many missed cancers.

Managed care plans

31, Room 10A16, Bethesda, MD 20892. (800) 4-CANCER (800) 422-6237. Fax: (800) 624-2511 or (301) 402-5874. , [email protected].

Lorraine K. Ehresman

Managed care plans Definition Managed care plans are health care delivery systems that integrate the financing and delivery of health care. Managed care organizations generally negotiate agreements with providers to offer packaged health care benefits to covered individuals.

Description A majority of insured Americans belong to a managed care plan, a health care delivery system that applies corporate business practices to medical care in order to reduce costs and streamline care. The managed care era began in the late 1980s in response to skyrocketing heath care costs, which stemmed from a number of sources. Under the fee-for-service, or indemnity, model that preceded managed care, doctors and hospitals were financially rewarded for using a multitude of expensive tests and procedures to treat patients. Other contributors to the high cost of health care included the public health advances after World War II that lengthened the average life span of Americans—putting increased pressure on the health care system, and efforts by providers to adopt state-of-the-art diagnostic and treatment technologies as they became available. Managed care companies attempted to reduce costs by negotiating lower fees with clinicians and hospitals in exchange for a steady flow of patients, developing standards of treatment for specific diseases, requiring clinicians to get plan approval before hospitalizing a patient (except in the case of an emergency), and encouraging clinicians to prescribe less expensive medicines. Many plans offer financial incentives to clinicians who minimize referrals and diagnostic tests, and some even apply financial penalties, or disincentives, on those deemed to have ordered unnecessary care. The primary “watchdog” and accreditation agency for managed care organizations is the National Committee for Quality Assurance (NCQA), a non-profit organization that also collects and disseminates health plan performance data. 1496

Three basic types of managed care plans exist: health maintenance organizations (HMOs), preferred provider organizations (PPOs), and point-of-service (POS) plans. • HMOs, in existence for over 50 years, are the best known and oldest form of managed care. Participants in HMO plans must see a primary care provider, who may be a physician or an advanced practice registered nurse (APRN) in order to receive care from a specialist. Four types of HMOs exist: the Staff Model, Group Model, Network Model, and the Independent Practice Association (IPA). The Staff Model hires clinicians to work on site. The Group Model contracts with group practice physicians on an exclusive basis. The Network Model resembles the group model except participating physicians can treat patients who are not plan members. The Independent Practice Association (IPA) contracts with physicians in private practice to see HMO patients at a prepaid rate per visit as a part of their practice. • PPOs are more flexible than HMOs. Like HMOs, they negotiate with networks of physicians and hospitals to get discounted rates for plan members. But, unlike HMOs, PPOs allow plan members to seek care from specialists without being referred by a primary care practitioner. These plans use financial incentives to encourage members to seek medical care from providers inside the network. • POSs are a blend of the other types of managed care plans. They encourage plan members to seek care from providers inside the network by charging low fees for their services, but they add the option of choosing an out-of-plan provider at any time and for any reason. POS plans carry a high premium, a high deductible, or a higher co-payment for choosing an out-of-plan provider.

Viewpoints Several managed care theories, such as those stressing continuity of care, prevention, and early intervention are applauded by health care practitioners and patients alike. But managed care has come under fire by critics who feel patient care may be compromised by managed care cost-cutting strategies, such as early hospital discharge and use of financial incentives to control referrals, which may make clinicians too cautious about sending patients to specialists. In general, the rise of managed care has shifted decision-making power away from plan members, who are limited in their choices of providers, and away from clinicians, who must concede to managed-care administrators regarding what is a medically necessary procedure. Many people would like to see managed care restructured to remedy this inequitable dis-

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Professional implications The health care industry today is dominated by corporate values of managed care and is subject to corporate principles such as cost cutting, mergers and acquisitions, and layoffs. To thrive in such an environment, and to provide health care in accordance with professional values, health care practitioners must educate themselves on the business of health care, including hospital operations and administrative decision-making, in order to influence institutional and regional health care policies. A sampling of the roles available for registered nurses in a managed care environment include: • Primary care provider. The individual responsible for determining a plan of care, including referrals to specialists. • Case manager. This person tracks patients through the health care system to maintain continuity of care. • Triage nurse. In a managed care organization, triage nurses help direct patients through the system by determining the urgency and level of care necessary and advising incoming patients on self care when appropriate. • Utilization/Resource reviewer. This individual helps manage costs by assessing the appropriateness of specialized treatments. According to an American Nursing Association statement, it is difficult to predict the effect of the managed care revolution on the nursing profession, but the profession will benefit from building broad nursing coalitions at the state and federal levels to publicize nursing’s views on patient care issues, and to monitor developing trends in the industry, including the impact of proposed mergers and acquisitions of health care institutions on the provision of care. Resources PERIODICALS

Simon, S., et al. “Views of Managed Care: A Survey of Students, Residents, Faculty, and Deans at Medical Schools in the United States.” The New England Journal of Medicine 12 (1999): 340. ORGANIZATIONS

Agency for Health Care Research and Quality. 2101 E. Jefferson St., Suite 501. Rockville, MD 20852. (301) 594-1364.

American Association of Managed Care Nurses. PO Box 4975, Glen Allen, VA 23058-4975. (804)-747-9698. . American Medical Association. The Council on Ethical and Judicial Affairs. 515 N. State Street, Chicago, IL 60610. (312) 464-4823. . American Nurses Association (ANA). 600 Maryland Avenue, SW, Suite 100 West, Washington, DC 20024. (800) 2744ANA. . Center for Bioethics at the University of Pennsylvania. Suite 320, 3401 Market Street, Philadelphia, PA 19104-3308. (215) 898-7136. . National Committee for Quality Assurance. 2000 L St. NW, Washington, DC 20036. (202) 955-3500. . National Student Nurses Association (NSNA). 555 West 57th Street, New York, NY 10019. (212) 581-2211. . OTHER

American Medical Association. Principles of Managed Care. . American Nurses Association. “Nursing’s Agenda for Health care Reform.” NursingWorld. . Health Care in Chaos: Will We Ever See Real Managed Care? American Nurses Association Continuing Education Module. .

Ann Quigley

Manic depression see Bipolar disorder Manual therapy see Joint mobilization and manipulation

Marijuana Definition Marijuana is prepared from the leaves and flowering tops of Cannabis sativa, the hemp plant, which contains a number of pharmacologically active principles, called cannabinoids.

Description Marijuana is most popularly used for its euphoric properties. Its many nicknames include grass, pot, Mary Jane, reefer, and cannabis, which is derived from Cannabis sativa, the scientific name for hemp. The beneficial effects of marijuana’s most active ingredient, tetrahydrocannabinol (THC), include the lowering of intraocular pressure, which may help control

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tribution of power. Such actions would maximize consumer choice and allow health care practitioners the freedom to provide the best care possible. According to the American Medical Association, rejection of care resulting from managed care stipulations should be subjected to an independent appeals process.

Marijuana

glaucoma, and the relief of pain, nausea, and appetite loss among chemotherapy and AIDS patients.

tobacco smoke and therefore increases the risk of lung cancer.

Marijuana’s short-term effects are psychological and physical, usually lasting for three to five hours after a person has smoked marijuana. The psychological reaction, more commonly known as a high, involves changes in the user’s feelings and thoughts. These changes are primarily caused by THC, which affects brain function.

Although a distinctive marijuana withdrawal syndrome has been identified, it is mild and short-lived. Symptoms include restlessness, irritability, mild agitation, insomnia, sleep disturbance, nausea, and cramping.

The effects of marijuana’s high vary for each individual. In most cases the high consists of a dreamy, relaxed state in which users seem more aware of their senses and feel that time is moving slowly. Sometimes, however, marijuana produces feelings of panic and dread. Reactions vary according to the concentration of THC, the setting in which marijuana is used, and the user’s expectations, personality, and mood.

Marijuana has been used as a medicine and intoxicant for thousands of years. In the United States, marijuana use has been prohibited by state and local laws since the early 1900s, and by federal law since 1937. In spite of these laws, use of the drug became widespread during the 1960s and 1970s. Between 1969 and 1978, the federal and many state governments reduced the criminal charge for possession of small amounts of marijuana from a felony to a misdemeanor. Some states even substituted fines for jail sentences. Use of marijuana in the United States declined from the mid-1970s through the early 1990s. In the mid-1990s, however, marijuana use again began to rise.

Marijuana’s short-term physical effects include reddening of the eyes and rapid heartbeat. The drug interferes with the individual’s judgment, coordination, and short-term memory. Long-term effects are not completely known. Marijuana use affects memory and motivation. Some chronic users experience bronchitis, coughing, and chest pains. Among males marijuana use can reduce sperm production and testosterone level. Among females it can cause menstrual irregularity and reduced fertility. Extended marijuana use often has a psychological impact and may result in the loss of interest in, for example, school, work, and social activities. Some regular marijuana users become dependent on it. Marijuana affects psychomotor performance. The effects depend on the nature of the task and the individual’s experience with marijuana. Cannabinoids, especially THC, can impact immune response, either enhancing or diminishing it. Human volunteers performing auditory attention tasks while smoking marijuana show impaired performance, which is associated with substantial reduction in blood flow to the brain’s temporal lobe. However, marijuana smoking increases blood flow in other brain regions, such as the frontal lobes and lateral cerebellum. Although some studies purported to show structural changes in the brains of heavy marijuana users, these results have not been replicated with more sophisticated techniques. Nevertheless, some studies have found subtle defects in the performance of cognitive tasks among heavy marijuana users. THC narrows bronchi and bronchioles and produces inflammation of the mucous membranes. Marijuana smoke contains many of the same chemicals and tars of 1498

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The Institute of Medicine recently released its findings on the medical merits of marijuana. Initially commissioned by the Office of National Drug Control Policy in 1997, the study concluded that cannabinoids, marijuana’s active components, can be useful in treating pain, nausea and appetite loss caused by advanced cancer and AIDS. For very ill patients with no other treatment options, investigators recommended short-term use of smoked marijuana under strict medical oversight. However, the Institute of Medicine found that the drug’s benefits were hampered by the toxicity of smoking, and that marijuana’s future lay in the development of synthetic cannabinoids and in smokeless delivery systems— ideally an asthma-type inhaler. Finally, researchers found no conclusive evidence that recommending marijuana medicinally would increase general use. Proponents of medical marijuana cite scientific research indicating the potential therapeutic value of cannabinoid drugs, primarily THC, for pain relief, control of nausea and vomiting, and appetite loss that often accompany cancer and AIDS. However, proponents lament the fact that the emphasis on pharmaceutical research will delay treatment because research and development for new drugs can cost $300 million and only about one in five are approved. In 1985, the U.S. Food and Drug Administration approved Marinol, a capsule containing THC, as a prescription drug. However, Marinol takes from one to several hours to take effect and many patients experience severe side effects. Since 1996, voters in Arizona,

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Opponents focus their arguments on marijuana’s addictive potential and other health problems.

Professional implications Because marijuana is a crude THC delivery system that also delivers harmful substances, smoked marijuana should generally not be recommended for medical use. Nevertheless, marijuana is widely used by certain patient groups, which raises both safety and efficacy issues. Marijuana’s future as a medicine lies in its isolated components, the cannabinoids and their synthetic derivatives. Isolated cannabinoids provide more reliable effects than crude plant mixtures. The accumulated data suggest a variety of indications, particularly for pain relief, antiemesis, and appetite stimulation. For patients such as those with AIDS or who are undergoing chemotherapy, and who suffer simultaneously from severe pain, nausea, and appetite loss, cannabinoid drugs might offer broad-spectrum relief not found in any other single medication. The therapeutic effects of cannabinoids are most well established for THC, marijuana’s primary psychoactive ingredient. Although marijuana smoke delivers THC and other cannabinoids it also delivers harmful substances, including most of those found in tobacco smoke. In addition, plants contain a variable mixture of biologically active compounds and cannot be expected to provide a precisely defined drug effect. For those reasons there seems to be little future in smoked marijuana as a medically approved medication. While clinical trials are the route to developing approved medications, they are also valuable for other reasons. For example, the personal medical use of smoked marijuana to treat certain symptoms is sufficient reason to advocate clinical trials to assess the degree to which the symptoms or course of diseases are affected. Trials testing the safety and efficacy of marijuana use are an important component to understanding the course of a disease, particularly diseases such as AIDS. The argument against the future of smoked marijuana for treating any condition is not that there is no reason to predict efficacy but that there is risk. That risk could be overcome by the development of a non-smoked rapid-onset delivery system for cannabinoid drugs. In addition to smoking, there are other means of cannabinoid delivery. Inhalers eliminate smoke toxicity while maintaining quick bloodstream entry. Pills are legal and smokeless, however, they can take over an hour

to enter bloodstream and some patients cannot tolerate the concentrated dose. The psychological effects of cannabinoids, such as anxiety reduction, sedation, and euphoria can influence their potential therapeutic value. Those effects are potentially undesirable for certain patients, although they may be beneficial for others. In addition, marijuana’s psychological effects can complicate the interpretation of other aspects of the drug’s effect. Since marijuana smoke contains many of tobacco smoke’s harmful components, it is important to consider the relationship between habitual marijuana smoking and lung disease. Given a cigarette of comparable weight, as much as four times the amount of tar can be deposited in the lungs of marijuana smokers as in the lungs of tobacco smokers. Marijuana smoke’s carcinogenicity is an important concern. Alveolar macrophages protect lungs against infectious microorganisms, inhaled foreign substances, and tumor cells. Marijuana smoking reduces the ability of alveolar macrophages to kill fungi, pathogenic bacteria, and tumor target cells. The reduction in ability to destroy fungal organisms is similar to that observed in tobacco smokers. Marijuana smoke and oral THC can cause tachycardia (fast heart beat). In some cases blood pressure increases while a person is in a reclining position but decreases inordinately on standing, resulting in postural hypotension or decreased blood pressure, which may cause dizziness and faintness. Advances in cannabinoid science have revealed a wealth of new opportunities for the development of medically useful cannabinoid-based drugs. The accumulated data suggest a variety of indications, particularly for pain relief, antiemesis, and appetite stimulation. For patients such as those with AIDS or who are undergoing chemotherapy, and who suffer simultaneously from severe pain, nausea, and appetite loss, cannabinoid drugs might offer broad-spectrum relief not found in any other single medication. The risks of smoking marijuana should be considered before recommending its use to any patient with preexisting immune deficits, including AIDS patients, cancer patients, and those receiving immunosuppressive therapies. The argument against the future of smoked marijuana for treating any condition is not the absence of efficacy but the risk. That risk could be overcome by the development of a non-smoked, rapid-onset delivery system for cannabinoid drugs.

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California, Oregon, several other states, and the District of Columbia have passed laws allowing medical use of marijuana.

Maslow’s hierarchy of needs

located at the base of the pyramid and needs for self-actualization located at the top.

Resources BOOKS

Gabriel N., Sutin, K., and Harvey, D., eds. Marijuana and Medicine. Humana Press, 1999. Joy J., Watson, S., and Benson, J., eds. Marijuana and Medicine: Assessing the Science Base. Institute of Medicine, 1999. Mack, A. and Joy, J. Marijuana As Medicine?: The Science Beyond the Controversy. National Academy Press, 2000. PERIODICALS

Kalb, C., Wingert, P., Rosenberg, D., Underwood, A., and Hammer, J. “No Green Light Yet: A long-awaited report supports medical marijuana. So now what?” Newsweek Section: Nation; Subsection: Medicine (March 29, 1999): 35. Sohn, E. “Is grass a proven tonic?” U.S. News & World Report (May 28, 2001). ORGANIZATIONS

Campaign to Legalise Cannabis International Association. Cannabis Campaigner’s Guide, Up-to-Date Chronology of Cannabis Hemp. . Center for Cardiovascular Education, Inc. Smoking Marijuana Increases Heart Attack Risk. Heart Information Network. .

Bill Asenjo, Ph.D., C.R.C.

Maslow’s hierarchy of needs Definition Maslow’s hierarchy of needs is a theory of motivation and personality developed by the psychologist Abraham H. Maslow (1908-1970). Maslow’s hierarchy explains human behavior in terms of basic requirements for survival and growth. These requirements, or needs, are arranged according to their importance for survival and their power to motivate the individual. The most basic physical requirements, such as food, water, or oxygen, constitute the lowest level of the need hierarchy. These needs must be satisfied before other, higher needs become important to individuals. Needs at the higher levels of the hierarchy are less oriented towards physical survival and more toward psychological well-being and growth. These needs have less power to motivate persons, and they are more influenced by formal education and life experiences. The resulting hierarchy of needs is often depicted as a pyramid, with physical survival needs 1500

Description Maslow’s hierarchy specifies the following levels: • Physiological needs: These are the basic requirements for human physical survival. They include such essentials as food, water, shelter, oxygen, and sleep. When these needs are unmet, human beings will focus on satisfying them and will ignore higher needs. • Safety needs: Once the individual’s basic physical needs are met, his or her needs for safety emerge. These include needs for a sense of security and predictability in the world. The person tries to maintain the conditions that allow him or her to feel safe and avoid danger. Maslow thought that inadequate fulfillment of these needs might explain neurotic behavior and other emotional problems in some people. • Love and belonging needs: When the individual’s physiological and safety needs are met, needs for love and belongingness emerge. These needs include longings for an intimate relationship with another person as well as the need to belong to a group and to feel accepted. Maslow emphasized that these needs involve both giving and receiving love. • Esteem needs: Esteem needs include both self-esteem and the esteem of others. Self-esteem is the feeling that one is worthwhile, competent, and independent. The esteem of others involves the feeling that other people respect and appreciate the person. Once the person has satisfied his or her basic needs, concerns about worthiness emerge. The focus becomes not just surviving, but doing well according to meaningful communal standards. • Self-actualization needs: These are the needs associated with realizing one’s full potential. As these needs emerge, the person focuses on doing what he or she is meant to do in life—developing his or her talents and abilities to their fullest extent. Other human needs Maslow described other needs that did not fit into his hierarchy. These included cognitive needs, such as curiosity and scientific interest, as well as aesthetic needs, which include the need for beauty and order. As Maslow studied self-actualizing individuals, he also discovered a range of needs that extend beyond self-actualization. He called these needs transcendence needs or Bvalues. They refer to needs to contribute to human welfare and to find higher meanings in life. Although transcendence needs are usually described as lying

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While Maslow described human needs as a hierarchy, he allowed for some departures from the strict order of his needs hierarchy. He stated that lower needs must be reasonably well satisfied in order for the person to focus on higher needs, but he noted that complete satisfaction of a given need may not be possible or necessary. He indicated that most people would show a range of need satisfaction levels at any given time. For example, a person might be 85% satisfied in the area of physiological needs, 60% satisfied in the area of safety needs, 45% satisfied in the area of love and belongingness needs, and so on. Maslow also noted situations in which lower needs might be ignored in favor of higher needs, as when an artist sacrifices comfort and security in order to pursue aesthetic goals, or when a student postpones looking for a romantic partner in order to earn high grades and get into a prestigious graduate program. Maslow thought, however, that these departures from a strict hierarchy did not invalidate his general theory. The historical context of Maslow’s theories At the time Maslow developed his theory in the early 1960s, psychology was dominated by two views of human behavior, the psychoanalytic and the behaviorist. The psychoanalytic view emphasized unconscious conflicts and drives, drawing many of its concepts from case studies of neurotic people. The behaviorist view emphasized the role of learning and derived many of its principles from observations of animal behavior. Maslow pointed out that the psychoanalysts had failed to consider the behavior of healthy human beings, while the behaviorists were too mechanistic and largely ignored subjective experience. He thought that no theory of human personality could be complete without a thorough study of healthy functioning, so he set out to examine the conscious motivations and experiences of healthy individuals. One important finding was that psychologically healthy people were more likely to report what Maslow called “peak experiences.” A peak experience, according to Maslow, is one in which the individual loses a sense of time and place and experiences a momentary feeling of unity with the universe. It is a particularly intense form of growth experience. Maslow’s perspective, together with similar approaches proposed by Carl Rogers, Gordon Allport, and others, came to be known as the “third force” in psychology. Because of their focus on the positive, growthoriented aspects of human behavior, these views are also described as humanistic theories of behavior. They stim-

Maslow’s hierarchy of needs

somewhere beyond the need for self-actualization, these needs are not included in most formulations of Maslow’s needs hierarchy. Selfactualization needs (Self-fulfillment and realization of one's potential)

Esteem needs (Fulfillment of approval by others; recognition)

Belongingness and love needs (Fulfillment of acceptance by others; to belong)

Safety needs (Fulfillment of security, safety)

Biological needs (Fulfillment of basic needs: food, water, etc.)

Maslow’s hierarchy of needs. (EPD Photos. Courtesy Gale Group.)

ulated the emergence and rapid growth of the human potential movement of the late 1960s and early 1970s.

Viewpoints Maslow’s theory and the other humanistic theories have had an important impact on psychology as well as in other fields. By emphasizing positive aspects of human behavior, these theories provide a framework for understanding human behavior outside the context of mental illness and dysfunction. Humanistic approaches to behavior allow for the possibility of growth and achievement, in addition to providing useful explanations for some forms of maladjustment that do not fit the traditional understanding of neurosis and mental illness. The humanistic viewpoint has been very influential on psychotherapy and counseling, and many therapists identify themselves as humanistic in orientation. Maslow’s need hierarchy provides a helpful way to understand human motivation in many settings. Maslow proposed many changes in business management in order to make workplaces more responsive to the needs of workers. He called his ideas “eupsychian management,” emphasizing the potential for human growth in the workplace. A small body of research has shown modest support for some of Maslow’s concepts. Maslow’s hierarchy

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KEY TERMS Behaviorism—The theory that human or animal psychology can be accurately studied only through analysis of objectively observable and quantifiable behaviors, in contrast to subjective mental states. Humanistic psychology—An approach to psychology that emphasizes the special qualities and potential of human beings. It emphasizes the positive qualities in people, rather than the characteristics of maladaptive or unhealthy individuals. Peak experience—An awe-inspiring emotional experience, characterized by a sense of timelessness, unity, and wonder. Maslow found that selfactualizing people were more likely to have peak experiences, but that ordinary individuals could have these experiences as well. Self-actualization—The development of one’s full potential as a person through creativity, independence, spontaneity, and a grasp of the real world. Self-esteem—A sense of competence, achievement, and self-respect. Maslow felt that the most stable source of self-esteem is genuine accomplishment rather than public acclaim or praise. Transcendence needs—Needs or values that go beyond the need for self-actualization. These values involve a higher purpose and concern for the good of the community rather than personal welfare.

of needs is also used in medical and social welfare settings, providing a set of theoretical guidelines for understanding the concerns of people suffering from physical illness, disabilities, or other life problems. In addition to these settings, the theory is frequently applied in educational and career counseling, in which it is used to help clients select appropriate goals for their lives. Maslow’s theory has been criticized because it is difficult to evaluate objectively. Many of the phenomena that Maslow describes are subjective and difficult to quantify. Most studies rely on self-reported data, which are notoriously subject to distortion and inaccuracies. Because studies based on Maslow’s concepts often focus on value-laden topics, it is also difficult for researchers to remain objective. Maslow acknowledged these difficulties himself, but thought that human potential was so important that it should be explored without regard to current limitations of scientific accuracy. 1502

The field of personality theory has changed considerably over the 30 years since Maslow’s death in 1970. The cognitive behaviorist approach has become increasingly influential, answering some of Maslow’s criticisms of earlier psychoanalytic and behaviorist theories. Humanistic theories have become less popular in academic and research settings, with newer approaches generating more research topics. Nonetheless, Maslow’s theory, with its positive emphasis, remains influential, particularly in such applied settings as counseling, industrial management, and health care.

Professional implications Maslow’s understanding of human motivation has had an important influence in the fields of nursing and allied health. The needs hierarchy provides a useful framework for understanding patients, and this framework has been incorporated into several important theories of medical and nursing care. One major approach to nursing theory has been described as a “needs” approach, and it relies on Maslow’s need hierarchy as well as the developmental theories of Erik Erikson. Needs-oriented theories emphasize the nurse’s role in helping the patient to meet his or her physiological and psychosocial needs. Although more recent theories have moved away from this position, the needs hierarchy has been useful in helping care providers look for the “big picture” of a given patient’s situation. A description of Maslow’s needs hierarchy is still included in many textbooks for students of nursing and allied health. As the realities of health care in a managed care environment have affected medical professionals, Maslow’s theory has also found a role in human resource management for health care. The needs hierarchy offers one approach to such human resource issues as quality assurance, employee burnout, and job satisfaction. By understanding the larger set of needs that health care providers bring to their professions, human resource managers can do a better job of coping with and planning for problems that arise in the medical workplace. Maslow’s ideas remain influential because they make sense of a certain range of human behavior. On the other hand, Maslow’s emphasis on a strict hierarchical ordering of human needs has not held up well in other respects because it has never been empirically substantiated. The connections between motivation and external behavior in human beings are more complex than Maslow’s theory allows. People strive to satisfy simultaneous needs for love, safety, self-esteem, etc. Moreover, people who have their “lower” needs met in a satisfactory fashion do not invariably seek the fulfilment of “higher” needs, as the behavior of many wealthy or

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Resources BOOKS

Burger, Jerry M. Personality. 5th ed. Belmont, CA: Wadsworth/Thomson Learning, 2000. Goble, Frank G. The Third Force: The Psychology of Abraham Maslow. New York: Grossman Publishers, 1970. Maslow, Abraham H. Motivation and Personality. 2nd ed. New York: Harper and Row, 1970. Maslow, Abraham H. Toward a Psychology of Being. 2nd ed. New York: Van Nostrand Reinhold, 1968. Meleis, Afaf I. Theoretical Nursing: Development and Progress. 2nd ed. Philadelphia: J. B. Lippincott Co., 1991. Sargent, S. Stansfeld. “Abraham H. Maslow (1908-1970).” International Encyclopedia of Psychiatry, Psychology, Psychoanalysis, & Neurology. Vol. 7. Ed. Benjamin B. Wolman. New York: Aesculapius Publishers, Inc., 1977. Smither, Robert D. The Psychology of Work and Human Performance. 2nd ed. New York: HarperCollins, 1994. PERIODICALS

Crapanzano, S. “Motivation, morale, education, and leadership.” Pelican News 56 (March 2000): 6. Zimberg, Stephen E., and Dolores G. Clement. “Physician motivation, satisfaction and survival.”Medical Group Management Journal 44 (July/August 1997): 19-26; 63. ORGANIZATIONS

American Psychological Association. 750 First Street, NE, Washington, DC 20002. (800) 374-2721.

Denise L. Schmutte, Ph.D.

Massage therapy Definition Massage therapy is the scientific manipulation of the soft tissues of the body for the purpose of normalizing those tissues and consists of manual techniques that include applying fixed or movable pressure, holding, and/or causing movement of or to the body.

Origins Massage therapy is one of the oldest health care practices known to history. References to massage are found in Chinese medical texts more than 4,000 years old. Massage has been advocated in Western health care practices at least since the time of Hippocrates, the “Father of Medicine.” In the fourth century B.C. Hippocrates wrote, “The physician must be acquainted with many things and assuredly with rubbing” (the ancient Greek term for massage was rubbing). The roots of modern, scientific massage therapy go back to Per Henrik Ling (1776–1839), a Swede, who developed an integrated system consisting of massage and active and passive exercises. Ling established the Royal Central Gymnastic Institute in Sweden in 1813 to teach his methods. Modern, scientific massage therapy was introduced in the United States in the 1850s by two New York physicians, brothers George and Charles Taylor, who had studied in Sweden. The first clinics for massage therapy in the United States were opened by two Swedish physicians after the Civil War period. Doctor Baron Nils Posse operated the Posse Institute in Boston and Doctor Hartwig Nissen opened the Swedish Health Institute near the Capitol in Washington, D.C. Although there were periods when massage fell out of favor, in the 1960s it made a comeback in a different way as a tool for relaxation, communication, and alternative healing. Today, massage is one of the most popular healing modalities. It is used by conventional, as well as alternative, medical communities and is now covered by some health insurance plans.

Benefits Generally, massage is known to affect the circulation of blood and the flow of blood and lymph, reduce muscular tension or flaccidity, affect the nervous system through stimulation or sedation, and enhance tissue healing. These effects provide a number of benefits: • reduction of muscle tension and stiffness

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famous individuals indicates. In addition, the drive to satisfy “higher” needs takes precedence over “lower” needs more frequently than Maslow thought. In sum, human beings are influenced by a wide range of needs and motives. For some people, love, safety, and security are paramount values, while others are motivated by desires for power and dominance. Lastly, human beings are shaped to a considerable extent by their cultures, and cultures differ widely in the sets of values that they emphasize and transmit to their members. For example, the very notion of a “self” is more consistently individualistic in Western societies, whereas it incorporates family relationships in Eastern cultures. Maslow’s hierarchy of needs reflects the values of twentieth-century Western middle-class males; it is not culture-neutral and is therefore not universally applicable to all periods of human history or to all contemporary societies.

Massage therapy

• relief of muscle spasms

phatic, nervous, and other systems of the body. The basic philosophy of massage therapy embraces the concept of vis Medicatrix naturae, which is aiding the ability of the body to heal itself, and is aimed at achieving or increasing health and well-being.

• greater flexibility and range of motion • increase of the ease and efficiency of movement • relief of stress and aide of relaxation • promotion of deeper and easier breathing • improvement of the circulation of blood and movement of lymph • relief of tension-related conditions, such as headaches and eyestrain • promotion of faster healing of soft tissue injuries, such as pulled muscles and sprained ligaments, and reduction in pain and swelling related to such injuries • reduction in the formation of excessive scar tissue following soft tissue injuries • enhancement in the health and nourishment of skin • improvement in posture through changing tension patterns that affect posture • reduction in stress and an excellent stress management tool • creation of a feeling of well-being • reduction in levels of anxiety • increase in awareness of the mind-body connection • promotion of a relaxed state of mental awareness Massage therapy also has a number of documented clinical benefits. For example, massage can reduce anxiety, improve pulmonary function in young asthma patients, reduce psycho-emotional distress in persons suffering from chronic inflammatory bowel disease, increase weight and improve motor development in premature infants, and may enhance immune system functioning. Some medical conditions that massage therapy can help are: allergies, anxiety and stress, arthritis, asthma and bronchitis, carpal tunnel syndrome and other repetitive motion injuries, chronic and temporary pain, circulatory problems, depression, digestive disorders, tension headache, insomnia, myofascial pain, sports injuries, and temporomandibular joint dysfunction.

Description Massage therapy is the scientific manipulation of the soft tissues of the body for the purpose of normalizing those tissues and consists of a group of manual techniques that include applying fixed or movable pressure, holding, and/or causing movement of or to the body. While massage therapy is applied primarily with the hands, sometimes the forearms or elbows are used. These techniques affect the muscular, skeletal, circulatory, lym1504

Touch is the fundamental medium of massage therapy. While massage can be described in terms of the type of techniques performed, touch is not used solely in a mechanistic way in massage therapy. One could look at a diagram or photo of a massage technique that depicts where to place one’s hands and what direction the stroke should go, but this would not convey everything that is important for giving a good massage. Massage also has an artistic component. Because massage usually involves applying touch with some degree of pressure and movement, the massage therapist must use touch with sensitivity in order to determine the optimal amount of pressure to use for each person. For example, using too much pressure may cause the body to tense up, while using too little may not have enough effect. Touch used with sensitivity also allows the massage therapist to receive useful information via his or her hands about the client’s body, such as locating areas of muscle tension and other soft tissue problems. Because touch is also a form of communication, sensitive touch can convey a sense of caring—an essential element in the therapeutic relationship—to the person receiving massage. In practice, many massage therapists use more than one technique or method in their work and sometimes combine several. Effective massage therapists ascertain each person’s needs and then use the techniques that will meet those needs best. Swedish massage uses a system of long gliding strokes, kneading, and friction techniques on the more superficial layers of muscles, generally in the direction of blood flow toward the heart, and sometimes combined with active and passive movements of the joints. It is used to promote general relaxation, improve circulation and range of motion, and relieve muscle tension. Swedish massage is the most commonly used form of massage. Deep tissue massage is used to release chronic patterns of muscular tension using slow strokes, direct pressure, or friction directed across the grain of the muscles. It is applied with greater pressure and to deeper layers of muscle than Swedish, which is why it is called deep tissue and is effective for chronic muscular tension. Sports massage uses techniques that are similar to Swedish and deep tissue, but are specially adapted to deal with the effects of athletic performance on the body and

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Massage therapy

Basic Effleurage

Circular Friction

Rolling Petrissage

Beating Percussion

Four basic massage techniques. In basic effleurage, keep firm contact with the skin as you stroke down your partner’s back. In rolling petrissage, push the heel of one hand across your partner’s back, while you pull and lift the skin with the fingers of the other. In circular friction, rotate your thumb in small circles on the ropelike tissues of your partner’s back. In beating percussion, use a loose fist to gently beat the fleshy areas of the body. (Illustration by Electronic Illustrators Group.)

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the needs of athletes regarding training, performing, and recovery from injury. Neuromuscular massage is a form of deep massage that is applied to individual muscles. It is used primarily to release trigger points (intense knots of muscle tension that refer pain to other parts of the body), and also to increase blood flow. It is often used to reduce pain. Trigger point massage and myotherapy are similar forms. Acupressure applies finger or thumb pressure to specific points located on the acupuncture meridians (channels of energy flow identified in Asian concepts of anatomy) in order to release blocked energy along these meridians that causes physical discomforts, and re-balance the energy flow. Shiatsu is a Japanese form of acupressure. The cost of massage therapy varies according to geographic location, experience of the massage therapist, and length of the massage. In the United States, the average range is from $35–60 for a one hour session. Massage therapy sessions at a client’s home or office may cost more due to travel time for the massage therapist. Most sessions are one hour. Frequency of massage sessions can vary widely. If a person is receiving massage for a specific problem, frequency can vary widely based on the condition, though it usually will be once a week. Some people incorporate massage into their regular personal health and fitness program. They will go for massage on a regular basis, varying from once a week to once a month. The first appointment generally begins with information gathering, such as the reason for getting massage therapy, physical condition and medical history, and other areas. The client is asked to remove clothing to one’s level of comfort. Undressing takes place in private, and a sheet or towel is provided for draping. The massage therapist will undrape only the part of the body being massaged. The client’s modesty is respected at all times. The massage therapist may use an oil or cream, which will be absorbed into the skin in a short time. To receive the most benefit from a massage, generally the person being massaged should give the therapist accurate health information, report discomfort of any kind (whether it’s from the massage itself or due to the room temperature or any other distractions), and be as receptive and open to the process as possible. Insurance coverage for massage therapy varies widely. There tends to be greater coverage in states that license massage therapy. In most cases, a physician’s prescription for massage therapy is needed. Once massage therapy is prescribed, authorization from the insurer may be needed if coverage is not clearly spelled out in one’s policy or plan. 1506

Preparations Going for a massage requires little in the way of preparation. Generally, one should be clean and should not eat just before a massage. One should not be under the influence of alcohol or non-medicinal drugs. Massage therapists generally work by appointment and usually will provide information about how to prepare for an appointment at the time of making the appointment.

Precautions Massage is comparatively safe. However, it is generally contraindicated, i.e., it should not be used if a person has one of the following conditions: advanced heart diseases, hypertension (high blood pressure), phlebitis, thrombosis, embolism, kidney failure, cancer if massage would accelerate metastasis (i.e., spread a tumor) or damage tissue that is fragile due to chemotherapy or other treatment, infectious diseases, contagious skin conditions, acute inflammation, infected injuries, unhealed fractures, dislocations, frostbite, large hernias, torn ligaments, conditions prone to hemorrhage, and psychosis. Massage should not be used locally on affected areas for the following conditions: rheumatoid arthritis flare up, eczema, goiter, and open skin lesions. Massage may be used on the areas of the body that are not affected by these conditions. In some cases, precautions should be taken before using massage for the following conditions: pregnancy, high fevers, osteoporosis, diabetes, recent postoperative cases in which pain and muscular splinting (i.e., tightening as a protective reaction) would be increased, apprehension, and mental conditions that may impair communication or perception. In such cases, massage may or may not be appropriate. The decision on whether to use massage must be based on whether it may cause harm. For example, if someone has osteoporosis, the concern is whether bones are strong enough to withstand the pressure applied. If one has a health condition and has any hesitation about whether massage therapy would be appropriate, a physician should be consulted.

Side effects Massage therapy does not have side effects. Sometimes people are concerned that massage may leave them too relaxed or too mentally unfocused. To the contrary, massage tends to leave people feeling more relaxed and alert.

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Before 1939, more than 600 research studies on massage appeared in the main journals of medicine in English. However, the pace of research was slowed by medicine’s disinterest in massage therapy. Massage therapy research picked up again in the 1980s, as the growing popularity of massage paralleled the growing interest in complementary and alternative medicine. Well designed studies have documented the benefits of massage therapy for the treatment of acute and chronic pain, acute and chronic inflammation, chronic lymphedema, nausea, muscle spasm, various soft tissue dysfunctions, anxiety, depression, insomnia, and psycho-emotional stress, which may aggravate mental illness. Premature infants treated with daily massage therapy gain more weight and have shorter hospital stays than infants who are not massaged. A study of 40 low-birthweight babies found that the 20 massaged babies had a 47% greater weight gain per day and stayed in the hospital an average of six days less than 20 infants who did not receive massage, resulting a cost savings of approximately $3,000 per infant. Cocaine-exposed, preterm infants given massage three times daily for a 10 day period showed significant improvement. Results indicated that massaged infants had fewer postnatal complications and exhibited fewer stress behaviors during the 10 day period, had a 28% greater daily weight gain, and demonstrated more mature motor behaviors. A study comparing 52 hospitalized depressed and adjustment disorder children and adolescents with a control group that viewed relaxation videotapes, found massage therapy subjects were less depressed and anxious, and had lower saliva cortisol levels (an indicator of less depression). Another study showed massage therapy produced relaxation in 18 elderly subjects, demonstrated in measures such as decreased blood pressure and heart rate and increased skin temperature. A combination of massage techniques for 52 subjects with traumatically induced spinal pain led to significant improvements in acute and chronic pain and increased muscle flexibility and tone. This study also found massage therapy to be extremely cost effective, with cost savings ranging from 15–50%. Massage has also been shown to stimulate the body’s ability to naturally control pain by stimulating the brain to produce endorphins. Fibromyalgia is an example of a condition that may be favorably affected by this effect. A pilot study of five subjects with symptoms of tension and anxiety found a significant response to massage

therapy in one or more psycho-physiological parameters of heart rate, frontalis and forearm extensor electromyograms (EMGs) and skin resistance, which demonstrate relaxation of muscle tension and reduced anxiety. Lymph drainage massage has been shown to be more effective than mechanized methods or diuretic drugs to control lymphedema secondary to radical mastectomy, consequently using massage to control lymphedema would significantly lower treatment costs. A study found that massage therapy can have a powerful effect upon psycho-emotional distress in persons suffering from chronic inflammatory bowel disease. Massage therapy was effective in reducing the frequency of episodes of pain and disability in these patients. Massage may enhance the immune system. A study suggests an increase in cytotoxic capacity associated with massage. A study of chronic fatigue syndrome subjects found that a group receiving massage therapy had lower depression, emotional distress, and somatic symptom scores, more hours of sleep, and lower epinephrine and cortisol levels than a control group.

Training and certification The generally accepted standard for training is a minimum of 500 classroom hours. Training should include anatomy, physiology, pathology, massage theory and technique, and supervised practice. Most massage therapists also take additional courses and workshops during their careers. In the United States, massage therapists are currently licensed by 29 states, the District of Columbia, and a number of localities. Most states require 500 or more classroom hours of training from a recognized training program and passing an examination. A national certification program was inaugurated in June 1992 by the National Certification Board for Therapeutic Massage and Bodywork (NCBTMB). The NCBTMB program is accredited by the National Commission for Certifying Agencies, the chief outside agency for evaluating certification programs. Those certified can use the title Nationally Certified in Therapeutic Massage and Bodywork (NCTMB). Most states use the NCBTMB exam for their licensing exams. A national accreditation agency, the Commission on Massage Therapy Accreditation, designed according to the guidelines of the U.S. Department of Education, currently recognizes about 70 training programs. The Accrediting Commission of Career Schools and Colleges of Technology and the Accrediting Council for Continuing Education and Training also accredit massage training programs.

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Research and general acceptance

Mastitis

Resources BOOKS

Beck, Mark F. Milady’s Theory and Practice of Therapeutic Massage. Milady Publishing, 1994. Capellini, Steve. Massage Therapy Career Guide for HandsOn Success. Milady Publishing, 1998. Downing, George. The Massage Book. New York: Random House, 1998. Loving, Jean E. Massage Therapy: Theory and Practice. Appleton & Lange, 1998. PERIODICALS

Field, T., W. Sunshine, M. Hernandez-Reif, and O. Quintino. “Chronic fatigue syndrome: massage therapy effects on depression and somatic symptoms in chronic fatigue syndrome.” Journal of Chronic Fatigue Syndrome (1997): 43-51. Ironson, G., T. Field, F. Scafidi, and M. Hashimoto. “Massage therapy is associated with enhancement of the immune system’s cytotoxic capacity.” International Journal of Neuroscience (February 1996): 205-217. Joachim, G. “The effects of two stress management techniques on feelings of well-being in patients with inflammatory bowel disease.” Nursing Papers (1983): 4, 5-18. Kaarda, B., and O. Tosteinbo. “Increase of plasma betaendorphins in connective tissue massage.” General Pharmacology (1989): 487-489. Scafidi, F., T. Field, A. Wheeden, S. Schanberg, C. Kuhn, R. Symanski, E. Zimmerman, and E. S. Bandstra. “Cocaine exposed preterm neonates show behavioral and hormonal differences.” Pediatrics (June 1996): 851-855. Weintraub, M. “Shiatsu, Swedish muscle massage, and trigger point suppression in spinal pain syndrome.” American Massage Therapy Journal 31, Summer 1992:3; 99-109. ORGANIZATIONS

American Massage Therapy Association. .

Elliot Greene

Mastitis Definition Mastitis is an infection of the ducts of the breast. It usually only occurs in women who are breastfeeding their babies.

Description In the process of breastfeeding, the unaccustomed pull and tug by the infant suckling at the breast may 1508

Mastitis is usually caused by bacterial infection through damaged nipples during breastfeeding. Mastitis can also be caused by a hormone imbalance and usually occurs at puberty or in the newborn. (Photograph by Dr. P. Marazzi, Photo Researchers, Inc. Reproduced by permission.)

result in the mother’s nipples may becoming sore, cracked, or slightly abraded. This creates a tiny opening in the breast, through which bacteria can enter. The presence of milk, with high sugar content, gives the bacteria an excellent source of nutrition. Under these conditions, the bacteria are able to multiply, until they are plentiful enough to cause an infection within the breast. Mastitis is most likely to occur in the fifth and sixth week of the postpartum period. Studies indicate an incidence of mastitis from 6–33% of all women who have a history of breastfeeding.

Causes and symptoms The most common bacteria causing mastitis is Staphylococcus aureus, but sometimes Escherichia coli is responsible. In rare instances, Streptococcus can also induce an episode of mastitis. In 25–30% of people, Staphylococcus aureus is present on the skin, lining normal, uninfected nostrils. It is probably this bacteria, clinging to the baby’s nostrils, that is available to create infection when an opportunity (i.e., a crack in the nipple) presents itself. A sluggish flow of milk and trauma to the nipples are the main contributing factors to the development of mastitis. Fatigue, stress, and returning to work may also predispose a nursing mother to developing the condition.

Diagnosis The clinic, midwife, or office of the physician will most likely receive a call from the mother at home. The condition rarely occurs in the hospital. She will likely report general malaise, fatigue, headache, chills, an increased heart rate, and flu-like symptoms. Usually, only one breast is involved. An area of the affected breast

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Lumps in the breasts may result from plugged milk ducts. Plugged ducts can contribute to mastitis. If the mother describes pain in both breasts, then the condition might be engorgement of the breasts, as opposed to mastitis, which almost always occurs unilaterally. A definitive diagnosis of the offending pathogen involves obtaining a sample of breast milk from the infected breast. A culture is done to identify the pathogen. In practice, however, laboratory studies are done infrequently because antibiotic therapy is initiated before results are returned, and insurance companies may not cover the cost of the tests.

Treatment A penicillinase-resistant penicillin or a cephalosporin, for six to 10 days, can both be used to treat mastitis. Low doses of erythromycin or trimethoprin-sulfamethoxazole over an extended period of time have been used to treat chronic mastitis. Breastfeeding should be continued, because the rate of abscess formation in the infected breast increases sharply among women who stop breastfeeding during a bout of mastitis. Some symptoms of mastitis respond solely to frequent breastfeeding and pumping, without requiring antibiotic therapy. Most practitioners allow women to take acetaminophen while nursing, to relieve both fever and pain. Since almost all drugs the mother takes appear in her breast milk, any medication taken by breastfeeding women must also be safe for the baby. Warm, moist compresses applied to the affected breast can be soothing. Increasing fluid intake and bed rest are also recommended.

Prognosis Prognosis for uncomplicated mastitis is excellent. A small percentage of women with mastitis will end up with an abscess within the affected breast. This complication will require a surgical procedure to drain the pus. In the case of a small abscess, aspiration with a needle under the direction of ultrasound may be the preferred method of treatment. A larger abscess requires an incision be made into the affected area, so that drainage can occur. A drain in the wound may be placed to facilitate further drainage. Manual expression of the site allows for elimination of pus and milk. The wound normally heals in one to two weeks.

Mastitis

becomes swollen, red, hard, and painful. A red streak may be evident. Often, the location of the infection is in the upper, outer quadrant, which is the location of most of the glandular tissue.

KEY TERMS Abscess—A persistent pocket of pus. Lactation consultant—A health care provider who is certified in managing the breastfeeding concerns of mothers.

Health care team roles The registered nurse (R.N.) and lactation consultant are frequently the first to speak with the mother who has mastitis. Rapid diagnosis, followed by treatment, can prevent the formation of an abscess. It is imperative to help the mother understand that continuation of breastfeeding is part of successful management of mastitis. It should be emphasized to her that abrupt cessation will actually worsen the problem. Patient education When counseling a mother who has mastitis, the health care provider should encourage her to breastfeed frequently and to use a breast pump if the baby does not adequately empty the breast. The mother should be instructed to start each nursing session by breastfeeding her baby on the breast that is not affected, because the baby’s initial sucks will be the most vigorous ones. Once the baby switches to the affected breast, the milk will have already started to flow in “letdown reflex,” and the baby’s sucking will be less painful. The health care provider should instruct the mother to rest, increase her fluid intake, and take medications as prescribed.

Prevention To prevent mastitis, mothers should breastfeed frequently, ensuring adequate emptying of each breast at least every other nursing session. Handwashing is important in decreasing the chance of spreading bacteria to the breasts. Mothers should also be instructed to avoid wearing tight bras, skipping feedings, and becoming overly tired. Resources BOOKS

Biancuzzo, Marie. Breastfeeding the Newborn. Herndon, VA: Mosby, 1999. Cunningham, F. Gary, et al., eds. Williams Obstetrics. Stamford, CT: Appleton & Lange, 1997. Riordan, Jan, and Kathleen Auerbach. Breastfeeding and Human Lactation. Boston, MA: Jones and Bartlett, 1999.

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ORGANIZATIONS

LaLeche League International. 1400 N. Meacham Rd., Schaumburg, IL 60173-4048. (847) 519-7730 or (800) LALECHE. .

then heart transplantation becomes the desired course of treatment. In this case intermediate- to long-term mechanical circulatory support devices are available. These longer-term devices include ECMO, Thoratec, Novacor, HeartMate, and Cardiowest products.

Nadine M. Jacobson

Description

MD see Muscular dystrophy Mean corpuscular hemoglobin see Red blood cell indices Mean corpuscular volume see Red blood cell indices

Mechanical circulation support Definition Mechanical circulatory support is used to treat patients with advanced heart failure. A mechanical pump is surgically implanted to provide pulsatile or nonpulsatile flow of blood to supplement or replace the blood flow generated by the native heart. Types of circulatory support pumps include pneumatic and electromagnetic pumps. Rotary pumps, which are also available, propel blood by axial or centrifugal force, or by the use of positive displacement roller pumps.

Purpose Heart failure causes low cardiac output, which results in inadequate blood pressure and reduced blood flow to the brain, kidneys, heart, and/or lungs. Pharmaceutical and palliative surgical treatments are typically exhausted before mechanical circulatory support is initiated. The extent of failure exhibited by one or both ventricles of the heart determines if univentricular or biventricular support is required. In either case, blood flow is supplemented or replaced by a mechanical circulatory support device. The device works by removing blood from the inlet of the ventricle(s) and reinjecting it at the outlet of the ventricle(s) in order to increase blood pressure and blood flow to the brain, kidneys, heart, and lungs. The Abiomed and Thoratec devices along with the intra-aortic balloon pump (IABP), centrifugal pump, and extracorporeal membrane oxygenation (ECMO) are systems that are meant to sustain the patient until the heart recovers. If recovery does not occur, or is not expected, 1510

Tertiary care facilities have the staff and equipment to provide treatment for heart failure patients, with the use of mechanical circulatory support devices. Short-, intermediate-, and long-term support requires bedside monitoring of the equipment and patient throughout treatment. The specialized nature of the equipment and intensive patient care requires dedicated staff who are able to provide continuous bedside treatment. In most instances, patients receive pharmaceuticals that anticoagulate the blood by blocking the clotting factors from interacting with the foreign surfaces of the device and each other. Frequent laboratory testing determines the proper amount of medication required to prevent blood clots. To mimic the lining of blood vessels, some surfaces of the device attract native cells, which stick to the device surface, thereby eliminating the need for anticoagulation. Blood flow generated by these devices is able to sustain blood pressure and flow to the heart, kidneys, liver, and brain. Temporary assist devices sustain vital organ tissues in situations where recovery of the heart function is anticipated. Long-term support devices sustain patients until a donor heart is available for transplantation. Venoarterial ECMO circulatory support provides cardiopulmonary bypass. Both cardiac and pulmonary function can be supplemented with this device. The complexity of care and highly trained staff with specialized equipment limit the availability of ECMO to tertiary care facilities. Surgical cannulation is venoarterial, using the femoral or intrathoracic vessels. Postoperative care in the critical care unit requires dedicated bedside staffing. Short- to intermediate-term devices VENOARTERIAL ECMO. The positive displacement

roller head pump provides pulsatile or non-pulsatile blood flow to the systemic circulation. Tubing connected to the venous cannula carries blood to the roller pump. The roller assembly rotates and engages the tubing, which is then compressed against the pump’s housing, propelling blood ahead of the roller head. Rotational frequency and tubing inner diameter determine blood flow. Blood flow to the lungs is reduced as blood is drained from the venous circulation. Blood pumped by the left ventricle is also reduced as blood is returned directly to

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Tertiary care facilities have the staff and equipment to provide treatment to heart failure patients with the use of mechanical circulatory support devices. Post-operative care in critical care units requires continuous monitoring by dedicated staff.

As cardiac function improves, flow from ECMO support is reduced, allowing the heart to gradually resume normal function. The cannulae are surgically removed from the patient once the heart can maintain adequate cardiac output. Systemic anticoagulation is required throughout the length of support, and often leads to complications of stroke and coagulapathies. Longterm use of ECMO is limited since the patient is immobilized and sedated during treatment.

The cannulae are passed through the chest wall to attach to a pump that is magnetically coupled to the control unit, which is kept at the patient’s bedside during treatment. The centrifugal force draws blood into the device and propels it to the arterial cannula. Rotational speed determines the amount of blood flow, which is measured by a flowmeter. If rotational frequency is too low, blood may flow in the wrong direction since the system is non-occlusive in nature.

IABP. Ease of insertion for placement in the aorta makes the IABP the most often used univentricular assist device. Tertiary care centers provide this service in the cardiac catheterization laboratory, operating room, critical care unit, and emergency room. Secondary care level hospitals can also employ this technology. Welltrained staff are required to monitor equipment at regular intervals and troubleshoot problems.

As the heart recovers, flow is decreased from the centrifugal pump until the device can be removed. The native heart is then able to maintain blood pressure and flow. Anticoagulant is delivered continuously during treatment with a centrifugal pump, and patient immobilization limits the length of support to several weeks.

Left ventricular support with the IABP reduces the workload of the heart and increases blood flow to the vital organs. Once in position, the IABP times the inflation and deflation of the balloon catheter to the electrocardiogram or arterial blood pressures waveform. Helium or carbon dioxide gases are used to fill the balloon, although low molecular weight helium is preferred because it can be transported rapidly. Carbon dioxide has the advantage that it is highly soluble in the blood in case of balloon rupture. The balloon inflates during diastole to deliver increased oxygen saturated blood to the heart. Blood flow is also increased to the arteries distal to the balloon, since flow is not occluded in either direction. Deflation of the balloon occurs prior to systole. Less contractile force is required for the heart to eject blood against a decreased afterload.

When short-term support devices, such as ECMO, IABP, and the centrifugal pump are ineffective to sustain the patient to recovery or organ transplantation, a medium or long-term device is required. An advantage of treatment with a medium to long-term device is that it allows the patient to be mobile. In some instances patients have been able to leave the hospital for continued treatment at home with the implanted device. Complete recovery of the heart has been demonstrated in 5–15% of patients being supported as a bridge to organ transplantation.

With recovery of the heart, the device is timed to inflate with every second or third heart beat. The catheter is removed, non-surgically, when the heart can sustain blood pressure and systemic blood flow. Therapeutic anticoagulation is achieved with minimal pharmaceutical anticoagulant throughout the treatment. The device can be in place up to several weeks, but duration is limited because the patient must be immobilized during the treatment. CENTRIFUGAL PUMPS. Centrifugal pumps are able to provide uni-ventricular or bi-ventricular support to the ventricles. Blood is removed from the left or right atrium and returned to the aorta or pulmonary artery, respectively, therefore surgery is required to place the device.

Intermediate- to long-term devices

PNEUMATIC PULSATILE. Pneumatically driven pulsatile paracorporeal mechanical circulatory support devices provide pulsatile support for the left or right ventricle, or both. Devices implanted in at least 100 patients by January 2001 include Abiomed, Thoratec, HeartMate, and Cardiowest brands. Staff are trained to monitor and troubleshoot equipment, thus limiting use to tertiary care facilities.

Cannulation of the left or right atrium, along with the aorta or pulmonary artery, respectively, requires a surgical approach. The cables that connect to the control center are tunneled out of the chest wall and the housing is typically implanted in the chest cavity, except Abiomed, which remains extracorporeal. The rigid outer housing encloses two compartments separated by a flexible boundary. Valves located at the inlet and outlet of the device direct the path of blood flow from high to low pressure, preventing back flow after ejection. Inflation of the gas chamber creates pressure in the blood chamber,

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the systemic circulation. The heart is allowed to rest, pumping less blood than needed to maintain pressure and flow to the vital organs. An oxygenator is placed after the roller pump in the circuit. Gas exchange occurs prior to return of the blood to the arterial circulation.

Mechanical circulation support

er, rather than cables tunneled through the chest wall decrease the risk of infection.

KEY TERMS Anticoagulant—Pharmaceuticals to prevent clotting proteins and platelets in the blood to be activated to form a blood clot. Cannulae—Tubes that provide access to the blood once inserted into the heart or blood vessels. Cardiac—Of or relating to the heart. Cardiac output—The liter per minute blood flow generated by contraction of the heart. Cardiopulmonary bypass—Diversion of blood flow away from the right atrium and return of blood beyond the left ventricle, to bypass the heart and lungs. Console—A freestanding device that monitors, measures, and controls parameters associated with the mechanical circulatory support device it operates. Extracorporeal—Circulation of blood outside of the body. Intracorporeal—Circulation of blood inside the body. Paracorporeal—Circulation of blood near or close to the body.

which opens the outlet valve. Blood is then ejected until the chamber empties and pressure in the chamber decreases, closing the outlet valve. The inlet valve opens when the pressure is low enough in the blood chamber. Blood fills from the atrium and the inlet valve closes once the blood volume has increased the pressure. The cycle repeats itself when the controller fills the gas chamber again. The ejection is not typically timed to that of the native heart. The heart is emptied of blood by the assist device so there is little ejection from the native heart. Removal of the device occurs at the time of cardiac transplant, unless the native heart has healed during support. Anticoagulation is achieved by low doses of pharmaceuticals. Some patients regain mobility while assisted by these devices. ELECTRICAL PULSATILE. Novacor and HeartMate make devices that run electrically. Pusher plates activate the compression of the blood chamber for pulsatile blood flow. Cannulation and cable positioning are the same as for pneumatic devices. Valves are required for direction of blood flow and operation is the same as for pneumatic mechanical circulatory support. Electronic connections that use magnetic induction to cross the skin barri-

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DESTINATION THERAPIES. Destination therapies intended to supplement or permanently replace the native heart are provided by chronic implantation of the mechanical circulatory support system. The Nimbus/TCI IVAS, the Jarvik 2000 IVAS, and DeBakey Micromed IVAS axial flow pumps are expected to achieve “first generation” chronic device trials in the United States. Low volume centrifugal pump technology includes the AB-180 Circulatory Support System, the HeartMate III LVAD, and the CorAide centrifugal blood pump. Pulsatile assist devices include the Thoratec Intracorporeal Ventricular Assist Device (IVAD), the Novacor II, the Worldheart HeartSaver VAD, and the Arrow Lionheart VAD. Total artificial hearts (TAH), made by Abiomed (AbioCor) and Penn State/3M, will replace the native heart. Upon removal of the native heart the TAH will be attached to the major blood vessels, thereby supplying blood pressure and flow to both the pulmonary and systemic circulation. No blood contact will be required with the Abiomed Heart Booster. The next five years, beyond 2001, expect to find these products in clinical trials, offering patients not eligible for organ transplantation a promising future.

Operation The operator powers up the control console as equipment in the surgical field is inserted into the patient. Any tubing that will be connected to the patient is filled with crystalloid solution, which displaces any air that would be harmful to the patient if it entered the bloodstream. Once all sterile connections are complete, the physician will request that mechanical circulatory support be initiated. Rotational frequency is then increased or pneumatic pumping commences. Initial adjustments may be frequent, but decrease as the patient stabilizes.

Maintenance Electrical maintenance is performed biannually to check consoles for leakage currents exceeding 100 mAmps. The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) requires documentation of all electrical and mechanical maintenance activities. Specific manufacturer maintenance protocols must be followed to prevent mechanical failure. Physician orders provide the nursing and allied health staff with specific treatment instructions for maintenance of the patient on the support device.

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The physician, nursing, and allied health staff work as a team when patients are treated with mechanical circulatory support. Support initiation requires clear communication by the device operator of changes in device status that will alert the team to the changing condition of the patient. Once stable, the patient is transported to the intensive care unit (ICU). Any change in patient status is reported to the physician. Around-the-clock bedside care is provided by nursing staff trained to operate the mechanical circulatory support, or by nursing staff and an allied health professional trained in the operation of the particular mechanical circulatory support device in use.

Training A circulation technologist earns a certificate of completion from a program accredited by the Commission on Accreditation of Allied Health Education Programs (CAAHEP). A bachelor’s degree is required before entering the certification program, or is achieved by the time of completion of the certificate-granting program. Registered nurses usually receive in-service training from a circulation technologist, an experienced nurse, or a manufacturer representative. A respiratory therapist can pursue additional training as an ECMO specialist. Those who receive on-the-job training may also provide support services. Electrical and mechanical maintenance of the control unit is provided by biomedical engineers, who hold an associates or undergraduate degree in engineering. Resources BOOKS

DeBakey, Michael, and Antonio M. Gotto. The New Living Heart. Holbrook: Adams Media Corporation, 1997. Gravelee, Glenn P., Richard F. Davis, Mark Kurusz, Joe R. Utley. Cardiopulmonary Bypass: Principles and Practice, Second Edition. Philadelphia: Lippincott Williams & Wilkins, 2000. PERIODICALS

Stevenson, Lynne W. and Robert L. Kormos, et al. “Mechanical Cardiac Support 2000: Current Applications and Future Trial Design.” The Journal of Heart and Lung Transplantation (January 2001): 1-38. ORGANIZATIONS

Commission on Accreditation of Allied Health Education Programs. 1740 Gilpin Street, Denver, CO 80218. (303) 320-7701. . Extracorporeal Life Support Organization (ELSO). 1327 Jones Drive Suite 101, Ann Arbor, MI 48105. (734) 998-6600. .

Joint Commission on Accreditation of Health Organizations. One Renaissance Boulevard, Oakbrook Terrace, IL 60181. (630) 792-5000. OTHER

“Spare Hearts: A Houston Chronicle Four-Part Series.” The Houston Chronicle, October 1997. .

Allison Spiwak

Mechanical traction see Spinal traction Mechanical ventilation see Ventilation assistance Median nerve entrapment see Carpal tunnel syndrome

Mediastinoscopy Definition Mediastinoscopy is a surgical procedure that allows physicians to view areas of the mediastinum, the cavity behind the breastbone that lies between the lungs. The organs in the mediastinum include the heart and its vessels, the lymph nodes, trachea, esophagus, and thymus. Mediastinoscopy is most commonly used to detect or stage cancer. It is also ordered to detect infection, and to confirm diagnosis of certain conditions and diseases of the respiratory organs. The procedure involves insertion of an endotracheal tube, followed by a small incision in the chest. A mediastinoscope is inserted through the incision. The purpose of this equipment is to allow the physician to directly see the organs inside the mediastinum, and to collect tissue samples for laboratory study.

Purpose This procedure allows direct visualization of the tissues and organs in the chest cavity behind the sternum (breastbone) and is used to detect or evaluate infections and various types of cancers. Originally the aim of mediastinoscopy was to retrieve tissue samples for microscopic analysis. Other indications for the procedure are diagnosing pulmonary lesions and predicting the benefit of surgery. Mediastinoscopy is often the diagnostic method of choice for detecting lymphoma, including Hodgkin’s disease. Diagnosis of sarcoidosis (a chronic

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lung disease) and the staging of lung cancer can also be accomplished through mediastinoscopy. The lymph nodes in the mediastinum are likely to show if lung cancer has spread beyond the lungs (metastatis). Mediastinoscopy allows a physician to observe and extract a sample from the nodes for further study. Involvement of these lymph nodes can indicate the diagnosis and staging of lung cancer. Alternatives to mediastinoscopy, such as computed tomography (CT), magnetic resonance imaging (MRI), and new developments in ultrasonography, have resulted in a decrease in the number of mediastinoscopies performed. In addition, fine-needle aspiration and coreneedle biopsy procedures coupled with new techniques in thoracoscopy have brought alternative possibilities in examining mediastinal masses. As of 2000, the choice of procedures is one of the most controversial issues in the staging of lung cancer.

Precautions Since mediastinoscopy is a surgical procedure, it should only be performed when the benefits of the exam’s findings outweigh the risks of surgery and anesthesia. Patients who previously had mediastinoscopy should not receive it again if there is scarring present from the first exam. Mediastinoscopy is contraindicated in those patients who have a superior vena cava obstruction, due to the risk of hemorrhage. The procedure is also contraindicated for patients with a tracheotomy.

Description Mediastinoscopy is usually performed in a hospital under general anesthesia. An endotracheal tube is inserted first, after local anesthesia is applied to the throat. Once the patient is under general anesthesia, a small incision is made usually just below the neck. The surgeon may clear a path and feel the patient’s lymph nodes first to evaluate any abnormalities within the nodes. Next, the physician will insert the mediastinoscope through the incision. The scope is a narrow, hollow tube with an attached light, which allows the surgeon to see inside the area. The surgeon can insert tools through the hollow tube to help perform the exam. A sample of tissue from the lymph nodes or one of the organs can be extracted and sent for study under a microscope or on to a laboratory for further testing. In some cases, analysis of the tissue sample that shows malignancy will suggest the need for immediate surgery while the patient is already prepared and under anesthesia. In other cases, the surgeon will complete the 1514

visual study and tissue extraction and stitch the small incision closed. The patient will remain in the surgery recovery area until it is determined that the effects of anesthesia have lessened and it is safe for the patient to leave the area. The entire procedure should take about an hour, not counting preparation and recovery time. Studies have shown that mediastinoscopy is a thorough and costeffective diagnostic tool with less risk than some other procedures. Mediastinoscopy has been shown to be an effective and safe technique for biopsy of mediastinal masses in the pediatric population.

Preparation Patients should sign a consent form after having reviewed the risks of mediastinoscopy and known risks or reactions to anesthesia. The patient should have nothing to eat or drink after midnight the day of the procedure, or at least 8 hours before the exam. A local anesthetic may be applied to the throat to ease discomfort during placement of the endotracheal tube.

Aftercare Following mediastinoscopy, patients will be carefully monitored for changes in vital signs or indications of complications of the procedure or the anesthesia. A patient may have a sore throat from the endotracheal tube and temporary chest pain, soreness, or tenderness at the site of incision.

Complications Complications from the actual mediastinoscopy procedure are relatively rare. Risks to internal organs consist of puncture of the esophagus, trachea, or the blood vessels in the area. Air leaks from the lung can also occur and occasionally require additional treatment. Infection and hemorrhage are other rare complications. The usual risks associated with general anesthesia apply to this procedure. General anesthesia is safe for most patients, but it is estimated to cause major or minor complications in 3–10% of those having surgery of all types.

Results In the majority of procedures performed to diagnose cancer, a normal result would involve evidence of normal lymph nodes and no tumors. In the case of lung cancer staging, results are related to the severity and progression of the cancer. If the lymph nodes are malignant, this indicates that a cancer such as lymphoma (including Hodgkin’s disease), lung cancer, or esophageal cancer are present.

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Either a surgeon or a trained pulmonary specialist performs this procedure. An anesthesiologist will obtain a medical history and supervise the anesthesia for the procedure. A Certified Registered Nurse Anesthetist (CRNA) may work under the direction of the anesthesiologist. Operating room personnel include the scrub person and a circulator. Depending on the facility, there may be unlicensed assistive personnel (UAPs) in attendance, as well. Patient education After the procedure, the patient will experience some pain and soreness at the incision site, and possibly a sore throat from the endotracheal tube. Pain at the incision site may last for up to two weeks after the procedure. Patients should be instructed that there will be a small scar wherever the instruments were inserted. There will be a small dressing over the incision. The incision site must be kept clean and dry for 48 hours, and then patients may shower. Patients should notify their health care provider if they develop any of these symptoms: • redness at the incision site • drainage of blood or pus from the incision site • fever more than 101°F (38.3 °C) • progressive swelling at the incision site Resources BOOKS

Fraser, R. S., and P. D. Pare. “Endoscopy and Diagnostic Biopsy Procedures.” In Diagnosis of Diseases of the Chest. 4th ed., vol. I. Philadelphia: W.B. Saunders Company, 1999. George, Ronald, Richard Light, Michael Matthay, and Richard Matthay. “Lung Neoplasms.” In Chest Medicine: Essentials of Pulmonary and Critical Care Medicine. 4th ed. Philadelphia: Lippincott, 2000. Pagana, Kathleen D., and Timothy J. Pagana. Diagnostic Testing and Nursing Implications. 5th ed. St. Louis: Mosby, 1999.

KEY TERMS Endotracheal—Within the trachea, which is commonly known as the windpipe. Hodgkin’s disease—A malignant disorder of lymph tissue (lymphoma) that appears to originate in a particular lymph node and later spreads to the spleen, liver, and bone marrow. Mediastinum—The mass of organs and tissues separating the lungs. It contains the heart and large vessels, trachea, esophagus, thymus, lymph nodes, and connective tissue. Sarcoidosis—A chronic disease known for development of nodules in the lungs, skin, lymph nodes, and bones. Superior vena cava—The principal vein that drains the upper portion of the body. Tracheotomy—Incision of the trachea through the skin and muscles of the neck.

ORGANIZATIONS

American Cancer Society. 1599 Clifton Rd. NE, Atlanta, GA 30329. (800) ACS-2345. . American College of Chest Physicians. 3300 Dundee Rd, Northbrook, IL 60062-2348. (800) 343-2227. . American Lung Association. 1740 Broadway, New York, NY 10019-4374. (800) LUNG-USA. . OTHER

Harvard Medical School Family Health Guide. 8 August 2001. .

Maggie Boleyn, RN, BSN

Medicaid

PERIODICALS

Glick, R. D., and I. A. Pearse. “Diagnosis of Mediastinal Masses in Pediatric Patients Using Mediastinoscopy and the Chamberlain Procedure.” Journal of Pediatric Surgery 34, no. 4 (April 1999): 559–64. Hammoud, Z. T., and R. C. Anderson. “The Current Role of Mediastinoscopy in the Evaluation of Thoracic Disease.”Journal of Thoracic and Cardiovascular Surgery 118, no. 5 (November 1999): 894–9.

Definition Medicaid is a federal-state entitlement program for low-income citizens of the United States. The Medicaid program is part of Title XIX of the Social Security Act that became law in 1965. Medicaid offers federal matching funds to states for costs incurred in paying healthcare providers for serving covered individuals. State partici-

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services. The remaining 41% pays for nursing home and long-term care.

KEY TERMS Categorically needy—A term that describes certain groups of Medicaid recipients who qualify for the basic mandatory package of Medicaid benefits. There are categorically needy groups that states participating in Medicaid are required to cover, and others that the states have the option to cover.

States that choose to participate in Medicaid must offer the following basic services: • hospital care, both inpatient and outpatient • nursing home care • physicians’ services • laboratory and diagnostic x-ray services

DHHS—The Department of Health and Human Service. It is a federal agency that distributes funds for Medicaid.

• immunizations and other screening, diagnostic, and treatment services for children

Entitlement—A program that creates a legal obligation on the federal government to any person, business, or government entity that meets the legally defined criteria. Medicaid is an entitlement both for eligible individuals and for the states that decide to participate in it.

• health center and rural health clinic services

Federal poverty level (FPL)—The federal government’s definition of poverty used as the reference point for Medicaid eligibility for certain groups of beneficiaries. The FPL is adjusted every year to allow for inflation.

• institutional care for the mentally retarded

HCFA—Health Care Financing Administration. A federal agency that provides guidelines for the Medicaid program.

• dental and vision care for eligible adults

Medically needy—A term that describes a group whose coverage is optional with the states because of high medical expenses. These persons meet Medicaid’s category requirements (they are children or parents or elderly or disabled) but their income is too high to qualify them for “categorically needy” coverage. Supplemental Security Income (SSI)—A federal entitlement program that provides cash assistance to low-income blind, disabled, and elderly people. In most states, people receiving SSI benefits are eligible for Medicaid.

pation is voluntary, but since 1982 all 50 states have chosen to participate in Medicaid.

Description Medicaid benefits Medicaid benefits cover basic health care and longterm care services for eligible persons. About 59% of Medicaid spending covers hospital and other acute care 1516

• family planning • nurse midwife and nurse practitioner services Participating states may offer the following optional services and receive federal matching funds for them: • prescription medications • home- or community-based care for the elderly, including case management • personal care for the disabled Because the participating states are allowed to design their own benefits packages as long as they meet federal minimum requirements, Medicaid benefits vary considerably from state to state. About half of all Medicaid spending covers groups of people and services above the federal minimum. Eligibility for Medicaid Medicaid covers three major groups of low-income Americans: • Parents and children. In 1997 Medicaid covered 21 million low-income children—one-fifth of all children in the United States—and 8.6 million low-income adults in families with children. Most of these low-income adults are women. • The elderly. In 1997 Medicaid covered 4 million adults over the age of 65. Medicaid is the largest single purchaser of long-term and nursing home care in the United States. In 1997, Medicaid paid for 38% of the $115 billion spent on long-term care and 47% of the $83 billion spent on nursing home care. • The disabled. About 17% of Medicaid recipients are blind or disabled. Most of these are eligible for Medicaid because they receive assistance through the Supplemental Security Income (SSI) program.

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In most cases, persons must be citizens of the United States to be eligible for Medicaid, although legal immigrants may qualify in some circumstances depending on their date of entry. Illegal aliens are not eligible for Medicaid except for emergency care. A person must fit into an eligibility category to receive Medicaid even if their income is low. Childless couples and single childless adults who are not disabled or elderly are not eligible for Medicaid. Medicaid costs Medicaid is by far the government’s most expensive general welfare program. In 1966, Medicaid accounted for 1.4% of the federal budget, but by 2001 its share had risen to nearly 9%. Combined federal and state spending for Medicaid takes nearly 20 cents of every tax dollar. The federal government covers about 57% of Medicaid’s costs, with the states paying for the remaining 43%. As of 2001, Medicaid’s costs rise at an average annual rate of 7.9%. The federal government spent $107 billion on Medicaid in fiscal year (FY) 1999, a sum that is expected to rise to $159 billion in 2004. The states spent $81 billion to cover Medicaid costs in FY 1999. These costs are projected to increase to $120 billion by FY 2004. Although 50% of all Medicaid beneficiaries are children, most of the money (72%) goes for services for the elderly and disabled. The single largest portion of Medicaid money pays for long-term care for the elderly. Only 17% of Medicaid funds are spent on services for children. There are several factors involved in the steep rise of Medicaid costs: • The rise in the number of eligible individuals. As the life span of most Americans continues to increase, the number of elderly individuals eligible for Medicaid also rises. The fastest-growing age group in the United States is people over 85. • The price of medical and long-term care. Advances in medical technology, including expensive diagnostic imaging, keep these costs high. • The increased use of services covered by Medicaid.

• The expansion of state coverage from the minimum benefits package to include optional groups and optional services.

Viewpoints The need to contain Medicaid costs is considered one of the most problematic policy issues that legislators will face in the coming years. In addition, the complexity of the Medicaid system, its vulnerability to billing fraud and other abuses, the confusing variety in the benefits packages available in different states, and the timeconsuming paperwork are other problems that disturb taxpayers and legislators alike.

Professional implications Medicaid has increased the demand for health care services in the United States without greatly improving the quality of health care for low-income Americans. On the one hand, Medicaid’s position as the largest health insurer in the United States means that it affects the employment of several hundred thousand health care workers. In 1997, Medicaid payments went to over 5,000 hospitals, 3,000 nursing homes, 7,000 homes for the mentally retarded, 670 community health clinics, and 550 managed care plans— all of which provide employment for thousands of health care providers, administrators, and support staff. On the other hand, participation in Medicaid is optional for physicians and nursing homes. Many do not participate in the program because the reimbursement rates are low. As a result, many low-income people who are dependent on Medicaid must go to overcrowded facilities where they often receive substandard health care. Resources BOOKS

Morris, Virginia. “Paying the Way.” How to Care for Aging Parents. New York: Workman Publishing, 1996. ORGANIZATIONS

Health Care Financing Administration. United States Department of Health and Human Services. 200 Independence Avenue SW, Washington, D.C. 20201. . Kaiser Commission on Medicaid and the Uninsured. 1450 G Street NW, Suite 250, Washington, DC 20005. (202) 3475270. Fax: (202) 347-5274. . National Center for Policy Analysis. 655 15th Street NW, Suite 375, Washington, DC 20005. (202) 628-6671. Fax: (202) 628-6474. . United States Department of Health and Human Services. 200 Independence Avenue SW, Washington, D.C. 20201. .

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All Medicaid recipients must have incomes and resources below specified eligibility levels. These levels vary from state to state depending on the local cost of living and other factors. For example, in 1999 the federal poverty level (FPL) was determined to be $13,880 for a family of three on the mainland of the United States, but $15,970 in Hawaii and $17,360 in Alaska.

Medical assisting

OTHER

KEY TERMS

Kaiser Commission on Medicaid and the Uninsured. Medicaid: A Primer. Washington, DC: Kaiser Commission on Medicaid and the Uninsured, 1999.

Chiropractor—A specialist who treats disorders by manipulating the spine and bones.

Peggy Elaine Browning

Ophthalmologist—A physician who treats vision problems and diseases of the eye.

Medical assisting

Physician assistant—A professional who examines, diagnoses, and treats patients under the supervision of a physician.

Definition Medical assisting involves supporting physicians and other health care staff in a variety of administrative and clinical duties.

Podiatrist—A physician who treats foot disorders.

ter eye-drops, maintain surgical instruments, and assist ophthalmologists in surgery.

Description Medical assistants are not to be confused with physician assistants who examine, diagnose, and treat patients under the supervision of a physician. Medical assistants support physicians and other health care staff through administrative and clinical duties. The scope of their duties varies according to the size of the facilities in which they work. For example, in a large office, the medical assisting duties may be divided among a number of staff, one arranging for hospital or outside laboratory testing for patients, another scheduling appointments, with still others handle only insurance forms, keep patient records, do the bookkeeping, or are involved with direct care of the patient. Small offices may require the medical assistant to do most of these duties or to share them with one other administrative person. Clinical duties are subject to the state laws in which the medical assistant works. Some of these duties include taking patient medical histories, preparing patients for medical exams and other procedures, taking patients’ vital signs, taking x rays, taking and preparing laboratory specimens such as drawing blood, and performing basic lab tests in the office. Medical assistants may also be responsible for disposing of contaminated supplies and sterilizing equipment. They may prepare and administer medications, authorize drug refills, remove sutures, and change dressings. Specialists may employ medical assistants who have training in their specific fields. Among these are podiatrists, ophthalmologists, and chiropractors. Podiatric medical assistants take x rays, make casts of feet, and assist podiatrists in surgery. Ophthalmic medical assistants administer vision tests, test eye function, adminis1518

Medical assistant—A professional who supports physicians and other health care staff in a variety of administrative and clinical duties.

All medical assistants deal with the public, and many directly with patients. They must be neat and well groomed and have a pleasant manner. They must be able to put patients at ease and explain to them medical procedures and medication requirements. Medical assistants may advance to office manager or other administrative support positions. They may also qualify to teach medical assisting.

Work settings Medical assistants work in clean, well-lighted offices and hospitals, interacting with patients, co-workers, and supervisors daily. Most medical assistants (about 65% in 1998) are employed in physicians’ offices, while about 20% work in hospitals, nursing homes, and other related health care facilities. All others work in the offices of chiropractors, ophthalmologists, and podiatrists.

Education and training There is no formal licensing for medical assistants, and on-the-job training was considered the norm in the past. In 2001, employers are beginning to require that medical assistants have formal training. Medical assisting programs can be found in vocational/technical high schools, technical colleges, community and junior colleges, and in universities and colleges. Most technical programs offer a certificate or diploma after one year of study. Two-year programs offer an associate degree. The course of study incorporates two main areas: administrative and clinical. The administrative emphasis

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Accredited programs are certified by the Commission on Accreditation of Allied Health Education Programs and the Accrediting Bureau of Health Education Schools. In 1999, there were 590 schools accredited by these organizations. The Committee on Accreditation for Ophthalmic Medical Personnel accredited 14 others. Among the certificates that verify a standard of competency for medical assistants are the Certified Medical Assistant (the American Association of Medical Assistants), Registered Medical Assistant (the American Medical Technologists), and the Podiatric Medical Assistant Certified (the American Society of Podiatric Medical Assistants). The Joint Commission on Allied Health Personnel in Ophthalmology offers three certificates: Ophthalmic Medical Assistant, Certified Ophthalmic Technician, and Certified Ophthalmic Medical Technologist.

Advanced education and training With additional training, medical assistants may enter other related health fields such as medical technology.

Future outlook The employment outlook for medical assistants will be increasing over the next decade. Demand for medical assistants is expected to increase faster than the average for all occupations through 2008. It is expected to be one of the 10 fastest growing occupations in the United States. This is due to the increased number of group medical practices, clinics, and related health care facilities that will require assistants. Due to the flexibility of the medical assistant’s job focus, medical assistants will be highly sought after. Private outpatient settings will experience the most growth. Formally trained medical assistants will be in high demand. Currently, earnings range from $14,000 to $24,000, with the average being around $21,000 annually. Private medical practices and hospitals have the highest salary range. This is expected to increase with demand. Resources BOOKS

Fremgen, Bonnie F. Essentials of Medical Assisting: Administrative and Clinical Competencies. Upper Saddle River, NJ: Brady Prentice Hall, 1998.

Occupational Outlook Handbook, First Edition. US Department of Labor, 2000. Primm, Russell E. Medical Assistant. Mankato, MN: Capstone High/Low Books, 1998. ORGANIZATIONS

The American Association of Medical Assistants. 20 North Wacker Dr., Suite 1575, Chicago, IL 60606-2903. . Registered Medical Assistants of American Medical Technologists. 710 Higgins Rd., Park Ridge, IL. 600685765. .

Janie F. Franz

Medical billing Definition Medical billing is the process of collecting fees for medical services. A medical bill is called a claim.

Purpose The purpose of medical billing is to ensure that the provider receives fair payment for services rendered. Payment should reflect the services performed and should be received in a timely manner.

Precautions There are laws regarding medical billing procedures. Staff members involved in collecting fees must be aware of these regulations. Some of these laws are: • The Fair Debt Collection Act. This federal law dictates how and when to collect a debt. It protects patients and consumers from unlawful threats. • The Health Insurance Portability and Accountability Act of 1996 (HIPAA) contains an administrative portion that increases the efficiency of data exchange for healthcare financial transactions and protects the privacy of electronic data transmission. This protection is especially important for confidential patient records. Violators are subject to financial penalties.

Description Medical billing may be handled directly by the physician and his or her staff, or it may be administered

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is on computer technology, accounting, record keeping, medical transcription, and insurance processing. The clinical area involves course work on laboratory techniques, clinical procedures, pharmaceuticals, medication administration, first aid, and universal sterilization precautions.

Medical billing

by a third party. The third party is an independent contractor or company that specializes in handling medical billing. Physician fees A physician sets fees for his or her services. There are some important concepts in fee-setting. One is usual, reasonable, and customary (UCR). Usual fees represent the fair value of a service; customary rates are similar to those of other physicians; and reasonable rates meet the criteria for the other two factors. Another method used in setting fees is the ResourceBased Relative Value Scale (RBRVS), which examines the relative value of a service and relates it to geographic peculiarities. This method considers the time and skills needed to perform a service, intensity of the service, office (overhead) expenses, and the malpractice insurance premiums that the physician pays. The geographic differences allow for consideration of health care cost variations around the nation. It is recommended that fees be discussed with the patient in advance of treatment. Often, the medical office personnel are called upon to do this. If any co-payments are due, they are collected at the time of service. Fees may be adjusted for certain payors, such as managed care companies (HMOs, PPOs, etc.). In these cases, physicians and managed care companies negotiate fees for various services. Sometimes certain patients receive discounts. This practice may be enforced when the patient works in the health care field. Basic bookkeeping There are a few systems that help physician office staffs keep records. A day sheet is a record of all transactions that occurred in one day. This information is placed into a board called a pegboard. Each patient’s card, called a ledger card, is also inserted into the peg board. It contains a record of his or her charges, credits, and payments. This legal document should be held as long as the patient’s medical record. The information, including patient’s name, diagnosis, treatments, charges, payments, and credits, are entered into a pre-printed bill called a superbill. The medical claim When a service such as an office visit is complete, the staff begins preparing the claim or sends the patient information to a third party for billing. A physician’s office will send out a claim if that physician accepts assignment of benefits. To accept assignment of benefits, the physician must receive the patient’s signature allow1520

ing his or her office to receive payment directly from the insurance company. Claim preparation begins with proper coding. Medical procedures and diagnoses have codes. The Current Procedural Terminology (CPT), developed in 1966 by the American Medical Association, lists medical procedures and corresponding codes. Each medical procedure has a code that is listed in a CPT manual. The book is divided into sections so that similar procedures appear in the same area. The major sections of the CPT book are: • evaluation/management • anesthesia • surgery • radiology • pathology and laboratory • medicine In addition to procedure codes, there are codes for diagnoses, called ICD-9 codes. This practice was established in 1983 when Medicare began using diagnosisrelated groups (DRGs). An ICD-9 book lists each diagnosis within the DRGs. Each DRG corresponds to a fee. Coding must be accurate because it determines reimbursement. Health plans issue identification numbers to providers. This number is placed on claim forms so that payors can quickly and accurately identify providers. The medical claim also contains important information, such as: • provider name, address, telephone number, and ID number • name of insurance plan and group number • ID number of insurance holder • patient’s name, date of birth • insured person’s name, date of birth • patient’s address and telephone number • insured person’s address and telephone number • relationship between patient and insured person • other health insurance the patient may have • patient’s medical condition, and whether it was related to a job automobile accident, or other type of accident • other information, such as the patient’s history of related illness, may need to appear on the claim The use of computer software allows medical offices to submit claims electronically. This method shortens the time between filing the claim and reimbursement.

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Medical bills may be paid by the patient or by third party payors, such as private insurance company, a managed care company, or a government insurance program such as Medicare. Often, the patient pays for a portion of the care (co-payment or deductible), and an insurance or managed care company is billed for the remaining fees. In some cases, patients may ask to pay their portion over time, and credit may be extended to them. The medical office may charge interest as long as the patient has been informed. This practice is called truth-in-lending. Credit laws vary by state. Payment received from an insurance or managed care company contains a document called the explanation of benefits (EOB). This statement explains what was paid and what services were not covered and is sent to the provider and the patient. A service may not be covered if a patient has not met his or her yearly deductible. In this case, the provider bills the patient for his or her fee. It is common to bill patients once a month. When a payment arrives, it is important to endorse it right away. This can be done with a rubber stamp that contains the name of the provider and the bank account number. Endorsing is a form of protection because only the provider who endorsed it can cash the check in the event it is lost or stolen. The provider should have a deposit procedure.

Complications Complications impact bill collection. Accurate coding, standard office procedures, and good communication within a provider group minimize complications. Overdue payments In some cases, a patient may not pay his or her bill within a month or by the claim’s due date. A document called an aging schedule lists overdue accounts. The information includes the patient’s name, amount due, payments received, and comments. An account is aged beginning with the billing date rather than the date the procedure was performed. Eighty percent of fees should be collected within a month of billing. If this number falls to 50% or less, collection procedures should be examined. A patient must be reminded of an overdue bill. This can be done with a written notice, phone call, or during the next office visit.

KEY TERMS Adjustment—Changes to a standard fee. Changes may be made because of managed care agreements or other discounts. Aging schedule—A list of overdue medical accounts calculated from date of original bill to current date. Claim—Medical bill. Diagnostic related groups (DRGs)—Diagnosis categories that are used when doing physician or hospital billing. Each diagnosis is placed into the appropriate category. Managed care—A type of health plan with a network of providers and pre-arranged fee schedule. Examples include a health maintenance organization (HMO) or preferred provider organization (PPO). Payor—One who pays a medical claim. A third party payor is an entity other than the patient, such as the insurance company. Provider—Health team professional or entity (hospital) that offers care.

Denied claims If the insurance or managed care company’s EOB indicates that the claim is denied, it is important to determine why this happened. The claim should be doublechecked to determine if an error has occurred. If the patient is not entitled to coverage, he or she is billed when the monthly billings are sent out. Fraud Medicare has the right to audit a physician’s office and examine its billing practices. Errors in claims are checked to determine the presence of fraudulent practices. A medical office must not bill for services that were not performed and must not inaccurately code a service to receive a higher level of payment. These practices are examples of fraud. Health care professionals who report fraud are called whistle-blowers. The Federal Claims Act protects and reward these individuals when they report Medicare fraud. States also have anti-fraud regulations.

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Payment

Medical chart

Collecting fees after a patient’s death If a patient has died, the physician may collect fees from his or her estate. Since death is followed by a period of grief, it is recommended that the physician’s office wait before sending a final statement to the patient’s next of kin as indicated on the chart.

Health care team roles Clear communication within a provider group helps ensure that claims are properly coded, patients are informed of fees, and fair reimbursement is billed and received. The physician must be questioned if there is any doubt that a service was performed or if the diagnosis is not clear. The team involved in billing includes the physician, office manager, nurse, receptionist, medical assistant, and insurance clerk, with these billing-related duties: • Performs billable service: physician, nurse, medical assistant. • Explains fees/billing: physician, receptionist, nurse, medical assistant, insurance clerk. • Prepares day sheet, ledger, superbill: nurse, medical assistant, insurance clerk. • Files (sends out) claim: insurance clerk. • Reminds patient of overdue payment: receptionist, nurse, medical assistant, insurance clerk. • Communicates with insurance companies: receptionist, medical assistant, nurse, insurance clerk. Resources BOOKS

Hosley, Julie B., Shirley A. Jones, Elizabeth A. MolleMatthews. Lippincott’s Textbook for Medical Assistants. Philadelphia: Lippincott-Raven Publishers, 1997. Jones, Marleeta K. St. Anthony’s ICD-9 CM Code Book, Volumes 1,2,3. Reston, VA: St. Anthony’s Publishing, 1997. ORGANIZATIONS

American Medical Association. 515 N. State Street, Chicago, IL 60610. (312) 464-5000. . Health Care Financing Association. 7500 Security Boulevard, Baltimore, MD 21244. (410) 786-3000. . OTHER

Goldsmith, Connie. “Blowing the Whistle: Laws protect nurses who report healthcare fraud.” NurseWeek (May 18, 2000): .

Rhonda Cloos, R.N. 1522

Medical chart Definition The medical chart is a confidential document that contains detailed and comprehensive information on the individual patient and their care experience.

Purpose The purpose of the medical chart is to serve as both a medical and legal record of patient clinical status, care, history, and caregiver involvement. The detailed information contained in the chart is intended to provide a of the patient’s clinical condition by detailing diagnoses, treatments, tests and response to treatment, as well as any other factors that may affect the clinical state of the patient.

Description The term medical chart or medical record is a general description of a collection of information on a patient. However, different clinical settings and systems utilize different forms of documentation to achieve this purpose. As technology progresses, more institutions are adopting computerized systems that aid in clear documentation, enhanced access, and efficient storage of patient records. New uses of technology have also raised concerns about confidentiality. Confidentiality, or patient privacy, is an important principle related to the chart. Whatever system may be in place, it is essential that the health care provider protect the patient’s privacy by limiting access to authorized individuals only. Generally, physicians and nurses write most frequently in the chart. The documentation by the clinician who is leading treatment decisions (usually the physician) often focuses on diagnosis and prognosis, while the documentation by the nursing team generally focuses on patient responses to treatment and details of day-to-day progress. In many institutions the medical and nursing staff may complete separate forms or areas of the chart specific to their disciplines. Other on-staff health care professionals that have access to the chart include physician assistants; social workers; psychologists; nutritionists; physical, occupational, speech, or respiratory therapists; and consultants. It is important that the various disciplines view the notes written by other specialties in order to form a complete picture of the patient and provide continuity of care. Quality assurance and regulatory organizations, legal bodies, and insurance companies may also have access to the chart for specific purposes such as documentation, institutional audits, legal proceedings, or verification of

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The medical record should be stored in a predesignated, secure area and discussed only in appropriate and private clinical areas. The patient has a right to view and obtain copies of his or her own record. Special state statutes may cover especially sensitive information such as psychiatric, communicable disease (i.e., HIV), or substance abuse records. Institutional and government policies govern what is contained in the chart, how it is documented, who has access, and policies for regulating access to the chart and protecting its integrity and confidentiality. In cases where chart contents need to be accessed by individuals outside of the immediate care system, the patient or patient representative is asked for written permission to release records. Patients are often asked to sign these releases so that caregivers in new clinical settings may review their charts.

Operation Documentation in the medical record begins when the patient enters the care system, which may be a specific place such as a hospital or a program such as a home health care service. Frequently the facility will request permission to obtain copies of previous records so that they have complete information on the patient. Although chart systems vary from institution to institution, there are many aspects of the chart that are universal. Frequently used chart sections include: • Admission paperwork: includes legal paperwork such as living will or health care proxy, consents for admission to the facility or program, demographics, and contact information. • History and physical: contains comprehensive review of patient’s medical history and physical exam. • Orders: contains medication and treatment orders by the doctor, nurse practitioner, physician assistant, or other qualified health care team members. • Medication record: records all medication administered. • Treatment record: documents all treatments received, such as dressing changes or respiratory therapy. • Procedures: summarizes diagnostic or therapeutic procedures, i.e., colonoscopy or open-heart surgery. • Tests: provides reports and results of diagnostic evaluations, such as laboratory tests and electrocardiography or radiography images or summaries. • Progress notes: includes regular notes on the patient’s status by the interdisciplinary care team.

• Consultations: contains notes from specialized diagnosticians or care providers. • Consents: includes permissions signed by patient for procedures, tests, or access to chart. May also contain releases, such as the release signed by the patient when leaving the facility against medical advice (AMA). • Flow records: tracks specific aspects of patient care that occur on a routine basis, using tables or chart format. • Care plans: documents treatment goals and plans for future care within the facility or following discharge. • Discharge: contains final instructions for the patient and reports by the care team before the chart is closed and stored following patient discharge. • Insurance information: lists health care benefit coverage and insurance provider contact information. These general categories may be further divided for the individual facility’s purposes. For example, a psychiatric facility may use a special section for psychometric testing, or a hospital may provide sections specifically for operations, x-ray reports, or electrocardiograms. In addition, certain details such as allergies or do not resuscitate orders may be displayed prominently (i.e., on large colored stickers or special chart sections) on the chart in order to communicate uniquely important information. It is important for the health care provider to become familiar with the charting systems in place at his or her specific facility or program. It is important that the information in the chart be clear and concise, so that those utilizing the record can easily access accurate information. The medical chart can also aid in clinical problem solving by tracking the patient’s baseline, or status on admission; orders and treatments provided in response to specific problems; and patient responses. Another reason for the standard of clear documentation is the possibility of the legal use of the record, when documentation serves as evidence in exploring and evaluating the patient’s care experience. When medical care is being referred to or questioned by the legal system, the chart contents are frequently cited in court. For all of these purposes, certain practices that protect the integrity of the chart and provide essential information are recommended for adding information and maintaining the chart. These practices include: • Include date and time on all records. • Include full patient name and other identifiers (i.e., medical record number, date of birth) on all records. • Mark continued records clearly (i.e., if note continued on reverse of page). • Sign each page of documentation.

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information for care reimbursement. It is important to know the institution’s policies regarding chart access in order to ensure the privacy of the patient.

Medical chart

KEY TERMS Consultation—Evaluation by an expert or specialist. Continuity—Consistency or coordination of details. Discipline—In health care, a specific area of preparation or training, i.e., social work, nursing, or nutrition. Documentation—The process of recording information in the medical chart, or the materials in a medical chart. Interdisciplinary—Consisting of several interacting disciplines that work together to care for the patient.

• Document any occurrence that might affect the patient. Only documented information is considered credible in court. Undocumented information is considered questionable since there is no written record of its occurrence. • Always use current date and time with documentation. For example, if adding a note after the fact, it can be labeled “addendum” and inserted in correct chronological order, rather than trying to insert the information on the date of the actual occurrence. • Record actual statements of patients or other individuals in quotes.

Objective—Not biased by personal opinion Prognosis—Expected outcome of an illness or injury. Regulatory organization—Organization designed to maintain or control quality in health care, such as the Joint Commission on Accreditation of Healthcare Organizations (JCAHO), Department of Health (DOH), or the Food and Drug Administration (FDA). Subjective—Influenced by personal opinion or experience.

• Use blue or black non-erasable ink on handwritten records. • Keep records in chronological order. • Prevent disposal or obliteration of any records. • Note documentation errors and correct clearly, i.e., by drawing one line through the error and noting presence of error, initialing the area. • Avoid excess empty space on the page. • Avoid abbreviations or use only universally accepted abbreviations. • Avoid other unclear documentation, such as illegible penmanship. • Avoid including contradictory information. For example, if a nurse documents that a patient has complained of abdominal pain throughout the shift, while the physician documents that the patient is free of pain, these discrepancies should be discussed and clarified. • Provide objective rather than subjective information. For example, do not allow personality conflicts 1524

between staff to enter into the notes. All events involving the patient should be described as objectively as possible, i.e., describe a hostile patient by simply stating the facts, such as what the patient said or did and surrounding circumstances or response of staff, without using derogatory or judgmental language.

• Never leave the chart in an unprotected environment where unauthorized individuals may read or alter the contents. Several methods of documentation have arisen in response to the need to accurately summarize the patient experience. In the critical care setting, flow records are often used to track the frequent patient evaluations, checks of equipment, and changes of equipment settings that are required. Flow records also offer the advantages of displaying a large amount of information in a relatively small space and allowing for quick comparison. Flow records can also save time for the busy clinician by allowing completion of checklists versus narrative notes. Narrative progress notes, while more time consuming, are often the best way to capture specific information about the patient. Some institutions require only charting by exception (CBE), which requires notes for significant or unusual findings only. While this method may decrease repetition and lower required documentation time, most institutions that use CBE notes also require a separate flow record that documents regular contact with the patient. Many facilities or programs require notes at regular intervals even when there no significant occurrence, i.e., every nursing shift. Frequently used formats in patient notes include SOAP (Subjective, Objective, Assessment, Plan) notes. SOAP notes use a subjective patient statement to capture an important aspect of care, then follow with a key objective statement regarding the patient’s status, a description of the patient assessment, and a plan for how to address patient problems or concerns. Focus charting and PIE (problem-interventionevaluation) charting use similar systems of notes that begin with a particular focus such as a patient concern or a nursing diagnosis. Nursing diagnoses are often used as

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Resources BOOKS

Marrelli, T. M., and Deborah S. Harper. Nursing Documentation Handbook, 3rd ed. St. Louis: Mosby Inc., 2000. Mastering Documentation, 2nd ed. Springhouse, Pennsylvania: Springhouse Corporation, 1999.

Katherine L. Hauswirth, APRN

Maintenance Current medical charts are maintained by the health care team and usually require clerical assistance, such as the unit clerk in the hospital setting. No alterations should be made to the record unless they are required to clarify or correct information and are clearly marked as such. After patient discharge, the medical records department of a facility checks for completeness and retains the record. Sometimes the record will be made available in another format, i.e., recording paper charts on microfilm or computer imaging. Institutional and state laws govern storage of charts on- and off-site and length of storage time required.

Health care team roles All members of the health care team require thorough understanding of the medical chart and documentation guidelines in order to provide thorough care and maintain a clear, concise, and pertinent record. Health care systems often employ methods to guarantee thorough and continuous use and review of charts across disciplines. For example, nursing staff may be required to sign below every new physician order to indicate that this information has been communicated, or internal quality assurance teams may study groups of charts to determine trends in missing or unclear documentation. In legal settings, health care team members may be called upon to interpret or explain chart notations as they relate to the individual legal case.

Medical codes and oaths see Ethical codes and oaths

Medical electrodes Definition The medical electrode transfers the energy of ionic currents in the body into electrical currents that can be amplified, studied, and used to help make diagnoses.

Purpose Medical electrodes permit surface quantification of internal ionic currents, yielding an ordinarily non-invasive test for a variety of nervous, muscular, ocular, cardiac, and other disorders that might otherwise have required surgical means to verify their presence. For instance, muscular exams using electrodes may produce evidence of diminished muscle strength and can discriminate between primary muscle disorders and neurologically-based disorders, in addition to detecting if a muscle is truly weak or seems so due to other reasons. The electrodes are typically easy to use, fairly cheap, disposable (or easily sterilizable), and often unique in the tasks they help to perform. The essential role of the electrode is to provide ideal electrical contact between the patient and the apparatus used to measure or record activity.

Training Thorough training is essential prior to independent use of the medical chart. Whenever possible, the new clinician should spend time reviewing the chart to get a sense of organization and documentation format and style. Training programs for health care professionals often include practice in writing notes or flow charts in mock medical records. Notes by trainees are often initially cosigned by supervisors to ensure accurate and relevant documentation and document appropriate supervision.

Description Medical electrodes are generally comprised of a lead (for conduction of electrical current), a metal electrode, and electrode-conducting paste or gel for surface electrodes. There is also often a metal (for good electrical contact) snap for the lead to snap into place so that the electrode can be disposable while the lead can be reused. Electrodes can be classified into many groupings; those useful for EEG, for example, follow:

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guides to nursing care by focusing on individual patient needs and responses to treatment. An example of a nursing diagnosis would be “Fluid volume deficit” for a patient that is dehydrated. The notes would then focus on assessment for dehydration, interventions to address the problem, and a plan for continued care, such as measurement of input and output and intravenous therapy.

Medical electrodes Electrodes are placed to monitor this man’s brain activity for Alzheimer’s research. (SIU BioMed/Custom Medical Stock Photo. Reproduced by permission.)

• disposable electrodes (both types, without gel and pregelled) • reusable disc electrodes (gold, silver, stainless steel, or tin) • headbands • saline-based electrodes, which include various kinds Electromyography requires more specialized needle electrodes that must be capable of piercing the skin. Electrodes are used for diverse procedures and check-ups in the health setting. Combined with monitoring systems, they can be powerful predictors of disease and disorders. Some of the main types of exams utilizing medical electrodes include: • Electrocardiography (ECG/EKG): Evaluates the electrical activity of the heart. It may be used to assess heart rate and regularity, in addition to damage, effects of drugs, and devices. ECG is also popularly used to determine the size and position of the chambers of the heart as they relate to the onset of various forms of heart disease. Diagnostic ECG may require 12 to 15 surface electrodes, while monitoring ECG usually employs three to five. 1526

• Electroencephalography (EEG): Helps to identify specific irregularities in the brain. Brain wave patterns can be recorded and observed by positioning typically 10 to 20 electrodes upon the scalp of the patient in different areas and measuring ionic, electrical waves of neuronal activity. • Electromyography (EMG): Assesses muscular response to electrical activity in innervated muscle. Utilizes needle electrodes that are inserted through the skin into relevant muscle fibers. • Electonystagmography (ENG): Records eye movements graphically by placing metal electrodes above, below, and to the side of the appropriate eye, in addition to a ground electrode on the forehead. Eye motion is then recorded relative to the ground electrode location. Testing is usually performed to verify the presence of nystagmus. • Electroretinography (ERG): Operates with an electrode positioned onto the cornea of the eye to record the electrical response of retinal rods and cones. Electrodes measure retinal electrical response to the impingement of light in order to assess a probable retinal disorder

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Offshoot technologies of electrodes, as of July 2001, are veering toward multi-functional processes. One original electrode application boasts hands-free defibrillator capabilities in addition to its normal electrode functions in ECG. It should also be noted that, using a voltage or current generator, electrical stimulation can be applied to precise areas of the body using medical electrodes (in addition to their more conventional utility in measuring ionic currents).

Operation Prior to performing EMG, ENG, and ERG tests, adults need not take any special precautions, except to inform their medical provider of any medications they take. EEG patients should thoroughly wash their hair the night before and use nothing in their hair (such as hair spray, lotions, or oils) on the day of the test. Discontinuance of medications may be necessary and patients should avoid caffeine for at least eight hours prior to the test. ECG patients should inform the provider of any medications taken, in addition to refraining from ingesting cold water and from exercising immediately before the test. Removal of all jewelry is also required. Since the role of medical electrodes is generally for monitoring of electrical impulses, there is no risk of shock. Electrical stimulation using electrodes carries more risk because electricity is delivered to the body and should thus only be performed by personnel with an understanding of the risks involved (especially electrical) and how to avoid them. Knowledge of the ground electrodes and how to use them is strictly required and differs for different systems.

Maintenance Maintenance of electrodes, if they are not disposable, involves sterilization and checking to ensure that the electrode is electrically viable by following the manufacturer’s instructions.

Health care team roles Doctors, nurses, or other technicians may need to perform tests involving medical electrodes. Often the technician or nurse applies the electrodes in patterns conforming to testing standards (i.e., Einthoven’s triangle). Training Electrode placement is essential and thus must be known well enough to position electrodes correctly to

KEY TERMS Einthoven’s triangle—An ECG reference system with the subject’s heart presumed to be the center of an equilateral triangle (both physically, in that electrodes are placed in form of a triangle on the body, and figuratively, in the mathematical measurement techniques used to assess a patient’s cardiac health) formed by three bipolar limb leads. Can be used to diagnose various disorders of the heart. Named after Wilhelm Einthoven, the Dutch electrocardiographer who advanced these recording techniques. Nystagmus—Rapid, repetitive involuntary movements of the eyes. Retinal rods and cones—The two types of lightsensitive photoreceptor cells in the retina. Saline—Containing a salt, or of the nature of a salt.

obtain viable data on many different types of patients. Since each procedure is unique, training must be appropriate to the specific procedure being performed. Electrode impedances may be checked to ensure superior electrical contact; the optimal values should be listed in the manufacturer’s manual. In using electrodes, the technician should follow the guidelines set in the manufacturer’s manual, because electrode handling is not conserved over all electrode types and applications. The following general guidelines have been adapted from Biomedical Life Systems (as of July 2001), a major manufacturer of medical electrodes, but do not apply to all types of electrodes: • Electrodes, gel, and tape (for securing the electrode) should not be applied over broken skin. • Body hair should be trimmed or shaved where electrodes are going to be applied. • Carbon electrodes should be cleaned with mild soap and water to remove skin oils, gel, and dirt. • Skin should be cleaned before and after applying electrodes. • Cleaning lead wires with mild soap and water will prevent them from becoming brittle. Resources PERIODICALS

Mroz, A., M. Borchardt, C. Diekmann, K. Cammann, M. Knoll, and C. Dumchat. “Disposable Reference Electrode.” The Analyst 123, no. 6. (June 1998): 1373–6.

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(both hereditary and acquired) and whether it may require surgery.

Medical ethics

your holding yourselves far aloof from wrong, from corruption, from the tempting of others to vice

OTHER

Medical Electrodes (ECG, EEG, EMG, ENG, ERG). .

Bryan Ronain Smith

Medical emergency kit see First aid kit

That whatsoever you shall see or hear of the lives of men or women which is not fitting to be spoken, you will keep inviolably secret These things do you swear. Let each bow the head in sign of acquiescence

Medical ethics Definition Medical ethics refers to the discussion and application of moral values and responsibilities in the areas of medical practice and research. While questions of medical ethics have been debated since the beginnings of Western medicine in the fifth century B.C., medical ethics as a distinctive field came into prominence only since World War II. This change has come about largely as a result of advances in medical technology, scientific research, and telecommunications. These developments have affected nearly every aspect of clinical practice, from the confidentiality of patient records to end-of-life issues. Moreover, the increased involvement of government in medical research as well as the allocation of health care resources brings with it an additional set of ethical questions.

Description The Hippocratic tradition Medical ethics generally traces its origins to the ancient Greek physician Hippocrates (460–377 BC), who is credited with defining the first ethical standard in medicine: “Do no harm.” The oath attributed to Hippocrates was traditionally recited by medical students as part of their medical school’s graduation ceremonies. A modernized version of the Hippocratic Oath that has been approved by the American Medical Association (AMA) reads as follows: You do solemnly swear, each by whatever he or she holds most sacred That you will be loyal to the Profession of Medicine and just and generous to its members That you will lead your lives and practice your art in uprightness and honor That into whatsoever house you shall enter, it shall be for the good of the sick to the utmost of your power, 1528

That you will exercise your art solely for the cure of your patients, and will give no drug, perform no operation, for a criminal purpose, even if solicited, far less suggest it

And now, if you will be true to this your oath, may prosperity and good repute be ever yours; the opposite, if you shall prove yourselves forsworn. Religious traditions and medical ethics Ancient Greece was not the only premodern culture that set ethical standards for physicians. Both Indian and Chinese medical texts from the third century B.C. list certain moral virtues that practitioners were to exemplify, among them humility, compassion, and concern for the patient’s well-being. In the West, both Judaism and Christianity gave extensive consideration to the importance of the physician’s moral character as well as his duties to patients. In Judaism, medical ethics is rooted in the study of specific case histories interpreted in the light of Jewish law. This case-based approach is known as casuistry. In Christianity, ethical reflection on medical questions has taken the form of an emphasis on duty, moral obligation, and right action. In both faiths, the relationship between the medical professional and the patient is still regarded as a covenant or sacred bond of trust rather than a business contract. In contemporary Buddhism, discussions of medical ethics reflect specifically Buddhist understandings of suffering, the meaning of human personhood, and the significance of death. The Enlightenment and the nineteenth century The eighteenth century in Europe witnessed a number of medical as well as general scientific advances, and the application of scientific principles to medical education led to a new interest in medical ethics. The first book on medical ethics in English was published by a British physician, Thomas Percival, in 1803. In the newly independent United States, Benjamin Rush—a signer of the Declaration of Independence as well as a physician—lectured to the medical students at the University of Pennsylvania on the importance of high ethical standards in their profession. Rush recommended service to the poor as well as the older Hippocratic virtues of honesty and justice.

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Viewpoints Theoretical approaches to medical ethics PHILOSOPHICAL FRAMEWORKS. Since the early Middle Ages, questions of medical ethics have sometimes been discussed within the framework of specific philosophical positions or concepts. A follower of Immanuel Kant (1724–1804), for example, would test an ethical decision by the so-called categorical imperative, which states that one should act as if one’s actions would serve as the basis of universal law. Another philosophical position that sometimes appears in discussions of medical ethics is utilitarianism, or the belief that moral virtue is based on usefulness. From a utilitarian perspective, the best decision is that which serves the greatest good of the greatest number of people. An American contribution to philosophical approaches to medical ethics is pragmatism, which is the notion that practical results, rather than theories or principles, provide the most secure basis for evaluating ethical decisions. CASUISTRY. Casuistry can be defined as a case-based approach to medical ethics. An ethicist in this tradition, if confronted with a complicated ethical decision, would study a similar but simpler case in order to work out an answer to the specific case under discussion. As has already been mentioned, casuistry has been used as a method of analysis for centuries in Jewish medical ethics. THE “FOUR PRINCIPLES” APPROACH. Another approach to medical ethics was developed in the 1970s by a philosopher, Tom Beauchamp, and a theologian, James Childress, who were working in the United States. Beauchamp and Childress drew up a list of four principles that they thought could be weighed against one another in ethical decision-making in medicine. The four principles are:

• the principle of autonomy, or respecting each person’s right to make their own decisions • the principle of beneficence, or doing good as the primary goal of medicine • the principle of nonmaleficence, or refraining from harming people • the principle of justice, or distributing the benefits and burdens of a specific decision fairly One limitation of the “Four Principles” approach is that different persons involved in an ethical decision might well disagree about the relative weight to be given to each principle. For example, a patient who wants to be taken off a life-support system could argue that the principle of autonomy should be paramount, while the clinical staff could maintain that the principles of beneficence and nonmaleficence are more important. The principles themselves do not define or imply a hierarchical ranking or ordering. Current issues in medical ethics One well-known writer in the field of medical ethics has recently written an article listing what he considers “cutting-edge” topics in medical ethics. While space does not permit discussion of these subjects here, they serve as a useful summary of the impact of technology and globalization on medical ethics in the new millennium: • End-of-life care. Medical advances that have led to a dramatic lengthening of the life span for adults in the developed countries and a corresponding increase in the elderly population have made end-of-life care a pressing issue. • Medical error. The proliferation of new medications, new surgical techniques, and other innovations means that the consequences of medical errors are often very serious. All persons involved in health care have an ethical responsibility to help improve the quality of care. • Setting priorities. The fair allocation of health care resources is one example of setting priorities. • Biotechnology. Medical ethicists are still divided over the legitimacy of stem cell research, cloning, and other procedures that advances in biotechnology have made possible. • “eHealth.” The expansion of the Internet and other rapid changes in information technology have raised many questions about the confidentiality of electronic medical records as well as the impact of online education on medical training. • Global bioethics. Global bioethics represents an attempt to consider the ethical problems confronting the poorer countries of the world, rather than concen-

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In the middle of the nineteenth century, physicians in the United States and Canada began to form medical societies with stated codes of ethics. These codes were drawn up partly because there was no government licensing of physicians or regulation of medical practice at that time. The medical profession felt a need to regulate itself as well as set itself apart from quacks, faith healers, homeopaths, and other practitioners of what would now be called alternative medicine. The AMA, which was formed in 1847, has revised its Code of Ethics from time to time as new ethical issues have arisen. The present version consists of seven principles. The Canadian Medical Association (CMA) was formed in 1867 and has a Code of Ethics with 40 guidelines for the ethical practice of medicine.

Medical gases

KEY TERMS Casuistry—A case-based approach to medical ethics. Categorical imperative—The principle that one should act in such a way that one’s deeds could become universal rules of conduct. Ethics—A system or set of moral principles; also, the study of values relating to human conduct. Hippocratic Oath—The ethical oath attributed to Hippocrates that is used as a standard for care by physicians worldwide. Pragmatism—A philosophical position that regards practical results, rather than abstract principles or theories, as the essential criterion of moral value. Utilitarianism—An ethical position based on the premise that usefulness is the best measure of moral worth, and that ethical decisions should promote the good of the largest number of persons.

trating on medical issues from the perspective of the wealthy countries. Of the 54 million deaths that occur each year around the world, 46 million occur in lowand middle-income countries.

Professional implications One implication for physicians is the importance of studying ethical issues during one’s professional education. Many medical, dental, and nursing schools now include courses in their curricula that deal with such topics as moral decision-making, definitions of life and death, the ethical complexities of professional-patient relationships, and the moral safeguards of medical research. As of 2000, more than 25 universities in the United States and Canada offer graduate degrees in medical ethics.

Burkhardt, Margaret A., and Alvita K. Nathaniel. Ethics and Issues in Contemporary Nursing. Albany, NY: Delmar Publishers, 1998. Davis, Anne J., et al. Ethical Dilemmas and Nursing Practice. Paramus, NJ: Prentice Hall, 1996. Dubler, Nancy N. “Legal and Ethical Issues.” The Merck Manual of Geriatrics. 2nd ed. Whitehouse Station, NJ: Merck Research Laboratories, 2000. PERIODICALS

Hughes, James J., and Damien Keown. “Buddhism and Medical Ethics: A Bibliographic Introduction.” Journal of Buddhist Ethics 7 (2000): 1-12. Sabatini, Margaret M. “Health Care Ethics: Models of the Provider-Patient Relationship.” Dermatology Nursing (June 1998): 201-206. Singer, Peter A. “Medical Ethics (Clinical review).” British Medical Journal 321 (July 29, 2000): 282-285. Wolinsky, Howard. “Steps Still Being Taken to Undo Damage of ‘America’s Nuremberg.’” Annals of Internal Medicine (August 15, 1997). ORGANIZATIONS

American Medical Association, Council on Ethical and Judicial Affairs. 535 North Dearborn St., Chicago, IL 60610. (312) 645-5000. American Nurses Association. 600 Maryland Ave. SW, Ste. 100 West, Washington, DC 20024. (800) 274-4262. . American Society of Bioethics and Humanities. 4700 W. Lake, Glenview, IL 60025. (847) 375-4745. . Canadian Medical Association. 1867 Alta Vista Drive, Ottawa ON K1G 3Y6. (613) 731-8610 x2307 or (888) 855-2555. Fax (613) 236-8864. . Institute for Jewish Medical Ethics. Hebrew Academy of San Francisco, San Francisco, CA. (415) 752-7333 or (800) 258-4427. . National Bioethics Advisory Commission. 6705 Rockledge Drive, Suite 700, Rockville, MD 20892. (310) 402-4242. . OTHER

Canadian Medical Association. Code of Ethics of the Canadian Medical Association. Policy statement approved by the CMA Board of Directors, October 15, 1996.

A second implication is recognizing the necessity of interdisciplinary conversation and cooperation. Physicians can benefit from the insights of scholars in the social sciences, philosophy, theology, law, and history. At the same time, they have much to offer professionals in other fields on the basis of their clinical experience.

Medical gases

Resources

Definition

BOOKS

Brody, Baruch A., et al. Medical Ethics: Codes, Opinions, and Statements. New York: BNA Books, 2000. 1530

Ken R. Wells

A medical gas is defined as one that is manufactured, packaged, and intended for administration to a patient in

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Purpose Medical gases are used within hospital settings for many purposes. They include the following elements and compounds: • Oxygen, used to provide supplemental oxygen to the respiratory system; in dentistry in combination with nitrous oxide; and as an emergency standby. • Nitrous oxide, used as an anesthetic agent in surgery; mixed with oxygen to help patients relax during dental procedures; and in cryosurgery (the use of extreme cold to destroy tissue). • Nitrogen, used to provide pneumatic pressure in medical equipment; to prevent combustion and other chemical reactions; and as a component of many gas mixtures. • Carbon dioxide, used to inflate areas of the body for “keyhole” surgery (small incisions made to accommodate surgical instruments); mixed with air or oxygen to stimulate breathing; and in cryosurgery or testing tooth sensitivity in dentistry. • Medical air, used in administering breathing treatments and as a mixing component for other respiratory gases. • Helium, used in breathing mixtures for patients with impaired lung functions. Since medical gases are the most frequently administered drugs in the United States, the FDA is attempting to heighten both consumer and industry awareness about this specialized category of regulated products. Such related delivery hardware as regulators and tubing is also regulated as medical devices.

Description Cylinder markings For the transport and delivery of a cylinder of compressed gas to a provider, the cylinder must have designated markings permanently affixed to its neck to identify the regulatory body governing the use of the cylinder; the service pressure; the serial number; the date of manufacture; the last test date; a stick-on label identifying its contents; its hazard class and color code (green for oxygen, blue for nitrous oxide, yellow for air). The cylinder is equipped with a valve threaded into it that is specifically designed only for the specific type of medical gas the cylinder is designated to contain. Pin index safety system The pin index safety system is used to prevent a cylinder of compressed gas from being filled with the wrong gas, or to prevent the connection of the wrong cylinder to a yoke on an anesthesia machine or to a pipeline within an institution. This system consists of three holes drilled in the valve of the gas cylinder that mate with matching pins on the yoke of the pipeline or anesthesia machine. The large central opening is the gas outlet of the cylinder. The other two holes are drilled to comply with the specifications of the safety system for the gas the cylinder is designed to contain. Despite the design of the safety system, it is not completely proof against mixups. Incidents have been reported of hospital personnel removing an oxygen fitting from an empty vessel, installing it on a nitrogen vessel and attaching it to the oxygen supply system in an institution. Patient deaths have been reported as resulting from such incidents. Safety of hospital employees In addition to concerns about patient safety, medical gases pose safety hazards to hospital personnel as well. The National Safety Council (NSC) has stated that hospital employees are 41% more likely to lose time from work because of injury or illness than employees in other fields. Hospital employees who work in or around laboratories or operating rooms are more likely to be injured by exposure to medical gases than workers in other areas. The highest risks are related to waste anesthetic gases, which result from inadequate maintenance of anesthesia machines or from poor work practices during the administration of anesthesia. The symptoms of acute exposure to waste anesthetic gases include drowsiness, depression, headaches, nausea, irritability, and loss of coordination. Chronic exposure can result in liver or kidney disease, cancer, or miscarriage.

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anesthesia, therapy, or diagnosis. Title 21 of the Code of Federal Regulations (CFR) designates medical gases as drugs, and mandates the Secretary of the Treasury and the Secretary of Health and Human Services to promulgate regulations for the efficient enforcement of the Federal Food, Drug, and Cosmetic Act (FDA)(drug portion of 21 CFR). Such other regulatory bodies as the Department of Transportation (DOT) and national organizations [e.g., the Compressed Gas Association (CGA) and the National Fire Protection Association (NFPA)] write regulations and standards for compressed gases. Medical gases are considered prescription drugs because their use as drugs is unsafe without the supervision of a licensed practitioner or by properly instructed emergency personnel. Regulations regarding the purity of these substances are established by the United States Pharmacopeia/National Formulary (USP/NF).

Medical gases

KEY TERMS Compressed medical gas—Any liquefied or vaporized gas alone or in combination with other gases. Cryogenic vessel—A metal container designed to hold liquefied compressed medical gases at extremely low temperatures. Cylinder—A metal container designed to hold compressed medical gases at a high pressure. Manifold—A pipe or chamber with several openings for funneling the flow of liquids or gases. Regulator—A mechanism that controls the flow of a medical gas.

Operation Storage and transport of liquid oxygen Pipelines serve as a convenient and economical method for the distribution of medical gases throughout a health care institution by reducing the number of gas cylinders required. This reduction contributes to the cleanliness of the facility, simplifies gas delivery, decreases the cost of the gas, and serves to decrease the number of personnel injuries related to the movement of heavy gas tanks. Liquid oxygen, stored at a temperature between -230– -283°F (-150°– -175°C) in double-walled stainless steel containers built to withstand a pressure of 250 lb per square inch gauge (psig), is the system used by most health care facilities for the main supply of this gas. Since liquid oxygen can vaporize rapidly with an abrupt rise in temperature to create dangerously high pressure, the bulk oxygen container must be located away from the institution for safety reasons. An underground pipeline, fitted with protective casings in areas of high surface loads, is used to transport the oxygen to the main facility’s distribution system. Alarm systems are used to monitor the condition and operation of the liquid oxygen container. To avoid misfillings of oxygen containers, hose connections must be noninterchangeable. A high-pressure cylinder manifold system with an automatic switchover valve serves as a reserve supply of liquid oxygen. Storage and transport of liquid nitrous oxide Cylinders of liquefied nitrous oxide connected to a gas manifold usually serve as the supply of this medical gas for facilities. The manifold controls the release of nitrous oxide from each tank. The gas is reduced to a working pressure of 45–55 psig before entering the main 1532

pipeline. Like liquid oxygen, liquid nitrous oxide has an automatic switch-over valve for a reserve bank of cylinders. These banks of gas cylinders are located in a designated storage room, which is usually adjacent to the facility’s loading dock. To prevent cross-filling of tanks or rupture of the pipeline, a system of check valves, shutoff valves and pressure relief valves is employed. Installation and inspection specifications Pipelines in health care facilities must be constructed from hard-drawn seamless medical gas type tubing. All pipelines delivered to these facilities must also be cleaned for oxygen service, permanently labeled, and capped. Supports for the pipelines must have a copper finish if the support is to make contact with the copper tubing. Only qualified technicians should undertake all welding of medical pipelines. Shutoff valves are required throughout a facility’s pipeline system; in particular, those that service a patient area should also have a pressure gauge. A newly installed pipeline system must be cleaned in accordance with set regulations before it is tested. The NFPA requires that both the installer and the user corroborate the findings of the pipeline testing before it is used with patients; and a record of these test results must be kept on file by the facility. Although this testing is designed to ensure the medical gas pipeline system is safe for patients, regulations addressing the requirements for the companies that perform the testing and the certification of pipeline systems have not been established. The American Hospital Association, however, does provide recommendations and verifications for the choice of a company to perform the inspection. Operating rooms Noninterchangeable outlets for medical gases located in operating rooms may be placed on the ceilings or walls. Each one must be color-coded and labeled with the name or chemical symbol of the medical gas it delivers. Automatic closing mechanisms in the outlet of each pipeline will prevent the leakage of gas when the mating end of the transfer hose is absent. The end of each hose used to connect the pipelines to an anesthesia machine must be color-coded and provided with a gas-specific noninterchangeable connection. Three gas sources supply an anesthesia machine: • a storage container of liquid oxygen backed up by a reserve supply of oxygen in a cylinder • liquid nitrous oxide in a cylinder • medical air, supplied by gas cylinders or generated on site by compressors

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States regulate and enforce building codes regarding these pipelines but the variability of these codes are extreme. Some states have separate codes for each county or even for different regions within a large city. The NFPA has updated standards for the pipelines of health care facilities. In addition, the American Welding Society, the Manufacturers’ Standardization Society of the Valve and Fittings Industry, the American Society of Mechanical Engineers, and the American National Standard Institute (ANSI) all have set standards for their installation, design and testing. With such varied coding, an enforcement mechanism is quite difficult. National standardization may come about only through the issue of medical liability.

Maintenance Written procedures must be established for the testing intervals and maintenance of the pipelines as well as policies indicating procedures to be instituted for a shutdown. The American Hospital Association and the NFPA should be contacted regarding maintenance recommendations. The tests and procedures performed by the pipeline installer include: • Pressurizing the pipeline to 1.5 times the working pressure for 24 hours, with each joint being checked for leaks. • Blowing out the pipelines with oil-free nitrogen, pressurizing the pipelines to 1.2 times the working pressure for 24 hours and rechecking for leaks. • Placing a white cloth over the outlets of the pipeline and intermittently purging it until the cloth is no longer discolored. • Checking each pipeline with nitrogen and every outlet for the delivery of the labeled gas. System users must repeat most of these tests and continue to ensure that each outlet is delivering the labeled medical gas. Further inspections of the manifolds, medical air compressors and alarms should be routinely performed. FDA inspectors are mandated to inspect gas liquefaction and container plants every other year.

Health care team roles Biomedical technicians are the primary caretakers of medical gas pipelines within a health care facility. They are usually responsible for accepting medical gas deliveries and validating the contents of the delivery as well as its date and source. They should conduct scheduled shutdowns; establish protocol; maintain written policies and

procedures; and remain informed of new standardized recommendations within the medical gas supply industry. They must also ensure that persons working under them have the proper training to identify medical gas cylinders, connection valves, regulators, and the distribution system within a facility. Respiratory therapists primarily utilize oxygen from outlets within patient areas or from individual cylinders. They are responsible for checking the labels on any cylinders they use. They should also be aware of their duties in the event of a shutdown. Certified registered nurse anesthetists and anesthesiologists should be aware of the location of the banks of gas cylinders and know the personnel responsible for changing them. They should also be knowledgeable about the workings of the cylinder bank and be able to troubleshoot the system with the biomedical technicians. Lastly, they should know the symptoms of exposure to waste anesthetic gases and the proper methods of treatment.

Training All employees handling medical gases should be alerted to the possible hazards associated with their use. These personnel should be trained to recognize the various medical gas labels and to examine all labels carefully. Personnel who receive medical gas deliveries should be trained to store medical grade products separately from industrial grade products. The storage area for these medical grade products should be well defined, with one area for receiving full cryogenic vessels and another area for storing empty vessels. All personnel responsible for changing or installing cryogenic vessels must be trained to connect medical gas vessels properly. They must understand how vessels are connected to the oxygen supply system and be alerted to the serious consequences of altering the connections. Emphasis must be placed on the fact that the fittings on these vessels should not be changed under any circumstances. If a cryogenic vessel fitting does not form a good connection with the oxygen supply system fitting, the supplier should be contacted immediately. The vessel should be returned to them for correction of the problem. Finally, before the medical gas is introduced into the system, a knowledgeable person should ensure that the correct vessel has been connected properly. Every opportunity should be taken to promote the importance of properly handling medical gases to all personnel and especially those who are directly involved with handling them.

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Building codes

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companies to provide more comprehensive testing or to perform more difficult tests not needed routinely.

Resources ORGANIZATIONS

Food and Drug Administration. 5630 Fishers Lane, Room 1061, Rockville, MD 20852. . National Fire Protection Association (NFPA). 1 Batterymarch Park, Quincy, MA 02269-9101. (617) 770-3000 or (800) 344-3555. Fax: (617) 770-0700. . OTHER

FDA Public Health Advisory. Guidance for Hospitals, Nursing Homes, and Other Health Care Facilities. March 2001. Occupational Safety and Health Administration (OSHA). OSHA Technical Manual, Section VI, Chapter 1, “Hospital Investigations: Health Hazards.” Washington, DC: United States Department of Labor, 2001. United States Food and Drug Administration. .

Linda K. Bennington, CNS

Medical history see Health history

Medical laboratories Definition The medical laboratory, also called the clinical laboratory or the pathology laboratory, provides diagnostic testing services for physicians to help identify the cause of disease and changes produced in the body by disease conditions. Medical laboratories are classified as either clinical pathology laboratories, which analyze blood, urine, culture products, and other body fluids; or anatomical (or surgical) pathology laboratories, which analyze tissue or organ samples obtained during surgery or autopsy and cervical and body fluid samples obtained by biopsy or lavage. A typical hospital medical laboratory will be called the Department of Pathology (investigation of disease-related processes) and will offer both types of testing. Medical laboratories of various sizes, offering a variety of testing services, can be found in acute-care hospitals, medical centers, doctor’s offices and group practices, skilled nursing facilities, and long-term care facilities. Commercial medical laboratories operate as independent businesses and serve as testing facilities for physicians and for companies engaged in medical or pharmaceutical research. Additional commercial laboratories that specialize in a specific type of testing such as genetic, drug, and fertility testing also serve the medical community. Reference laboratories are often established by universities, state governments, organizations, and 1534

Purpose Medical laboratory science, or medical technology, is an important part of diagnostic medicine. It uses sophisticated instruments and methods to evaluate hundreds of body processes that occur constantly as body organs do their work. Combinations of laboratory tests are needed to help diagnose a patient’s condition. Clinical pathology evaluates disease by identifying (qualitative testing) and measuring (quantitative testing) chemical substances found in blood, urine, spinal fluid, sputum, feces, and other body fluids. Bacteria and sometimes viruses are grown and identified in culture products (samples of blood, urine, sputum, wounds, etc. that are transferred onto culture media and incubated until they grow enough to be identified). Biochemical substances such as hormones, enzymes, minerals, and other chemicals produced in the body can be measured, as well as chemicals ingested (eaten with food or consumed as medications or poisons) or produced as waste products. Normal levels or reference levels of these substances are determined by performing the tests on large numbers of people and establishing a typical range of results expected in the absence of disease. These reference ranges are often gender and age specific and will vary from laboratory to laboratory depending upon the methods used. A level that is higher or lower than normal gives physicians information about a patient’s condition at the time of testing and may help physicians diagnose a disorder or disease in that patient. Measuring changes in the levels of chemicals may also help to monitor changes in the patient’s condition during and after treatment. For example, a substance produced by the prostate gland called prostate specific antigen is used to screen for prostate cancer. Following treatment, the physician will request that this test be performed because complete removal of the tumor will cause the blood level to return to normal. Following demonstration of successful treatment, the test will be performed at regular intervals to detect any recurrence of the tumor. Anatomical pathology identifies either the cause of disease or, through autopsy, the consequences of disease (cause of death). Samples of cells, tissues, or organs obtained during surgery or autopsy are examined macroscopically (by the naked eye) and microscopically (by powerful microscopes). Advances in the relatively new sciences of genomics (study of DNA and RNA) and proteomics (study of molecular proteins), cell genetics, and molecular analysis may also be performed to better understand the origins of disease in individuals.

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Doctors order laboratory tests to make, confirm, or rule out a diagnosis, to select or monitor therapy (drugs, physical therapy, surgery, etc.), to monitor a patient’s progress during therapy and help determine a prognosis for the patient. A single test is usually not enough to confirm a diagnosis. Combinations of laboratory tests are used along with the patient’s history, physical examination, and diagnostic imaging exams (such as x ray, MRI, CAT scans, and ultrasound) to make a definitive diagnosis. Laboratory screening tests are often performed on apparently healthy patients to make sure they have no underlying disease. Test profiles are also designed that combine a series of related tests (such as a hematology profile or chemistry profile) or organ-related tests (such as a cardiac profile, liver profile, or thyroid profile) to get a broad view of a patient’s condition. More specific testing is usually required to make a definitive diagnosis.

Description Testing laboratories rely on well defined technical procedures, complex precise instruments, and a variety of automated and electronic equipment to do diagnostic testing. Tests are performed by medical technologists, technicians, and laboratory assistants. The technical staff works under the direction of a pathologist, who interprets the results of the laboratory tests. Laboratories, laboratory equipment, and testing personnel are evaluated and accredited by national scientific organizations and government agencies, including the American Society of Clinical Pathologists (ASCP) and the Joint Commission on Accreditation of Healthcare Organizations (JCAHO). This accreditation process helps to standardize lab procedures, establish quality control standards, and ensure that labs provide physicians with accurate and timely test results. The medical laboratory is typically divided into sections that perform related groups of tests. The standard laboratory sections include, but are not limited to: • Clinical chemistry: the study of body chemistry and the detection and measurement of chemicals such as hormones, enzymes, proteins, fats, vitamins, minerals,

metals, and drugs. The chemistry department has subspecialties that include enzymology, toxicology, and immunochemistry. • Hematology: the study of red and white blood cells, including their concentration and morphology(appearance and stages of growth), and the measurement of hemoglobin (iron-bearing protein in the blood) and other substances in the blood that may help diagnose bleeding and coagulation problems, anemia, infection, and various other illnesses including cancer. In large laboratories it is common practice to combine the automated components of both clinical chemistry and hematology into one section that is staffed by personnel who are skilled in both disciplines. • Microbiology: the study of microorganisms, and the isolation and identification of disease-causing bacteria, yeasts, fungi, parasites, and viruses. Microbiologists also determine the antibiotic susceptibility of pathogenic bacteria that are grown from clinical specimens. • Immunology: the study of the body’s immune system and immune processes that mediate and regulate the body’s defense against bacteria, viruses, and foreign cells or antigens (proteins). Immunology is also the section of the laboratory that tests for organ transplant compatiblity, a specialized area called histocompatibility testing, and autoimmune disease (i.e., an immunological response to one’s own tissues). In addition, a branch of immunology called serology measures the concentration of specific antibodies that indicate infectious disease, previous exposure to a pathogen, or immunity resulting from vaccination. • Urinalysis: the examination of urine and the study of waste products that are eliminated by the kidneys may indicate or help explain metabolic or kidney disease processes and monitor treatment with therapeutic drugs. Urinalysis also includes the analysis of cells, crystals, and other objects that enter the urine or are formed by the kidney or urinary tract. • Every clinical laboratory will offer testing capabilities within these categories. All hospitals that perform surgery will also have an immunohematology department, which comprises the blood bank and those tests that are used to determine whether blood from a donor will be compatible with the intended recipient. In addition, the blood bank technologists perform tests to detect antibodies on red blood cells, store blood and blood products, and prepare blood products for transfusion. The blood bank also performs therapeutic bleeding or removal of specific blood components for some patients. Smaller laboratories, such as those in doctors’ offices, will perform routine testing and screening tests

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Anatomical pathology gives doctors the most definitive information on the disease process causing a patient’s symptoms, illness, or death. Results of anatomical pathology depend upon the qualified opinion of a pathologist, a physician trained and experienced in identifying the causes of disease and changes in body chemistry or tissues in the presence of disease. The anatomical pathology report is written in appropriate detail for the testing physician, and will be used along with clinical data to determine the stage (extent) and prognosis (outlook) of the disease.

Medical laboratories

Vent to atmosphere

Safety valve

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Exhaust

Steam deflector

Door baffle

Control handle

Door wheel

Steam jacket

Vacuum drier

Screened outlet Gasket on door Air line trap

Swing check valve Return line trap Steam strainer

Thermometer Pressure regulator Steam supply valve

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A steam autoclave is used to disinfect lab equipment. (Delmar Publishers, Inc. Reproduced by permission.)

related to the physician’s specialty, usually testing blood and urine samples only, and will still need the hospital or independent testing laboratories for special diagnostic tests. Smaller laboratories generally use state-of-the-art equipment and automated instruments that are designed for less testing volume and that are less complex than those used in larger laboratories. While some tests are performed manually, medical laboratories depend upon computer-controlled automated equipment for as many tests as possible to keep up with the volume and variety of tests ordered. Multichannel analyzers are commonly used to perform clinical chemistry tests. These large, complicated instruments are computer-controlled to perform many separate chemistry tests simultaneously (often called a chemistry panel or profile) on each patient’s sample. The goal of such automation is to reduce the amounts of sample required; reduce the amount of chemicals (reagents) needed per test; reduce the time of analysis; eliminate contamination and error that results from excessive sam1536

ple handling; and reduce the number of technologists needed to perform the testing. The precise operation of automated systems provides a higher degree of precision avoiding the differences in operator technique that increases the variance of manual testing methods. Computer-calculated results have been shown to be far more reliable than results subject to human manipulation, which is more likely to introduce transcription and random computational errors. Cost savings achieved through automation are important to both the testing facility and the patient. Time savings are important to the testing physicians and unit nurses who are waiting for test results to make critical patient-care decisions. Laboratory computerization also includes laboratory information systems (LIS) that can access patient information and allow reporting of test results directly to the patient’s record. Patient orders and test results can be viewed on a terminal or printed out in a comprehensive record, showing daily or hourly results side by side for comparison. This is especially valuable to physicians

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Hundreds of different types of tests are performed daily in the medical laboratory using different methods on a variety of special instruments. The demand for both rapid and reliable results has led to increased reliance on automation and to new portable testing methods that can be performed at the bedside or other point-of-care. Some of the most common automated testing methods are: • Automated general chemistry analyzer (automated spectrophotometry. Most automated tests performed on multichannel analyzers use this technique. The instrument consists of components that perform all of the steps of a manual procedure. Robotic arms may be used to convey the samples from the centrifuge to the analyzer and bar code readers are used to input test order and patient information directly to the analyzer’s computer. Sample and reagents are added to reaction cells in precise amounts, mixed mechanically, and incubated at constant temperature for a specific period of time. The chemical reaction typically results in production of a colored product. The color intensity (absorbance) is determined by the instrument’s optical system or spectrophotometer. The instructions for how to perform each different test (i.e., sample volume, reagent volume, incubation time, wavelengths for analysis) are stored in the computer’s memory. The computer also stores calibration information needed to calculate results, and quality control data that is needed to validate instrument performance. Reaction cells may be disposable or cleaned and reused by an automated wash system on the analyzer. In addition to optical analysis, these instruments usually have electrochemical sensors for analysis of electrolytes such as sodium and potassium. The test menu is usually large, for example 40 to 60 different analytes that can be measured in any order or combination. Smaller, single-channel spectophotometers are also used in doctor’s offices, clinics, and nursing units to perform a more restrictive number of procedures. Another type of light measuring instrument called a reflectance photometer is often used to read dry reagent strip urine or dry slide chemistry tests. • Immunoassays. This comprises a wide range of laboratory methods that utilize specific antibodies to facilitate a measurement. Immunoassay platforms are incorporated into several large autoanalyzers (automated chemistry analyzers), and are used to identify minute amounts of analytes (substances analyzed in blood, urine or body fluids), which include hormones, drugs,

tumor markers, specific proteins, and cardiac markers. Some systems also support immunological tests to identify bacterial and viral antigens and allergens (responsible for allergies). The technology is based upon the measurement of antigen-antibody complexes and usually involves the use of a label such as an enzyme, radioactive isotope, or fluorescent molecule to measure the amount of immune complexes formed. New technology allows the selection of individual tests in any order or combination without the need to change reagents or instrument settings manually. • Electrophoresis. Electrically charged particles of varying size and electrical charge, will move at different rates under the influence of an electric field. These differences can be measured by a technique called electrophoresis. The process permits separation of similar molecules such as proteins with different net charges or of different sizes. Serum protein electrophoresis separates proteins found in blood serum, the clear portion of a blood sample after it clots. It is used as an aid to the diagnosis of diseases such as multiple myeloma, acute and chronic inflammation, kidney disease, liver disease, and nutritional disorders. Immunofixation electrophoresis uses the separation of proteins in conjunction with specific antibodies to help diagnose multiple myeloma (a malignant disease) and immunodeficiency states that occur in disorders such as AIDS. Hemoglobin electrophoresis separates the red pigment in blood cells to diagnose certain anemias and blood disorders. • Chromatography. Substances can be separated and identified on the basis of their molecular size or chemical properties (how they interact). High performance liquid chromatography (HPLC), thin-layer chromatography, and gas-liquid chromatography each use a different type of medium to separate drugs, certain proteins, amino acids, lipids, organic acids, and hormones in blood or urine. Various detectors can be used to measure the quantity of the analytes following their separation. • Mass spectrometry. This technology is coupled to gas chromatography in order to conclusively identify a compound based upon its unique chemical structure. The mass spectrometer is most often used to confirm positive drug tests performed by immunoassay. Mass spectrometry equipment is highly specialized and the testing is more likely offered by an independent laboratory specializing in this technique than by a hospital laboratory. Pharmaceutical companies often requires this type of testing on thousands of samples in the research and development of therapeutic drugs.

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and nurses who are monitoring the patient’s treatment. Results may be reported more quickly when the LIS interfaces with the healthcare facility’s medical information system (MIS), which displays results on computer terminals in point-of-care nursing units, or transfers the information to the testing physician’s office.

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KEY TERMS Analyte—A chemical substance in body fluids, cells, or tissues that is the subject of laboratory investigation. Biochemistry—The study of biochemical origins of humans in health, growth, nutrition, and disease. Clinical chemistry—A broad field of analytical techniques that detect and measure chemicals in body fluids, cells, or tissues, such as enzymes, hormones, proteins, drugs, or other naturally occurring chemicals or those either ingested or used to treat disease.

Immunoassay—This type of assay is a measurement technique that uses binding reactions between different types of proteins, one protein being an antigen, the other an antibody that attaches to it. Known amounts of either antigen or antibody are combined with a blood sample or other body fluid to attract the analyte of interest and allow it to be detected and measured. Antigen-antibody reactions can be measured using enzyme technology, fluorescence, or radioisotopes.

Diagnostic medicine—Diagnostic medicine is the scientific study of body fluids, tissues, and organs to diagnose disease, monitor the course of disease, and monitor the response to treatment, particularly drug therapy.

Immunology—The scientific study of the immune system, which the body’s defense system against bacteria, viruses, foreign cells (as in transfusion or transplantation). Immune reactions in the body involve antigen-antibody reactions that can be detected and evaluated using similar antigen-antibody technology.

Enzymes—Important naturally occurring biological catalysts present in the body. They enhance all body processes, including growth, maturation, and reproduction, and can be detected and measured in body fluids to diagnose and monitor disease. Synthetic enzyme reagents (not manufactured in the body) can be used as markers or labels in tests for other analytes.

Markers—Also called labels or tags. They attach to analytes in patient samples and allow them to be detected and measured by various measurement techniques using light, heat, or radioactivity. The term also refers to analytes that signal the presence of a specific diseaase. For example, troponin I is a maker for a heart attach because it is liberated from myocardial cells following infarction.

Fluorescence—A phenomenon exhibited by molecules that absorb light energy and then give off the energy as light of a longer wave length. Fluorescent technology is a measurement technique used in clinical laboratory procedures and equipment.

Pathology—The scientific study of the causes and consequences of disease.

• Atomic absorption and ion-selective electrodes. These techniques are used to measure trace metals and electrolytes, respectively. Atomic absorption spectrophotometry is an optical method that converts ions to atoms and then measures the absorbance of a wavelength of light by the atoms. Metals most commonly measured are lead, zinc, mercury, selenium, and copper. Ion selective electrodes are sensors that produce a small potential difference (voltage) in response to specific ions. This technique is accurate but not as sensitive as atomic absorption spectrophotometry. Therefore, it is used for measuring ions that are relatively abundant in blood such as sodium, potassium, chloride, hydrogen ions, magnesium, calcium, and lithium. • Automated blood cell counters. Hematology laboratories count red and white blood cells, measure hemoglobin (the iron-bearing protein in blood), and determine 1538

Reagents—Reagents are chemical preparations (compounds) used to perform laboratory tests or used in the operation of laboratory equipment.

the hematocrit (the volume percentage of blood occupied by the red cells), as well as other tests reported in a complete blood count (CBC). These tests can all be performed on an automated hematology system. Some automated systems can also identify each type of white cell in what is called a differential blood test. This automated system and its results are useful in diagnosing anemias, infections, leukemia and other blood disorders related to various types of cancer, and for general health screening. • Flow cytometry. A flow cytometer is a more specialized type of cell counter that can differentiate, count, and in some cases sort specific subpopulations of cells. Flow cytometers make use of some of the rapidly expanding tools and molecular diagnostics. Fluorescent labeled antibodies are used to tag the cells of interest and these cells are counted as they flow in single file past through

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Operation Clinical instruments use a variety of measuring technologies to evaluate patient samples, but the principles of operation between analyzers share some fundamental characteristics. All methods on all instruments must undergo a preliminary evaluation of precision and accuracy to demonstrate that they meet the manufacturer’s claims for analytical performance. All methods must be calibrated on a regular basis by analyzing samples of known concentration to which the measured signals from patient samples are compared. All methods must be validated using quality control specimens on a daily basis. The quality control sample is made of the same composition as patient samples and has an expected concentration that is specific for the method of assay. When results for quality control samples do not fall within the expected range, the operator must institute correction actions before patient specimens can be analyzed and reported. Automated instruments have intricate computerized monitoring systems and software codes that signal the operator when results are likely to be invalid. The operator must troubleshoot these problems and perform whatever steps are required to facilitate successful measurement of affected patient samples. Every test result is reviewed and evaluated with respect to quality control performance and its reasonableness before it is electronically transferred to the LIS for reporting.

Maintenance and safety Laboratory personnel often are trained in the operation and maintenance of new equipment by the manufacturers of each type of instrument. Technologists are responsible for calibrating measuring devices such as pipets, equipment such as centrifuges, as well as all instruments. In addition, all incubators, refrigerators, and freezers are monitored for temperature accuracy and electrical lines are checked for current leakage and unstable voltage. All reagents are dated, examined for contamination, and stored in a manner than complies with safety regulations and manufacturer specifications. Instruments, equipment, glassware, and work surfaces are regularly cleaned and disinfected. Gloves, leak-proof

gowns, and other forms of barrier protection are utilized to reduce the risk of transmission of bloodborne pathogens and exposure to chemical and physical agents that may be harmful. While large hospitals may rely on staff biomedical engineers to perform some maintenance and instrument repairs, the laboratory personnel are responsible for day-to-day operation, cleaning and maintenance procedures. Each laboratory must maintain records of equipment calibration, cleaning and maintenance, and a manual of all laboratory procedures and policies. Laboratory operations, facilities, and services are inspected by external accrediting agencies that evaluate compliance by the laboratory with the Clinical Laboratory Improvement Act of 1988 (CLIA 88) as well as their own standards.

Health care team roles Physicians order diagnostic tests from the medical laboratory to help diagnose and treat their patients. When an order is received by the laboratory, either on a manual lab request form or through the hospital MIS, the lab will first obtain the proper type of sample. This may involve drawing blood (venipuncture), which is typically performed by a phlebotomist (person who specializes in venipuncture). Samples such as urine, feces, sputum, or tissue usually are obtained by nurses or physicians in the nursing unit. Surgical samples will be delivered to the lab by surgical technicians. Some samples, such as single or 24-hour urine samples, are brought to the lab by patients themselves (if they are outpatients). Laboratory personnel are responsible for checking all specimens received in order to determine that they are properly labeled and collected in the proper container. Personnel responsible for specimen processing will separate the blood components if required and store the sample at the proper temperature prior to testing. Technologists or technicians perform the analysis, evaluate the test system using quality control procedures, and review each result before reporting it. Inappropriate specimens are rejected, and suspicious results may require repeat testing using a new sample. Critical values and stat requests must be called immediately to the ordering physician. Some physicians have issued a written request for follow-up testing when results are abnormal. Timely communication between the laboratory staff and the primary care provider is essential for effective utilization of laboratory tests and results.

Training Laboratory medicine is a well developed field based upon natural and physical sciences that requires education in medical science, techniques and research methods. Pathologists are physicians (MDs) who have completed

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an aperature into which a laser is focused. The laser stimulates the fluorochrome to emit light of a specific color. Light filters and detectors respond to the specific colors and the instrument’s computer processes the resulting electrical signals to determine the cell count. Two rapidly advancing biosciences, genomics and proteomics, are being applied to flow cytometry to permit measurement of the DNA content of cells to determine if they are benign or cancerous.

Medical laboratory technology

four years of medical school, followed by a residency in a pathology laboratory. Medical laboratory technologists, technicians, and assistants who work in all fields of medical laboratory science are educated and trained at various levels. Those with more education will have greater technical and administrative decision-making responsibilities in the laboratory. Some may have advanced degrees (Ph.D. or M.S.) in sciences such as biochemistry or immunology. Certified technologists are required to have a Bachelor of Science degree and to have successfully completed an accredited laboratory training program. Their course of study typically includes anatomy, physiology, molecular biology, organic and biochemistry, immunology, microbiology, mathematics and statistics. Professional laboratory training includes courses in hematology, diagnostic and pathogenic microbiology, clinical immunology, immunohematology, and clinical biochemistry and urinalysis. A clinical practicum (internship) is typically required either as part of the baccalaureate degree or afterwards. After this training, graduates will be eligible for certification by examination by the American Society of Clinical Pathologists (ASCP) or National Certification Agency for Clinical Laboratory Personnel (NCA). Certified clinical laboratory technicians earn an associate degree from an accredited medical laboratory technician program. The program will include a clinical practicum as part of the training. Following this graduates are eligible for certification by examination by the American Society of Clinical Pathologists (ASCP) or National Certification Agency for Clinical Laboratory Personnel (NCA). Some vocational schools offer basic education and training for medical laboratory assistants, allowing graduates to perform some laboratory procedures and assist more skilled laboratory personnel. Resources BOOKS

Henry, J. B. Clinical Diagnosis and Management by Laboratory Methods. 20th edition. St. Louis: W. B. Saunders, 2001. ORGANIZATIONS

American Society for Clinical Laboratory Science (ASCLS). 7910 Woodmont Avenue, Ste. 530, Bethesda, MD 20814. (301) 657-2768. . American Society of Clinical Pathologists (ASCP). 40 West Harrison Street, Chicago, IL 60612 (312). 738-1336. . OTHER

Definition Medical laboratory technology is the branch of medical science responsible for performing laboratory investigations relating to the diagnosis, treatment, and prevention of disease.

Description Laboratory scientists (medical and clinical technologists as well as medical and clinical laboratory technicians) facilitate the diagnosis of diseases, as well as the implementation and monitoring of therapies to treat disease. Laboratory scientists are responsible for examining and analyzing blood, body fluids, tissues, and cells in an effort to help clinicians determine the underlying cause of an illness, the stage of a disease, or the effectiveness of therapy. To accomplish their objectives, laboratory scientists perform a wide variety of laboratory tests, often with the aid of complex, computerized, and automated instrumentation. Tests performed by laboratory scientists include: • Microbiology tests that isolate and identify pathogenic bacteria, yeast, fungi, parasites, and viruses and determine antibiotic sensitivity. • Chemistry tests that measure the chemical content of plasma, body fluids and cells including electrolytes, glucose, lipids, proteins, hormones, enzymes, trace metals, drugs, and toxins. • Blood banking tests, such as typing, antibody screening, and cross matching, that are used to identify and prepare blood components that are compatible for transfusion. • Immunology tests that are used to determine a person’s ability to resist infections, diagnose autoimmune diseases, allergies, and infectious diseases, and determine tissue compatibility for organ transplantation. • Hematology tests that count and classify blood cells, diagnose blood diseases, diagnose bleeding disorders, and monitor anticoagulant therapy. • Histology procedures that prepare specimens for microscopic examination by pathologists. • Cytology procedures such as the Pap smear test, which identify cancerous changes within cells.

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Medical laboratory technology

• Cytogenetic procedures which identify abnormal chromosome counts, morphology, and disease genes.

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Over the past few decades the proliferation of laboratory automation has significantly decreased the handson nature of the work. Today, many experienced laboratory scientists spend more time analyzing results, developing and modifying procedures, and establishing and monitoring quality control programs than they do performing tests.

Work settings An article published in the July 1999 issue of Medical Laboratory Observer reported that “in general, medical technologists and medical laboratory technicians are stable professionally.” Laboratory scientists in their study, which was conducted in 1998 and 1999, had been employed at their current lab for 12 years and had been in the lab profession for 21 years. This job stability may be due in part to job flexibility. Because many large hospitals and reference laboratories operate 24 hours a day, seven days a week, they offer opportunities for laboratory scientists to work full or part-time, days, evenings, or nights. However, smaller hospitals with a more limited staff often require their laboratory scientists to rotate shifts, while others place laboratory workers on call several nights a week or on weekends to ensure coverage during an emergency situation. Working an occasional weekend and holiday is also quite common. Clinical laboratories are well lit and clean, and the work is not physically demanding or particularly dangerous. That said, in a typical day most laboratory scientists will spend a significant portion of their day on their feet and be exposed to odiferous reagents and specimens, some of which will be infectious. Wages for laboratory personnel are rising and correlate with the level of education and training. According a survey conducted by the American College of Clinical Pathologists, the median annual salary for a staff medical technician in 2000 was $29,120, an increase of 8.5% since 1998. In contrast, the median annual salary for a staff medical technologist in 2000 was $37,232, an increase of 11.9% since 1998. For both technicians and technologists, salaries on the coasts were higher than elsewhere in the United States. As the MLO article and others have reported, the majority of laboratory scientists work full-time in hospitals, reference and physician office laboratories. However, there are also numerous employment opportunities for laboratory scientists in forensic, environmental and food industry laboratories. In addition, manufacturers of home diagnostic testing kits and laboratory equipment and supplies seek experienced technologists to work in product development, marketing, and sales.

Medical laboratory technologists perform a variety of tests on body fluids and tissues to help physicians determine diagnoses and evaluate therapies. (Custom Medical Stock Photo. Reproduced by permission.)

Education and training The Clinical Laboratory Improvement Act of 1988 (CLIA ‘88) sets minimum standards for testing personnel who work in clinical laboratories. For labs performing high complexity tests, the minimum requirement for testing personnel is an associate’s degree in laboratory science. Persons who hold an associate degree from an accredited training program and certification are referred to as technicians. Persons who hold a bachelor’s degree and certification in a clinical laboratory field are referred to as technologists. Certification is a prerequisite for most jobs, and some states require laboratory scientists to be licensed. Those holding a bachelor’s degree with a major in medical technology or in one of the life sciences typically earn more money and receive more opportunities for advancement. While both technicians and technologists perform laboratory procedures, the technologist has greater knowledge of scientific principles and problem solving skills, and is responsible for oversight of quality assurance, method evaluation, and laboratory management. Both bachelor and associate degree pro